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Strong motion record processing for the PEER center
... The baseline correction consisted of fitting a polynomial (degree greater than two) to the displacement time series and subtraction of the corresponding acceleration from the filtered acceleration time series. Examples of PEER processing results at both high-and lowfrequencies can be found in Darragh et al. (2004). ...
... There are two main reasons why many records were entered into the NGA database without additional processing (Darragh et al., 2004 ). First, more recent digitallyrecorded data generally do not benefit from additional processing and were entered into the database after review of the Fourier amplitude spectra and time series (for example, for glitches). ...
... Standard PEER processing of the time histories does not allow for the displacements to have a static offset or residual displacement (i.e., frequency= 0 Hz). To preserve the static displacement, a static baseline correction method such as those described in Iwan et al. (1985), Grazier (1979, and Darragh et al. (2004) could be used in lieu of a high-pass filtering. The peak ground displacement and, to a lesser extent, peak ground velocity values for PEER processed records are typically lower than for static baseline corrected cases. ...
A key component of the NGA research project was the development of a strong-motion database with improved quality and content that could be used for ground-motion research as well as for engineering practice. Development of the NGA database was executed through the Lifelines program of the PEER Center with contributions from several research organizations and many individuals in the engineering and seismological communities. Currently, the data set consists of 3551 publicly available multi-component records from 173 shallow crustal earthquakes, ranging in magnitude from 4.2 to 7.9. Each acceleration time series has been corrected and filtered, and pseudo absolute spectral acceleration at multiple damping levels has been computed for each of the 3 components of the acceleration time series. The lowest limit of usable spectral frequency was determined based on the type of filter and the filter corner frequency. For NGA model development, the two horizontal acceleration components were further rotated to form the orientation-independent measure of horizontal ground motion (GMRotI50). In addition to the ground-motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record was also developed. NGA data have been systematically checked and reviewed by experts and NGA developers.
... To remove the baseline-errorinduced shifts and achieve true ground motion records, scholars have proposed various baseline correction methods. At present, the baseline correction methods for ground motion recorded by modern digital accelerometers can be classified into two categories: the filtering method [1,[8][9][10] removing low-frequency errors and the piecewise correction method [2,4,11,12] based on velocity seismogram. ...
... Therefore, the baseline errors relating to the low-frequency component can be effectively removed by applying a high-pass filter [1,10]. The high-pass filtering of the recorded strong ground motion time histories is also a processing step of the standard procedure used by the PEER Strong Motion Database [8,9,14]. However, high-pass filtering removes not only the baseline errors but also the low-frequency signal content including the static offset of displacements [11]. ...
... Reliable response analysis relies on the reliable definition of the input ground motion, which in turns relies on the appropriate and accurate selection of strong ground motion acceleration records (SGMR). Past studies has shown that SGM data processing and removing unavoidable low and high frequency noise that exists in the measured accelerograms can have adverse effects on the SGM characteristics and consequently on the response estimations, especially on the nonlinear response of the structures [1,2,3,4,5,6,7]. In all SGM signal processing methods, filtering is used to clean up the recorded accelerograms from the low and high frequency noises. ...
... Selection of the type and filtering parameters such as order, phase, corner frequencies, stop-band and pass-band frequencies, etc. can affect the corrected SGMRs; and consequently the responses of structures. The most commonly used filter for SGM data processing is band-pass Butterworth filters [7]. Filters can be applied by linear or zero (acausal) and nonlinear phases (causal). ...
Collapse of structures has been the main cause of human losses in the past earthquakes. Evaluation of nonlinear responses of structures is an advisable way to show how structures behave during the future earthquakes. It needs a number of processed accelerograms which are compatible with the site-specific, furthermore. Studies partially have shown that strong ground motion (SGM) signal processing has some effects on nonlinear responses of SDOF systems especially nonlinear displacement spectra. However, it has not been clear whether SGM signal processing how affects nonlinear response of MDOF systems or IDA analysis, for instance. Hence, in this paper, two accelerograms with different properties have been processed with different filter parameters, filter types, orders and phases. Then, they have been used in performing nonlinear dynamic analyses using different SDOFs and a MDOF structure, and finally the results has been presented.
... 2. Recordings. We sought events with numerous uniformly processed recordings using standard Pacific Earthquake Engineering Research (PEER) procedures (Darragh et al., 2004;Chiou et al., 2008) as of 12/2012. The crustal & interface events produced 520 & 472 records. ...
... A total of 554 and 641 three-component uncorrected digital accelerograms were selected for the crustal and interface events, respectively. Sponsored by the PEER center, those motions were processed by Pacific Engineering and Analysis following PEER/NGA protocols (Darragh et al., 2004;Chiou et al., 2008), which include selection of record-specific corner frequencies to optimize the usable frequency range. For Kik-net sites, only data from the ground surface stations are considered. ...
... The PEER (Pacific Earthquake Engineering Research Center, USA) database, for example, uses causal filtering for most records. They reduce the noise through causal Butterworth filter at both high-and-low-pass frequencies to produce a frequency range over which the ground motion in the recorded signal significantly exceeds the noise level ( Darragh et al. 2004). As a whole, causal and acausal Butterworth filters are widely used in many data processing procedures. ...
... As we have mentioned above, some of the methods used to process strong ground motion time histories include bandpass filtering of the recorded motions based on the frequency range with substantial signal to noise ratios, e.g. PEER standard procedure ( Darragh et al. 2004). For data correction of our accelerograms, we have decided to work with the procedure proposed by Zaré and Bard (2002) based on the level of 3 (∼10 dB) for the normalized signal to noise ratio (SNR). ...
