Stochastic Ground Motion Simulation Research Articles

Regionally adjusted stochastic earthquake ground motion models, associated variabilities and epistemic uncertainties

An optimisation-based calibration technique, using the area metric, is applied to determine the input parameters of a stochastic earthquake-waveform simulation method. The calibration algorithm updates a model prior, specifically an estimate of a region’s seismological (source, path and site) parameters, typically developed using waveform data, or existing models, from a wide range of sources. In the absence of calibration, this can result in overestimates of a target region’s ground motion variability, and in some cases, introduce biases. The proposed method simultaneously attains optimum estimates of median, range and distribution (uncertainty) of these seismological parameters, and resultant ground motions, for a specific target region, through calibration of physically constrained parametric models to local ground motion data. We apply the method to Italy, a region of moderate seismicity, using response spectra recorded in the European Strong Motion (ESM) dataset. As a prior, we utilise independent seismological models developed using strong motion data across a wider European context. The calibration obtains values of each seismological parameter considered (such as, but not limited to, quality factor, geometrical spreading and stress drop), to develop a suite of optimal parameters for locally adjusted stochastic ground motion simulation. We consider both the epistemic and aleatory variability associated with the calibration process. We were able to reduce the area metric (misfit) value by up to 88% for the simulations using updated parameters, compared to the initial prior. This framework for the calibration and updating of seismological models can help achieve robust and transparent regionally adjusted estimates of ground motion, and to consider epistemic uncertainty through correlated parameters.

Stochastic ground motion simulation of the 26 September 2019 Mw 5.8 Silivri (Istanbul) earthquake

Stochastic ground motion simulation of the 26 September 2019 Mw 5.8 Silivri (Istanbul) earthquake

Stochastic simulation of earthquake ground motions based on improved finite-fault model

In the seismic reliability analysis of engineering structures, it is often necessary to adopt stochastic ground motions as inputs. However, the current methods used to generate stochastic samples, such as the spectral representation method, the spectral transfer method, the dynamic source method, the physical source method, and the comprehensive method, etc., are not very convincing since they do not contain the complete information of seismic occurrence and propagation. In this study, an improved finite-fault model for stochastic simulation of ground motions is proposed. Compared to existing stochastic finite-fault model, the improved model considers the propagation law of phase spectrum, local site effect, and the impact of wave velocity on the arrival time of seismic waves. Besides, identification and statistics of model parameters are carried out based on ground motion records. Reasonable samples of stochastic ground motions are then obtained. In addition, parameter sensitivity analysis is conducted to determine critical random variables, which reduces the complexity of stochastic simulation. Simulation results are compared with recorded accelerograms from the 1999 Chi-Chi earthquake. It is shown that the improved stochastic finite-fault model is reliable, and the acceleration response spectra of simulated samples are consistent with those of station records collected at various site classes and the design spectra.

Regional spectral characteristics, quality factor and site responses in western-central Sichuan, China (II): Application to stochastic ground motion simulation

The stochastic finite-fault approach was used to model the 2022 Luding earthquake with a magnitude of Mw 6.6 in China at 16 selected near-field stations. To investigate the impact of the site effect on the synthetic results, two models were taken into account: One model was obtained from the generalized inversion technique, and the other model was obtained from the horizontal-to-vertical spectral ratio method. The high-frequency attenuation parameter was estimated to be 0.040 s and the value of 4.0 MPa for the stress parameter was adopted. Comparisons of the recorded and simulated Fourier amplitude spectrum, pseudospectral acceleration, peak ground acceleration, and peak ground velocity were performed to investigate the capability of the selected input parameters. In addition, the model bias, simulated peak ground acceleration and peak ground velocity were calculated by the local site amplification estimated by the two methods. The results show that the site effects estimated by the generalized inversion technique can well simulate the high-frequency response spectra and Fourier amplitude spectrum and can provide peak ground acceleration and peak ground velocity values consistent with the recorded values, while the local site amplification roughly calculated by the horizontal-to-vertical ratio method underestimates the main ground motion characteristics. Furthermore, strong-motion records with the same magnitude but different hypocentral distance ranges in the generalized inversion technique are used to estimate near-surface site effects, which shows that the distance range has a small impact on the estimation of local site amplification. Model parameters that performed well in this study provide confidence in understanding and quantifying seismic hazards in the Luding area from earthquake scenarios with different magnitudes.

