No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Strong-motion earthquake measurement using a digital accelerograph
Abstract
This paper presents results of a study of some of the characteristics of the Kinemetrics PDR-1 digital strong-motion accelerograph. The paper gives the results of laboratory tests of the background noise level of the instrument and compares these results with previously reported observations for optical instruments. The determination of displacement from acceleration data is discussed and results of laboratory tests are presented. Certain instrument anomalies are identified, data correction algorithms proposed, and examples given. The paper also presents the results of a comparison of earthquake records obtained from side-by-side digital and optical analog instruments. Finally, some results obtained from a recent Chinese earthquake are discussed.
... The absence of the lowfrequency component reduces the practicability of accelerations in near-field seismic research (Somerville et al., 1997;Somerville, 2003;Jousset and Douglas, 2007). Baseline-fitting methods (Graizer, 1979;Iwan et al., 1985;Chiu, 1997) were proposed based on experience with multistage corrections. As a widely applied criterion, the principle of multi time segment method separates the acceleration record into three segments by two times: t 1 and t 2 (Fig. 1e). ...
... Because the observed ground truth of the baseline drift is theoretically unknowable and the manually corrected baselines are relatively insufficient, it is difficult to obtain high performance by training on observational data. We further proposed a novel baseline simulation method based on the multi time segments principle (Graizer, 1979;Iwan et al., 1985) to extend the training data set. The generated baselines are both fused with the observed records and used as training labels for TraceNet. ...
... We assume that a drifted accelerogram contains two main elements: (1) a seismic signal, including the seismic wave from sources and ambient noise, and (b) a baseline drift, which is due to instrument limitations or other complex influences. The baseline drift accumulates significantly after two integrations to convert the acceleration to displacement (for instance, Fig. 1 The orange and blue vectors represent the selected times t 1 and t 2 from the multi time segment principle (Graizer, 1979;Iwan et al., 1985). baseline first and remove the effect of drift second to obtain a corrected result. ...
In strong ground-motion observations, accelerograms are an important material in both seismic research and earthquake engineering. However, the ubiquitous baseline drift in near-field acceleration records has a large impact on the integrated velocity and double-integrated displacement with linear and parabolic drift, respectively. Conventionally, high-pass filtering and two-stage baseline fitting methods are commonly applied in baseline corrections to obtain reliable strong-motion records. However, these filtering methods exclude low-frequency components from acceleration records and cause unexpected waveform loss. The baseline fitting method, which is based on the experiential selection of intersection moments, is easily affected by external factors and requires a large amount of time for operations. Currently, as the number of accelerometers grows, conventional methods are insufficient in both efficiency and precision to process vast acceleration records. Here, we propose TraceNet, a deep-learning-based method, to correct baseline drifts in velocity records integrated from accelerograms. The training data set is developed with the fusion of artificial baselines and nondrift velocities from corrected accelerations and displacements from events. TraceNet extracts the baseline from the input velocity trace. After TraceNet prediction, the drift can be corrected by subtracting the extracted baseline. In addition, the potential coseismic ground displacement can be recovered from the integration in the corrected velocity. In this study, we used acceleration records and continuous Global Positioning System observations from the 2008 Wenchuan earthquake to demonstrate the ground offset recovery. As a deep learning application, TraceNet can extract and correct the baseline drifts automatically without subjective factors. The coseismic displacements estimated from accelerograms can provide additional insight into the ground deformation.
... The pre-and postevent corrections are typically done by eliminating the linear trend present in the integrated velocity from the corrected acceleration at the pre-event phase. The method to remove baseline trends present in ground motion records can be attributed to Graizer (1979), with later contributions of several other authors (e.g., Iwan et al., 1985;Boore, 2001). Unfortunately, the determination and correction of the transient baseline shift is the most complex task, because it cannot be easily separated from the actual translational ground motion. ...
... Unfortunately, the determination and correction of the transient baseline shift is the most complex task, because it cannot be easily separated from the actual translational ground motion. Iwan et al. (1985) proposed two correction options to locate the start and end times, t 1 and t 2 , of the transient baseline offset, depending on whether the final displacement offset is known or not. Later, Boore (2001), proposed that t 1 was selected at the zero crossing of the postevent linear velocity correction. ...
... A historical problem in correcting an acceleration waveform is to remove the baseline distortion in the transient phase that appears in the integrated velocity. This baseline shift can be attributed to instrumental effects and ground rotation and tilt (Graizer, 1979;Iwan et al., 1985;Boore, 2001). Different methods have been suggested to correct this, and early works focused mainly in correcting only the velocity trend (Trifunac, 1971;Chiu, 1997), but more recent works seek to correct for the permanent ground deformation implicit in each waveform (Chao et al., 2010;Wang et al., 2011;Lin et al., 2018;Tian et al., 2019). ...
Since the 1985 M 8.0 central Chile earthquake, national strong-motion seismic networks have recorded ten megathrust earthquakes with magnitudes greater than M 7.5 at the convergent margin, defined by the contact between the Nazca and South American plates. The analysis of these earthquake records have led to improved hazard analyses and design codes for conventional and seismically protected structures. Although strong-motion baseline correction is required for a meaningful interpretation of these records, correction methods have not been applied consistently in time. The inconsistencies between correction methods have been neglected in the practical use of these records in practice. Consequently, this work aims to provide a new strong-motion database for researchers and engineers, which has been processed by traceable and consistent data processing techniques. The record database comes from three uncorrected strong motion Chilean databases. All the records are corrected using a four-step novel methodology, which detects the P-wave arrival and introduces a baseline correction based on the reversible-jump Markov chain Monte Carlo method. The resulting strong motion database has more than 2000 events from 1985 to the date, and it is available to download at the Simulation Based Earthquake Risk and Resilience of Interdependent Systems and Networks (SIBER-RISK) project website.
... In the study of ground motion during an earthquake, Iwan et al. 6 attributed the source of the baseline shift to hysteresis in the transducer that occurred when the acceleration exceeded approximately 50 cm/s 2 . Consequently, the baseline could be changed in a complicated manner during the strongest shaking interval, and the baseline offset after the strong shaking would likely differ from the baseline before shaking. ...
... The results of previous studies indicate that the digital recordings are often plagued by baseline offsets, which are small steps or distortions in the reference level of motion. [6][7][8][9] Boore et al. 10 extensively elaborated on these challenges when correcting the Chi-Chi and Hector Mine earthquake records. There may be numerous sources for the offsets (e.g., hysteresis in the sensor, static buildup in the analog-to-digital converter, or tilting of the ground), and for this reason, there is no universal correction scheme that can be automatically applied to the records. ...
... In the EW direction, the bracing system was designed with large bucking load (to prevent transverse motion during the test). In the F I G U R E 1 6 The schematic diagram of a twin-tower steel structure and its photo on shaking table F I G U R E 1 7 Fourier amplitude spectrum of relative acceleration between the second floor and the first floor NS direction, the bracing system was designed with smaller buckling load as compared to the EW direction (to simulate the weak location). The first floor of tower A was installed a week bracing member to create a soft first story phenomenon. ...
... (1) The ground rotates or tilts [4]; (2) The recorded data is mixed with low-frequency noise from environmental vibration or the vibration of the instrument itself; (3) The assumed initial value of velocity or displacement is inconsistent with the actual situation; (4) Data processing errors and transducer hysteresis [5]. ...
... (2) The displacement is corrected piecewise based on the corrected acceleration and velocity [5,[9][10][11]; (3) Eliminate drift error by eliminating velocity and displacement polynomial trend. ...
... The piecewise correction method based on corrected acceleration and velocity was first proposed by Iwan et al. [5], who assumed that the baseline drift of strong earthquake records was caused by the tiny mechanical vibration or electrical lag that occurred in the most intense part of the ground motion in the transducer system. The basic idea of Iwan's method was to divide the whole acceleration time history into three stages: before earthquake, strong earthquake, and postearthquake. ...