This contribution discusses the application of Chebyshev Type I filter for processing real earthquake records. Consideration
is given to the effects of filtering parameters (passband amplitude ripple and order of the filter) on the time series, strong-motion
parameters, Fourier Amplitude Spectrum of acceleration, and elastic displacement response spectra. Time histories of five
earthquakes with different moment magnitudes have been examined (from stations located close to the epicenters). Data processing
is based on application of bandpass Chebyshev filtering over frequency range with substantial signal to noise ratio (level
of 3 or approximately 3 dB). Applying different filters, we have monitored several important strong-motion parameters: peak
values of acceleration, velocity, and displacement; Arias intensity, acceleration/velocity spectrum intensity, significant
duration, etc. Some new results and conclusions concerning the influence of Chebyshev filter in data processing of records
have been summarized. The graphical and numerical outcomes obtained, as well as the comparison with a Butterworth causal filter,
are included in the work. The results could be potentially useful to engineering seismologists who need to evaluate and better
understand the merits of this type of filtering for strong-motion data processing.
... In the east-west component of TCU102 recording, PGA is measured as 0.30 g and PGV as 91.3 cm/s (Fig. 1). The displacement time histories obtained through the PEER Strong Motion Database do not show static displacements due to the applied standard data processing procedures [23]. Therefore, to investigate the fling-step effect, raw recordings are required so that displacement-time history recordings showing static displacements can be obtained. ...
... When deriving displacement from acceleration, some signal-processing technique, such as demean and detrend, may be required to perform the baseline correction. 32 Substituting Equations (23) and (26) to Equations (19) and (20), the jth rank component of hysteretic loops can be obtained. To choose the appropriate that constitute the predominant mode, the rank with largest cyclic area representing the largest dissipated energy during vibration, would be selected as the temporary predominant mode. ...
... A time window for data processing was selected following the recommendations of previous studies (Goulet et al. 2014, Kishida et al. 2014b). An acausal Butterworth bandpass filter was applied after reviewing the FAS shape and the signal-to-noise ratio between the S-wave and the pre-event noise window (when available) on a component-bycomponent basis (e.g.Darragh et al. 2004, Chiou et al. 2008, Boore et al. 2012). 5%-damped PSA were calculated at selected frequencies for all processed time series followingAncheta et al. (2013). ...
The 2014 South Napa mainshock caused significant damage in the Northern California Bay Area. Time series from a foreshock, mainshock, and three aftershocks were collected from various agencies. These were processed following the Pacific Earthquake Engineering Research Center (PEER) standard data-processing methods, and a ground-motion database was developed. Metadata such as fault style, source-to-site distance, average shear wave velocity in the top 30 m (Vs30), and basin depth were collected. Shear wave velocity profiles were also measured by the Spectral Analysis of Surface Wave Dispersion (SASW) technique at selected strong-motion stations. These datasets were combined in the ground motion database and compared to the Ground Motion Models (GMMs) from the NGA-West2 studies to evaluate the regional attenuation of these events. Time series at two geotechnical downhole array sites were also collected from 29 earthquakes to calculate apparent wave velocities from wave travel times and empirical transfer functions to understand wave amplification. Characteristics of pulse-like records from the South Napa and NGA-West2 databases were also analyzed to compare near-fault regions between these databases. The influence of pulse-like records was also investigated using inelastic response spectra to understand the damage potential on structures. These observed ground-motion characteristics are summarized in this study.
... Most of the V S30 parameters are taken from Lee and Tsai (2008), a few are obtained from the Engineering Geological Database for TSMIP (Kuo et al., 2012). Baseline correction and filtering of the data are performed according to the standard procedures suggested by the Pacific Earthquake Engineering Research Center (PEER; Darragh et al., 2005). ...
This article describes a new approach, the path diagram, for the presentation of the path component of the error in ground-motion estimates for future earthquakes. We use 19,887 records for 150 crustal earthquakes with moment magnitudes greater than 4.0 obtained from the Taiwan Strong Motion Instrumentation Program network to build the Taiwan ground-motion prediction equations for peak ground acceleration (PGA) and spectral accelerations (SAs). The record-to-record residuals are divided into small brackets in a path diagram for six source-to-site distance bins and eight source-to-site azimuth bins. The mean residuals are estimated for each path bin, from which we can get 48 path-to-path residuals for a site and compute a repeatable path term for all residuals of all stations. The remaining unexplained residuals are then estimated through the decomposition of the variance components. Comparing the results with those obtained with the same data, but using the closeness index approach, shows that we get a lower remaining variance and the higher repeatable path term with the new method. For PGA and SAs at periods of 0.3, 1.0, and 3.0 s, the remaining unexplained intraevent standard deviations obtained in the path diagram approach are 29%-40% smaller than the record-to-record standard deviation.
... Therefore, the ground motions recorded at different depths at the KAP and the BES stations are used to validate the accuracy of site response methods. The raw earthquake data are processed via several standard procedures, including the baseline correction, truncation and downsampling techniques, band-pass filter and tapered window methods [38]. The proper signal processing tasks are necessary to remove the high-frequency and low-frequency noises, as well as to reduce the computational time. ...
... Ground-motion prediction equations (GMPEs), another important component, are to date the most representative equations for evaluating the ground-shaking induced by seismic sources. Using data from the Taiwan Strong Motion Network, Lin and Lee (2008) and Lin (2009) published regional Taiwan GMPEs for crustal and subduction-zone earthquakes, respectively, following the data processing criteria of the Next-Generation Attenuation (NGA) models (Darragh et al. 2004). Various databases such as those on active faults, GMPEs and earthquake catalogs are currently maintained. ...