Stochastic Ground-Motion Simulation of the 2021 Mw 5.9 Woods Point Earthquake: Facilitating Local Probabilistic Seismic Hazard Analysis in Australia

ABSTRACT The 2021 Mw 5.9 Woods Point event is the largest onshore earthquake that has occurred in the recorded history of southeastern Australia since European settlement. To study its source and ground-motion characteristics and to extract information for local seismic hazard analysis, we employ a stochastic finite-fault simulation approach to simulate ground motions for this event based on the observations collected from 36 onshore stations. We determine the regional distance-dependent attenuation parameters using the horizontal Fourier acceleration amplitude spectrum in the frequency range of 0.1–20 Hz. We parameterize path parameters using different models to consider uncertainties and sensitivities. To investigate local site effects, we construct a VS30-based site amplification model. Source parameters are then determined by fitting the theoretical Brune’s ω2 model with a reference Fourier source spectrum at 1.0 km. The κ0 value for the reference rock site is estimated as κ0=0.01 s, and dynamic stress drop is found to be 41.0 MPa by minimizing the overall absolute residual of 5% damped pseudospectral acceleration. We validate the simulations by comparing simulated and observed ground motions in terms of various intensity measurements; analyses of residuals show that the simulations are in good agreement with observations (average residual is close to 0). To facilitate future probabilistic seismic hazard analysis, six selected ground-motion models are ranked using the deviance information criteria based on an independent data set consisting of field observations and simulated ground motions.

Influence of source uncertainty on stochastic ground motion simulation: a case study of the 2022 Mw 6.6 Luding, China, earthquake

Influence of source uncertainty on stochastic ground motion simulation: a case study of the 2022 Mw 6.6 Luding, China, earthquake

New Empirical Equations for Determination of Fourier Amplitude Spectrum of Acceleration

ABSTRACT In this study, new empirical relations are proposed to determine the Fourier amplitude spectrum of acceleration. The FASAs form the white-noise spectrum in the stochastic ground motion simulation methods. So far, various analytical and experimental models have been proposed to determine the FASA. ω−2 is among the most well-known models are used in the computational programs of ground motion simulation such as SMSIM or EXSIM. In this study, the relationship between the FASA, and the important seismological parameters such as moment magnitude, closest distance from rupture plane, site conditions and faulting mechanism is determined, and appropriate relations are presented. There are limited experimental models of FASA, and present models are mainly analytical. Therefore, the results of this research can be beneficial. To present models, the Iran Plateau earthquake catalog is used, including 2228 acceleration records of 749 earthquakes with magnitudes of 4.5–7.6 and rupture distance up to 200 km.

Stochastic ground motion simulation and seismic damage performance assessment of a 3-D subway station structure based on stochastic dynamic and probabilistic analysis

In practical engineering of underground structures, it is well-known that the randomness of earthquake generation and a structure's seismic response need to be considered for the safety of the project. The dynamic response and reliability level of a subway station are analyzed from the perspective of random vibration and the effect of stochastic ground motions on seismic responses is considered in this paper. This research proposes a model that can generate completely nonstationary ground motions and combines it with the probability density evolution method (PDEM) to analyze the seismic response and reliability level of a subway station. First, combining random function spectrum representation and evolutionary power spectrum density function, a probability model of nonstationary ground motion is established. According to the code (Gb 50909-2014), the model parameters of 5 sites are suggested, and the efficiency and accuracy are verified. A series of intensity–frequency nonstationary stochastic earthquakes are generated for the seismic response analysis. Then, a 3-D finite element analysis is performed for the deterministic dynamic response of the Daikai subway station, and the second-order statistics of three evaluation indicators (interstory drift, relative settlement, damage area ratio) are attained. Finally, the stochastic dynamic response and reliability level of the station structure are obtained by processing the data with the PDEM. The limit state related to the three evaluation indicators is established through probability density function (PDF) and cumulative distribution function (CDF). In addition, this probability evaluation system is more intuitive and effective than conventional methods. The statistical and probabilistic results show that the characteristics of earthquakes have a significant influence on the seismic response of subway stations, furthermore, the stochastic earthquakes generated by the intensity–frequency nonstationary ground motion model match well with the target value and the PDEM can comprehensively evaluate the seismic performance and reliability level of subway stations. Therefore, combing the stochastic earthquake and PDEM is an effective way to analyze the seismic response of subway stations.

