Ground Motion Simulation Research Articles

A Partially Nonergodic Ground-Motion Model for Cascadia Interface Earthquakes

ABSTRACT The Abrahamson and Gulerce (2020) ground-motion model (GMM), called AG20, is modified to include the nonergodic effects from the suite of 3D numerical simulations of long-period ground motions from M 9 megathrust earthquakes on the Cascadia subduction zone developed by the M 9 project (Frankel et al., 2018). Three modifications are made to the AG20 model. First, the scaling of the basin effects as a function of the depth to a shear-wave velocity of 2.5 km/s (Z2.5) is modified to be consistent with the Z2.5 scaling from the 3D simulations. Second, the spatial distribution of the nonergodic site terms is estimated using the varying coefficient model for the region covered by the 3D velocity model. The change in the median ground motion due to the nonergodic site terms ranges from factors of 0.25 to 5 at a period of 3 s. Third, a reduction in the aleatory variability for single-station sigma is estimated. On average, including the nonergodic site terms reduces the sigma by 15%–25% compared with an ergodic sigma for Cascadia. In addition, a spatially varying single-station sigma model is developed, showing the highest variability for sites near the basin edges. Application of nonergodic GMMs requires an estimate of the epistemic uncertainty in the nonergodic terms. Without simulation results for different 3D velocity models, we assumed that the epistemic uncertainty due to uncertainty in the 3D velocity model is half of the between-site standard deviation from the simulations. As an example, the seismic hazard for interface events using the nonergodic GMM is compared with the hazard using the original AG20 GMM.

Semi-automated stochastic simultaneous simulation of macroseismic information and strong ground motion records for recent strong earthquakes of the Aegean area

We apply a stochastic simulation approach for the simultaneous modeling of macroseismic data and strong ground motion records for several shallow strong earthquakes (M ≥ 6.0) that occurred in the Aegean area from 1980 to 1995 Alkyonides (1981, M6.7), Kalamata (1986, M6.0), Kozani (1995, M6.6) and Aigio (1995, M6.4). The application is semi-automatic, as several of the selected input parameters for the stochastic simulation modeling were automatically calibrated using a priori information (e.g., magnitude, stress parameter, site effects). Other parameters (e.g., fault type, depth) were pre‑determined, based on published information, most of which are usually derived during standard earthquake analysis. The validity and reliability of this approach was examined, to test if this method could be applied either in a fully automated manner, or for the study of source properties of historical earthquakes. While the results obtained from the semi-automated simulations were satisfactory, they also suggest that it is not possible to achieve the same level of reliability and robustness when modeling complicated seismic sequences, as e.g., is the case of the Alkyonides earthquake (1981, M6.7).

Validation of physics‐based regional‐scale ground‐motion simulations of the 2008 Mw 7.9 Wenchuan earthquake for engineering applications

AbstractThe 2008 Mw 7.9 Wenchuan earthquake, one of the largest continental intraplate events instrumentally recorded, struck the central part of Sichuan Province in southwestern China causing great destruction and loss of life but also providing a wealth of seismological data, geodetic measurements, and tectonic observations. The Wenchuan earthquake ruptured two northwest‐dipping imbricate oblique reverse faults along the middle segment of the Longmenshan fault zone—a northeast‐trending thrust belt located at the boundary between the Tibetan Plateau and the Sichuan Basin. In this study, a hybrid approach that combines deterministic modeling at low frequencies with stochastic modeling at high frequencies is used to simulate broadband ground motions at 52 strong‐motion stations and 506 geodetic sites in the vicinity of the causative fault. The low‐frequency components of the synthetic ground motion are simulated using an extended kinematic source model embedded in a layered medium, whereas the high‐frequency components are generated using a stochastic finite‐fault model. The two independently derived ground‐motion components are then combined using matched filtering at a crossover frequency of 0.8 Hz to generate broadband ground‐motion time histories and response spectra. The temporal and spectral characteristics of the synthetic and recorded ground motions at the 52 strong‐motion stations are compared and the effect of soil nonlinearity on the simulated ground motions is investigated through 1‐D nonlinear site response analysis. Finally, the simulated permanent ground displacements at the 506 geodetic sites are evaluated against geodetic observations and the peak amplitudes of the synthetic ground motions at the same locations are compared with predictions of empirical ground‐motion models.