The Taiwan Earthquake Model (TEM) was established to assess the seismic hazard and risk for Taiwan by considering the social and economic impacts of various components from geology, seismology, and engineering. This paper gives the first version of TEM probabilistic seismic hazard analysis for Taiwan in these aspects. We named it TEM PSHA2015. The model adopts the source parameters of 38 seismogenic structures identified by TEM geologists. In addition to specific fault source-based categorization, seismic activities are categorized as shallow, subduction intraplate, and subduction interplate events. To evaluate the potential ground-shaking resulting from each seismic source, the corresponding ground-motion prediction equations for crustal and subduction earthquakes are adopted. The highest hazard probability is evaluated to be in Southwestern Taiwan and the Longitudinal Valley of Eastern Taiwan. Among the special municipalities in the highly populated Western Taiwan region, Taichung, Tainan, and New Taipei City are evaluated to have the highest hazard. Tainan has the highest seismic hazard for peak ground acceleration in the model based on TEM fault parameters. In terms of pseudo-spectral acceleration, Tainan has higher hazard over short spectral periods, whereas Taichung has higher hazard over long spectral periods. The analysis indicates the importance of earthquake-resistant designs for low-rise buildings in Tainan and high-rise buildings in Taichung.
... Thus, it may be intuitive that the removal of permanent displacement through standard filtering affects the response only in very long-period regimes in which the structural response is more directly related to ground displacement. It is interesting to note that a comparison of the peak-to-peak displacement shows that the value from the standard PEERprocessed time history is approximately the same as the value from the static baseline-corrected time history (Darragh et al. 2004; Ancheta et al. 2013), which suggests that the standard processing, which does not preserve static offset, may result in similar dynamic loads to structures. In fact, the filtering of records introduces " little discernable difference between the filtered and unfiltered accelerations " (Boore and Bommer 2005). ...
Lateral load-resisting structural members, such as piers, are often analyzed under one component base excitation. The influence of bidirectional shaking is accounted for by using a simplified 30% rule. During seismic shaking, piers are often subjected to bidirectional ground motion, which leads to a complex combination of biaxial moments. In this backdrop, a RC bridge pier has been analyzed under a set of bidirectionally applied near-field motions with forward directivity (FD) and fling-step characteristics. Bidirectional interaction under near-fault motion is observed to substantially amplify damage, particularly for a stiff system (30% and 45%-50% under FD and fling motions, respectively). A complex combination of bidirectional load paths may have also contributed to increased vulnerability. Additional studies have shown that pulses with fling-step characteristics may often be more detrimental than FD, at least for the first mode-dominated systems. The roles of important ground-motion parameters, such as Arias intensity, mean period, and significant duration, that regulate this interaction effect are discussed. Using energetic length and mean period as characteristic linear and time dimensions, a self-similar response scenario has emerged even when degradation, complex loading patterns under bidirectional shaking, and record-to-record variability coexisted. Geometric nonlinearity in the presence of an axial force may have intensified the interaction effect, as revealed through a sample code-designed pier.
... This database contains strong-motion data collected from TSMIP from 1993 to 2003; this includes the main shock and five aftershocks of the Chi-Chi earthquake (Lee, Shin, et al., 2001a,b). Base-line correction and filtering of the data were performed according to the standard procedures suggested by PEER (Darragh et al., 2005). ...
... The strong-motion data required initial base-line correction and filtering . These were carried out using standard procedures suggested by the Pacific Earthquake Engineering Research Center (PEER) (Darragh et al., 2004). Totally, 449 three-component strong-motion records were processed. ...
... A total of 1,238 three-component, uncorrected digital accelerograms were selected as described above. Sponsored by the Pacific Earthquake Engineering Research (PEER) center, those motions were processed by Pacific Engineering and Analysis following PEER/NGA protocols (Darragh et al. 2004, Chiou et al. 2008), which include selection of record-specific corner frequencies to optimize the usable frequency range. For KiK-net sites, only data from the ground surface stations are considered. ...
The M w 9.0 Tohoku-oki Japan earthquake produced approximately 2,000 ground motion recordings. We consider 1,238 three-component accelerograms corrected with component-specific low-cut filters. The recordings have rupture distances between 44 km and 1,000 km, time-averaged shear wave velocities of V S30 ¼ 90 m=s to 1,900 m/s, and usable response spectral periods of 0.01 sec to >10 sec. The data support the notion that the increase of ground motions with magnitude saturates at large magnitudes. High-frequency ground motions demonstrate faster attenuation with distance in backarc than in forearc regions, which is only captured by one of the four considered ground motion prediction equations for subduction earthquakes. Recordings within 100 km of the fault are used to estimate event terms, which are generally positive (indi-cating model underprediction) at short periods and zero or negative (overpredic-tion) at long periods. We find site amplification to scale minimally with V S30 at high frequencies, in contrast with other active tectonic regions, but to scale strongly with V S30 at low frequencies. [
... This database contains strong-motion data collected from TSMIP from 1993 to 2003; this includes the main shock and five aftershocks of the Chi-Chi earthquake (Lee, Shin, et al., 2001a,b). Base-line correction and filtering of the data were performed according to the standard procedures suggested by PEER (Darragh et al., 2005). ...
Arias Intensity is a ground-motion parameter that captures the potential destructiveness of an earthquake as the integral of the square of acceleration time history. It obtains more reliable prediction of the level of anticipated damage than other ground-motion parameters by incorporating amplitude, frequency content, and duration of strong ground-motion. It correlates well with several commonly used demand measure of structural performance, liquefaction, and seismic slope stability. A new empirical relationship for crustal earthquake is developed to estimate Arias Intensity as a function of magnitude, distance, fault mechanism, and continuous site variable - Vs30. It is based on strong-motion data from TSMIP array in Taiwan. Its functional form is derived from the point-source model, and the coefficients are determined through non-linear regression analyses using a mixed-effects model. The results show that Vs30 can reduce the regression error significantly. The Arias Intensity value predicted by the present study is similar with that of Travasarou et al. (2003) in general; the value predicted by the present study is slightly higher in the near distance (40~70 km). The total standard deviation of regression error in this study is 0.994 (in ln unit), which is much smaller than that of most other previous studies.