Measuring displacement response is essential in the field of structural health monitoring and seismic engineering. Numerical integration of the acceleration signal is a common measurement method of displacement data. However, due to the circumstances of ground tilt, low-frequency noise caused by instruments, hysteresis of the transducer, etc., it would generate a baseline drift phenomenon in acceleration integration, failing to obtain an actual displacement response. The improved traditional baseline correction methods still have some problems, such as high baseline correction error, poor adaptability, and narrow application scope. This paper proposes a deep neural network model based on empirical mode decomposition (EMD–DNN) to solve baseline correction by removing the drifting trend. The feature of multiple time sequences that EMD obtains is extracted via DNN, achieving the real displacement time history of prediction. In order to verify the effectiveness of the proposed method, two natural waves (EL centro wave, Taft wave) and one Artificial wave are selected to test in a shaking table test. Comparing the traditional methods such as the least squares method, EMD, and DNN method, EMD–DNN has the best baseline correction effect in terms of the evaluation indexes: Mean Absolute Error (MAE), Mean Square Error (MSE), Root Mean Square Error (RMSE), and degree of fit (R-Square).
... In the study of ground motion during an earthquake, Iwan et al. 6 attributed the source of the baseline shift to hysteresis in the transducer that occurred when the acceleration exceeded approximately 50 cm/s 2 . Consequently, the baseline could be changed in a complicated manner during the strongest shaking interval, and the baseline offset after the strong shaking would likely differ from the baseline before shaking. ...
... The results of previous studies indicate that the digital recordings are often plagued by baseline offsets, which are small steps or distortions in the reference level of motion. [6][7][8][9] Boore et al. 10 extensively elaborated on these challenges when correcting the Chi-Chi and Hector Mine earthquake records. There may be numerous sources for the offsets (e.g., hysteresis in the sensor, static buildup in the analog-to-digital converter, or tilting of the ground), and for this reason, there is no universal correction scheme that can be automatically applied to the records. ...
... In the EW direction, the bracing system was designed with large bucking load (to prevent transverse motion during the test). In the F I G U R E 1 6 The schematic diagram of a twin-tower steel structure and its photo on shaking table F I G U R E 1 7 Fourier amplitude spectrum of relative acceleration between the second floor and the first floor NS direction, the bracing system was designed with smaller buckling load as compared to the EW direction (to simulate the weak location). The first floor of tower A was installed a week bracing member to create a soft first story phenomenon. ...
Story and roof drift ratios play a key role in the assessment of the structural damage of a building if structural displacement can be measured or calculated. In general, for building seismic monitoring, accelerometers are used to compile the responses for analysis instead of using displacement meters because they are more cost effective. Therefore, an accurate estimate of the displacement response of a building using acceleration measurements will be helpful for the rapid assessment of the damage to its structure after an earthquake. In this study, the combination of an algorithm with singular spectrum analysis (SSA) and an integration scheme is proposed to estimate structural displacement directly from acceleration measurements. The SSA was conducted with varying sizes of the data trajectory matrix, using the approximation part as a weighting factor and the detailed part to integrate for the temporary displacement, to obtain a final weighted temporary displacement. The proposed algorithm was verified using the shaking table test data for four large-scale reinforced concrete frames. Through the proposed method, both the displacement waveform and the induced residual displacement after earthquake excitations can be estimated. The application of the proposed algorithm to building seismic response data is also discussed.
... Because permanent ground offsets are far less sensitive to the subsurface structure than transient motions are, and are more directly related to the final deformation at depth, they constitute a prime dataset for constraining the final fault-slip distributions (Segall, 2010). To date, however, near-field permanent offsets cannot be recovered straightforwardly through double integration of near-field accelerograms as these are often distorted by baseline shifts (e.g., Iwan et al., 1985;Boore, 2001;Wu and Wu, 2007;Melgar et al., 2013). A common cause for acceleration baseline shift is ground tilt, the effect of which is to shift the horizontal and vertical baselines according to Δg hor g sinθ and Δg ver g1 − cosθ; 1 with g being the reference gravitational acceleration, θ being the tilt angle, and the superscripts hor and ver standing for the horizontal and vertical components, respectively. ...
... In the following, commonly used approaches for correcting distorted SM data are described. Iwan et al. (1985) introduced a scheme for obtaining permanent offsets through double integration of SM accelerograms. According to this approach, corrections are applied to two consecutive intervals of the acceleration time series. ...
... As already noted by Boore (2001), the permanent offsets resulting from the application of the bilinear correction of Iwan et al. (1985) are sensitive to the choice of t 1 and t 2 , which may not be determined by visual inspection of the acceleration records or use of simple rule of thumb as suggested by Iwan et al. (1985). It is worth noting that Graizer (1979) introduced an optimization approach for minimizing the baseline shift following strong shaking in which the integrated acceleration is approximated using a set of polynomial functions. ...
Permanent ground offsets, constituting a prime dataset for constraining final fault-slip distributions , may not be recovered straightforwardly by double integration of near-field accelerograms due to tilt and other distorting effects. Clearly, if a way could be found to recover permanent ground offsets from acceleration records, then static datasets would be enlarged, and thus the resolution of fault-slip inversions would be enhanced. Here, we introduce a new approach for extracting permanent offsets from near-field strong-motion accelerograms. The main advantage of the new approach with respect to previous ones is that it corrects for source time functions of any level of complexity. Its main novelty is the addition of a constraint on the slope of the ground velocity spectra at long periods. We validated the new scheme using collocated accelerograms and Global Navigation Satellite Systems (GNSS) records of the 2011 M w 9 Tohoku-Oki earthquake. We find a good agreement between accelerogram-based and GNSS-based ground offsets over a range of 0.1-5 m. To improve the spatial coverage of permanent ground offsets associated with the 2004 Parkfield earthquake, near-field accelerograms were baseline corrected using the new scheme. Static slip inversion of the combined GNSS-based and accelerogram-based ground displacements indicates appreciable seismic moment release south of the epicen-ter, about 5 km into the Cholame section of the San Andreas fault. We conclude that the strong shaking observed to the south of the epicenter is directly related to the slip in that area and is not the result of local amplification. KEY POINTS • WA new technique for extracting permanent ground offset from near-field accelerograms is introduced.
... The acquisition of a large number of valuable strong motion records can provide reliable basic data for the study of focal mechanisms, ground motion prediction equations (GPMEs), site and active fault effects on ground motion, soilstructure interactions, and seismic response characteristics of typical structures [1][2][3]. Baseline drift often exists in strong-motion acceleration records [4][5][6][7]. [8] pointed out that small acceleration drift would result in huge numerical errors in the velocity and displacement obtained by integration. For example, when the acceleration drift of 0.01 gal is held for 60 s, the integral velocity will have an error of 0.6 cm/s, but the final displacement (also called permanent displacement or residual displacement in some references) will reach an error of 18 cm. ...
... The digital strong-motion seismograph developed in the 1970s has high precision, wide band, and pre-storage characteristics [15], and effectively overcomes the weaknesses of analog recorders. Since then, researchers have studied the digital strong-motion records of a series of major earthquakes, such as the Parkfield Earthquake, Chi-Chi Earthquake, and Wenchuan Earthquake [4,5,[16][17][18][19][20][21][22]. Displacements obtained by integrating the acceleration records of digital strong-motion seismographs are believed to contain long-term information. ...
... A polynomial formula was used to correct the baseline to determine the final displacement [16], which is one of the earliest influential developments in this field. To date, the most widely used method for baseline correction is that of [4]; which laid a foundation for the characteristics of baseline drifts. ...
... The baseline of each record was drifted during large shaking from ground tilting (Graizer 2005), instrument impact or seriously permanent displacement occurred. Iwan et al. (1985) mentioned that the processes of baseline drifting could divide into three parts, and the corrected method could base on the slope of these three lines in velocity records. Boore (2001) then tested and verified the difference corrected results from changing the length of the corrected lines. ...
... The given waveforms were decomposed into several modes by HHT method and try to find out the divided time and offset. Iwan et al. (1985) mentioned the baseline drifting models were associated with starting time of the strong shaking T1 and the end of shaking time T2. Wu and Wu (2007) then added another possible model, which was associated with another important time T3. ...
On May 12, 2008, there was an Ms 8.0 earthquake occurred in Wenchuan, China region. The earthquake inflicted severe damage in China, especially in the near-fault region. The mainshock was recorded by over four hundreds strong motion stations in whole China, and there were over sixty stations near Longmenshan fault. In this study, the method which was modified from Wu and Wu (2007) was used to correct the baseline of each strong motion record for near fault stations. After three-parts-correction and double integral, the co-seismic displacements were found from strong motion data only. The results were compared with that from GPS measurements. Finally, there were some near fault records showed the baselines can divided into more than three parts. So in this study, the appropriateness of applying Hilbert-Huang Transform (HHT) method to find each divided time points was also discussed.
