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Site classification of Taiwan free-field strong-motion stations
Abstract
Based on the available geologic and geomorphologic data, 708 Taiwan Strong-Motion Instrumentation Program (TSMIP) free-field strong-motion station sites are classified using a scheme compatible with the 1997 Uniform Building Code (UBC) provisions. Results show that an extensive usage of geologic maps and geomorphologic data for site classification is satisfactory and is a quick and effective method for categorizing large numbers of strong-motion station sites. The response spectral shapes (RSS) method and the horizontal-to-vertical spectral ratio (HVSR) method both provide good supplements for checking purposes. Field checks are definitely necessary, especially for sites located near geologic boundaries or geomorphologic boundaries. Final comments for each station site have been made after these checks. Some problematic sites do exist and are mentioned in the text. Data from these sites must only be used with care. To increase the accessibity of our results, we have developed a web-based query site at http://gis.geo.ncu.edu.tw/query/site/, and an appendix for site classification of the 708 TSMIP stations is given in the CD-ROM attached to this issue.
... Presently, there is not a frequency-dependent function to show site amplification and site attenuation in the study area. Lee et al. (2001) classified the station sites of this study to be Class C or Class D. Based on the US's criteria, the shear velocities are 360 -760 m sec −1 for Class C sites and 180 -360 m sec −1 for Class D ones. Hence, the amplification at the study sites should be larger than that given by Boore and Joyner (1997), because of the lower shear velocities based on the US's criteria. ...
... Hence, the amplification at the study sites should be larger than that given by Boore and Joyner (1997), because of the lower shear velocities based on the US's criteria. However, Lee et al. (2001) classified the sites just based on surface geology rather than the shear velocities. Except for a few station sites in the southwestern part of the study, most of them are at soil or rock sites. ...
... Hence, the approximated corrections are taken into account. The only indication to show site effect is the ratio of spectral acceleration to maximum ground acceleration with period obtained by Lee et al. (2001) from a huge number of data. Their results show that the site effect exists mainly in the frequency range 2 -10 Hz, with a maximum at f = 5 Hz for the Class C sites, and 6 Hz for the Class D ones. ...
... A practical application of a hybrid site classification is described by LEE et al. (2001), who used response spectra shape and horizontal-to-vertical spectral ratio of earthquake records for classification of strong-motion sites in Taiwan. Categorization of response spectra was done by using the mean acceleration spectral shapes from SEED et al., 1976 (Figure 4.3a), while HVSR were classified according to the regulations of the Japanese code (JAPAN ROAD ASSOCIATION, 1980). ...
... Normalized response spectra (a) and H/V spectral ratio (b) for hybrid site classification as proposed byLEE et al., 2001 (figures taken from (a) SEED et al., 1976and (b) LEE et al., 2001. ...
... Normalized response spectra (a) and H/V spectral ratio (b) for hybrid site classification as proposed byLEE et al., 2001 (figures taken from (a) SEED et al., 1976and (b) LEE et al., 2001. ...
The main objective of the present work is to establish a link between the scientific fields of engineering seismology and structural engineering. Substantially it deals with the application and enhancements of methods coming from engineering seismology as well as their junctions to the fields of structural engineering respectively earthquake engineering. Based on real occurred earthquake damage inflicted to multistoried reinforced-concrete frame buildings, the influence of local site effects on the grade of structural damage is worked out. This relying on comprehensive investigations conducted during numerous field missions of German TaskForce after damaging earthquakes in Venezuela and Türkiye. Instrumental investigations on both the structure and its local subsoil in order to identify the damage potential of seismic ground motion take center stage of the thesis. Thereby it is examined whether or not an estimated seismic demand representative in amplitude level and frequency characteristics is able to cause structural damage considering the vulnerability of the structure itself as well as the local site and subsoil conditions. Investigations are concentrated on selected RC frame structures with or without masonry infill walls.
... A total of 117 TSMIP stations (the first three characters of station code are labeled with "CHY") located in Yun-lin, Chia-yi, and Tainan Counties were chosen for searching available accelerograms (Fig. 1). Their site conditions have been categorized into four classes, namely, B, C, D, and E based on the geologic and geomorphologic data (Lee et al. 2001), and are listed in Table 1. It is obvious that most of the sites at the western flood plain are classified to class E (soft soil). ...
... R and M represent hypocentral distance and moment magnitude, respectively. The character in parenthesis following the station code represents the soil class based on the classification ofLee et al. (2001). ...
... The site classification of TSMIP/CHY array based onLee et al. (2001) ...
Empirical regional attenuation relationships for the amplitude of S and Lg waves were achieved by performing regressions over a large number of accelerograms, collected from TSMIP stations in southwestern Taiwan over a ∼7-year period. From estimations of effective ground-motion duration, utilized to characterize the source term and path effects, a piecewise continuous duration function relating to hypocentral distance was derived. For simplicity, Brune's ω-square model was used in this article. Assuming a high-frequency approximated decay parameter of κ 0 = 0.03 sec and static stress drop Δσ = 100 bars for the averaging characteristics of the source spectra, the attenuation curves of peak horizontal accelerations that relate to the hypocentral distance for the given moment magnitudes were effectively obtained using random vibration theory. However, the current model cannot be arbitrarily generalized for the prediction by individual specific earthquake and does not include extended faults based on the source assumption applied. Due to sensitive variation of peak ground motion predictions (strongly associated with the stress drop and attenuation factors), it is suggested that the source parameters and the sites chosen should be localized into several subsets (as far as this is possible) through analyses of historic earthquakes and strong-motion records. In practice, this work should be valid in predicting peak ground motions well when simulating a characterized event.
... 3). The free-field strong-motion station sites in the Taiwan region were classified (Lee et al. 2001 ) using a scheme compatible with the 1994 and 1997 NEHRP provisions (BSSC 1998 ) which is based on the properties of the top 30 meters of the soil column, disregarding the characteristics of deeper geology. For Taiwan five site categories are defined on the basis of average shear wave velocity Vs30, namely: B -rock; C -very dense or stiff soil; D -stiff soil; E -soft soil; F -soils requiring special studies. ...
... The existing geological and geomorphologic data were analyzed, and the response spectral shape and the horizontal-to-vertical spectral ratio of response spectra data were used for the classification . It has been noted (Lee et al. 2001; Sokolov et al. 2004; Huang et al. 2005) that further studies on site classification should be carried out in the Taiwan region. We used moment magnitude in our analysis. ...
... It seems also that the characteristics of residuals are of the array-or region-dependent quantities (Table 3 ); however , the phenomenon may be caused by different numbers of events and of records collected by the considered arrays (see also Tsai et al. 2006). In this study we used the site classification proposed for TSMIP stations by Lee et al. (2001). The classification is under revision at present (e.g., Huang et al. 2005; Kuo et al. 2010 ). ...
In this work we analyzed characteristics of aleatory variability with regard to intra-event and inter-event components in the prediction of peak ground acceleration in Taiwan and the spatial (site-to-site) correlation of ground motion residuals. The characteristics are very important for an assessment of seismic hazard and loss for regionally located building assets (portfolio) and spatially distributed systems (lifelines) and Shake Map generation. The strong-motion database collected by the TSMIP network in Taiwan, which includes about 4650 records from 66 shallow earthquakes (M(L) > 4.5, focal depth < 30 km) occurred in 1993 - 2004, was used for this purpose. The results of the analysis show that the ground motion correlation structure is highly dependent on local geology and on peculiarities of the propagation path (azimuth-dependent attenuation). Thus, a single generalized spatial correlation model may not be adequate for all of Taiwan territory or similar large areas.
... The free-field strong-motion station sites in the Taiwan region were classified (Lee et al., 2001) based on the properties of the top 30 meters of the soil column, disregarding the characteristics of the deeper geology. Six site categories are defined on the basis of average shear wave velocity, namely: A -hard rock; B -rock; C -very dense or stiff soil; D -stiff soil; E -soft soil; F -soils requiring special studies. ...
... The existing geological and geomorphologic data were analyzed and the response spectral shape and the horizontal-to-vertical spectral ratio of response spectra data were used for the classification. However, as it has been noted recently (Lee et al., 2001;Sokolov et al., 2004;Huang et al., 2005), further studies on site classification should be carried out in the Taiwan region. ...
... Site Class A is not applicable in Taiwan (Lee et al., 2001), therefore we used acceleration records obtained at 53 class-B stations located in the northern and eastern Taiwan (Fig. 1b). The characteristics of the H/V spectral ratios were estimated using the whole dataset, which contains more than 2800 records from earthquakes of M L > 3.0 (Sokolov et al., 2005b). ...
... These data have been processed with baseline correction and band-pass filtering by the PEER. Site conditions for each strong-motion station were downloaded from the same website except for the Chi-Chi data set, for which data from Lee et al. (2001) were used. The magnitude and distance distribution of the ground-motion data set used in this study are 6.7-7.6 and 1-175 km, respectively ( Figure 1). ...
... We first divided the Chi-Chi strong-motion data into rock-site data and soil-site data according to Lee et al. (2001). The site conditions for the Duzce earthquake and Kocaeli earthquake data were adopted from Rathje (2001). ...
This study employs strong-motion data from the 1999 Chi-Chi earthquake, the 1999 Kocaeli earthquake, the 1999 Duzce earthquake, the 1995 Kobe earthquake, the 1994 Northridge earthquake and the 1989 Loma Prieta earthquake to refine the relationship among critical acceleration (Ac), Arias intensity (Ia), and Newmark displacement (Dn). The results reveal that, as expected, logDn is proportional to logIa when Ac is large. As Ac gets smaller however, the linearity becomes less. We also found that logDn is proportional to Ac, and that the linearity is very stable through all Ia values. These features are common to all six sets of data. Therefore, we add a third term in addition to the Jibson's form which covers the aforementioned problem, and propose a new form for the relationship among Ia, Ac and Dn. Two alternative forms were tested using each of the six data sets, before a final form was selected.The final analyses grouped the data into a worldwide data set and a Taiwanese data set. Coefficients for the selected form were derived from regression with the data, and two final empirical formulas, one for global, the other for local, proposed. Site conditions are also considered in this study with empirical formulas being developed for soil and rock sites, respectively. The estimation error is smaller and the goodness of fit is higher for both the local soil-site and rock-site formulas. Since landslides are more likely to occur on hillsides, the rock site formula may be more applicable for the landslide cases, whereas the soil site formula should be used for side slope of landfills.