Machine learning-aided PSDM for dams with stochastic ground motions

Probabilistic seismic demand models are widely used for structures to establish a relation between the engineering demand parameter (EDP) and ground motion intensity measures (IM). For the complex infrastructures such as dams two challenges in implementation of probabilistic seismic demand models are scarcity of the appropriate real ground motions, and computational limitation to perform hundreds of simulations. This paper addresses both concerns by using a series of stochastic ground motion records as an alternative for real ones, and also employing machine learning algorithms to predict the IM-EDP relation. A 3D concrete arch dam with foundation and reservoir interaction is used as a case study of a demanding system (as opposed to 2D framed building). A large group of about 600 real and stochastic ground motion records are used to analyze the coupled system. In addition, five machine learning algorithms were used to develop the predictive meta-models. This paper also highlights the feasibility of using stochastic ground motions to predict the probabilistic seismic demand meta-models and fragility curves from real records, and vice versa. While the outcomes illustrate promising results, they also show that the existing stochastic ground motion simulation models do not cover all the inherent characteristics of the real records.

GMSS2.0: An Enhanced Software Program for Stochastic Finite-Fault Ground-Motion Simulation

AbstractThis 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).

Constraints on near-source saturation models for avoiding over-saturation of response spectral ordinates in RVT-based stochastic ground-motion simulations

Inversions of empirical data and ground-motion models to find Fourier spectral parameters can result in parameter combinations that produce over-saturation of short-period response spectral ordinates. While some evidence for over-saturation in empirical data exists, most ground-motion modellers do not permit this scaling within their models. Host-to-target adjustments that are made to published ground-motion models for use in site-specific seismic hazard analyses frequently require the identification of an equivalent set of Fourier spectral parameters. In this context, when inverting response spectral models that do not exhibit over-saturation effects, it is desirable to impose constraints upon the Fourier parameters to match the scaling of the host-region model. The key parameters that determine whether over-saturation arises are the geometric spreading rate (γ) and the exponential rate within near-source saturation models (hβ). The article presents the derivation of simple nonlinear constraints that can be imposed to prevent over-saturation when undertaking Fourier spectral inversions.

Seismic risk assessment of on-ground circular reinforced concrete and prestressed concrete water tanks using stochastic ground motion simulations

This case-study is dedicated to the seismic risk assessment of cylindrical fixed-based reinforced concrete and prestressed concrete water tanks situated in Romania. The fixed-based water tanks are designed according to the current seismic design prescriptions in Romania. The six selected sites are all under the influence of the Vrancea intermediate-depth seismic source. The seismic performance is evaluated using site-specific ground motion stochastic simulations and using the approach given in Eurocode 8-4 (2006). The largest mean annual failure probabilities are obtained for the two sites (Amara and Bucharest) with the highest long-period spectral amplifications. The study shows that from the strength point of view, the two types of tanks have very small corresponding failure probabilities and from the serviceability point of view, depending on the type of the tank and its position, sloshing or cracking due to bending are the prevalent failure modes.