... When coseismic displacements are calculated by using acceleration records, ideally, a stable and non-drifting permanent ground displacement can be obtained after the acceleration records are integrated twice, and the coseismic displacement can be identified from the displacement time history. But in practical applications, due to ground tilt [4,5] , instrument defects [6] , background noise [7] , and other reasons, the velocity and 2 displacement time history obtained by acceleration integration would show baseline shifts, which still remains an unchanged problem. It means that the acceleration and ground velocity are not zero and the displacement is not a constant after the earthquake. ...
... Trifunac (1971) proposed to use the method of least squares to fit acceleration and velocity time history [9] . Iwan et al. (1985) divided the baseline shift of acceleration time history into of the strong motion phase ( ) and after the strong motion phase ( ) [6] . In this case, how to determine the segmentation parameters and is the key to the method. ...
The Whitney (2018) linear baseline correction method is used to analyze the near-fault strong motion data of the 1999 Chi-Chi earthquake and quickly calculate the co-seismic displacement. The feasibility of this method is verified by comparison with the coseismic displacement data of adjacent GPS stations. The results show that the coseismic displacement of the hanging wall is significantly larger than that of the foot wall, and largest displacements reached 707.0cm north and 369.7cm up respectively, and occurred at the hanging wall station TCU052. The results in this paper can provide references for the rapid identification of coseismic displacements using strong motion data.
... Studies on how to recover permanent displacements from strong motion data and methods for baseline correction have been published since the 1970s, right after the development of the modern digital recordings [17]. Among the principal approaches based on piecewise correction of the signal baseline, noteworthy are Graizer [18], Iwan et al. [19], Boore [10], Graves [11], Wu and Wu [17], Chen and Loh [20], Chao et al. [21], Rupakhety et al. [22], Wang et al. [12] and D'Amico et al. [9]. A review of some of such studies with emphasis on their limitations can be found in [22]. ...
... A review of some of such studies with emphasis on their limitations can be found in [22]. Recently, Inbal and Ziv [13] proposed a novel methodology based on the bilinear correction approach of [19] and subsequently improved by [12,17]. However, the new scheme works in the frequency domain for the selection of time correction points, as opposed to the time domain. ...
We present an upgraded processing scheme (eBASCO, extended BASeline COrrection) to remove the baseline of strong-motion records by means of a piece-wise linear detrending of the velocity time history. Differently from standard processing schemes, eBASCO does not apply any filtering to remove the low-frequency content of the signal. This approach preserves both the long-period near-source ground-motion, featured by one-side pulse in the velocity trace, and the offset at the end of the displacement trace (fling-step). The software is suitable for a rapid identification of fling-containing waveforms within large strong-motion datasets. The ground displacement of about 600 three-component near-source waveforms has been recovered with the aim of (1) extensively testing the eBASCO capability to capture the long-period content of near-source records, and (2) compiling a qualified strong-motion flat-file useful to calibrate attenuation models for peak ground displacement (PGD), 5% damped displacement response spectra (DS), and permanent displacement amplitude (PD). The results provide a more accurate estimate of ground motions that can be adopted for different engineering purposes, such as performance-based seismic design of structures.
... 40,41 Figure 4 shows an example of the ground motion baseline correction using Iwan, Moser, and Peng's method. 39 Basically, this scheme applies a piecewise linear correction to compensate for the baseline shifts in the velocity time history. In particular, two portions are determined for correction, namely, the strong-shaking portion from t 1 to t 2 and the final portion from t 2 to t f . ...
... More details about the baseline correction can be found in the study by Iwan, Moser, and Peng. 39 In addition to the baseline correction, some signal processes are also required in the first step. For example, time scaling should be applied according to the similitude, and resampling may also be necessary to let the input ground motion be compatible with the shaking table system. ...
Extended engineering structures such as bridges, tunnels, and pipelines are vulnerable to surface fault ruptures, and thus large-scale tests using multi-shaking tables are necessary to investigate the structural performance in this special scenario. Because of the properties of the conventional displacement-controlled shaking table system with proportional-integral-derivative controllers, acceleration and displacement input strategies have respective drawbacks when used to reproduce across-fault ground motions. This study presents a new hybrid input strategy to reproduce across-fault ground motions on multi-shaking tables, which overcomes the limitations of traditional acceleration or displacement input. In particular, the new input strategy aims to match both low-frequency displacements and high-frequency accelerations. The proposed hybrid input strategy was validated by the previously performed shaking table tests of a steel-concrete composite rigid-frame bridge under the across-fault ground motions. For comparison, conventional acceleration and displacement input strategies were also used in the tests to excite the bridge model. Test results including the reproduced ground motions and the structural responses obtained by the three input strategies are presented and compared. The test results indicate that the proposed hybrid input strategy can reproduce across-fault ground motions with improved fidelity on conventional multi-shaking tables. This study can provide useful references for the shaking table tests of bridge, tunnel and pipeline structures with the consideration of crossing fault-rupture zones.
... It is well-known that the fling-step is removed from recorded motions in standard processing, which involves base-line correction and filtering (Boore and Bommer 2005;Yang et al., 2017). Based on the authors' experience, structural engineers are yet less familiar with the advanced processing techniques that can retain the actual fling (Iwan et al. 1985;Boore 2001). On the other hand, ground motions libraries (such as the PEER database) generally Content courtesy of Springer Nature, terms of use apply. ...
A reasonable estimate of residual deformation is crucial for assessing a structure’s post-earthquake performance, safety, and serviceability. Residual deformation may be significant, especially in near-fault regimes. Residual deformation is also influenced by the simultaneous action of two horizontal components of a motion that may incident at an arbitrary angle. However, conducting bidirectional analyses across admissible incidence angles is challenging and time-consuming. Against this background, changes in the (i) appropriate ground motion parameters over orientations and (ii) residual deformation of a bridge column over incidence angles under unidirectional and bidirectional shaking are collectively explored. Ground motions are selected and modeled to represent the effects of forward directivity and fling-step. It is shown that, for a given pair of ground motions, there exist two characteristic orientations namely, the most preferred orientation and the least preferred orientation. As the names suggest, the most preferred orientation corresponds to the smallest difference between the responses obtained from the unidirectional and the bidirectional analyses while the least preferred orientation corresponds to the largest difference between those two responses. The values of the residual deformation estimated per unidirectional analysis in the most preferred orientation can be further improved by using the 40% combination rule. Based on a more straightforward unidirectional analysis in a predefined orientation, the proposed strategy may prove helpful for practical purposes.
... Seismic networks also include strong-motion accelerometers that do not clip. However, for earthquake source parameter determination methods requiring surface displacement information, acceleration waveforms must be doubly integrated, often causing drifts in displacement as a result of "baseline" errors (Graizer, 1979;Iwan et al., 1985;Boore, 2001;Boore et al., 2002;Smyth & Wu, 2007;Melgar et al., 2013a). To improve local tsunami warnings, other real-time sensors may ...
We estimate a seismogeodetic earthquake moment magnitude using unclipped, broadband velocity and displacement waveforms from collocated Global Navigation Satellite Systems and seismic stations located within 800 km epicentral distance for nine 7.2 < Mw ${M}_{w}$ < 9.1 earthquakes. We consider the vertical component of seismogeodetic displacement as an approximate source time function and integrate the associated time series to obtain the seismic moment. By continuing to integrate vertical displacement beyond the initial P‐waves, we obtain rapid estimates of Mw ${M}_{w}$ that are within 0.2 magnitude units for 8 thrust faulting events and within 0.3 units for the single normal faulting event. Because our estimates of the seismic moment are based on the maximum value of integrated displacement, no regression against other source parameters, or distance, is necessary. Our new method shows promise for integration into earthquake and local tsunami early warning systems, including tsunami earthquakes characterized by relatively slow moment release over a longer rupture time, and earthquakes with complex source time functions.