... The interstation spacing of the T system is about 30 km. This spacing is still too large for the damage assessment due to complex geology in Taiwan (Lee et al., 2001). On the other hand, the Taiwan Strong Motion Instrumentation Program (TSMIP) was successfully implemented six years ago by the CWB, with about 650 modern digital accelerographs at free-field sites (Fig. 2). ...
... Generally, site effect is one of the important factors for predicting ground motion. The TSMIP sites still have not been well classified (Lee et al., 2001). However, those stations have recorded many earthquakes. ...
During a disastrous earthquake, the early assessment and timely reporting of the peak ground acceleration (PGA) and peak ground velocity (PGV) maps will be crucial in an effective emergency response operation. In this study, we first derive an empirical relationship between M-L and M-W. The PGA and PGV attenuation relationships are deduced with data from the Taiwan Strong Motion Instrumentation Program (TSMIP) and the Taiwan Rapid Earthquake Information Release System (TREIRS). Site corrections of the attenuation relationships for shallow and large earthquakes in Taiwan region are also obtained. Peak values of earthquake strong ground motion can be well determined in Taiwan as soon as the earthquake location is determined, and magnitudes are calculated by the TREIRS. This peak ground motion value information can be immediately turned into the calculated PGA and PGV maps that can be issued within two minutes of the earthquake origin time. During any disastrous earthquake, these maps are found to be very useful for immediate seismic damage assessment and dispatching of emergency response missions.
... The most significant part of the records, starting from S-wave arrival, was analyzed. The records were obtained on various types of soil: from rock sites (class B) to to soft soils (class E) of different thickness (see Lee et al., 2001, for description of site classification). Therefore, averaging the variety of site conditions, the spectral model corresponds to the so-called average soil. ...
... On the one hand, the difference may relate to so-called finite-fault effect (i.e., the peculiarities of strong ground motion near the extended fault); two-cornerfrequency spectral models were developed to satisfy the peculiarities (e.g., Atkinson, 1993;Atkinson and Silva, 2000). On the other hand, most of the near-field stations used belong to soil class D (Lee et al., 2001). In general, the type of site condition in the Taiwan region is characterized by amplification at frequencies greater than 1 Hz. ...
The design of buildings and structures in earthquake-prone regions must be based on information relating to expected seismic effect. Estimations of time domain and spectral parameters of ground motion are obtained by empirical relations that connect these to earthquake magnitude, distance, and local soil conditions. In the Taiwan region, the models for estimating ground motion parameters were obtained recently on the basis of recordings of small to moderate (5.0 less than or equal to M-L less than or equal to 6.5) earthquakes. A large collection of acceleration records from the recent M-L 7.3 (M-w 7.6) Chi-Chi earthquake and aftershocks makes it possible to test the applicability of the established models in the case of larger events. We compared modeled Fourier amplitude spectra and peak accelerations and response spectra, which were calculated using the stochastic approach from the Fourier spectra, and the data obtained during the mainshock and the largest aftershocks (M-L 6.6-6.8). It has been shown that the previously established regional spectral model (Fourier spectra of ground acceleration) may be applied for evaluation of ground motion parameters for earthquakes (reverse faulting) of magnitudes up to M-L 6.8-7.0 and hypocentral depth more than 10 km. To satisfy to the peculiarities of ground-motion propagation during shallow (depth less than 10 km) events, the model should be revised. The analysis of accelerograms from the mainshock (M-L 7.3, depth 8 km, 314 records) and large shallow aftershock (M-L 6.8, depth 10 km, 350 records) allows the authors to obtain the revised spectral model for average-soil conditions.
... He suggested that the high PGA in the southeastern part of the basin can be interpreted as the PmP, SmP, and SmS phases, which are reflected from the Moho and amplified by soft sediments. Lee et al. (2001) classified the 708 free-field strongmotion station sites in Taiwan from surficial geology on the basis of US's criteria. However, from the well-logging data, it is necessary to re-classify numerous sites. ...
... However, the anomalously high PGA values appeared at station TAP041, which is located about 17 km to the western most of the epicenter. The site condition at TAP041 has been classified as class D (Lee et al. 2001;Lin and Lee 2008). The anomalously high PGA values at this station might be resulted from the amplification effect due to soils at the site. ...
Strong-motion seismograms from the 11 February, 2014 Tatunshan earthquake were recorded at stations around the source area. These recordings were used to analyze the strong-motion characteristics in the area. The largest peak ground acceleration (PGA) values of 100.7, 93.4, and 66.6 cm sec(-2) in the vertical, EW, and NS directions, respectively, were recorded at station TAP056, about 4.9 km to the northwest of the epicenter. The PGA decays fast with distance, indicating high attenuation in the Tatun volcanic area. The PGA ratio of vertical to horizontal ground motions decreases with increasing epicenter distance. The PGA values in the EW component are larger than those in the NS component. This might be associated with the focal mechanism of the earthquake. The spectral accelerations decrease rapidly with increasing period.
... 자료, 시추자료 등 다양한 자료를 함께 이용하여 지반 을 분류한 선행연구가 있다(Fumal and Tinsley, 1985; Lee et al., 2001; Wald and Allen, 2007; 강수영과 김 광희, 2009; Iwahashi et al., 2010). Lee et al.(2001)Bortherdt et al., 1991). ...
... 자료, 시추자료 등 다양한 자료를 함께 이용하여 지반 을 분류한 선행연구가 있다(Fumal and Tinsley, 1985; Lee et al., 2001; Wald and Allen, 2007; 강수영과 김 광희, 2009; Iwahashi et al., 2010). Lee et al.(2001)Bortherdt et al., 1991). 특히 지반특성 규명의 과정에서 Digital Elevation Model(DEM)으로 부터 추출한 경사도는 시추, 지진, 지질자료 등과 함께 지반분류 시 중요한 고려사항 중 하나로 활용될 수 있 다(Wald and Allen, 2007; Iwahashi et al., 2010) ...
Site conditions affect the magnitude of loss due to geologic hazards including, but not limited to, earthquakes, landslides and liquefaction. Reliable geologic loss estimation system requires site information which can be achieved by GIS-based method using geologic or topographic maps. Slope data derived from DEM can be an effective indicator for classifying the site conditions. We studied and discussed the effect of different DEM resolutions in the site classification. We limited the study area to the south-eastern Korea and used two different resolutions of DEMs to observe discrepancies in the site classification results. Largest discrepancy is observed in the areal coverage of site class C(very dense soil and soft rock) and E(soft soil). Comparison of results shows that more areas are classified as site class B(general rock) or E(soft soil) when we use higher resolution DEM. The comparison also shows that more areas are classified as site class C or D(stiff soil) using lower resolution DEM. The comparison of results using resampled DEMs with different resolutions shows that the areal coverage of site class B and E decreases with decreasing resolutions. On the contrary, areal coverage of site class C and D increase with decreasing resolutions. Loss estimation system can take advantage of higher-resolution DEMs in the area of rugged or populated to obtain precise local site information.
... The reason is very explicit, that is, most engineering projects tend to be located at more accessible places. This leads to oversampling in small areas such as urban regions and flat terrain (Lee et al., 2001;Stewart et al., 2014;Vilanova et al., 2018). In other words, the V S30 data are spatially clustered. ...
We propose a new framework of VS30 proxy based on Cokriging method and apply the framework to build a VS30 map for mainland China. This framework utilizes the VS30–topographic slope correlation in the cross-semivariogram to benefit VS30 estimation and has the following benefits: (1) the estimation results are consistent with the measurement data; (2) the estimation uncertainty can be represented by error variance at each unsampled location according to the spatial structure of VS30 and topographic slope; (3) the result map does not have artificial boundaries; and (4) the estimation results can reflect the spatial relation between VS30 and topographic slope and the spatial relation of local spatial environment of topographic slope. We quantify the performance of this framework and compare it with that of three other topographic slope-based VS30 proxy models, including original models developed from exogenous data and models developed from China local data. The result shows that the framework proposed in this article has the best performance. The framework is applied to 7797 borehole VS30 measurements to build a VS30 map for mainland China. The map can capture the high VS30 values in regions where the geological conditions are dominated by flat-lying rocks. Moreover, we consider the effect of sample bias that comes from oversampling of borehole profiles in flat terrain regions when applying borehole data in the proposed framework. We utilize the relation of VS30 and topographic slope to quantify this bias, and use a distance-related data spatial declustering method to eliminate it.
... The classification methods stated in section 5.3 and 5.4 have been applied in many countries or regions, namely Japan (Zhao et al., 2006), Iran (Ghasemi et al., 2009), Taiwan (Lee et al., 2001), China (Ji et al., 2017Wen et al., 2011) andItaly (Alessandro et al., 2012), etc. They have used standard curves and applied methods to calculate site indexes for classification. ...
Site classification is vital to carry out seismic hazard analysis of a region and get the damage patterns caused by earthquakes. In the present study, the ground motion of earthquakes recorded from 2015 to 2019 at 84 sites of the seismic network array of Earthquake Early Warning System for Uttarakhand are analyzed for site classification purposes. The predominant period from the mean horizontal to vertical spectral ratio curves was estimated. The classification schemes devised by Japan Road Association and National Earthquake Hazards Reduction Program are applied to classify the sites. Along with this, two other site classification indexes schemes are also applied for classification purposes. Data winnowing techniques are used over the ground motion records to pick out desirable quality records. Conclusively, the site class with the highest recurrence rate amongst the used methods is selected as the final class for that particular site. The effect of magnitude, distance and depth on horizontal to vertical spectral ratio are described and concluded that these factors do not significantly affect the ratio curves. The average horizontal to vertical spectral ratio curves obtained for all the sites matches well with the existing literature. The classification of a few sites are verified from the classification done by other methods in recent studies. It is evident from the results that the classification done in this study matches well with them.