... The strong-motion data required initial baseline correction and filtering. These were carried out using standard procedures suggested by the Pacific Earthquake Engineering Research Center (PEER) (Darragh et al. 2004). PGA, PGV and AI were then calculated from each corrected seismogram. ...
A large number of landslides were triggered by the 1999 Chi-Chi Earthquake (Mw 7.6) and subsequent aftershocks. They were re-mapped from fused SPOT images and recently checked by using aerial photo-pairs. Some omitted landslides due to the limitation of satellite images resolution were added to the dataset. Deposit areas that previously recognized as landslides are removed. The new dataset was then re-examined to sieve out some exceptional cases of landslide not intended in statistical analysis, for example, structural-controlled landslides of the Tsaoling landslide and the Chiufengerhshan landslide. To better characterize the factors affecting earthquake triggered landslides, we used newly surveyed 5-m resolution DEM for statistical analysis. Result can be summarized as follows: (1) Slope gradient is the most important factor affecting landslides in each drainage basin. (2) Closest distant to fault-rupture plane is the most important source-distance factor controlling landslides. (3) Arias intensity presents good correlation to landslide failure, especially the corrected Arias intensity does. (4) Most landslides concentrated in the region exceeding 250 gals. (5) Slope aspect shows some correlations to landslide occurrence in each drainage basin. (6) Slope height also plays an important role in the occurrence of landslides. (7) Goodness of correlation for each landslide controlling factor shows some differences among six drainage basins.
... These dimensions are commonly larger than the expected rupture area (e.g., Cirella et al. 2009, Scognamiglio et al. 2010 (Celebi et al. 2010) and through ITACA protocols that utilize a single corner frequency for each recording from a triaxial accelerograph . Pacific Engineering and Analysis processed the data following PEER/NGA protocols (Darragh et al. 2004. The PEER processing examined the Fourier amplitude spectrum of each component to initially select high-and lowfrequency filter corners. ...
The 2009 L’Aquila earthquake sequence includes the April 6 Mw 6.3 main
shock and triggered events on April 7 and 9, each recorded on a digital network
having five stations on the hanging wall of the main shock fault. We describe a
geometric source model drawing upon inversions by others. We describe
record-specific ground motion data processing that includes the incorporation of
static displacements of up to 13 cm (downdrop of hanging wall). The resulting
database includes 47, 38, and 31 corrected triaxial recordings from the April 6,
7, and 9 events, respectively. We present site conditions for recording stations,
including recent surface wave and borehole geophysics. We demonstrate that
the high-frequency data are weaker than expected for normal fault earthquakes
of these magnitudes and that the data attenuate with distance at rates generally
consistent with modified next generation attenuation (NGA) equations for Italy
that were available prior to the event.
... This database contains strong-motion data collected from TSMIP from 1993 to 2003; this includes the main shock and five aftershocks of the Chi-Chi earthquake (Lee, Shin, et al., 2001a,b). Base-line correction and filtering of the data were performed according to the standard procedures suggested by PEER (Darragh et al., 2005). ...
The Arias intensity is a measure of earthquake intensity arrived at through the integration of a square of the acceleration time history. It has been demonstrated to be an effective predictor of earthquake damage potential in relation to short-period structures, liquefaction, and seismic slope stability, and has begun to be considered as a ground-motion measure suitable for use in probabilistic seismic hazard analysis (PSHA), as well as earthquake loss estimation. A new empirical Arias intensity attenuation relationship for shallow crustal earthquakes is developed where both fault type and a continuous site variable V-S30 are considered. The relationship is based on a large number of strong-motion records (6570) from a wide range of earthquake magnitudes (3.9-7.6) from the Taiwan Strong Motion Instrument Program (TSMIP) network. Its functional form is modified from that of Travasarou et al. (2003), which is derived from a point-source model, and the coefficients are determined through nonlinear regression analyses using a mixed-effects model. The results show that the incorporation of V-S30 can significantly reduce regression error. The Arias intensity value predicted in the present study is generally similar to that obtained by Travasarou et al. (2003), but is different in detail, being more suitable for usage in PSHA for a tectonically young orogenic belt like that in Taiwan or New Zealand.
... 1. Strong-motion seismograms in and around the study area were collected by the Central Weather Bureau, Taiwan. Base-line correction and filtering of the data were performed according to the standard procedure suggested by the Pacific Earthquake Engineering Research Center (PEER) (Darragh et al., 2004). The Arias intensity (Arias, 1970) was then calculated from each corrected seismogram. ...
Susceptibility analysis for predicting earthquake-induced landslides has most frequently been done using deterministic methods; multivariate statistical methods have not previously been applied. In this study, however, we introduce a statistical methodology that uses the intensity of earthquake shaking as a landslide triggering factor. This methodology is applied in a study of shallow earthquake-induced landslides in central western Taiwan. The results show that we can accurately interpret landslide distribution in the study area and predict the occurrence of landslides in neighboring regions. This susceptibility model is capable of predicting shallow landslides induced during an earthquake scenario with similar range of ground shaking, without requiring the use of geotechnical, groundwater or failure depth data.
... The recorded raw ground motion signals are always preprocessed by seismologists before any engineering and seismological analysis takes place. Strong-motion data processing has two main objectives to make the data useful for engineering analysis: (1) correction for the response of strongmotion instrument itself (analogue or digital type of instrument can be used) and (2) reduction of random noise in the recorded signals [1] . Different authors and agencies around the world use various steps in data processing. ...
The paper presents an application of digital filtering in data processing of acceleration records from earthquakes. Butterworth, Chebyshev, and Bessel filters with different orders are considered to eliminate the frequency noise. A dataset under investigation includes accelerograms from three stations, located in Turkey (Dinar, Izmit, Kusadasi), all working with an analogue type of seismograph SMA-1. Records from near-source stations to the earthquakes (i.e., with a distance to the epicenter less than 20 km) with different moment magnitudes Mw = 3.8, 6.4, and 7.4 have been examined. We have evaluated the influence of the type of digital filter on time series (acceleration, velocity, displacement), on some strong motion parameters (PGA, PGV, PGD, etc.), and on the FAS (Fourier amplitude spectrum) of acceleration. Several 5%-damped displacement response spectra applying examined filtering techniques with different filter orders have been shown. SeismoSignal software tool has been used during the examples.