... This permanent displacement, known as the fling step, 'inflict large irrecoverable deformations on structural and/or geotechnical systems' (Garini et al. 2015). Even though the raw ground motion data can be specially processed to retain fling (Iwan et al., 1985;Boore, 2001), standard processing such as the one adopted in the database of the Pacific Earthquake Engineering Research (PEER) Centre effectively removes fling (Boore and Bommer, 2005). Keeping the (i) complexities of the special processing techniques and (ii) sensitivity to the parameters involved in view, several studies have been made on the mathematical simulation and parameterization of fling (e.g., Makris and Chang, 2000;Mavroeidis and Papageorgiou, 2003;Kamai et al., 2014;Burks and Baker, 2016;Yadav and Gupta, 2017). ...
An essential signature of the near-fault motions is the fling-step, which contains a one-sided velocity pulse and ultimately results in permanent ground displacement. It is well-known that the standard processing of ground motion removes such fling. However, some researchers believe that dynamic action is hardly affected by such removal of permanent static displacement. So, such processed motions can be used to examine the effect of fling-step. In the current investigation, two mathematical analogues, rigid sliding and rigid rocking blocks are extensively studied under near-fault motions with fling-step. The response is computed using the processed motions (without explicit fling) and the processed motions with fling mathematically reintroduced. A comparison in response confirms that using motions without explicit fling is essentially deficient from a structural engineering perspective. The study has also noted the peculiarities in the dynamics of rocking oscillators, which may be of significance for assessing the consequences of the sequence of motions.
... Baseline correction is required to solve the problem of unphysical shifts in the velocity and displacement traces in groundmotion simulations, and the shifts may be caused by low-frequency noise, the small initial values for acceleration and velocity, simulated ground rotation and tilting, and so on. The baseline correction approaches for recorded digital and simulated accelerometers can be classified into two types: the filtering approach removing low-frequency errors (Trifunac, 1971;Chiu, 1997;Boore, 2005) and the empirical piecewise correction approach based on velocity seismogram (Iwan et al., 1985;Boore, 2001;Wang et al., 2011). The filtering approach is straightforward and quite simple to use. ...
This article introduces an enhanced software program for stochastic ground-motion simulations using finite-fault sources, named Ground-Motion Simulation System version 2.0 (GMSS2.0). GMSS2.0 embodies an updated theoretical model of corner frequency and source duration, making the seismological model for defining the Fourier amplitude spectrum for each subfault more theoretically consistent. In addition, GMSS2.0 provides four rupture scaling relationships and five baseline correction techniques for end users to select the most suitable one for a specific application. For validation purposes, comprehensive comparisons between GMSS2.0 and EXtended SIMulation (EXSIM) for wide ranges of magnitude (M 4–8), distance (∼6–300 km) and spectral period (0.01–10 s) have been performed. The results show that GMSS2.0 can give remarkably close estimates to EXSIM with reasonable levels of accuracy. Finally, further validation is performed by comparing GMSS2.0 simulations with five Next Generation Attenuation-West2 ground-motion models for multiple scenario earthquakes with the updated site amplification for the generic California condition (VS30=500 m/s).
... For the first approach, the main objective is to preserve the permanent ground static offset from actual records. Wu et al. [16] developed an improved baseline correction method by modifying the models proposed by Iwan [17] and Boore [18]. The improved method is applied to the Chichi and Chengkung earthquake data to compute the coseismic displacements, and the results show favorable agreement with GPS measurements. ...
Current studies lack probabilistic evaluations on the performance of fault-crossing bridges. This paper conducts seismic fragility analyses to evaluate the fragility of cable-stayed bridges with the effects of fault ruptures. Synthetic across-fault ground motions are generated using existing simulation methods for the low-frequency pulses and high-frequency residuals. Incremental dynamic analysis is utilized to generate the seismic responses of the bridge. The optimal intensity measure (IM) for a cable-stayed bridge that crosses a fault is identified based on the coefficient of determination (R2). Root-mean-square velocity (Vrms) is found to be the best IM for cable-stayed bridges traversed by fault ruptures, instead of the commonly used ones such as peak ground acceleration or velocity (PGA or PGV). Fragility curves for the critical components of fault-crossing cable-stayed bridges, including pylons, cables, and bearings, are developed using the IM of Vrms, and are subsequently compared with those for the cable-stayed bridge near faults. Results show that the bearings on transition piers are the most vulnerable component for fault-crossing cable-stayed bridges because of the rotation of their girder. Compared to cable-stayed bridges near faults, pylons and bearings are more vulnerable in the transverse direction for cable-stayed bridges crossing faults, whereas the vulnerability of cables is comparable.
... Now, since most of the collected accelerograms are raw, they are processed using the procedure proposed by Khansefid, Bakhshi, and Ansari (2019). This procedure contains three distinct steps, including wavelet denoising (Ansari et al. 2010), baseline adjustment (Iwan, Moser, and Peng 1985), and high-pass filtering (Boore and Bommer 2005). This approach is selected due to its superiority in removing the nonstationary noises in comparison with the traditional filtering method. ...
This research paper focuses on the development of ground motion models for simulating the main characteristics of recorded earthquake accelerograms induced by geothermal power plants (GPPs) operation. In this regard, firstly, a worldwide database for the GPP-induced earthquakes is gathered, containing 110 events and 664 recorded accelerograms. All the data are processed using a combined denoising method. Afterward, their main seismic characteristics are studied statistically, in both horizontal and vertical directions. Finally, different sets of ground motion models are developed for simulating the ground motion peak values, duration, 5% damped spectral acceleration and velocity in horizontal, and vertical directions.
... The fling-step effect went largely disregarded until the 1999 Chi-Chi and 1999 Izmit earthquakes, because the permanent displacement was typically excluded from ground motion records due to baseline correction and filtering processing [6]. A number of studies have proposed an appropriate baseline correction for fling-step ground motion records [6][7][8]. ...
PurposeThis study aimed at investigating the non-linear seismic performances of steel Moment-Resisting Frames (MRFs) exposed to the simulated near-fault pulse-type fling-step ground motion records. Since serious damages to the near-fault bridges and buildings as well as loss of lives have been occurred due to strong earthquakes, evaluating the analytical modeling and characteristics of near-fault seismic ground motions seems necessary.Methods
Thus, a random vibration-based combination model was proposed to simulate the records of near-fault pulse-type fling-step ground motions. In this model, it was assumed that the record of each pulse type is a combination of pulse and non-pulse components. For structural modeling, three 3-, 9-, 20-story steel frames were simulated in OpenSees; and through employing the non-linear time-history analysis, the structural response was obtained.ResultsThe comparison between the seismic performances of steel MRFs exposed to the motion of the ground with and without the fling-step pulse showed that the near-fault earthquake generated a high seismic demand, so that a difference of about 50% in story drift and 30% in maximum roof displacement was observed.Conclusion
The seismic demand of steel MRFs in pulse-type earthquake records was greater than the ones in the non-pulse records. Also, in near-fault pulse-type earthquake records, tall buildings, and complex structures with long periods will endure greater forces and deformations due to the effect of pulse and high-velocity response spectrum in long periods.
... Now, for the collected accelerograms, since most of them are raw, they are processed using the procedure proposed by Khansefid et al. (2019a). This procedure contains three distinct steps, including wavelet denoising (Ansari, et al 2010), baseline adjustment (Iwan et al. 1985), and highpass filtering (Boore and Bommer 2005). This approach is selected due to its superiority in removing the nonstationary noises in comparison with the traditional filtering method. ...
Due to a lack of available energy resources, the development of geothermal power plants (GPPs) as a renewable and green energy source has risen globally, notably in Germany, in recent decades. However, several aspects of this new technology are still unclear and need further investigation to be understood. This study focused on one of the important side effects of geothermal power plant activities. According to available reports, the operation of GPPs in various sites throughout the world coincided with low-to-moderate earthquakes. The population of the surrounding region may experience disruptions in their everyday lives as a result of these earthquakes. Even in the past, these earthquakes caused the entire plant to be shut down due to the induced damage to the neighboring buildings and their people. The primary goal of this study is to evaluate the seismic risk imposed on masonry buildings, as a vulnerable type of building, due to the GPP operation. In this regard, the earthquake phenomenon itself is studied statistically in the first phase to generate a model capable of probabilistically simulating the key characteristics of the induced earthquakes by the GPP operation. In the next step, the ground motions recorded as a result of GPP operations in various regions of the world are analyzed statistically. This analysis serves as the basis for the development of probabilistic ground motion prediction equations for simulating the main intensity measurements of GPP-induced ground motions. Following the development of these seismic hazard simulation models, a typical masonry structure in Germany, is considered. A macro-scale 3-dimensional finite element analysis approach is used to analyze the nonlinear behavior of masonry walls. Then, the performance of this building is evaluated under a set of selected real ground motions induced by GPPs activity from two perspectives: structural damage and occupant comfort. In the last section, an attempt is made to evaluate the seismic risk and losses of the considered building due to various GPP-induced earthquake hazard scenarios. Besides developing some models for GPP-induced earthquake hazard scenarios and proposing fragility curves for structural damage and occupant discomfort of masonry buildings, the main result of this research work can be summarized in this sentence: earthquakes induced by GPP activities, especially located near the buildings , may disrupt the daily lives of the selected masonry building occupants; however, major structural damage is not expected.