... Grace et al. (2017) developed a hybrid geology-slope approach for V S30 estimation in central and eastern North America. Extensive efforts have been also made on a global scale, for example, Lee et al. (2001), Matsuoka et al. (2005), and more recently Stewart et al. (2014) among others. These efforts have contributed to the USGS global V S30 mosaic (Heath et al., 2020; and references therein). ...
The Alaska Regional Network and Transportable Array provide an invaluable waveform data set for studying ground motions in Alaska. However, the data set is useful only after the site effects at each station are well understood. Considering the large number of stations associated with these networks, it would be onerous to measure the sub-surface velocity structure beneath every station using geophysical exploration techniques involving arrays, such as active-source or passive-source non-invasive array methods. Instead, it is more economical to estimate the site conditions using waveforms recorded at the seismic stations. Most of the methods for estimating site response from recorded waveforms use the frequency-dependent ratio between the horizontal and vertical component of either ambient noise or S waves from earthquakes. We instead use the horizontal and vertical component of P waves to infer the sub-surface velocity structure. It has been demonstrated that the ratio of radial to vertical P waves is mostly sensitive to sub-surface shear velocity. Therefore, the sub-surface velocity structure can be estimated using an approach similar to teleseismic P receiver functions, but at much smaller scale and higher frequency. The results from this method are in good agreement with results from active-source or passive-source non-invasive array methods and have been widely used in the Central Eastern United States. The Alaska Regional Network and Transportable Array have recorded numerous earthquakes in the magnitude range of interest and at shallow depth, which provides an ideal opportunity for this study. V S 30 is used to represent the site amplification of ground motions in all ground motion models that are used in generating the US Geological Survey’s National Seismic Hazard Maps, as well as in the professional practice of seismic hazard analysis. The results of this work provide a basis for improved site-specific hazard estimates in Alaska.
... The LSA-based models can be divided into qualitative and quantitative methods [1,2]. The approaches of statistical analysis, geotechnical engineering analysis (deterministic and probability), artificial intelligence [3][4][5][6][7][8][9], and data mining were commonly used for quantitative LSA modeling. Artificial intelligence has become a popular data analysis method in recent years [8] utilizing machine learning, and deep learning algorithms have become more efficient and reliable in recent years. ...
With the unique rainfall patterns of typhoons, plum rains, and short-term heavy rainfalls, the frequent landslide and debris flow disasters have caused severe loss to people in Taiwan. In the studies of landslide susceptibility, the information of factors used for analysis was usually annual-based content, and it was assumed that the same elements from different years were independent between each year. However, the occurrence of landslides was usually not simply due to the changes within a year. Instead, landslides were triggered because the factors that affected the potential of landslides reached critical conditions after a cumulative change with time. Therefore, this study had well evaluated the influence of temporal characteristics and the ratios of antecedent landslide areas in the past five years in the landslide potential evaluation model. The analysis was conducted through the random forest (RF) algorithm. Additional rainfall events of 2017 were used to test the proposed model’s performance to understand its practicality. The analysis results show that in the study area, the RF model had considerably acceptable performance. The results have also demonstrated that the antecedent landslide ratios in the past five years were essential to describe the significance of cumulative change with time when conducting potential landslide evaluation.
... And the predominate period of sites is often used as an indicator of site classification in many countries, which is the original site classification by HVSR. Zara et al. and Lee et al. classified the sites according to the predominate period by the strong vibration recordings from Iran and Taiwan, respectively [4,5]. The advantages of this method are that it is not subject to the reference site, simple and easy to operate, and low cost. ...
The horizontal-to-vertical spectral ratio (HVSR) has been extensively used in site characterization utilizing recordings from microtremor and earthquake in recent years. This method is proposed based on ground pulsation, and then it has been applied to both S-wave and ambient noise, accordingly, in practical application also different. The main applications of HVSR are site classification, site effect study, mineral exploration, and acquisition of underground average shear-wave velocity structure. In site response estimates, the use of microtremors has been introduced long ago in Japan, while it has long been very controversial in this research area, as there are several studies reporting difficulties in recognizing the source effects from the pure site effects in noise recordings, as well as discrepancies between noise and earthquake recordings. In practice, the most reliable way is the borehole data, and the theoretical site response results were compared with the HVSR using shear wave to describe site response. This paper summarizes the applications of the HVSR method and draws conclusions that HVSR has been well applied in many fields at present, and it is expected to have a wider application in more fields according to its advantages.
... These maps are prepared for several active regions of the world (e.g. Petersen et al. 1997;Park and Elrick 1998;Lee et al. 2001;Lee and Tsai 2008;Wills and Clahan 2006;Wills et al. 2015;Kanlı et al. 2006) and are further utilized for generating the ground motion models (e.g. Boore and Atkinson 2008;Stewart et al. 2015;Bozorgnia et al. 2014;Boore et al. 2014;Goulet et al. 2014), probabilistic seismic hazard assessment (e.g. ...
... It is an orogeny with the highest elevation at ∼3952 m, linking the opposite-dipping Ryukyu and Manila subduction systems. Earlier studies have indicated a general increasing metamorphic grade of sedimentary rocks eastward, from shale/mudstone/sandstone in the Coastal Plain, through slate, phyllite, marble, schist in the Hsuehshan and the western Central Range, to gneisses in the eastern Central Range in Taiwan ( Fig. S1; Liu et al., 1987;Lee et al., 2001;Yui, 2005). A combination of humid climate, with an average of 5.3 typhoons per year and annual precipitation of 2.1 m yr −1 (Kao and Milliman, 2008), frequent earthquakes, high relief, and erodible rocks, lead to an average erosion rate of 3.9 mm yr −1 in Taiwan (Dadson et al., 2003). ...
... These maps are prepared for several active regions of the world (e.g. Petersen et al. 1997;Park and Elrick 1998;Lee et al. 2001;Lee and Tsai 2008;Wills and Clahan 2006;Wills et al. 2015;Kanlı et al. 2006) and are further utilized for generating the ground motion models (e.g. Boore and Atkinson 2008;Stewart et al. 2015;Bozorgnia et al. 2014;Boore et al. 2014;Goulet et al. 2014), probabilistic seismic hazard assessment (e.g. ...
... These maps are prepared for several active regions of the world (e.g. Petersen et al. 1997;Park and Elrick 1998;Lee et al. 2001;Lee and Tsai 2008;Wills and Clahan 2006;Wills et al. 2015;Kanli et al. 2006) and are Q2 further utilized for generating the ground motion models (e.g. Boore and Atkinson 2008;Stewart et al. 2015;Bozorgnia et al. 2014;Boore et al. 2014;Goulet et al. 2014), probabilistic seismic hazard assessment (e.g. ...
... It is time and cost prohibitive to apply this approach to generate a site-condition classification map for a country as great in size as China. Research efforts were hence focused on establishing the relation between V S30 and topographic slope in attempt to estimate the spatial distribution of shear-wave velocity across large areas (Lee et al., 2001;Iwahashi et al., 2010, Lemoine et al., 2012Wills et al., 2015;Xie et al., 2016;Wu et al., 2018). Several large-scale site-condition maps were derived using the slope method, which contained the variable V S30 across a geological unit (Wald and Allen, 2007;Allen and Wald, 2009;Thompson and Wald, 2012;Thompson et al., 2014). ...
Earthquake insurance has become a topic of major importance in mainland China ever since the Mw 7.9 Wenchuan earthquake in 2008. Site‐condition amplification is one of the essential factors that influences the prediction of strong ground motion and the assessment of damages of buildings and structures. The site effects should hence be included in calculating earthquake damage and determining the insurance rate for insurance companies. In particular, large‐scale site classification is required for the implementation of earthquake insurance. This study first used a slope method for site classification in China through the VS30 values from the topographic slope data and the correlation between VS30 and the topographic slope. A novel site classification method, called the slope–geological method, was then proposed in this study to improve the slope method by combining geological characteristics, including geological age, the depositional environment, and soil properties. Four hundred and fifty three pieces of borehole data in Northern Plain and Sichuan of China were used to verify the effectiveness and difference of the slope method and the slope–geological method proposed in this study. Site‐condition classification maps of China were drawn using the slope method and slope–geological method, respectively.
... The principle is to evaluate spectral ratios, from which the peak site frequency (fundamental frequency) and the associated amplification factor could be determined. This method has been widely utilized for the onland area, including the determination of seismic microzonation (Bour et al. 1998;Lee et al. 2001;LeBrun et al. 2004), seismic site effect evaluation (e.g., Sokolov et al. 2007), bedrock depth mapping (Ibs-von Seht and Wohlenberg 1999), and shallow soil shear-wave velocity structure profiling (e.g., Scherbaum et al. 2003), etc. However, few studies have been introduced for the marine area, where site characterizations are even more difficult to investigate than those onland. ...
Widely distributed Bottom-Simulating Reflectors (BSRs) have been observed in the area offshore of southwestern Taiwan where the active accretionary complex meets with the passive China continental margin. In order to clarify the link between seismic site response and sedimentary properties of submarine slope, we evaluate the response of seafloor sediments in regard to passive dynamic loads. The local site effect produced by shallow marine sediments was characterized by estimating the horizontal-to-vertical (H/V) spectral ratios of data recorded by the short-period Ocean Bottom Seismometers (OBSs). The results show that the maximal H/V ratios appeared in the range of 3.66 - 9.28 Hz, suggesting that the fundamental frequency is dominated by the effect related to the very shallow sediments. For most stations, the H/V ratios estimated based on the earthquakes and noise records were characterized by different patterns. Relatively broad H/V pattern was obtained when the signals were extracted from earthquakes. This phenomenon may be related to soil nonlinearity when a stronger motion applies. In comparison with the available geological structures and bulk density distribution obtained from coring experiments, we found a relatively higher fundamental frequency of about 8 - 9 Hz for the more rigid material, such as mud diapir and folding axes. For most of the area along the slope, the fundamental frequency shows a relatively low value, about 6 - 8 Hz. Finally, when a site is characterized by thick or lowest bulk density sedimentary layer, we observed a fundamental frequency lower than 5 Hz, which is the lowest in our assessment.
... Later on, Zare et al. (1999) succeeded in performing a site classification for a set of Iranian stations using these H/V spectral ratios, in addition to V S30 . Based on these results, recent studies used this information to verify previous classifications developed with traditional methods (Lee et al., 2001;Ghasemi et al., 2009). Furthermore, some studies relied on the H/V spectral ratio to classify or complement other parameters used for soil classification (Luzi et al., 2011;Castellaro and Mulargia, 2014). ...