In the actual measurement of offshore wind turbines (OWTs), the measured accelerations usually contain a large amount of noise due to the complex and harsh marine environment, which is not conducive to the identification of structural modal parameters. For OWTs with remarkably low structural modal frequencies, displacements can effectively suppress the high-frequency vibration noise and amplify the low-frequency vibration of the structure. However, finding a reference point to measure structural displacements at sea is difficult. Therefore, only a few studies on the use of dynamic displacements to identify the modal parameters of OWTs with high-pile foundations are available. Hence, this paper develops a displacement conversion strategy to study the modal parameter identification of OWTs with high-pile foundations. The developed strategy can be divided into the following three parts: zero-order correction of measured acceleration, high-pass filtering by the Butterworth polynomial, and modal parameter identification using the calculated displacement. The superiority of the proposed strategy is verified by analyzing a numerical OWT with a high-pile foundation and the measured accelerations from an OWT with a high-pile foundation. The results show that for OWTs with high-pile foundations dominated by low frequencies, the developed strategy of converting accelerations into displacements and then performing modal parameter identification is advantageous to the identification of modal parameters, and the results have high accuracy.
The finite-fault stochastic method was applied to simulate the Mw 6.9, 2008 Iwate-Miyagi earthquake at 44 selected KiK-net sites using EXSIM computer code. To investigate the effects of source characteristics on the simulated results, three models were considered: two models with prescribed slip distribution (Model 1 and Model 3) and a model with random slip distribution (Model 2). S-wave regional attenuation indicates an obvious difference between fore-arc and back-arc regions which are formed by volcanic front. Site amplification was determined by corrected surface to borehole spectral ratio and Quarter wavelength methods. The high-frequency decay parameter (kappa) was estimated to be 0.0473 s. The value of 16 MPa for stress drop was calculated by minimizing the absolute residual of 5% damped pseudo-spectral accelerations (PSA). Comparison of the observed and simulated PGAs and PSAs was performed to investigate the capability of our finite-fault models. The residual models represent that the simulated results by Model 2 are in good agreement with the observations in f < 3 Hz, while the other models can better simulate higher frequency motions. We also focused on the effects of slip patches sitting on the fault plane on near-field stations placed in the directions of slip propagation. For these stations, the simulated results by Model 1 and Model 3 were preferred over those of Model 2. Finite-fault models successfully interpreted the real forced motions to AKTH04 where the recorded peak values were abnormal for non-seismological reasons. Finally, the comparison of intensity measures with the GMPEs showed agreement.
The Next-Generation Attenuation for subduction zone regions project (NGA-Sub) has developed data resources and ground motion models for global subduction zone regions. Here we describe the NGA-Sub database. To optimize the efficiency of data storage, access, and updating, data resources for the NGA-Sub project are organized into a relational database consisting of 20 tables containing data, metadata, and computed quantities (e.g. intensity measures, distances). A database schema relates fields in tables to each other through a series of primary and foreign keys. Model developers and other users mostly interact with the data through a flatfile generated as a time-stamped output of the database. We describe the structure of the relational database, the ground motions compiled for the project, and the means by which the data can be accessed. The database contains 71,340 three-component records from 1880 earthquakes from seven global subduction zone regions: Alaska, Central America and Mexico, Cascadia, Japan, New Zealand, South America, and Taiwan. These data were processed on a component-specific basis to minimize noise effects in the data and remove baseline drifts. Provided ground motion intensity measures include peak acceleration, peak velocity, and 5%-damped pseudo-spectral accelerations for a range of oscillator periods.
This article documents the earthquake ground motion database developed for the NGA-East Project, initiated as part of the Next Generation Attenuation (NGA) research program and led by the Pacific Earthquake Engineering Research Center (PEER). The project was focused on developing a ground motion characterization model (GMC) model for horizontal ground motions for the large region referred to as Central and Eastern North America (CENA). The CENA region covers most of the U.S. and Canada, from the Rocky Mountains to the Atlantic Ocean and is characterized tectonically as a stable continental region (SCR). The ground-motion database includes the two- and three-component ground-motion recordings from numerous selected events relevant to CENA ( M > 2.5, with distances up to 3500 km) that have been recorded since 1976. The final database contains over 27,000 time series from 82 earthquakes and 1271 recording stations. The ground motion database includes uniformly processed time series, 5% damped pseudo-spectral acceleration (PSA) median-component ordinates for 429 periods ranging from 0.01 to 10 s, duration and Arias intensity in 5% increments, and Fourier amplitude spectra for different time windows. Ground motions and metadata for source, path, and site conditions were subjected to quality checks by topical working groups and the ground-motion model (GMM) developers. The NGA-East database constitutes the largest database of processed recorded ground motions in SRCs and is publicly available from the PEER ground-motion database website.