The Great 1822 Aleppo Earthquake: New historical sources and strong ground motion simulation

El terremoto de 1822 fue devastador y se considera uno de los eventos relativamente recientes que azotaron el noroeste de Siria y las áreas cercanas del centro-sur de Turquía, es decir, en la unión del sistema de fallas del Mar Muerto con el sistema de fallas del este de Anatolia. En este trabajo, se vuelve a estudiar este terremoto, con base en nuevas fuentes de información originales contemporáneas y casi contemporáneas, que no habían sido citadas anteriormente.El análisis de estas fuentes revela lo siguiente:(1) se proporcionan descripciones más detalladas de los efectos del terremoto para las ciudades de Aleppo, Antakia y Latakia, y la identificación de seis nuevas ubicaciones afectadas; (2) evaluación de los parámetros pertinentes del terremoto, como el epicentro, la onda de superficie, las magnitudes de momento y la intensidad sísmica; (3) se muestra documentación de evidencias de una ola marina sísmica que ocurrió entre las costas chipriota y Siria, e (4) identificación de la falla de San Simeón, ubicada al oeste de Aleppo, como la probable falla causante. Además, el movimiento del suelo generado por el terremoto de 1822 ha sido simulado utilizando el método de estocástica extendida. Se generaron series temporales de aceleración y espectros de pseudoaceleración amortiguados para la ciudadela de Aleppo, donde la aceleración máxima del suelo, debido al terremoto, se estimó en 0.4 g.Los resultados contribuirán a actualizar la configuración de riesgo sísmico en el noroeste de Siria y el centro-sur de Turquía.

Microtremor array surveys and development of the velocity model in the Hakodate Plain, Hokkaido, Japan

The Hakodate Plain in the southern part of the Oshima Peninsula, Hokkaido, Japan, is a sedimentary basin surrounded by mountains. The vertical displacements caused by active faults along the western margin of the Hakodate Plain increased the basin depth in the western part of the Hakodate Plain. Small-to-large-sized microtremor array surveys were conducted at five sites in the Hakodate Plain to estimate the S-wave velocity structure down to the seismic bedrock for each site to develop a detailed velocity structure model. A new three-dimensional velocity structure model of the Hakodate Plain was developed by integrating the results of microtremor array surveys and other existing geophysical explorations data. This three-dimensional velocity model was modeled as a stack of homogeneous isotropic layers to facilitate its incorporation into the present nation-wide three-dimensional velocity model for ground motion prediction. The bottom depth of the Quaternary sediments is deep along the western margin of the Hakodate Plain. The total thickness of the Quaternary and Neogene sedimentary layers reaches 2.9 km in the western Hakodate Plain. The proposed velocity model was validated by gravity anomaly modeling and ground motion simulation of a moderate-sized inland earthquake. The location of the low-gravity anomaly around the coastline of the Hakodate Bay was improved using the new model. The numerical ground motion simulation using FDM also demonstrated that the amplification and long duration observed in the western part of the Hakodate Plain were reproduced effectively using this velocity model. The spatial variation in long-period ground motion amplifications (period > 1 s) is discussed based on numerical simulations utilizing our three-dimensional velocity model. The highest amplifications at periods of 4 and 5 s were expected in the southwestern Hakodate Plain. The amplification at a period of 3 s was relatively high near the western margin of the plain. Conversely, the spatial characteristics below 2 s were quite complex due to interference of the seismic wavefield inside the basin structure. Variation due to the source location was also relatively high in the shorter period range.Graphical abstract

Wavelet-Hilbert transform-based simulation of pulse-like ground motion

Wavelet-Hilbert transform-based simulation of pulse-like ground motion

Testing Site Amplification Curves in Hybrid Broadband Ground Motion Simulations of M6.0, 24 August 2016 Amatrice Earthquake, Italy

This research focuses on predicting and assessing earthquake impact due to future scenarios regarding the ground motion seismic hazard by accounting mainly for site effect in the Central Apennines. To this end, we produced synthetic broadband seismograms by adopting a hybrid simulation technique for the Mw6.0 Amatrice earthquake, Central Italy, on 24 August 2016, accounting for site conditions by means of amplification curves, computed with different approaches. Simulations were validated by comparing with data recorded at 57 strong-motion stations, the majority installed in urban areas. This station sample was selected among stations recording the Amatrice earthquake within an epicentral distance of 150 km and potentially prone to experience site amplification effects because of lying in particular site conditions (sedimentary basins, topographic irregularities, and fault zones). The evaluation of amplification curves best suited to describe local effects is of great importance because many towns and villages in central Italy are built in very different geomorphological conditions, from valleys and sedimentary basins to topographies. In order to well reproduce observed ground motions, we accounted for the site amplification effect by testing various generic and empirical amplification curves such as horizontal-to-vertical spectral ratios (calculated from Fourier spectra using both earthquake, HVSR, and ambient noise, HVNSR, recordings) and those derived from the generalized inversion technique (GIT). The site amplifications emanated from GIT improve the match between observed and simulated data, especially in the case of stations installed in sedimentary basins, where the empirical amplification curve effectively reproduces spectral peaks. On the contrary, the worst performances are for the spectral ratios between components, even compared to the generic site amplification, although the latter ignores the strong bedrock/soil seismic impedance contrasts. At sites on topography, we did not observe any systematic behavior, the use of empirical curves ameliorating the fit only in a small percentage of cases. These results may provide a valuable framework for developing ground motion models for earthquake seismic hazard assessment and risk mitigation, especially in urban areas located in the seismically active central Italy region.