The National Seismological Center of the University of Chile (CSN, Centro Sismológico Nacional) has been operating more than 400 seismic stations throughout the country. The data collected from this network, from March 2012 to August 2017, includes more than 4000 Chilean strong‐motion records, from more than 1000 events (magnitudes ranging from 4.0 up to 8.3). In this study, we use this data set and classify 118 stations from this network, using the horizontal‐to‐vertical response spectral ratio (HVRSR) of strong‐motion records. This classification considers not only the predominant period obtained from the average HVRSR but also the peak amplitude from this curve. The results indicate no correlation between the two parameters, despite the common practice of combining all curves with similar predominant periods. Even more, we believe that relevant information of the site’s impedance contrast between the soil and bedrock is lost in the process of averaging HVRSR curves from different stations.
... Invasive P-S logging was accomplished at all KiK-net stations in Japan (Aoi et al., 2004), whereas surface seismic and standard penetration tests were used to investigate seismic station site conditions in Turkey (Sandıkkaya et al., 2010). A wide range of in situ measurements, combined with information on surficial geology, are used to determine V S30 in the United States (Yong et al., 2013) and Taiwan (Lee et al., 2001). Seismic network sites have most often been classified using noninvasive seismic surveys; some examples are sites in Iran (Zaré, 1999;Zare and Sinaiean, 2014), France (Hollender et al., 2016), and Puerto Rico (Odum et al., 2007). ...
We collected site-specific geophysical data at 28 seismic stations on various soils in Alberta, Canada. Noninvasive seismic procedures are combined with the earthquake database and other available regional data sets to improve current understanding of earthquake site effects at the stations. Such an understanding allows the separation of site effects from source and path effects, which is important for groundmotion modeling. Dispersion data sets were compiled using multichannel analysis of surface waves and ambient vibration array field methods. We also computed microtremor horizontal-to-vertical spectral ratios using three-component single-station measurements. Independent and joint inversion of these two data sets allowed us to characterize 18 seismic stations in terms of shear-wave velocity-depth profiles. We report the range in the time-weighted average shear-wave velocity in the upper 30 m (VS30) derived from average shear-wave velocity-depth profiles for each site and their corresponding National Building Code of Canada (NBCC) site classification. Corresponding time-averaged velocity values are also computed for the top 5, 10, and 15 m. The parameter that is best constrained is VS15, which is related to relatively thin (<30 m) sedimentary overburden in Alberta. In general, Alberta seismic stations are typically characterized by regolith <30 m thick with low shear-wave velocity (≤200 m/s), underlain by material with a higher shear-wave velocity (>400 m=s). NBCC site classes are limited to C and D for the sites we surveyed, with D being the predominant site class.
... The most widely used site classification parameter is the time-averaged shear-wave velocity over the top 30 m of the soil deposit (V S30 ), as suggested by the NEHRP (Building Seismic Safety Council (BSSC), 2003) and Eurocode 8 (European Committee for Standardization (CEN), 2004). Several methods were developed to predict V S30 considering the surface geological profile or topography slope as a proxy of V S30 (Wills et al., 2000;Lee et al., 2001;Wald and Allen, 2007;Allen and Wald, 2009). These methods are generally used for estimating the overall V S30 distribution covering a relatively wide region rather than for a site-specific estimation, especially work well for where high slope contrasts could be observed such as mountain and basin areas. ...
Reliable site classification of the stations of the China National Strong Motion Observation Network System (NSMONS) has not yet been assigned because of lacking borehole data. This study used an empirical horizontal-to-vertical (H/V) spectral ratio (hereafter, HVSR) site classification method to overcome this problem. First, according to their borehole data, stations selected from KiK-net in Japan were individually assigned a site class (CL-I, CL-II, or CL-III), which is defined in the Chinese seismic code. Then, the mean HVSR curve for each site class was computed using strong motion recordings captured during the period 1996–2012. These curves were compared with those proposed by Zhao et al. (2006a) for four types of site classes (SC-I, SC-II, SC-III, and SC-IV) defined in the Japanese seismic code (JRA, 1980). It was found that an approximate range of the predominant period Tg could be identified by the predominant peak of the HVSR curve for the CL-I and SC-I sites, CL-II and SC-II sites, and CL-III and SC-III + SC-IV sites. Second, an empirical site classification method was proposed based on comprehensive consideration of peak period, amplitude, and shape of the HVSR curve. The selected stations from KiK-net were classified using the proposed method. The results showed that the success rates of the proposed method in identifying CL-I, CL-II, and CL-III sites were 63%, 64%, and 58% respectively. Finally, the HVSRs of 178 NSMONS stations were computed based on recordings from 2007 to 2015 and the sites classified using the proposed method. The mean HVSR curves were re-calculated for three site classes and compared with those from KiK-net data. It was found that both the peak period and the amplitude were similar for the mean HVSR curves derived from NSMONS classification results and KiK-net borehole data, implying the effectiveness of the proposed method in identifying different site classes. The classification results have good agreement with site classes based on borehole data of 81 stations in China, which indicates that our site classification results are acceptable and that the proposed method is practicable.
Keywords: Site classification; horizontal-to-vertical (H/V) spectral ratio; National Strong Motion Observation Network System (NSMONS); strong motion station; KiK-net data
... In Japan, velocity profiles from borehole logging are available for every KiK-net station (Aoi et al., 2004). In Taïwan, the sites of the whole network have been classified for a long time (Lee et al., 2001). In Iran (Zaré et al., 1999), Turkey (Sandıkkaya et al., 2009), and Puerto Rico (Odum et al., 2013), 1D S-wave velocity profiles are provided at a number of sites using mostly active seismic techniques. ...
L'invention de la sismologie est intimement liée à l'avènement des premiers instruments permettant d'enregistrer les vibrations du sol, à la fin du XIXe siècle. Cependant, il existait alors déjà une large connaissance des tremblements de terre, de leurs effets et des moyens de s'en protéger, peu à peu organisée en savoir scientifique. La sismologie de l'ingénieur est née de la volonté de quantifier l'amplitude des mouvements du sol, à travers la mesure et la modélisation, pour une utilisation rationnelle des protections contre les tremblements de terre, en particulier dans la construction. Cette volonté s'est exprimée parallèlement au développement de l'instrumentation sismologique, en particulier au Japon et en Californie, par la construction de modèles de prédiction des mouvements forts et de la réponse des structures de génie civil à ces mouvements. Les modèles empiriques font aujourd'hui peu à peu place à des modèles fondés sur la physique, sur des domaines de plus en plus grands et sur des maillages de plus en plus petits. Il faut cependant rappeler que la modélisation numérique en dynamique des sols et des structures a pour objectif minimal de reproduire les observations et que ses nombreux paramètres d'entrée sont choisis de manière bien plus adéquate après une campagne de mesure qu'à la lecture d'une table de valeurs génériques. En effet, en géosciences, mais aussi en génie civil, les propriétés mécaniques de nombreux matériaux mais aussi la géométrie des structures sont très incertaines, voire inconnues et doivent donc être mesurées. Il ne s'agit pas (seulement) d'améliorer la précision des modèles de prédiction mais bien de leur permettre de livrer les bons ordres de grandeur, il en va donc de leur pertinence même. Enfin, si des modèles entièrement basés sur la physique des phénomènes sont souhaitables puisqu'ils sont les seuls à permettre une extrapolation objective à des situations qui ne se sont jamais produites, les modèles empiriques combinant physique des phénomènes et observations sous forme statistique sont toujours nécessaires. Ils sont en général plus simples à mettre en œuvre, moins précis mais souvent plus justes et permettent des calculs sur des domaines plus grands, avec plus d'éléments. L'objectif de mon travail est de proposer de nouvelles méthodes pour intégrer des observations sismologiques dans des modèles de prédiction du mouvement du sol et de la réponse des structures puis d'appliquer ces méthodes à des cas réels, typiques, afin de diriger les recherches méthodologiques futures vers les maillons de la chaîne de l'analyse du risque sismique qui peuvent bénéficier d'améliorations. Il s'agit également, suite à un événement destructeur, de comprendre l'origine des dommages observés et d'aider à l'analyse de la sécurité à court et à long terme. L’exposé est structuré en trois parties : l'étude des effets de la géologie locale sur l'amplification des ondes sismiques, l'étude de la réponse des structures de génie civil, en particulier les bâtiments et enfin la sismologie de l'ingénieur dans le contexte de l'après-séisme.
... In the second group, we referred to in situ tests such as standard penetration test (SPT), cone penetration test (CPT) to evaluate liquefaction potential (Seed and Idriss 1971). The SPT-based method becomes more accurate in the liquefaction prediction approach in the presence of the database ( Chang et al. 2011;Lee et al. 2001). A simplified deterministic procedure proposed by Seed and Idriss (1971) was commonly used to evaluate the liquefaction potential using standard penetration test (SPT). ...
In this study the relation between liquefaction probability (P L) and factor of safety against liquefaction (F s) was investigated to check the reliability of different procedures influenced by SPT-N. The determination of the P L method can be useful for a preliminary stage of prediction of liquefaction behavior along an area with variable soil and seismic conditions. Soil and seismic parameters varied during the liquefaction probability analyses. With this purpose in mind, a computer program was developed to calculate the Fs and P L
... Following the recent work of Idini and colleagues [22], we classify all our HVSR results considering the observed predominant period and amplitude; this kind of classification has been previously applied to strongmotion stations in Iran [23,24], Taiwan [25], Japan [26,27], and Italy [28]. It basically considers the observed predominant frequency and the HVSR amplitude as shown in Table 2, right and left. ...