A Generic Shear Wave Velocity Profiling Model for Use in Ground Motion Simulation

This study presents a generic model for constructing shear-wave velocity (VS) profiles for various conditions that can be used for modeling the upper-crustal modification effects in ground motion simulations for seismic hazard analysis. The piecewise P-wave velocity (VP) profiling model is adopted in the first place, and the VS profile model is obtained by combining the VP profiling model and VS/VP model. The used VS/VP model is constructed from various field measurements, experimental data, or CRUST1.0 data collected worldwide. By making the best use of the regionally/locally geological information, including the thickness of sedimentary and crystalline layers and reference VS values at specific depths, the VS profile can be constructed, and thus the amplification behavior of VS for a given earthquake scenario can be predicted. The generic model has been validated by four case studies of different target regions world around. The constructed profiles are found to be in fair agreement with field recordings. The frequency-dependent upper-crustal amplification factors are provided for use in stochastic ground motion simulations for each respective region. The proposed VS profiling model is proposed for region-specific use and can thus make the ground motion predictions to be partially non-ergodic.

Source modelling and strong ground motion simulations for the 24 January 2020, Mw 6.8 Elazığ earthquake, Turkey

SUMMARYOn 24 January 2020 an Mw 6.8 earthquake occurred at 20:55 local time (17:55 UTC) in eastern Turkey, close to the town of Sivrice in the Elazığ province, causing widespread considerable seismic damage in buildings. In this study, we analyse the main features of the rupture process and the seismic ground shaking during the Elazığ earthquake. We first use Interferometric Synthetic Aperture Radar (InSAR) interferograms (Sentinel-1 satellites) to constrain the fault geometry and the coseismic slip distribution of the causative fault segment. Then, we utilize this information to analyse the ground motion characteristics of the main shock in terms of peak ground acceleration (PGA), peak ground velocity (PGV) and spectral accelerations. The absence of seismic registrations in near-field for this earthquake imposes major constraints on the computation of seismic ground motion estimations in the study area. To do this, we have used a stochastic finite-fault simulation method to generate high-frequency ground motions synthetics for the Mw 6.8 Elazığ 2020 earthquake. Finally, we evaluate the potential state of stress of the unruptured portions of the causative fault segment as well as of adjacent segments, using the Coulomb stress failure function variations. Modelling of geodetic data shows that the 2020 Elazığ earthquake ruptured two major slip patches (for a total length of about 40 km) located along the Pütürge segment of the well-known left-lateral strike-slip East Anatolian Fault Zone (EAFZ), with up to 2.3 m of slip and an estimated geodetic moment of 1.70 $\,\, \times $ 1019 Nm (equivalent to a Mw 6.8). The position of the hypocentre supports the evidence of marked WSW rupture directivity during the main shock. In terms of ground motion characteristics, we observe that the high-frequency stochastic ground motion simulations have a good capability to reproduce the source complexity and capture the ground motion attenuation decay as a function of distance, up to the 200 km. We also demonstrate that the design spectra corresponding to 475 yr return period, provided by the new Turkish building code is not exceeded by the simulated seismograms in the epicentral area where there are no strong motion stations and no recordings available. Finally, based on the Coulomb stress distribution computation, we find that the Elazığ main shock increased the stress level of the westernmost part of the Pütürge fault and of the adjacent Palu segment and as a result of an off-fault lobe.

Modeling energy release parameters in stochastic simulation of ground motions generated by Vrancea intermediate-depth seismic source