... Baseline correction is required to solve the problem of unphysical shifts in the velocity and displacement traces in groundmotion simulations, and the shifts may be caused by low-frequency noise, the small initial values for acceleration and velocity, simulated ground rotation and tilting, and so on. The baseline correction approaches for recorded digital and simulated accelerometers can be classified into two types: the filtering approach removing low-frequency errors (Trifunac, 1971;Chiu, 1997;Boore, 2005) and the empirical piecewise correction approach based on velocity seismogram (Iwan et al., 1985;Boore, 2001;Wang et al., 2011). The filtering approach is straightforward and quite simple to use. ...
Cite this article as Tang, Y. (2022). GMSS2.0: An Enhanced Software Program for Stochastic Finite-Fault Ground-Motion Simulation, Seismol. Res. Lett. XX, 1-12, doi: 10.1785/ 0220210228. This article introduces an enhanced software program for stochastic ground-motion simulations using finite-fault sources, named Ground-Motion Simulation System version 2.0 (GMSS2.0). GMSS2.0 embodies an updated theoretical model of corner frequency and source duration, making the seismological model for defining the Fourier amplitude spectrum for each subfault more theoretically consistent. In addition, GMSS2.0 provides four rupture scaling relationships and five baseline correction techniques for end users to select the most suitable one for a specific application. For validation purposes, comprehensive comparisons between GMSS2.0 and EXtended SIMulation (EXSIM) for wide ranges of magnitude (M 4-8), distance (∼ 6-300 km) and spectral period (0.01-10 s) have been performed. The results show that GMSS2.0 can give remarkably close estimates to EXSIM with reasonable levels of accuracy. Finally, further validation is performed by comparing GMSS2.0 simulations with five Next Generation Attenuation-West2 ground-motion models for multiple scenario earthquakes with the updated site amplification for the generic California condition (V S30 500 m= s).
... For these ground motion records, the most widely accepted baseline correction approaches are based on baseline adjustments. Graizer et al. [3] proposed that the baseline offset can be fitted by a polynomial, and then, according to the hysteresis of a specific instrument, Iwan et al. [4] tried to divide the velocity time history into three segments by a fixed threshold (a>50cm/s2) and fitted two shifts by polynomial respectively. Boore [5] simplified and generalized Iwan et al.'s work, and an improvement that considered the displacement history in the selection of critical time points was also proposed by Wu and Wu [6]. ...
A new automatic baseline correction method based on the Hilbert spectral analysis (HSA) is proposed to recover a relatively reasonable time history of baseline offset, permanent displacement, and stable peak ground motion displacement (PGD) from a raw near-fault ground motion record. This method can get rid of the selection of the start time of strong motion (corresponding to t1 in traditional methods) by an adaptive extraction procedure, then a stable PGD as well as an accurate permanent displacement can be obtained. For baseline offsets, there is no two-stage-segment assumption in this procedure, and the extracted time histories of these offsets include complex frequency changes, which is more consistent with the explanations of causes for baseline offsets. All causes of baseline offsets are treated as contaminants that exist in all frequency ranges in a record. Uncontaminated components can be extracted from the original record by the HSA, then information about strong motions can be retained as much as possible. The residual part is regarded as a heavily contaminated component of which the energy of the noise rivals that of the real ground motion. It is corrected based on only one time point. Finally, the corrected record is contributed by both of the uncontaminated and adjusted contaminated components. The HSA method, which depends on the energy distribution of original record in different frequency component, can obtain the baseline offset, PGD, and permanent displacement reasonably, stably, and automatically.
... The t 1 and t 2 are free parameters, and the choices of t 1 and t 2 might lead to different final correction results. We test different t 1 values around the starting of strong ground shaking when the acceleration component exceeds 50 cm=s 2 (Iwan et al., 1985;Boore, 2001). For the acceleration of three components, the starting time points for strong ground shaking are between 20 and 21 s. ...
Inferring Critical Slip-Weakening Distance from Near-Fault To better assess potential earthquake hazards requires a better understanding of fault friction and rupture dynamics. Critical slip-weakening distance (D c) as one of the key friction parameters, however, is hard to determine on natural faults. For strike-slip earthquakes, we may directly estimate the D c from D 00 c-the double near-fault ground displacement at the time of the peak velocity (Fukuyama and Mikumo, 2007). Yet near-fault observations are very few, and, thus, there were only limited earthquakes with such D 00 c estimation. In 2014, an M w 6.2 strike-slip event-the Ludian earthquake-occurred in southwest China. The strong-motion station (LLT) that is ∼ 0:45 km from the fault recorded the earthquake and enabled us to estimate D 00 c from the accelero-grams. We inspect the polarity of the accelerometers and compare the integrated velocities with waveforms of nearby broadband stations. We also analyze the particle motion at the LLT station and retrieve the earthquake initiation at the intersection of the conjugated faults. We then apply the baseline correction to the seismograms, recover the ground velocities and displacements, and obtain the value of D 00 c 0:1 m at the station. The recovered final displacements are compared with the predicted ground displacements of a finite-fault model. The discrepancy of fault-parallel displacements might imply limited underestimation of D 00 c , and the estimated upper limit is 0.3 m. Comparison between the D 00 c and final slip on the fault patch follows the scaling of previous larger earthquakes. Analysis of the near-fault accelerometer data enhances our understanding on the earthquake source of the Ludian earthquake. This case extends the lower magnitude boundary of the D 00 c values obtained from natural faults and opens a window into the friction property in the seismically active region.
... For K-NET stations with soil profile depth less than 30 m, we use a V SZ -to-V S30 extrapolation model for Japan (Boore et al., 2011) to calculate V S30 , in which V SZ is the average shear-wave velocity of soil layers from surface to depth Z. Source-to-site distances for each station are calculated using the earthquake source geometry (Fig. 1) provided by Yagi et al. (2016). To avoid missing displacement information after high-pass filtering and recover reliable permanent displacements, we process the records using a modified version of the multi-consecutive-segment baseline correction method (e.g., Boore, 2001;Akkar and Boore, 2009), initially proposed by Iwan et al. (1985). ...
We focus here on the rupture directivity effect on the spatial distribution and attenuation characteristics of near-field ground motions during the 2008 MW7.9 Wenchuan earthquake. We examine the difference between the observed ground motions in and opposite the rupture directions and compare them with Next Generation Attenuation-West2 (NGA-West2) ground motion prediction models. The isochrone directivity predictor is used to quantify the band-limited nature of the rupture directivity effect on strong ground motion. Our results show that the observed peak ground velocity (PGV) and spectral accelerations of periods of 1.0 s and longer are significantly amplified in the rupture direction, but de-amplified in the opposite direction affected by rupture directivity effect of this event. In contrast, the effect of rupture directivity on the observed peak ground acceleration (PGA) and periods of shorter than 1.0 s are relatively weak. The rupture directivity of this event shows clear period dependent and band limited characteristics with the strongest effect occurring around the period of 7.5 s.
... This kind of baseline cannot be well fit by the polynomial fitting as shown in Fig. 13(b). In effect, numerous studies have focused on this issue and proposed some effective ways to solve this problem (Iwan, et al. 1985); Boore (2001); Wang et al. (2011)). In this study, we would choose the method proposed by Wang et al. (2011) since it is more convenient and reliable to derive the parameters of t 1 and t 2 . ...