The Chilean Seismological Networks has been rapidly growing these past years, going from few dozens of stations, to nearly a 100 installed all over the country. Even more, this network is complemented by the Accelerographic National Network, with nearly 300 strong-motion stations, deployed on a large effort by the National Office of Emergencies (Onemi), in a variety of cities and site conditions all over the country. All of these stations are currently providing very useful information of the earthquakes that take place in Chile, and are expected to record moderate to large events. However, the lack of appropriate site characterization sets an important limit to its usefulness. In the present work, we propose a methodology to begin a geophysical characterization of all of these stations, based on array measurements of microtremors and horizontal-to-vertical spectral ratios. In the present work, we present some preliminary results for some stations located in Valparaíso, Coquimbo, Tarapacá, and the Metropolitan regions. This information will help improve our understanding of the behavior of soils during an earthquake, providing relevant information for seismic codes.
... For example, Lin et al. (2011) used the TSMIP database to develop a series of local ground motion models for the region around Taiwan [1], essential to local seismic hazard assessments conducted later [2]. Besides, basin effects and site effects in Taiwan were also studied with the TSMIP strong-motion database, in an attempt to develop proper earthquake-resistant designs for several major cities in Taiwan [34,35]. ...
... The international literature includes several other articles that can be considered as scientific background on this topic in which, for example, the lithotypes derived from smallscale geological maps were directly related to ranges of V s30 (Su et al. 1992;Wills et al. 2000;Lee et al. 2001;Wills & Clahan 2006). In some cases, geological maps at different scales (1:50 000, 1:100 000, 1:250 000) were merged in order to cover all the studied areas (Chyi-Tyi et al. 2001). ...
In this article a method developed for the creation of a site classification map at a territorial scale, starting from
the geological mapping available at 1:100 000 scale, is described. This map has been used to embed amplification factors as provided by the Italian seismic code in seismic hazard studies, in order to consider the contribution of the surface geology on the expected ground motion values. The Italian territory has been divided into polygons classified on the basis of lithologies that the seismic code considers homogeneous in their average seismic response. The data processing has been conducted in a GIS environment, starting from the digital format of the lithological map of Italy at 1:100 000 scale. Our results can be used in seismic risk analyses that take into account the local seismic amplification due to the geological characteristics of an area, and in studies on ground motion prediction equations (GMPE).
... The use of Vs 30 to characterize sites arose primarily after the implementation of the 1997 Uniform Building Code (ICC, 1997). Among the proxies for Vs 30 , surface elevation (Lee et al., 2001;Chiou and Youngs, 2008), topographic slope (Wald and Allen, 2007;Allen and Wald, 2009;Thompson and Wald, 2012), local geology (Romero and Rix, 2001;Wills and Clahan, 2006;Scasserra et al., 2009), and geomorphologic factors, such as convexity and texture, are most commonly used. ...
To determine the near-surface shear wave velocities (Vs) and characterize seismic site conditions in Gangneung, on the east coast of South Korea, passive and active surface waves were recorded at 136 sites. Dispersion images of the Rayleigh waves were obtained by the spatial autocorrelation method and inverted to Vs models. From these one-dimensional Vs models, the depth to the soft bedrock, average Vs at the top of the bedrock, average Vs of the overburden layer, average Vs in the top 30-m interval (Vs
30
), and average resonance frequency were estimated to be 16 ± 1 m, 481 ± 14 m/s, 254 ± 5 m/s, 374 ± 16 m/s, and 5.5 ± 0.3 Hz, respectively. A lower estimate for Vs
30
and a relatively thick overburden layer make the downtown and agricultural areas in the region more prone to significant ground amplifications. Multiple regression analysis of Vs
30
yielded a correlation coefficient of 0.79 with respect to the variables of elevation and topographic slope. Using this proxy-based empirical relationship, Vs
30
values were computed at 13,583 sites covering the entire city. A microzonation map, constructed based on the Vs
30 data, indicates that the ground in Gangneung is categorized mainly into B (44%), C (39%), and D (15%) National Earthquake Hazards Reduction Program site classes, with minor constituents assigned to the A and E classes.
... The velocities were over 250 m s À1 below the depth of 30 m (after ''Geo-Data'' from Geologic Survey Database of CWB Strong Motion Stations), and station TCU109 [16], with average velocities between 180 and 360 m s À1 . Fig. 2 shows the site classification of Taiwan free-field strong-motion stations, which uses a scheme compatible with the 1997 Uniform Building Code (UBC) provisions [17]. When looking at the accelerograms recorded at seismic stations located on very dense soils (class C) and stiff soils (class D) near the study site (within a distance of 13 km), we observe that the shape and frequency content of the accelerations are quite similar. ...
Observations during strong earthquakes (Mexico 1985, Kobe 1995, Algiers 2003, etc.) have shown that losses are generally concentrated near surficial soft soil deposits. Since such deposits are quite common under large built-up areas, there is an urgent need to assess the possible impact of soft soils on seismic ground motion. Under seismic loading, a soft soil will generally behave in a non-linear manner, meaning that some permanent strain will occur (settlement, lateral displacement), which is not directly proportional to the amplitude of the input motion and that may lead to the destruction of structures located on the ground surface. Since it is still difficult to account for such behaviour when predicting strong ground motions, practitioners need to know when they may neglect this factor. Through this paper, we show that even if it is not an easy task, non-linear soil behaviour should be considered in the analyses. Since a few years now, many countries throughout the world have launched studies in order to better integrate this factor into their anti-seismic design regulations.
... Microtremor H/V ratios have been shown to reliably measure predominant site period in comparison with weak to strong earthquake recordings e.g., [14,[17][18][19]. Site classification based on the predominant period of the average H/V ratio has been proposed for strong-motion stations in Iran [20,21], Taiwan [22], Japan [23,24], and Italy [25]. Table 2 lists seven proposed period-based site classifications [25]; a short site period corresponds to rock or stiff soils, whereas a long site period corresponds to soft soils. ...
A blind comparison of independent invasive (downhole, standard penetration, bender element) and non-invasive microtremor shear-wave velocity (VS) profiling is presented for 11 strong-motion stations in central and southern Chile that recorded the 2010MW 8.8 Maule earthquake. For the majority of stations, site classification based on average VS in the upper 30m (VS30) is consistent irrespective of methodology. For a variety of geological conditions, excellent to good agreement is obtained between invasive and non-invasive VS structure at five stations over the entire borehole length and in the uppermost layer at three stations. Site classification based on site period is evaluated using earthquake and microtremor recordings. Short site periods are observed at stiff coarse-grained stations whereas longer site periods are observed at soft fine-grained stations. The use of both VS30 and site period criteria are recommended in future revisions of the Chilean building code for robust earthquake site response characterization.
... The velocities were over 250 m s À1 below the depth of 30 m (after ''Geo-Data'' from Geologic Survey Database of CWB Strong Motion Stations), and station TCU109 [16], with average velocities between 180 and 360 m s À1 . Fig. 2 shows the site classification of Taiwan free-field strong-motion stations, which uses a scheme compatible with the 1997 Uniform Building Code (UBC) provisions [17]. When looking at the accelerograms recorded at seismic stations located on very dense soils (class C) and stiff soils (class D) near the study site (within a distance of 13 km), we observe that the shape and frequency content of the accelerations are quite similar. ...
http://www.iitk.ac.in/nicee/wcee/article/13_1923.pdf
... For comparison, station spacing of the free-field accelerographs in the Ilan area of Taiwan is about 3-5 km, versus a 25 km uniform spacing of the K-NET in Japan (Bolt and Abrahamson, 2003). Ⓔ Information about the 65 free-field TSMIP stations in the Ilan area that were used in this study are given in Table S1 (available in the electronic supplement to this article), and their locations are shown in Figure 2. Ⓔ Table S1 shows the 1997 Uniform Building Code (UBC; International Council of Building Officials [ICBO], 1997) site classification of all but one of the 65 TSMIP stations based on surface geology and borehole data by Lee et al. (2001). It also shows similar site classification of the 46 TSMIP stations where onsite V S30 data are available. ...
The purpose of this paper is to study the site effects for Ilan in northeastern Taiwan based on attenuation relationships of spectral acceleration (SA). Over 2660 accelerograms recorded from 92 shallow earthquakes with M-w magnitude ranging from 4.0 to 7.7 are used to develop these regional attenuation relationships. Site effects are investigated using the site residuals obtained from the SA attenuation relationships. The results show the standard deviations of residuals decrease by 1.7%-16.4% in horizontal SA after incorporating the site-effect term V-S30 in the attenuation relationship of periods greater than 0.3 s. Clearly, the attenuation relationships are improved by including the site-effect term, especially for the longer periods. In addition, from the contour maps of intraevent site residuals relative to an attenuation equation of our model 2 phase 1 for horizontal SA, we find high amplification factors of short period (0.1-0.2 s), reaching 2.7 in Nanao with hard schist rocks. High amplification factors of intermediate periods (0.3-1.0 s) reach 1.9 and 2.0, respectively, in the city of Ilan and Zhuangwei. High amplification factors of long period (1.0-3.0 s) reach 2.1 in Zhuangwei, where there is the greatest sediment thickness. The results call for special attention to the seismic design of structures in these locations. Furthermore, the intraevent residuals of the four site classes converging the 0.15-0.2 s period range are in agreement with the findings by Aki (1988). Accordingly, site classes D and E have the largest ground-motion amplification factor in the 0.15-0.5 s and > 0.5 s period ranges, respectively. Finally, the predominant-period contour maps deduced from V-S30, V-S75, and sediment depth in the Ilan Plain fall in the ranges of 0.4-1.0, 1.0-1.5, and 1.5-8.0 s, respectively. This suggests that construction of buildings taller than nine stories in the Zhuangwei area should pay special attention to avoid resonance of seismic excitation.
... Similar to Wills and Clahan (2006), Matsuoka et al. (2006) defined categories they describe as geomorphic, but which we interpret to be more geologic in their description (e.g., mountain tertiary and alluvial fan), and compute V S30 statistics for applicable profiles within each category. Lee et al. (2001) related V S30based site categories to surface geologic conditions in Taiwan. Kottke et al. (2012) present preliminary relations between mean V S30 and 19 geologic categories in the central and eastern United States, although the data were only sufficient to provide stable means for nine of the categories. ...