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.

Focal Mechanism Influence with Azimuth Using Near-Field Simulated Ground Motion: Application to a Multispan Continuous Concrete Single-Frame Box-Girder Bridge

Focal Mechanism Influence with Azimuth Using Near-Field Simulated Ground Motion: Application to a Multispan Continuous Concrete Single-Frame Box-Girder Bridge

Hybrid Broadband Ground Motion Simulation for 2015 Mw 7.9 Nepal Earthquake

The present study aims at simulating broadband ground motions in the epicentral region of the 2015[Formula: see text]Mw 7.9 Nepal event, using hybrid broadband technique. The spectral element method is used to simulate the low-frequency ground motion. The three-dimensional material property variation and the basin geometry at the Kathmandu basin are incorporated in the spectral element model. High frequency synthetics are simulated using scattering Green’s function approach by consistently using the source and medium model of low frequency simulation. The simulated Low Frequency (LF) (0–0.3[Formula: see text]Hz) results are combined with high-frequency scatterograms to generate broadband ground motions (0–10[Formula: see text]Hz). The scattering parameters for broadband ground motion simulation are estimated from the recorded data of Nepal mainshock. These parameters are used further for simulating the ground motions over a grid of stations at 2[Formula: see text]km [Formula: see text] 2[Formula: see text]km spacing at the epicentral region. The simulated results are shown as peak ground acceleration (PGA), peak ground velocity, and spectral acceleration contours plots. The maximum PGA in the horizontal and vertical directions are 0.35[Formula: see text]g and 0.32[Formula: see text]g in the epicentral region. Also, the acceleration time histories and corresponding response spectra are presented for some of the selected cities in the region where no records are available. These simulated outcomes are used for analyzing the validity of Indian seismic codal provisions at the near-field of large Himalayan earthquakes. The results show the significant underestimation of near-field hazard by the codal provisions at the Himalayan region.

0–5 Hz deterministic 3-D ground motion simulations for the 2014 La Habra, California, Earthquake

SUMMARYWe have simulated 0–5 Hz deterministic wave propagation for a suite of 17 models of the 2014 Mw 5.1 La Habra, CA, earthquake with the Southern California Earthquake Center Community Velocity Model Version S4.26-M01 using a finite-fault source. Strong motion data at 259 sites within a 148 km × 140 km area are used to validate our simulations. Our simulations quantify the effects of statistical distributions of small-scale crustal heterogeneities (SSHs), frequency-dependent attenuation Q(f), surface topography and near-surface low-velocity material (via a 1-D approximation) on the resulting ground motion synthetics. The shear wave quality factor QS(f) is parametrized as QS, 0 and QS, 0fγ for frequencies less than and higher than 1 Hz, respectively. We find the most favourable fit to data for models using ratios of QS, 0 to shear wave velocity VS of 0.075–1.0 and γ values less than 0.6, with the best-fitting amplitude drop-off for the higher frequencies obtained for γ values of 0.2–0.4. Models including topography and a realistic near-surface weathering layer tend to increase peak velocities at mountain peaks and ridges, with a corresponding decrease behind the peaks and ridges in the direction of wave propagation. We find a clear negative correlation between the effects on peak ground velocity amplification and duration lengthening, suggesting that topography redistributes seismic energy from the large-amplitude first arrivals to the adjacent coda waves. A weathering layer with realistic near-surface low velocities is found to enhance the amplification at mountain peaks and ridges, and may partly explain the underprediction of the effects of topography on ground motions found in models. Our models including topography tend to improve the fit to data, as compared to models with a flat free surface, while our distributions of SSHs with constraints from borehole data fail to significantly improve the fit. Accuracy of the velocity model, particularly the near-surface low velocities, as well as the source description, controls the resolution with which the anelastic attenuation can be determined. Our results demonstrate that it is feasible to use fully deterministic physics-based simulations to estimate ground motions for seismic hazard analysis up to 5 Hz. Here, the effects of, and trade-offs with, near-surface low-velocity material, topography, SSHs and Q(f) become increasingly important as frequencies increase towards 5 Hz, and should be included in the calculations. Future improvement in community velocity models, wider access to computational resources, more efficient numerical codes and guidance from this study are bound to further constrain the ground motion models, leading to more accurate seismic hazard analysis.