The dependence of displacement on the low-cut frequency suggests that the low-frequency noise is responsible for the drift. Although the cause of the noise is unknown, at least one case is certain that the low-cut frequency should ensure the displacement drift within a reasonable range. To obtain the low-cut frequency, this paper proposes an adaptive method to quantify the threshold for newly-proposed parameters regarding the displacement. Low-cut frequencies determined by this study and those derived using traditional methods are compared. Their divergence on the inelastic spectra is studied by wavelet package decomposition which verifies the validity of the low-cut frequency.
... In the literature (e.g., Iwan et al., 1985;Zahradnik & Plesinger, 2005;Vacka et al., 2015) the phenomenon we are investigating here is sometimes referred to as "long-period disturbances", "acceleration offsets", or even "mice", all generally describing the same type of data disturbance. Throughout the present publication, however, we choose to apply the term "glitch" to these disturbances as it has been established as such since their first observations in InSight's seismic data and hence been communicated so to a wider audience on various occasions. ...
OFFICIAL SOFTWARE:
https://pss-gitlab.math.univ-paris-diderot.fr/data-processing-wg/seisglitch
The instrument package SEIS (Seismic Experiment for Internal Structure) with the three very broadband and three short‐period seismic sensors is installed on the surface on Mars as part of NASA's InSight Discovery mission. When compared to terrestrial installations, SEIS is deployed in a very harsh wind and temperature environment that leads to inevitable degradation of the quality of the recorded data. One ubiquitous artifact in the raw data is an abundance of transient one‐sided pulses often accompanied by high‐frequency spikes. These pulses, which we term “glitches”, can be modeled as the response of the instrument to a step in acceleration, while the spikes can be modeled as the response to a simultaneous step in displacement. We attribute the glitches primarily to SEIS‐internal stress relaxations caused by the large temperature variations to which the instrument is exposed during a Martian day. Only a small fraction of glitches correspond to a motion of the SEIS package as a whole caused by minuscule tilts of either the instrument or the ground. In this study, we focus on the analysis of the glitch+spike phenomenon and present how these signals can be automatically detected and removed from SEIS's raw data. As glitches affect many standard seismological analysis methods such as receiver functions, spectral decomposition and source inversions, we anticipate that studies of the Martian seismicity as well as studies of Mars' internal structure should benefit from deglitched seismic data.
... The station locates on the soft sedimentary rock, where the measured time-averaged shear-wave velocity in the top 30 m (Vs30) is 422 m/s [30]. Unprocessed 3-component acceleration time series were downloaded from Center for Engineering Strong Motion Data (CESMD) [31], then processed to remove baseline errors using the methodology [32][33][34]. The timing of fling steps was estimated by following the approaches [34][35] with reference to the high sampling rate GPS observation at nearby stations [36]. ...
Natural gas pipelines are subject to a complex set of natural and manmade threats. Earthquakes can generate forces and permanent ground displacements that threaten the integrity of the California gas infrastructure. Earthquakes and landslides have the potential to simultaneously compromise pipelines over a broad region, leading to fires and widespread disruption of gas supply. Current understanding of seismic threats to gas pipelines rely upon models that are too simplistic using limited empirical data resulting in significant uncertainties in predictions. In this study, we will conduct high-fidelity nonlinear soil-structure interaction (SSI) analyses using geohazard characteristics (e.g., displacement magnitude, direction of displacement) and pipeline characteristics (e.g., pipe diameter, thickness), to create models that can predict the seismic response of gas transmission pipelines to the full range of seismic hazards, including ground motion, fault displacement, landslide and liquefaction. This effort is part of a larger project that will examine seismic demands on natural gas infrastructure. The study explores the development of a seismic performance assessment methodology that will complement a broader effort on devising a regional probabilistic seismic risk assessment framework for gas infrastructure in California.
... A typical procedure is to remove the error-prone low frequencies with a highpass filter, though this also discards any information about the static offset and usually the largest displacement. Alternatively, baseline correction schemes have been proposed (Boore and Bommer, 2005;Iwan et al., 1985;Wang et al., 2013Wang et al., , 2011. In these schemes, the objective is to find and remove the erroneous drift of the integrated acceleration record and by that, recover the true displacement. ...
The 2016 Mw 7.0 Kumamoto earthquake resulted in exceptional datasets of Global Navigation Satellite Systems (GNSS) and seismic data. We explore the spatial similarity of the signals and investigate procedures for combining collocated sensor data. GNSS enables the direct observation of the long-period ground displacements, limited by noise levels in regimes of millimeters to several centimeters. Strong-motion accelerometers are inertial sensors and therefore optimally resolve middle- to high-frequency strong ground motion. The double integration from acceleration to displacement amplifies long-period errors introduced by tilt, rotation, noise, and nonlinear instrument responses and can lead to large nonphysical drifts. For the case study of the Kumamoto earthquake, 39 GNSS stations (1 samples/s) with nearby located strong-motion accelerometers (100 samples/s) are investigated. The GNSS waveforms obtained by precise point positioning under real-time conditions prove to be very similar to the postprocessed result. Real-time GNSS and nearby located accelerometers show consistent observations for periods between ∼3–5 and ∼50–100 s. The matching frequency range is defined by the long-period noise of the accelerometer and the low signal-to-noise ratio (SNR) of GNSS, when it comes to small displacements close to its noise level. Current procedures in fusing the data with a Kalman filter are verified for the dataset of this event. Combined data result in a very broadband waveform that covers the optimal frequency range of each sensor. We explore how to integrate fused processing in a real-time network, including event detection and magnitude estimation. Carrying out a statistical test on the GNSS records allows us to identify seismic events and sort out stations with a low SNR, which would otherwise impair the quality of downstream products. The results of this study reinforce the emerging consensus that there is real benefit to collocation GNSS and strong-motion sensors for the monitoring of moderate-to-large earthquakes.
... All of the accelerograms existed in the database, and the ones added to it are denoised applying the procedure suggested by Khansefid et al. [17]. Accordingly, a combination of wavelet-based denoising [25,26], baseline adjustment [27], and the band-pass Acasual filtering [28] are applied. The main advantage of this combined procedure, in comparison with the traditional filtering method, is that the non-stationary noises are also eliminated through the whole time series, and frequencies which are inside the lower-and upper-bound corner frequencies of the band-pass filter can be omitted too. ...
This research attempts to study the pulse-like ground motions, recorded on the Iranian plateau, and propose predictive equations for simulating the main features of this type of signal. In this regard, firstly, the statistical characteristics of pulse-like records of the Iranian database, containing 770 events and 1206 accelerograms, are statistically investigated. The probability density function of facing a pulse-like signal, for a given location, is obtained, and the main features of acceleration and velocity spectra of these signals are evaluated for the horizontal and vertical directions. Interestingly, the mean value of vertical to horizontal ratio of spectral acceleration of signals reaches above one in many cases. In the next part, a set of ground motion prediction equations are presented for simulating the major properties of velocity pulse itself, including the amplitude, period, and the occurrence time during the recorded time series. Besides to these equations, another set of GMPEs is proposed for generating the 5% damped spectral acceleration of the horizontal and vertical pulse-like ground motions simultaneously considering their component's correlation. These newly developed equations are compared and validated with the existing GMPEs of the Iranian plateau. All of the suggested equations are applicable for the magnitude between 4.0 and 6.5, the site-to-source distance of 2 km–100 km, the focal depth of 2–40 km, and the shear wave velocity of underlying soil varying between 200 m/s to 900 m/s.
... Using the extensive data compiled for the 1964 Niigata and 1983 Nihonkai-Chubu earthquakes in Japan (Hamada et al. 1986), Bartlett and Youd (1995) identified two general types of lateral deformations: (i) lateral spread in a level ground towards a free face or near quay wall, sheet pile wall or yielding retaining structure and (ii) lateral spread down a mild ground inclination where a free face is absent. In addition to the above two types of lateral spreads, permanent co-seismic lateral displacement has been documented from records of near-fault ground motion (Elnashai et al. 2010;Hall et al. 1995;Iwan et al. 1984Iwan et al. , 1985Vigny et al. 2011). ...