The time-averaged shear-wave velocity in the upper 30 m of a site (Vs30)
is commonly used for ground-motion prediction. When measured velocities are
unavailable, Vs30 is estimated from proxy-based relationships developed for application
on global or local scales. We describe the development of a local relationship for
Greece, which begins with compilation of a profile database (PDB) from published
sources and engineering reports. The PDB contains 314 sites; 238 have profile
depths ≥ 30 m and 59 are within 100 m of accelerographs. We find existing relations
for extrapolating a time-averaged velocity for depths less than 30 m to VS30 to overpredict
VS30. We present equations for these extrapolations.
We then compile proxies for PDB sites, including terrain type, surface geology,
and surface gradients at 30 and 3 arcsec resolution (from radar-derived digital elevation
models [DEMs]). When checked against ground survey data, we find ground
elevations from 3 arcsec DEMs to be more accurate relative to survey data than alternative
30, 9, and 1 arcsec DEMs. Drawing upon expert opinion, we develop geologic
categories based on age, gradation, and depositional environment and assign such
categories to PDB sites. We find an existing 30 arcsec gradient-based global model
to be biased relative to local Vs30 data for gradients >∼0:05 m=m. Bias relative to a
California model is also found for four of the eight well-populated geomorphic categories,
and new (local) values are provided. We find statistically significant effects of
the 3 arcsec gradient on VS30 for Quaternary and Tertiary materials but no gradient
effect for those from the Mesozoic. Among Quaternary sediments, Holocene, mapped
Quaternary (age unspecified), and mixed/fine-gradation materials exhibit consistent
VS30-gradient trends, whereas Pleistocene and coarse-gradation sediments have faster
velocities. For the study region, we recommend use of the modified terrain- and geology-based methods in combination for proxy-based Vs30 estimation.
... In Japan, velocity profiles from borehole logging are available for every KiK-net station (Aoi et al., 2004). In Taïwan, the sites of the whole network have been classified for a long time (Lee et al., 2001). In Iran (Zaré et al., 1999), Turkey (Sandıkkaya et al., 2009), and Puerto Rico (Odum et al., 2013), 1D S-wave velocity profiles are provided at a number of sites using mostly active seismic techniques. ...
In the framework of the renewal project of the Swiss Strong Motion Network (SSMNet), a procedure for site characterization has been established. The aim of the procedure was to systematically derive realistic 1D velocity profiles at each station. It is mainly based on the analysis of surface waves, particularly from passive experiments, and includes cross checks of the derived amplification functions with those obtained through spectral modeling of recorded earthquakes. The systematic use of three component surface‐wave analysis, allowing the derivation of both Rayleigh and Love dispersion curves, also contributes to the improvement of the quality of the retrieved profiles.
The procedure is applied to the 30 SSMNet stations installed on various site types within the project, covering different aspects of seismic risk. The characterization of these 30 sites gives an overview of the variety of possible effects of surface geology on ground motion in the Alpine area. Such effects ranged from deamplification at hard‐rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the Swiss reference rock velocity model. The derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling. Although many sites are found to exhibit 1D behavior, the procedure allows the detection and qualification of 2D and 3D effects. The sites are therefore classified with respect to the occurrence of 2D/3D resonance and edge‐generated surface waves. In addition to the large and deeply incised alpine valleys of the Rhône, the Rhine, and the Aar, smaller structures such as local alpine valleys and alluvial fans are shown to exhibit 2D/3D behavior.
... The ground-motion database was also used for evaluation of generalized site amplification functions for typical soil classes B, C and D (Sokolov et al., 2003bc), and for particular sites in Taipei basin Sokolov and Jean, 2002). Description of soil classes B, C, and D may be found in (Lee et al., 2001). ...
The paper describes an integrated approach to seismic hazard assessment, which was applied for the Taiwan region. First, the theoretical seismic catalogue (2001-2050) for the Taiwan region had been calculated using the 4D-model (location, depth, time) for dynamic deformation of the Earth ’ crust and 5D-model (location, depth, time, magnitude) for seismic process. The models were developed on the basis of available geophysical and geodynamic data that include regional seismic catalogue. Second, empirical models for ground motion estimation in the region were obtained on the basis of records from recent (1993-1999) earthquakes. The database includes strong-motion data collected during the recent Chi-Chi earthquake (M=7.6, 21 September 1999) and large (M=6.8) aftershocks. The ground-motion database was also used for evaluation of generalized site amplification functions for typical soil classes (B, C and D). Third, the region & site & time-dependent seismic analysis, which is based on schemes of probable earthquake zones evaluated from the theoretical catalogue, regional ground motion models, and local site response characteristics, has been performed. The seismic hazard maps are compiled in terms of Peak Ground Acceleration (PGA) and Response Spectra (RS) amplitudes. The maps show distribution of amplitudes that will not be exceeded with certain probability in condition of typical soil classes
... For Chi-Chi earthquake, the moment magnitude is 7.7, and the distance from the source of earthquake to the center of the study area is adapted as 10km. The site condition for the study area is class B (Lee et al., 2001). Use those parameters with the attenuation relations, the PGA and Arias intensity of incidence at the base of the hill are calculated as 0.443g and 5.73 m/sec respectively. ...
This paper describes the result of a case study, which uses two calculation models for the zoning of landslide hazard induced by earthquake. The calculation models is based on the basic concept of cumulative displacement and operated by GIS soft wares. The case study area is located at the central part of Taiwan, which was heavily hit by 1999 Chi-Chi earthquake. The difference between these two models is that one of them considers the seismic topographic amplification factor and another does not. A numerical is employed to obtain the seismic topographic amplification factor of each DEM cell. The result shows that the model with topographic amplification will produce a higher probability of failure for the larger cumulative displacement cells. The curves, which show the relationship between the probability of failure and the amount of cumulative displacement, are also different. The curve without topographic amplification is flatten after 35 cm of displacement, and another curve keeps climb up in the range of 100 cm. This difference may be made by the effect of topographic amplification, which will make the steep slopes near the ridges to have larger cumulative displacement than the steep slopes at other locations.
... The site classifications for stations with unknown site conditions were estimated from the spectral shape technique as described by Phung et al. [14,15]. Phung et al. [14,15] have also compared the classifications by this technique to classifications based on the interpretation of geologic maps and geomorphologic data as described by Lee et al. [16], and found general agreement. Among the 420 sites, 248 sites are classified as soil (S=1) and 172 sites are classified as rock (S=0). ...
It has been observed in some recent strong earthquakes that ground motion amplitudes are often enhanced in the direction of fault rupture propagation. Damage pattern observations in the 1999 M w =7.6 Chi-Chi Taiwan earthquake indicated that severe damage was concentrated near and along the fault rupture, particularly in the northern part of the fault. Directivity effects for this thrust earthquake would be expected to enhance ground motions up-dip of the hypocenter. There may also be some directivity to the north, as slip distributions have shown that displacements significantly increased from the south to the north along the fault as the rupture propagated in that direction. This paper aims to quantify the directivity effects on the peak ground acceleration (PGA) and 5%-damped response spectral accelerations (PSA) of strong-motions recorded during the Chi-Chi earthquake. The median relationships of ground motion amplitudes as a function of the closest distance to the fault and site category are determined in the first step, using 420 ground motion time histories recorded on rock and soil sites. Then the residuals (model errors) of these relationships as a function of selected geometrical parameters related to the fault are used to describe the directivity effects. The geometrical parameters include the fraction of the fault rupture that lies between the hypocenter and the site, and the angle between the fault plane and the path from the hypocenter to the site. Since the Chi-Chi earthquake is of thrust type, dip-slip directivity effects as well as along-strike propagation effects are studied. All sites are used to quantify along-strike directivity effects, while only sites within 50 km of the fault rupture are used to quantify dip-slip directivity effects. The dip-slip component of the directivity effects has a strong influence, increasing ground motion amplitudes up dip of the hypocenter by a factor of approximately 2.7. The along-strike effects are also significant: ground motion amplitudes are approximately 1.5 times higher for stations in which rupture propagated strongly towards the site than those for which rupture propagated away from the station. Directivity effects are observed for PGA and PSA at all periods.
... The average S-wave velocity in the top 30 m is ~200 m/s (http://geo.ncree.org.tw/). This site is classified with class D according to the 1997 UBC Provisions (Kuo 1994; Lee et al. 2001; Chung 2006). However, the drilling sample between 30 and 200 m in this site is not available. ...
Temporal changes of seismic velocity and anisotropy in the shallow crust are quantified using local earthquakes recorded at a 200-m-deep borehole station CHY in Taiwan. This station is located directly above the hypocenter of the 10/22/1999, M6.4 Chia-Yi earthquake. Three-component seismograms recorded at this station show clear direct (up-going) and surface-reflected (down-going) P- and S-waves, and S-wave splitting signals. The two-way travel times in the top 200 m is obtained by measuring the time delays between the up-going and down-going waves in the auto-correlation function. The S-wave travel times measured in two horizontal components increase by ~1-2% at the time of Chia-Yi main shock, and followed by a logarithmic recovery, while the temporal changes of S-wave splitting and P-wave are less than 1% and are not statistically significant. We obtain similar results by grouping earthquakes into clusters according to their locations and waveform similarities. This suggests that the observed temporal changes are not very sensitive to the seismic ray path below CHY, but are mostly controlled by the variation of material property in the top 200 m of the crust. We propose that strong ground motions of the Chia-Yi main shock cause transient openings of fluid-filled microcracks and increases the porosity in the near-surface layers, followed by a relatively long healing process. Because we observe no clear changes in the shear wave anisotropy, we infer that the co-seismic damages do not have a preferred orientation. Our results also show a gradual increase of time delays for both the fast and slow S-waves in the previous 7 years before the Chia-Yi main shock. Such changes might be caused by variations of water table, sediment packing or other surficial processes. M.S. Committee Chair: Peng, Zhigang; Committee Member: Assimaki, Dominic; Committee Member: Newman, Andrew V.
... (1), has the inherent advantage of minimizing the variability of the site response, which can be approached by analyzing seismograms recorded at rock sites. Taking this into account, a total of 65 strong motion stations denoted in Fig. 1, recognized as class B (rock sites) based on geologic and geomorphologic data (Lee et al., 2001;Lee and Tsai, 2008) were selected as reference stations. The mean shear-wave velocities in the upper 30 m (V S30 ) at these rock sites, which were mostly located in the Central Range and the northern mountain area, could be summarized to be in the range 760 ∼ 1,500 m/s from the P-S logging profiles. ...