For offshore structures in service such as offshore platforms and offshore wind turbines, their displacements are expected but can be difficult to measure directly due to the lacking of fixed reference points in ocean. Aiming at obtaining displacements of offshore structures from accelerations which can be easily measured by accelerometers, a new non-integration displacement reconstruction method is proposed in this paper. The complex exponential series is adopted to establish a relationship between the measured acceleration and the targeted displacement. Compared to direct-integral or high-pass filtering methods, one theoretical development in the present approach is that the reconstructed displacement is derived from the estimated complex exponential parameters of measured acceleration signal with a form of fraction, and the components that cause the drift could be identified and removed, thus significantly reducing the drift issue typically experienced by traditional methods. Additionally, a challenging problem involving the estimation of velocity and displacement at the measured starting moment is solved, which implies that the noises contained in the measured acceleration signal will not be amplified during the conversion from acceleration to velocity and displacement. To investigate the performance of the proposed method, one numerical example and two physical experiments are carried out sequentially. The selected numerical example is a 4-dof system, which aims at verifying the correctness and investigating the robustness of the proposed method. Numerical results show: (1) velocities and displacements can be accurately reconstructed from noise-free acceleration signals with an obvious baseline offset; (2) even when the acceleration signals are contaminated with 15% Gaussian noise, a good estimation of velocities and displacements can still be obtained. Subsequently, a steel beam fixed on a shaking table is tested, and two accelerometers and two laser displacement sensors are used to measure the dynamic responses of the table as well as the top of the beam, respectively. The experimental results show a good agreement between the reconstructed displacements and the measured data from the laser displacement sensors. Finally, a four-leg offshore platform is investigated experimentally to assess the potential application of the present method in ocean engineering. It is observed from the experimental results that the maximum absolute difference in the amplitude between the reconstructed and measured displacements is 0.47 mm with the computed peak displacement error of 0.3166, which further confirms the feasibility and correctness of the proposed method.
In the design of damped structures, the additional equivalent damping ratio (EDR) is an important factor in the evaluation of the energy dissipation effect. However, previous additional EDR estimation methods are complicated and not easy to be applied in practical engineering. Therefore, in this study, a method based on energy dissipation is developed to simplify the estimation of the additional EDR. First, an energy governing equation is established to calculate the structural energy dissipation. By means of dynamic analysis, the ratio of the energy consumed by dampers to that consumed by structural inherent damping is obtained under external excitation. Because the energy dissipation capacity of the installed dampers is reflected by the additional EDR, the abovementioned ratio can be used to estimate the additional EDR of the damped structure. Energy dissipation varies with time, which indicates that the ratio is related to the duration of ground motion. Hence, the energy dissipation during the most intensive period in the entire seismic motion duration is used to calculate the additional EDR. Accordingly, the procedure of the proposed method is presented. The feasibility of this method is verified by using a single-degree-of-freedom system. Then, a benchmark structure with dampers is adopted to illustrate the usefulness of this method in practical engineering applications. In conclusion, the proposed method is not only explicit in the theoretical concept and convenient in application but also reflects the time-varying characteristic of additional EDR, which possesses the value in practical engineering.
The results of probabilistic seismic hazard analysis (PSHA) are sensitive to the standard deviation of the residuals of the ground‐motion prediction equations (GMPEs), especially for long‐return periods. Recent studies have proven that the epistemic uncertainty should be incorporated into PSHA using a logic‐tree method instead of mixing it with the aleatory variability. In this study, we propose using single‐station GMPEs with a novel approach (an epistemic‐residual diagram) to improve the quantification of epistemic uncertainty per station. The single‐station attenuation model is established from the observational recordings of a single station, hence, site‐to‐site variability (σS) can be ignored. We use 20,006 records of 497 crustal earthquakes with moment magnitudes (Mw) greater than 4.0, obtained from the Taiwan Strong Motion Instrumentation Program network, to build the single‐station GMPEs for 570 stations showing the peak ground acceleration (PGA) and spectral accelerations. A comparison is made between the total sigma of the regional GMPE (σT), the single‐station sigma of the regional GMPE as estimated by the variance decomposition method (σSS), and the sigma of single‐station GMPEs (σSS,S), for different periods. For most stations (70%), the σSS,S is about 20%–50% smaller than the σT. Furthermore, we adopt the epistemic‐residual diagram to separate the σSS,S into the epistemic uncertainty (σEP,S) and the remaining unexplained variability (σSP,S) for each station. The results show that in most areas, the σSP,S for the PGA is about 50%–80% smaller than the σT. Finally, the variations in the various sigma and model coefficients are mapped with the geographical locations of the stations for analysis of different regional characteristics.
This study proposes a novel design concept, referred to as the uniform damping ratio (UDR) concept, to improve the seismic energy dissipation efficiency of damped structures with metallic yielding dampers (MYDs) by maximizing the use of the capability of each damper. Furthermore, this new concept can simplify the design procedure of structures with MYDs. The UDR concept implies that all installed MYDs have the same equivalent damping ratio under dynamic excitations, which enables each MYD to be fully utilized. The UDR concept can simplify the estimation process of the additional equivalent damping ratio of a damped structure and decouple the stiffness and damping effects caused by MYDs, which can be designed separately. A performance demand-oriented design procedure is presented based on the UDR concept considering the nonlinear properties of an original structure and MYDs under an intense earthquake. The design procedure involves the following three steps: (1) determine seismic performance demand and obtain the elastic and elastoplastic properties of the original structure using pushover analysis; (2) determine key design parameters based on the formulae derived under the UDR concept; (3) verify seismic performance via nonlinear dynamic analyses. In addition, a few empirical suggestions are provided for determining the key design parameters more efficiently. A nine-story steel frame structure with MYDs is used to exemplify the UDR-based design procedure. The seismic performance demand of the structure with designed MYDs is achieved, and the energy dissipation capacity of all installed MYDs is sufficiently utilized. The proposed UDR concept is found to be effective, and the procedure based on this concept is efficient and simple.
This study presents a comparative analysis of several methods to estimate displacements from measured accelerations records, with the objective of assessing their performance to compute displacements caused by different types of excitation (harmonic, vehicular, pedestrian, or seismic). The acceleration records were selected to be unaffected by tilts and rotation around a vertical axis. The study relevance is founded on the lack of agreement among researchers in relation to the validity/precision of displacements obtained from accelerations. Results show that there are two main groups of methods: one applies to signals with zero end displacements, and the other applies to more general movements. Except for cases with both much noise and small displacements, it is possible to compute displacements with high cross correlation coefficients and small errors, with respect to measured displacements. Results also indicate that the selection of the method to estimate displacements depends on: displacement amplitudes, type of waveform, type of information requiered (either the peak displacement or the whole displacement signal), and magnitude of the displacements at the record end.