Due to seismic response, accumulation of permanent ground deformation (lateral spreading) is an important mechanism of much practical significance. Such deformations typically occur near a ground slope, behind retaining structures such as sheet-pile and quay walls, and in mildly-sloping ground. In conducting a shake table test, the generation of permanent deformations further elucidates the underlying mechanisms and allows for related ground-foundation-structure response insights. In this paper, an approach for development of accumulated ground deformations is presented, in which asymmetric inertial loading results in a biased dynamic one-dimensional shear state of stress. As such, the proposed approach allows for further insights into the soil cyclic response and pore pressure build-up, with deformations accumulating in a preferred direction. In order to permit a virtually unlimited number of such loading cycles, focus is placed on motions that do not cause the shake-table actuator to accumulate displacement, in view of its possible limited stroke. Using this approach, representative experimental response is outlined and discussed. This experimental response can be used for calibration of numerical models to emulate the observed permanent strain accumulation profile and associated mechanisms. In addition to liquefaction-induced lateral spreading, this asymmetric shaking approach might be beneficial for a wide class of earthquake engineering shake table testing applications.
This paper proposes a time-domain baseline correction method of the acceleration time history based on the target residual displacement and convex optimization. The objective of the method is to reproduce accurately the displacement time history from the baseline corrected acceleration time history records. Compared with traditional time-domain methods, the proposed method can automatically determine the number of occurrence, the time of occurrence, and the amplitude of the baseline drifts, without manual intervention. Six acceleration time history records, including three ground-motions and three floor responses, were selected for numerical simulation. The simulation results suggest that the differences of the peak displacements between the reproduced displacement time history and the original time history are within 5%, and the Pearson Correlation Coefficients are more than 95%. The reproduction effect for floor responses is better than that of ground-motions owing to the characteristic of oscillation in the attenuation section. The form of the objective function and the influence of key parameters are discussed. Feasibility of this method was also verified by shaking table tests.
The general objective of this thesis is to conduct a thorough source study covering different aspects of earthquake characterization. First, I focused on the initiation phase of earthquakes. Specifically, I analyzed the initiation phase of the 2017 Valparaiso earthquake (magnitude Mw=6.9). This earth-quake is an interesting case study because it was preceded by a transient displacement accompanied by many pre-shock earthquakes. We show that this earthquake was probably preceded by an asismic slip on the fault. In a second part of my thesis, I am interested in the detailed characterization of the co-seismic slip distribution associated with large earthquakes. In particular, I examine the 2014 Illa-pel earthquake (Mw=8.3). The kinematic characterization of the source of this earthquake is there-fore performed via a Bayesian sampling approach, which has proven useful in characterizing the a posteriori uncertainty. Our kinematic models indicate a high complexity in the rupture process, asso-ciated with "encircling asperities" that have been previously suggested by previous studies.
Depremleri izlemede kullanılan hız algılayıcılarının dinamik aralıkları (en büyük genliğin en düşük genliğe oranı) 165 dB civarında olmasına rağmen, bazen deprem dalgalarının meydana getirdiği yer hareketi hızı güçlü olduklarında, bu cihazların verisi doyuma giderek kırpılacağından, bu veriler kullanılamaz hale gelirler. Depremleri izleyen en önemli kurulumların başında Boğaziçi Üniversitesi Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü (KRDAE) ve Afet ve Acil Durum Yönetimi Başkanlığı (AFAD) gelmektedir. Bu kurumlar; genişband sismik algılayıcı kullanmaktadır. Van ilinde, 23.10.2011 tarihindeki depremden sonra bu kurumlardaki sismik algılayıcıların kaydettiği sinyallerinin çoğunun doyuma ulaşması sonucu, sinyalin üstten ve/veya alttan kırpılmasıyla depremin büyüklüğü ve yerinin belirlenmesi konusunda sıkıntılar yaşanmıştır. Ülkemizde, yanlış bir şekilde yerleşmiş olan genişband sismik algılayıcılar doyuma ulaşmazlar inanışını değiştirmek amacı ile bu makalede genişband sismik algılayıcıların nasıl doyuma ulaştıkları hakkında bilgi verilecektir.
The cables of the long-span bridge are usually featured as ultra-low frequency, hence making the acceleration unable to accurately capture the information, e.g. damping ratios, for assessing the cable state assessment and mitigating the excessive structural vibration. The displacement was approved to be more sensitive to the low-frequency vibration than the acceleration. However, there is still a lack of effective method to accurately monitor the long-term displacements of bridge cables using reference-free methods. To address this issue, this paper develops a novel acceleration-based approach for monitoring the long-term displacements of the cables of long-span bridges. In the monitoring scheme, recursive least squares method is utilized to conduct baseline correction in the time domain integration of acceleration. An adaptive band-pass filtering method considering cable vibration characteristics is used to eliminate noise, thus avoiding the difficulty of selecting the cut-off frequency by experience in traditional methods. A numerical test of an analytical cable model and a field experiment of the hanger of a full-scale suspension bridge are applied to the applicability and robustness of the developed method. Result shows that adaptive band-pass filter considering the vibration characteristics is suitable for estimating the displacements of the cables. The estimated displacements using the developed method agree well with the background truth in both time and frequency domains.
In this study, a method for detecting the step and pulse components as well as estimating the displacement waveform based on seismic ground motion records was developed. These components represent the residual displacement and pulse-like ground motion in the near-fault region. In addition, the displacement waveforms were synthesized by combining the observed Fourier spectrum and obtained model spectrum instead of using a low-cut filter. Applying the proposed method to strong ground motion records during the mainshock of the 2016 Kumamoto earthquake, the displacement waveforms containing the step and pulse components were appropriately estimated.
Because output accelerographs always contain noise, to use data in analysis and design of structures, there is a need for rational correction of raw data. These corrections include baseline correction, instrument correction, and filtration practices. In this paper, a 1-story
steel moment frame and 3-story steel moment frame as benchmark have been used to study the effect of causal and acausal filtration. Accelerogram records have been used from five stations in successive earthquakes of Ahar-Varzaghan on August 11, 2012, and six stations that recorded the Sarpole-Zahab earthquake on November 12, 2017, for incremental dynamic analysis (IDA). The results show that the behavior of the representative structures by process of correction with causal and acausal filters in the elastic region, are roughly similar. Also the IDA summary curves show that the structures is subjected to higher intensity in acausal filters than in causal ones, so causal filtration in nonlinear analysis of low-rise structures seems to have more conservative responses in comparison with acausal one, not more than 15%.
The Iranian strong motions are recorded in the last 42 years in the national strong motion network of Iran. There are actually more than 11,800 of 3 component accelerograms recorded in this network. In this study, we employ the strong motion records, which are recorded by Iran Strong Motion Network (ISMN), established by the Building and Housing Research Center (BHRC) of Iran. In the last years (2004-2014) there are important earthquakes recorded in this network (among which the greatest Iranian earthquake in the last 50 years, which was the 16 April 2013 M w 7.8 Saravan, Makran SE Iran earthquake; occurred in the subduction zone of Makran). More than 6200 three component accelerograms have been recorded in this 11 years period of time, of which 100 records having greater peak acceleration have been processed with a more focus in this study. In this respect, the data selected are processed in order to achieve the most important strong motion parameters in aspect of engineering seismology and carrying out a preliminary analysis of the available data.
Due in large part to the advent of GPS, geodesy has become an important discipline within the Earth sciences. It is practiced and taught at a growing number of universities and research institutions worldwide, and provides the underpinnings for geographical information and locational awareness in modern life and commerce. The main advantage of GPS geodesy is the ability to directly measure very precise static, kinematic‚ and dynamic positions and displacements with respect to a global reference frame. GPS geodesy attracted the attention of geophysicists in the early 1980s when the potential for significant advances in the understanding of tectonic motion, crustal deformation‚ and geodynamics became apparent. Since then – something that was certainly not anticipated by the pioneers of the GPS in the 1970s – it has been applied to investigations of natural and anthropogenic processes and hazards, including earthquakes, tsunamis, volcanoes, the cryosphere, extreme weather, sea level rise, climate change‚ and hydrology. Contributing to its success have been advances in technology and the development of a global GPS infrastructure consisting of thousands of continuous stations spanning nearly all of the tectonic plate boundaries and hundreds of global stations to provide precise orbits and access to a global reference frame. GPS as a measuring tool is complementary to other terrestrial, ocean, atmospheric‚ and spaceborne instrumentation including seismometers, synthetic aperture radars, GPS/acoustic methods, gravimeters, radiometers, and UAV and LiDAR imaging. This chapter provides a historical perspective of GPS geodesy through to its current practice.