A stochastic method called the random vibration theory (Boore, 1983) has been used to estimate the peak ground motions caused by shallow moderate-to-large earthquakes in the Taiwan area. Adopting Brune’s ω-square source spectrum, attenuation models for PGA and PGV were derived from path-dependent parameters which were empirically modeled from about one thousand accelerograms recorded at reference sites mostly located in a mountain area and which have been recognized as rock sites without soil amplification. Consequently, the predicted horizontal peak ground motions at the reference sites, are generally comparable to these observed. A total number of 11,915 accelerograms recorded from 735 free-field stations of the Taiwan Strong Motion Network (TSMN) were used to estimate the site factors by taking the motions from the predictive models as references. Results from soil sites reveal site amplification factors of approximately 2.0 ~ 3.5 for PGA and about 1.3 ~ 2.6 for PGV. Finally, as a result of amplitude corrections with those empirical site factors, about 75% of analyzed earthquakes are well constrained in ground motion predictions, having average misfits ranging from 0.30 to 0.50. In addition, two simple indices, R
0.57 and R
0.38, are proposed in this study to evaluate the validity of intensity map prediction for public information reports. The average percentages of qualified stations for peak acceleration residuals less than R
0.57 and R
0.38 can reach 75% and 54%, respectively, for most earthquakes. Such a performance would be good enough to produce a faithful intensity map for a moderate scenario event in the Taiwan region.
Classification of local soil conditions is important for the interpretation of structural seismic damage, which also plays a vital role in site‐specific seismic hazard analyses. In this study, we propose to classify sites as an image recognition task using a deep convolutional neural network (DCNN)‐based technique. We design the input image as a combination of the topographic slope and the mean horizontal‐to‐vertical spectral ratio (HVSR) of earthquake recordings. A DCNN model with five convolutional layers is trained using 1649 sites in Japan. The recall rates for site classes C, D, and E using our DCNN classifier for Japanese sites are 82%, 70%, and 60%, respectively. When compared with existing site classification schemes relying on predefined standard HVSR curves, our proposed method achieves the highest total accuracy rate (between 73% and 75%). The generality and applicability of our trained classifier are further validated using sites in Europe with a total accuracy between 64% and 66%. The proposed data‐driven approach could be extended to other types of site amplification functions in the future.
Time-averaged shear-wave velocity to 30 m ( V S30 ) is commonly used in ground motion models as a parameter for evaluating site effects. This study used a collection of boreholes in Beijing, Tianjin, Guangxi, Guangdong, and three other municipalities and provinces, which were divided into three regions with reference to the seismic ground motion parameter zonation map of China, to establish V S30 prediction models based on terrain categories. Regional effects were verified by comparing morphometric parameters (topographic slope, surface texture, and local convexity) thresholds and terrain classification maps obtained from the global digital elevation model (DEM) data and the regional DEM data of the three regions. Additionally, V S30 prediction models for the three regions using both types of terrain classification maps were established and analyzed comparatively to provide credible regional V S30 models for China. Through analysis of the correlations between the measured V S30 values and the predicted V S30 values, and with consideration of the geological characteristics of the boreholes, the V S30 prediction models based on terrain classification maps from regional data were finally applied in developing regional V S30 models for China. Intercomparison of the V S30 prediction models for the three regions indicated that subregional consideration is necessary in terrain classification. Finally, a spatial analysis method adopting inverse distance weighting of the residuals was used to update the initial V S30 models. The developed V S30 models could be used both in developing regional ground motion models and in the construction of earthquake disaster scenarios.
Les codes du bâtiment ont longuement considéré l'analyse de la vitesse de propagation des ondes de cisaillement pour faire une classification sismique fiable de profils de sol, basée sur la connaissance des propriétés mécaniques des dépôts sédimentaires surmontant le rocher. Cette approche a, cependant, des limitations dues à l'absence de données géophysiques qui sont souvent très coûteuses. Récemment, d'autres techniques ont été proposées basées sur les mesures de bruit de fond et l'estimation de la courbe d'amplification H/V. Néanmoins, l'utilisation de cette technique requiert un cadre réglementaire permettant de fournir une classification réaliste. Ce travail propose une nouvelle méthode pour la caractérisation des sites classés dans les Règles Parasismiques Algériennes (RPA99/ver.2003) par des fonctions de transfert moyennes, suivant une approche stochastique combinée à une étude statistique. Pour chaque type de sol, le calcul déterministe de la fonction de transfert moyenne est réalisé sur un large échantillon de profils de sol 1-D, où la vitesse moyenne des ondes de cisaillement (SW) dans les couches de sol, Vs, est simulée en utilisant la théorie des champs aléatoires. Les fonctions de transfert moyennes sont ensuite utilisées pour calculer les facteurs de sites moyens et les spectres de réponse d'accélération moyens normalisés pour mettre en évidence le potentiel d'amplification de chaque site, sachant la similarité sensible en contenu fréquentiel entre la fonction de transfert et la courbe d'amplification H/V. Une comparaison est faite avec les spectres de réponse du RPA99 / ver.2003 et ceux de l’Eurocode8 (EC8), respectivement. En l'absence de données géophysiques, l'approche de classification proposée, en plus des mesures de bruit de fond, peut être utilisée pour une classification des sols plus réaliste. Des modèles de bâtiments sont également construits pour lesquels la fonction de transfert a été combinée avec les fonctions de transfert du sol et de la fondation, permettant ainsi la modélisation du système sol-fondation-structure et la prédiction de la réponse de la structure tenant compte de l'interaction sol-structure.
Mots clés : Champs aléatoires ; fonction de transfert ; classification de sol ; RPA99/ ver. 2003 ; EC8 ; facteur de site ; spectre de réponse ; interaction sol-structure.
HAZUS is a damage- and loss-estimation software package used in the management of natural disasters. The software enables federal and local authorities to provide rapid and effective recovery measures under actual earthquake situations. It also provides the information required to establish a realistic and comprehensive earthquake risk mitigation plan for future potentially damaging earthquakes. This chapter examines the HAZUS input parameters for earthquake loss estimations in Korea. Historic records for 1900 years, as well as a recent instrument-based earthquake catalog, were examined in detail to identify areas where a high probability of large earthquakes was indicated. The chapter particularly considers southeastern Korea, where the largest historic earthquake was reported, and small- to moderate-sized earthquakes have frequently occurred during the modern period of instrument observations. It estimates losses due to a magnitude 6.7 earthquake scenario in the Gyeongju area by applying the site classification map.
Seismic hazard evaluations require an estimate of the expected ground motion at the site of interest usually by using attenuation relationships. The mean shear-wave velocity over the top 30 m (Vs30) is incorporated in the ground motion attenuation relationships in this study. By comparing the standard deviations of the residuals between the observed and predicted values before and after incorporating the site effect term Vs30, the reduction in standard deviation for the peak ground velocity (PGV) is significantly reduced by about 11%. Clearly, the refined attenuation relationships will be more useful for engineering purposes. Analyzing the site effect term using the amplification factor (relative to a site with Vs30 = 760 m s(-1)), has revealed that the Changhua Plain, Chianan Plain, Pingtung Valley, Ilan Plain, and Taipei Basin have high values, implying large ground motion amplification. Following a disastrous earthquake, quick assessment and timely peak ground acceleration (PGA) and PGV map reporting will be critical for effective emergency response operations. After an earthquake we can combine the simple attenuation relationships, as determined from Model 1, to provide near real-time estimation and reporting of the PGA and PGV values for the Taiwan area. We can also use the relations between the intra-event site residual and the Vs30 to estimate the Vs30 for stations that have recorded strong motions, but do not yet have Vs30 information. Our approach including sites with estimated Vs30 has resulted in a refined Vs30 contour map that can be used for more realistic seismic hazard assessment for Taiwan. This approach is especially applicable to the foothill and mountain areas.
The site effect has been a polular topic in the field of earthquake engineering for a long time. Much effort has been made in studis on site effect by means of numerical simulation and theoretical computation. However, some methods based on strong-motion recordings are recently recognized and widely used, due to their simplicity and no need of many assumptions any more. In the 2008 Wenchuan earthquake, the China National Strong Motion Observation Network System (NSMONS) captured a large number of strong-motion recordings at free field both in the main shock and aftershocks. This makes a good chance for studying the site effect in the Wenchuan earthquake. In this paper, based on a database of these recordings, it takes a systematical study on the site classification, generalized inversion of site response and identification of nonlinearity of site response. That manages to extend the application of strong-motion recordings in the field of scientific research and engineering practice, and promote the development of strong-motion observation in China. The contents are summarized as follows:
(1) The merits and drawbacks of three common-used HVSR (Horizontal-to- Vertical Spectral Ratio) methods of site classification are summarized. Then an improved HVSR method using entropy weight theory is proposed. The site classes of 54 permanent stations and 66 temporary stations in the Wenchuan earthquake are classified by using these four methods. The comparisons between the results given by each method shows that the new method has a more scientific rationality.
(2) An updated classification criterion for six site classes is proposed and used in the process of site classification of temporary strong-motion stations in the Wenchuan earthquake. The results comfirms that it can raise the classification accuracy and effectively solve the problem that HVSR method can not be used for the sites where HVSR curves appear multiple peaks or no any peak. Finally, a preliminary analysis of the correlation between station elevation and its natural period TG identified by HVSR indicates that TG is generally smaller at higher elevations in Sichuan area.
(3) A total of 602 strong-motion recordings obtained by 28 stations from 96 aftershocks of the Wenchuan earthquake are selected as a dataset. The source, path and site effect of these recordings are separated by the generalized inversion technique (GIT). The inversion results have been verified as reliable by comparing the site response at station 62WUD using the GIT method and the the standard spectral ratio (SSR) method. For all 28 stations, the site predominant frequency Fp and the average site amplification in different frequency bands of 1.0-5.0 Hz, 5.0-10.0 Hz and 1.0-10.0 Hz are calculated based on the inversion results. Compared with the results from the HVSR method, it shows that the HVSR method can reasonably estimate the site predominant frequency but underestimates the site amplification. The linear fitting between the average site amplification for each frequency band and the Vs20 (the equivalent uppermost-20 m shear wave velocity) shows a good correlation.