A continually increasing number of high-quality digital strong-motion records from stations of the National Strong-Motion Project (NSMP) of the U.S. Geological Survey (USGS), as well as data from regional seismic networks within the United States, call for automated processing of strong-motion records with human review limited to selected significant or flagged records. The NSMP has developed the Processing and Review Interface for Strong Motion data (PRISM) software to meet this need. In combination with the Advanced National Seismic System Quake Monitoring System (AQMS), PRISM automates the processing of strong-motion records. When used without AQMS, PRISM provides batch-processing capabilities. The PRISM version 1.0.0 is platform independent (coded in Java), open source, and does not depend on any closed-source or proprietary software. The software consists of two major components: a record processing engine and a review tool that has a graphical user interface (GUI) to manually review, edit, and process records. To facilitate use by non-NSMP earthquake engineers and scientists, PRISM (both its processing engine and review tool) is easy to install and run as a stand-alone system on common operating systems such as Linux, OS X, and Windows. PRISM was designed to be flexible and extensible in order to accommodate new processing techniques. This report provides a thorough description and examples of the record processing features supported by PRISM. All the computing features of PRISM have been thoroughly tested.
Human perception to tremors during earthquakes in high-rise buildings is usually associated with psychological discomfort such as fear and anxiety. This paper presents a methodology for estimating the level of perception to tremors for occupants living in high-rise buildings subjected to ground motion excitations. Unlike other approaches based on empirical or historical data, the proposed methodology performs a regression analysis using the analytical results of two generic models of 15 and 30 stories. The recorded ground motions in Singapore are collected and modified for structural response analyses. Simple predictive models are then developed to estimate the perception level to tremors based on a proposed ground motion intensity parameter—the average response spectrum intensity in the period range between 0.1 and 2.0 s. These models can be used to predict the percentage of occupants in high-rise buildings who may perceive the tremors at a given ground motion intensity. Furthermore, the models are validated with two recent tremor events reportedly felt in Singapore. It is found that the estimated results match reasonably well with the reports in the local newspapers and from the authorities. The proposed methodology is applicable to urban regions where people living in high-rise buildings might feel tremors during earthquakes.
The influence of noise in strong-motion records is most problematic at low and high frequencies where the signal to noise ratio is commonly low compared to that in the mid-spectrum. The impact of low-frequency noise (< 1Hz) on strong-motion intensity parameters such as ground velocities, displacements and response spectral ordinates can be dramatic and consequentially it has become standard practice to low-cut (high-pass) filter strong-motion data with corner frequencies often chosen based on the shape of Fourier amplitude spectra and the signal-to-noise ratio. It has been shown that response spectral ordinates should not be used beyond some fraction of corner period (reciprocal of the corner frequency) of the low-cut filter. This article examines the effect of high-frequency noise (>5Hz) on computed pseudo-absolute response spectral accelerations (PSAs). In contrast to the case of low-frequency noise our analysis shows that filtering to remove high-frequency noise is only necessary in certain situations and that PSAs can often be used up to 100Hz even if much lower high-cut corner frequencies are required to remove the noise. This apparent contradiction can be explained by the fact that PSAs are often controlled by ground accelerations associated with much lower frequencies than the natural frequency of the oscillator because path and site attenuation (often modelled by Q and kappa, respectively) have removed the highest frequencies. We demonstrate that if high-cut filters are to be used, then their corner frequencies should be selected on an individual basis, as has been done in a few recent studies.
Landslides triggered by the 1999 Chi–Chi earthquake were re-mapped from high-resolution SPOT images taken before and after the quake. Their distribution was studied and landslide controlling factors statistically analyzed. Slope gradient, relative slope height, total slope height, closest distance to fault-rupture plane, and Arias Intensity were the most significant factors affecting landsliding. Earthquake-induced landslides were most common on longer and steeper slopes, and occurred at a high position on the slope. Most landslides were concentrated in the regions with peak ground accelerations exceeding 250 gals.
This paper includes a comparative application of the digital filters on data processing for the strong motion data recorded during earthquakes. Three types of digital, acausal filters (designed by Butterworth, Bessel, and Chebyshev type I) with N=4 were used to remove the unwanted noise. The data has been collected from three different stations located in Turkey (Adana, Van, and Bingol) that are working with a digital type of seismograph (Guralp cmg5td and SigSasmach). Those stations are close to the earthquake events with different moment magnitudes Mw = 4.5, 3.8, and 3.3. The SAC software tool has been used to evaluate digital filter influence on time series (acceleration, velocity, and displacement). This has been done by measuring and comparing some strong motion parameters (peak ground acceleration, peak ground velocity, and peak ground displacement).
During the NGA-West 2 and NGA-East projects the PEER processing methodology (Darragh et al. 2004; Chiou et al, 2008) has expanded to be an automated comprehensive record processing (removal of unwanted noise) and time series metric calculator. The full documentation and code are in development with plans for a public distribution. This is to continue the transparency as promised in NGA-West 2 and NGA-East and to aid in more consistent time series processing and metric calculations in the research and engineering community. A demonstration of the methodology is illustrated.