After destructive earthquakes, it is a challenge to estimate magnitude rapidly and accurately for dissemination to emergency responders and the public. Here, we propose criteria to calculate peak ground displacement (PGD) from strong-motion records, which can be used to calculate unsaturated event magnitude. Using collocated strong-motion and Global Navigation Satellite Systems observations of five major earthquakes in Japan, we demonstrate the effectiveness and accuracy of our strategy. Our results show that, with the right filtering criteria, PGD estimated from strong-motion acceleration waveforms is consistent with geodetic estimates. The methodology, however, does not allow for calculation of reliable estimates of coseismic deformation or other ground displacement metrics. We demonstrate a simulated real-time magnitude estimation that suggests it is feasible to generate an unsaturated magnitude estimate in real time from near-field strong-motion records. These findings have important implications for early warning and emergency response in seismically active areas, especially where real-time strong-motion data are more widely available than geodetic measurements.
A method to detect the step and pulse components and estimate the displacement waveform based on the seismic ground motion record was developed. These components represent the residual displacement and the pulse-like ground motion in the near-fault region. In addition, the displacement waveforms were synthesized by combining the observed Fourier spectrum and the obtained model spectrum, instead of using the low-cut filter. Applying the method to the strong motion records during the main shock of the 2016 Kumamoto earthquake, the displacement waveforms containing the step and pulse components were estimated appropriately.
In traditional tight integration of high-rate GNSS and strong motion sensors, an appropriate process variance is crucial for obtaining accurate broad-band coseismic deformations. In this paper, instead of using a subjectively empirical value, we present an approach for determining the process variance adaptively based on the adaptive Kalman filter for real-time use. The performance of the approach was validated by the colocated stations collected during the 2010 Mw 7.2 earthquake in El-Mayor, 2016 Mw 7.8 earthquake in New Zealand and 2016 Mw 6.5 earthquake in central Italy. The results show that this method complements the advantages of GNSS and strong motion accelerometers and can provide more accurate coseismic waveforms especially during the strong shaking period, due to the ability of the method to adjust the process variance in real time according to the actual status of the station. In addition, this method is also free from the influence of the baseline shift. Testing of the new method for the integration of strong motion and multi-GNSS indicates that multi-GNSS has an obvious improvement in the precision while single GPS has a poor observation condition.
Offshore real‐time ocean bottom networks of seismometers and ocean bottom pressure (OBP) gauges have been recently established such as DONET and S‐net around the Japanese islands. One of their purposes is to practice rapid and accurate tsunami forecasting. Near‐fault OBP records, however, are always contaminated by nontsunami components such as sea‐bottom acceleration change until an earthquake stops its fault or sea‐floor motions. This study proposes a new method to separate tsunami and ocean bottom displacement components from coseismic OBP records in a real‐time basis. Associated with the Off‐Mie earthquake of 2016 April 1, we first compared OBP data with acceleration, velocity, and displacement seismograms recorded by seismometers at common ocean bottom sites in both time and frequency domains. Based on this comparison, we adopted a band‐pass filter of 0.05–0.15 Hz to remove ocean‐bottom acceleration components from the OBP data. Resulting OBP waveforms agree well with the tsunami components estimated by a 100‐s low‐pass filter with records of several hundred seconds in length. Our method requires only an early portion of a given OBP record after 30 s of an origin time in order to estimate its tsunami component accurately. Our method enhances early tsunami detections with near‐fault OBP data; that is, it will make a tsunami forecasting system faster and more reliable than the previous detection schemes that require data away from source regions or after coseismic motions are over.
Permanent ground offsets, constituting a prime dataset for constraining final fault-slip distributions, may not be recovered straightforwardly by double integration of near-field accelerograms due to tilt and other distorting effects. Clearly, if a way could be found to recover permanent ground offsets from acceleration records, then static datasets would be enlarged, and thus the resolution of fault-slip inversions would be enhanced. Here, we introduce a new approach for extracting permanent offsets from near-field strong-motion accelerograms. The main advantage of the new approach with respect to previous ones is that it corrects for source time functions of any level of complexity. Its main novelty is the addition of a constraint on the slope of the ground velocity spectra at long periods. We validated the new scheme using collocated accelerograms and Global Navigation Satellite Systems (GNSS) records of the 2011 Mw 9 Tohoku-Oki earthquake. We find a good agreement between accelerogram-based and GNSS-based ground offsets over a range of 0.1–5 m. To improve the spatial coverage of permanent ground offsets associated with the 2004 Parkfield earthquake, near-field accelerograms were baseline corrected using the new scheme. Static slip inversion of the combined GNSS-based and accelerogram-based ground displacements indicates appreciable seismic moment release south of the epicenter, about 5 km into the Cholame section of the San Andreas fault. We conclude that the strong shaking observed to the south of the epicenter is directly related to the slip in that area and is not the result of local amplification.
This article presents a simple and effective method for generating across‐fault seismic ground motions for the analysis of ordinary and seismically isolated bridges crossing strike‐slip faults. Based on pulse models available in the literature, two simple loading functions are first proposed to represent the coherent (long‐period) components of ground motion across strike‐slip faults. The loading functions are then calibrated using actual near‐fault ground‐motion records with a forward‐directivity velocity pulse in the fault‐normal direction and a fling‐step displacement in the fault‐parallel direction. The effectiveness of the proposed method is demonstrated by comparing time history responses and seismic demands of ordinary and seismically isolated bridges obtained from nonlinear response history analyses using the actual ground‐motion records and the calibrated loading functions. A comprehensive methodology is also presented for selecting the input parameters of the loading functions based on empirical equations and practical guidelines. Finally, an analysis procedure for bridge structures crossing strike‐slip faults is introduced based on the proposed method for generating across‐fault ground motions and the parameter selection methodology for the loading functions.
Filtering is one of the critical steps of earthquake ground motion processing before its application to engineering practice, and high-pass filtering is particularly important due to rich contents of low frequency in ground motion signals. In particular, the impulsive properties of the ground motion recorded in near-fault zones are susceptible to the high-pass filtering, and thus selecting a reasonable filtering method becomes a critical issue that determines the reliability of the structural analysis results. This study investigates how the high-pass filtering of pulse-like ground motions affect the subsequent responses of long-period base-isolated building. A set of near-fault ground motions were selected and classified into short-to-mid and mid-to-long period groups, with 2 s being the threshold, and they were subjected to filter with varied parameters. The filtering induced variations of elastic response spectra, inelastic response spectra, and the impulsive property identification were analyzed. The highest cutting frequency of 0.20 Hz and 0.10 Hz of the high-pass filter were recommended for short-to-mid and mid-to-long period pulse records, respectively, while the impulse properties and spectral properties of engineering interest were not disturbed considerably. The ground motions were input to a high-rise base-isolated building, and the responses were computed from different filtering settings and compared, which further verified the suggested high-pass filtering method for pulse-like ground motions.
Past earthquakes have demonstrated that fault-crossing bridges were susceptible to damage or even collapse. This study focused on investigating the effects of fault rupture on seismic responses of a simply-supported highway bridge. Six sets of ground motions with fling-step effect in fault-parallel direction and forward directivity effect in fault-normal direction were selected as the inputs from four strike-slip earthquakes. A simplified baseline correction method was used to recover the permanent ground displacement in these records. A typical simply-supported girder bridge located in China was taken as the prototype bridge and the numerical model of the bridge was generated in OpenSees. Effects of fault crossing angles (from 15° to 165°) and the amplitude of permanent ground displacement on the seismic behaviors of the bridge were evaluated. More specially, two special cases, i.e. contact case and separation case, are considered and compared considering the contact and separation between the girder and abutment in bridge longitudinal direction. Results revealed that the piers and bearings in contact case have larger seismic damage compared to separation case, and the separation case causes the unseating of the bridge spans. It was found that the fault crossing angle has a great impact on the seismic responses of the fault-crossing bridge. The fault crossing angle from 60° to 90° causes the lowest structural seismic responses. The permanent ground displacement is another important influence factor of the bridge. Unlike the bridges without crossing fault, the peak values of the responses of the bridge increase as the pulse amplitudes and pulse periods increase.
ResearchGate has not been able to resolve any references for this publication.