(4) A distance measurement called the asperity distance DAsp is proposed to reasonably characterize the source-to-site distance for large earthquakes such as the Wenchuan earthquake, and is verified to be much better than the other three kinds of distance measurements, including the rupture distance (DRup), fault distance (DFau) and hypocentral distance (DHyp). Then it’s used for generalized inversion of site responses in the main shock of Wenchuan earthquake.
(5) The S transform is suggested to be used for identifying the nonlinearity of site seismic response. Combined with GIT method and HVSR method, it is practiced to identify the site responses of 33 strong-motion stations behave linearity or nonlinearity in the main shock of Wenchuan earthquake. The result shows that the site response appears obvious nonlinearity when PGA larger than 300 cm/s2 or PGV larger than 20 cm/s. In this regard, the sites of station 051AXT, 051GYS, 051GYZ, 051JYC, 051JYD, 051JYH, 051JZW, 051MXN, 051SFB and 062WUD also behave significant nonlinear responses. Compared with the results given by GIT method and HVSR method in the frequency domian, it is verified that the S transform can effectively identify the nonlinerity behavior of site seismic response in the time domain, and have an ablitity to determine the particular time when the nonlinearity occurs.
(6) The correlations between the ratio of Fp under weak motions and strong motion (RFp) and ground motion levels such as PGA and PGV, and site coefficients such as Vs20 and Vs30 are analyzed respectively. The results show RFp has a strongly positive correlation with PGA and PGV, but is uncorrelated with Vs20 and Vs30. A new definition called ADNL (absolute degree of nonlinearity) is proposed to characrize the degree of nonlinearity of site seismic response. Then the ADNL of each site and other parameters such as fNL (frequency of nonlinerity), DNL (degree of nonlinearity) and PNL (percentage of nonlinearity) are calculated. The empirical regression analysis between these parameters and PGA represents that each one has a strong correlation with PGA.
We observe crustal damage and its subsequent recovery caused by the 1999 M7.6 Chi-Chi earthquake in central Taiwan. Analysis of repeating earthquakes in Hualien region, ~approximately 70 km east of the Chi-Chi earthquake, shows a remarkable change in wave propagation beginning in the year 2000 revealing damage within the fault zone and distributed across the near surface. We use moving window cross correlation to identify a dramatic decrease in the waveform similarity and delays in the S-wave coda. The maximum delay is up to 59 ms, corresponding to a 7.6% velocity decrease averaged over the wave propagation path. The waveform changes on either side of the fault are distinct. They occur in different parts of the waveforms, affect different frequencies, and the size of the velocity reductions is different. Using a finite-difference method, we simulate the effect of postseismic changes in the wavefield by introducing S-wave velocity anomaly in the fault zone and near the surface. The models that best fit the observations point to pervasive damage in the near surface and deep, along-fault damage at the time of the Chi-Chi earthquake. The footwall stations show the combined effect of near-surface and the fault zone damage, where the velocity reduction (2-7%) is 2-3 fold greater than the fault zone damage observed in the hanging wall stations. The physical models obtained here allow us to monitor the temporal evolution and recovering process of the Chi-Chi fault zone damage.
This paper presents a derivation of attenuation relations of Arias intensity for various site conditions based on the strong-motion data recorded in the 1999 Chi-Chi Taiwan earthquake. The data are from the mainshock and three large aftershocks with stations in the footwall area and in the area away from the fault. At each station, Arias intensity is computed from two horizontal acceleration time histories. The Arias intensity data are separated into four groups according to site classes assigned to recording stations. For each site class, the attenuation relation of Arias intensity is derived using a two-step regression analysis method. The attenuation relations established in this study can be used to estimate Arias intensity from a rupture of a thrust fault for sites in the footwall area or in the area away from the fault.
In Taiwan, the hillside is about 70 % of total area. These areas also have steep topography and geological vulnerability. When an event of torrential rain comes during a typhoon, the landslide disasters usually occur at these areas due to the long duration and high intensity of rainfall. Therefore, a design which considers the potential landslide has become an important issue in Taiwan. In this study, a temporal characteristic of landslide fragility curve (LFC) was developed, based on the geomorphological and vegetation factors using landslides at the Chen-Yu-Lan watershed in Taiwan, during Typhoon Sinlaku (September 2008) and Typhoon Morakot (August 2009). This study addressed an effective landslide hazard assessment process, linking together the post-landslide damage and post-rainfall data for LFC model. The Kriging method was used to interpolate the rainfall indices (R
0, R, I) for numerical analysis. Remote sensing data from SPOT images were applied to analyze the landslide ratio and vegetation conditions. The 40-m digital elevation model was used for slope variation analysis in the watershed, and the maximum likelihood estimate was conducted to determine the mean and standard deviation parameters of the proposed empirical LFC model. This empirical model can express the probability of exceeding a damage state for a certain classification (or conditions) of landslides by considering a specific hazard index for a given event. Finally, the vulnerability functions can be used to assess the loss from landslides, and, in the future, to manage the risk of debris flow in the watershed.
Recent code provisions for buildings and other structures (1994 and 1997 NEHRP Provisions, 1997 UBC) have adopted new site amplification factors and a new procedure for site classification. Two amplitude-dependent site amplification factors are specified: Fa for short periods and Fv for longer periods. Previous codes included only a long period factor S and did not provide for a short period amplification factor. The new site classification system is based on definitions of five site classes in terms of a representative average shear wave velocity to a depth of 30 m (V̄ s). This definition permits sites to be classified unambiguously. When the shear wave velocity is not available, other soil properties such as standard penetration resistance or undrained shear strength can be used. The new site classes denoted by letters A - E, replace site classes in previous codes denoted by S1 - S4. Site classes A and B correspond to hard rock and rock, Site Class C corresponds to soft rock and very stiff / very dense soil, and Site Classes D and E correspond to stiff soil and soft soil. A sixth site class, F, is defined for soils requiring site-specific evaluations. Both Fa and Fv are functions of the site class, and also of the level of seismic hazard on rock, defined by parameters such as Aa and Av (1994 NEHRP Provisions), Ss and S1 (1997 NEHRP Provisions) or Z (1997 UBC). The values of Fa and Fv decrease as the seismic hazard on rock increases due to soil nonlinearity. The greatest impact of the new factors Fa and Fv as compared with the old S factors occurs in areas of low-to-medium seismic hazard. This paper summarizes the new site provisions, explains the basis for them, and discusses ongoing studies of site amplification in recent earthquakes that may influence future code developments.
Recent borehole‐geotechnical data and strong‐motion measurements constitute a new empirical basis to account for local geological conditions in earthquake‐resistant design and site‐dependent, building‐code provisions. They provide new unambiguous definitions of site classes and rigorous empirical estimates of site‐dependent amplification factors in terms of mean shear‐wave velocity. A simple four‐step methodology for estimating site‐dependent response spectra is specified herein. Alternative techniques and commentary are presented for each step to facilitate application of the methodology for different purposes. Justification for the methodology is provided in terms of definitions for the new site classes and derivations of simple empirical equations for amplification as a function of mean shear‐wave velocity and input ground‐motion level. These new results provide a rigorous framework for improving estimates of site‐dependent response spectra for design, site‐dependent building‐code provisions, ...
The relationship between the amplification ratio of earthquake ground motion and geologic conditions at Japan Meteorological Agency (JMA) stations nationwide was examined to propose an estimation method of the amplification ratio that is applicable to entire Japan. The amplification ratios for the instrumental JMA intensity, as well as for the peak ground acceleration and velocity, were obtained from the station coefficients of the attenuation relationships using strong motion records measured at 77 JMA stations over a period of more than 8 years. A combined use of geomorphological land classification and subsurface geology was found to yield the best estimate of the site amplification ratio. This result suggests that these data, and hence the Digital National Land Information, which is a nationwide GIS database, may be conveniently used for the estimation of strong motion distribution over large areas in Japan.
Response spectral shapes (Sa/a) computed from the BLWN (Band Limited White Noise) ground motion model combined with RVT (Random Vibration Theory) compare favorably with shapes computed from WNA (Western North American) earthquakes recorded at rock
sites. The comparisons are made at close distances and for moment magnitudes 4 1/2, approximately 5, 6, and 6 1/2. Predicted spectral shapes for the ENA (Eastern North America) show reasonably good agreement with empirical results at frequencies of 1 and 10 Hz and with other random process models at frequencies of 0.5, 1, 2, 5, 10, and 20Hz. Magnitude dependence of Sa/a is predicted to be significant for periods greater than 0.2 seconds in WNA and for periods greater than 0.1 seconds in ENA and increases with increasing period. Distance scaling appears to be significant only in WNA and at
distances exceeding 50 km.
Twenty-six sites of the Iranian strong motion network, having provided numerous records of good quality, were selected for a site effect study with the objective of obtaining a reliable site categorization for later statistical work on Iranian strong motion data. For each site, superficial Vp and Vs profiles were measured with refraction techniques, microtremor recordings were obtained and analysed with the H/V technique and the available three-component accelerograms by the receiver function technique. The aggregation of these results allows the proposition of a four-class categorization based on the H/V spectral ratio of strong ground motions, which demonstrate a satisfactory correlation with the S-wave velocity profile. Iran has a particular geological and meteorological situation compared to other seismic countries such as Japan or California, a mountainous country with dry weather conditions and a low water table in most areas. These conditions result in a relatively small number of sites with low frequency amplification, while many sites exhibit moderate amplifications in the intermediate and high frequency range.
In the early morning (01:47 local time) of September 21, 1999, the
largest earthquake of the century in Taiwan (Mw=7.6, ML=7.3) struck the
central island near the small town of Chi-Chi. The hypocenter was
located by the Central Weather Bureau Seismological Center at
23.87°N, 120.75°E, with a depth of about 7 km.There were
extensive surface ruptures for about 85 km along the Chelungpu fault
with vertical thrust and left lateral strike-slip offsets. The maximum
displacement of about 9.8 meters is among the largest fault movements
ever measured for modern earthquakes. There was severe destruction in
the towns of Chungliao, Nantou,Taichung, FengYuan, and Tungshi, with
over 2300 fatalities and 8700 injuries.