Ground motion time-domain stochastic simulations are performed by generating a white or a Gaussian noise, shaping it with a window, loading its normalized spectrum with the spectrum of the motion at a specific site and transforming it back in time-domain (Boore in Pure Appl Geophys 160: 635–676, 2003). The outcome of the resulted simulations is compared to the target parameters, namely amplitude, frequency content and duration parameters. Using SMSIM (Boore in SMSIM: Fortran programs for simulating ground motions form earthquakes, 2005) and EXSIM (Motazedian and Atkinson in Bull Seismol Soc Am 95(3): 995–1010, 2005. https://doi.org/10.1785/0120030207), Coțovanu (J Mil Technol 1(2): 27–32, 2018. https://doi.org/10.32754/jmt.2018.2.05) and Coțovanu and Vacareanu (J Seismol 24(1): 229–241, 2020. https://doi.org/10.1007/s10950-019-09892-5) applied the stochastic simulation method for generating ground motions produced by intermediate-depth Vrancea (Romania) earthquakes and found inconsistent results for duration parameters (significant duration and energy distribution in time-domain). In simulations, the duration of the motion results from the source and path duration, but the significant duration (that contains 90% of the energy) depends on the way the energy is distributed in time, and this distribution is controlled through a noise shaping window. The objective of this paper is to provide an appropriate form of the shaping window that can describe the specific energy release of ground motions generated by Vrancea intermediate depth seismic source (the first 50–70% of energy being rapidly released, the rest of it having a very slow release). For this matter, 371 recorded motions were analyzed and 5 types of energy release were defined. The set with the above described pattern that contained almost half of the analyzed accelerograms was used to define a mean normalized cumulative energy that describes the Vrancea specificity. On this basis, the parameters for the SMSIM implemented exponential window were determined and, because the results were inconsistent, a more adequate window function was defined and implemented in SMSIM. For the newly defined two-interval window function an algorithm for calculating the parameters was described, and the parameters of the mean release of energy were determined. By using the two-interval function for describing the Vrancea specific release of energy, more appropriate ground motion simulations resulted.

Erratum to: <i>Stochastic simulation of ground motions based on NGA-West2 strong motion records</i>

Erratum to: <i>Stochastic simulation of ground motions based on NGA-West2 strong motion records</i>

Continuity and Derivability Issues in Modeling the Energy Release Shaping Window in Stochastic Simulation of Ground Motions Generated by Vrancea Intermediate-Depth Seismic Source

Continuity and Derivability Issues in Modeling the Energy Release Shaping Window in Stochastic Simulation of Ground Motions Generated by Vrancea Intermediate-Depth Seismic Source

Local site conditions modeling in stochastic simulation of ground motions generated by Vrancea (Romania) intermediate-depth seismic source

Analyses of stochastic simulations methods for Vrancea (Romania) intermediate-depth earthquake recorded at seismic station INCERC Bucharest were made. The main research topic highlighted in this paper is the quest for the best model able to simulate the influence of the local site conditions considering to this aim different types of soil behavior. Two types of linear behavior and one type of nonlinear behavior of the soil layers were considered to investigate the site effects. Comparisons between the simulations and the recorded accelerograms and between the simulation methods were made in terms of amplitude parameters, frequency content, duration parameters, and energy release. A better approximation was found when the nonlinear behavior of the soil layers was employed.

Probabilistic assessment of seismic stability of a rock slope by combining the simulation of stochastic ground motion with permanent displacement analysis

A probabilistic framework that considers the variability and uncertainty of the ground motions caused by earthquakes and the parameters of the slope material is proposed to assess the seismic stability of rock slopes. A stochastic ground motion simulation method, which reflects certain earthquake scenarios and site characteristics, was used to generate accelerograms as seismic inputs. Then, the probabilities of failure (Pf) of the slopes when subjected to earthquake ground motions were computed via Monte-Carlo simulations based on the simulated ground motions and the decoupled Newmark permanent-displacement analysis. An example rock slope was used to illustrate the proposed procedure and verify its rationality. The results showed that the magnitudes of the earthquakes and the source-to-site distances had significant influences on the seismic stability of the slopes. For an earthquake of the same magnitude, the Pf of the slope decreased rapidly as the source-to-site distance increased. In addition, given the same source-to-site distance, the Pf of the slope increased steadily as the magnitudes of the earthquakes increased. Also, it was found that the influence of coefficient of variation of the slope's shear strength parameters (i.e., c, φ) was not negligible when the uncertainty of earthquakes was not considered. However, it may be overshadowed by the significant influence of a great earthquake, especially when the variability of ground motions is taken into account. The results that were obtained agreed well with observed earthquake-induced landslide phenomena and the statistical data of two typical earthquakes that occurred in Japan and China, which implies that the proposed method is accurate.

Stochastic simulation of ground motions based on NGA-West2 strong motion records

Stochastic simulation of ground motions based on NGA-West2 strong motion records