This study investigates spatial cross-correlation models for two sets of vector intensity measures (IMs) considering the influence of regional site conditions. The first set of the vector IM consists of the peak ground acceleration, Arias intensity, and the peak ground velocity; the second set is for spectral accelerations at multiple periods. Geostatistics analyses are performed using 2686 strong-motion data from 11 recent earthquakes that occurred in California, Japan, Taiwan, and Mexico. The results indicate that the spatial cross correlations of the vector IMs are strongly influenced by the spatial distribution of regional site conditions, which can be quantified using R-VS30, the correlation range of shear-wave velocity in the top 30 m. The linear model of coregionalization is proposed to construct a permissible spatial correlation model, and the short-range and long-range coregionalization matrices is specified to vary linearly with R-VS30. The proposed model demonstrated excellent performance in quantifying the influence of regional site conditions on the spatial cross correlations for the vector IMs, meanwhile the model guarantees a positive-definite covariance matrix for any reasonable value of R-VS30, a mathematical condition required for stochastic generation of the spatially correlated random fields. The spatial cross-correlation models proposed in this study can be conveniently used in regional-specific seismic risk analysis and loss estimation of spatially distributed infrastructure using vector IMs.
A dataset of site conditions at 101 Italian ground motion stations with recorded motions has been compiled that includes geologic characteristics and seismic velocities. Geologic characterization is derived principally from local geologic investigations by ENEL that include detailed mapping and cross sections. For sites lacking such detailed geologic characterization, the geology maps of the by Servizio Geologico d'Italia are used. Seismic velocities are extracted from the literature and the files of consulting engineers, geologists and public agencies for 33 sites. Data sources utilized include post earthquake site investigations (Friuli and Irpinia events), microzonation studies, and miscellaneous investigations performed by researchers or consulting engineers/geologists. Additional seismic velocities are measured by the authors using the controlled source spectral analysis of surface waves (SASW) method for 18 sites that recorded the 1997-1998 Umbria Marche earthquake sequence. The compiled velocity measurements provide data for 51 of the 101 sites. For the remaining sites, the average seismic velocity in the upper 30 m (Vs30) is estimated using a hybrid approach. For young Quaternary alluvium, Vs30 an existing empirical relationship for California sites by Wills and Clahan (2006) is used, which we justify by validating this relationship against Italian data. For Tertiary Limestone and Italian Mesozoic rocks, empirical estimates of Vs30 are developed using the available data. This work is also presented in Scasserra et al. (2008: JEE, in review).
A new engineering source model consistent with seismological concepts for simulating strong-motion accelerograms (SMAs) is presented in this paper. The source region is modeled as a horizontally layered elastic medium to cater for site dependency. The moment field acting on the rupture plane is decomposed into space and time functions, which is a novel concept. The spatial and temporal components are determined for six well-recorded earthquakes using the corresponding recorded SMA. The obtained spatial variations indicate that they can be modeled as an anisotropic random field. The temporal components of all the six events are transients, with typical frequency spectra. Based on these results, a simplified source model is proposed for the synthesis of SMA during strong earthquakes. The model is validated by simulating strong-motion acceleration time histories at stations deliberately kept out of the modeling exercise. It is found that the present model is efficient in simulating observed time histories. The proposed model is also illustrated by simulating an ensemble of acceleration time histories for the Kutch earthquake of 26th January 2001 using only the few known source parameters.
In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion
(NFGM) characteristics had a distinct impact on causing damage to civil engineering structures that could not be predicted
by using far field ground motions. Since then, seismic responses of structures under NFGMs have been extensively examined,
with most of the studies focusing on structures with relatively short fundamental periods, where the traveling wave effect
does not need to be considered. However, for long span bridges, especially arch bridges, the traveling wave (only time delay
considered) effect may be very distinct and is therefore important. In this paper, the results from a case study on the seismic
response of a steel arch bridge under selected NFGMs is presented by considering the traveling wave effect with variable apparent
velocities. The effects of fling step and long period pulses of NFGMs on the seismic responses of the arch bridge are also
discussed.
Displacements derived from many of the accelerogram recordings of the 1999 Chi-Chi, Taiwan, earthquake show drifts when only a simple baseline derived from the pre-event portion of the record is removed from the records. The appearance of the velocity and displacement records suggests that changes in the zero level of the acceleration are responsible for these drifts. The source of the shifts in zero level are unknown, but in at least one case it is almost certainly due to tilting of the ground. This article illustrates the effect on the ground velocity, ground displacement, and response spectra of several schemes for accounting for these baseline shifts. A wide range of final displacements can be obtained for various choices of baseline correction, and comparison with nearby GPS stations (none of which are colocated with the accelerograph stations) do not help in choosing the appropriate baseline correction. The results suggest that final displacements estimated from the records should be used with caution. The most important conclusion for earthquake engineering purposes, however, is that the response spectra for periods less than about 20 see are usually unaffected by the baseline correction. Although limited to the analysis of only a small number of recordings, the results may have more general significance both for the many other recordings of this earthquake and for data that will be obtained in the future from similar high-quality accelerograph networks now being installed or soon to be installed in many parts of the world.
An essential element in the seismic design of critical facilities is a quantitative estimate of ground motion characteristics due to earthquakes. This report confirms the validity of a simple relationship between magnitude, site condition and frequency content of the ground motion that is extremely useful for engineering design purposes.
Using a database of 655 recordings from 58 earthquakes, empirical response spectral attenuation relations are derived for
the average horizontal and vertical component for shallow earthquakes in active tectonic regions. A new feature in this model
is the inclusion of a factor to distinguish between ground motions on the hanging wall and footwall of dipping faults. The
site response is explicitly allowed to be non-linear with a dependence on the rock peak acceleration level.
Preliminary report on aftershock sequence for earthquakes of
- R D Borcherdt
Borcherdt RD. "Preliminary report on aftershock sequence for earthquakes of January 31, 1986
near Painesville, Ohio." U.S. Geological Survey Open File Report 86-181.
Effect of Baseline Corrections on Response Spectra for Two Recordings of the
- D M Boore
Boore DM. "Effect of Baseline Corrections on Response Spectra for Two Recordings of the
Development of attenuation relation for peak particle velocity and displacement
- N Gregor
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- R Darragh
Gregor N, Silva W, Darragh R. "Development of attenuation relation for peak particle velocity
and displacement." A PEARL report to PG&E/CEC/Caltrans 2002.