Calibration of the near-surface seismic structure in the SCEC community velocity model version 4

SUMMARYThe near-surface seismic structure (to a depth of about 1000 m), particularly the shear wave velocity (VS), can strongly affect the propagation of seismic waves and, therefore, must be accurately calibrated for ground motion simulations and seismic hazard assessment. The VS of the top (<300 m) crust is often well characterized from borehole studies, geotechnical measurements, and water and oil wells, while the velocities of the material deeper than about 1000 m are typically determined by tomography studies. However, in depth ranges lacking information on shallow lithological stratification, typically rock sites outside the sedimentary basins, the material parameters between these two regions are typically poorly characterized due to resolution limits of seismic tomography. When the alluded geological constraints are not available, models, such as the Southern California Earthquake Center (SCEC) Community Velocity Models (CVMs), default to regional tomographic estimates that do not resolve the uppermost VS values, and therefore deliver unrealistically high shallow VS estimates. The SCEC Unified Community Velocity Model (UCVM) software includes a method to incorporate the near-surface earth structure by applying a generic overlay based on measurements of time-averaged VS in top 30 m (VS30) to taper the upper part of the model to merge with tomography at a depth of 350 m, which can be applied to any of the velocity models accessible through UCVM. However, our 3-D simulations of the 2014 Mw 5.1 La Habra earthquake in the Los Angeles area using the CVM-S4.26.M01 model significantly underpredict low-frequency (<1 Hz) ground motions at sites where the material properties in the top 350 m are significantly modified by the generic overlay (‘taper’). On the other hand, extending the VS30-based taper of the shallow velocities down to a depth of about 1000 m improves the fit between our synthetics and seismic data at those sites, without compromising the fit at well-constrained sites. We explore various tapering depths, demonstrating increasing amplification as the tapering depth increases, and the model with 1000 m tapering depth yields overall favourable results. Effects of varying anelastic attenuation are small compared to effects of velocity tapering and do not significantly bias the estimated tapering depth. Although a uniform tapering depth is adopted in the models, we observe some spatial variabilities that may further improve our method.

Modeling response spectrum compatible pulse-like ground motion

The seismic response analysis of near-fault pulse-like ground motions is severely restricted due to the scarcity of pulse-like records. The requirement in regulations that the response spectra of artificial ground motions should be compatible with the target response spectrum makes the relevant studies more difficult. As a result, this study proposes a trigonometric series-based stochastic method to simulate pulse-like ground motions, with the advantage that the corresponding pseudo-spectral acceleration is compatible with the given target response spectrum. This goal is achieved by two parts. (1) The envelope function of pulse-like records obtained by the Hilbert transform is utilized as the amplitude modulation function to ensure that the simulated ground motion contains a pulse. (2) A novel iteration scheme based on random frequency parameters is proposed to guarantee the response spectrum compatibility. The velocity ground motion is first simulated since the pulse usually exists in velocity. The ground-motion acceleration subsequently obtained by differentiating the velocity is adopted to calculate the response spectrum. Two cases are implemented and verified the effectiveness of the proposed method in enriching existing pulse-like databases and generating pulse-like ground motion in areas that lack records. Moreover, the amplitude modulation function and target spectrum, as two key factors in the proposed method, determines the presence of a pulse and the pulse periods, respectively. This property makes the proposed method potentially universal applicability for stochastic pulse-like ground motion simulation in engineering.

Source rupture characteristics and ground motion simulation of the southernmost Ryukyu subduction zone 31 March 2002 Mw7.1 earthquake

An Mw 7.1 Ryukyu subduction zone earthquake struck northern Taiwan in 2002. The joint source inversion result indicates that rupture mainly propagated toward the northwest and produced a significant directivity. The long-period strong ground motion observed in northern Taiwan was directly related to source rupture effects. To assess the seismic risk in Taiwan and even East Asia more generally, it is necessary to carefully consider the various types of megathrusts that occur in the southern Ryukyu subduction zone. • An Mw 7.1 Ryukyu subduction zone earthquake struck northern Taiwan in 2002. • Rupture mainly propagated toward the northwest resulted in a strong directivity. • Long-period strong ground motion was directly related to source rupture effects. • Megathrust in Ryukyu subduction needs to carefully consider to assess seismic risk. On March 31, 2002, a magnitude 7.1 earthquake occurred off the coast of eastern Taiwan. The Taipei 101 Financial Building was under construction at that time and due to extremely strong long-period shaking, two cranes on the top floor collapsed and fell to the ground, killing five people. This earthquake was caused by a rupture of the southern Ryukyu subduction zone. The result of a joint source inversion showed that the slip originated at the mid-depth subduction interface off the eastern coast and then propagated to the western fault plane with a rupture velocity of approximately 3.0 km/s. Forward ground motion simulation indicated that the main cause of the long-period strong motion in northern Taiwan was directly related to source effects, including long rupture lasting, rupture directivity and source radiation. The seismic waves were further amplified by the soft sediments in the Taipei basin which also resulted in longer vibration time in Taipei City.

Seismic Traveltime Tomography of Southern California Using Poisson‐Voronoi Cells and 20 Years of Data

AbstractWe derive new, 3D, isotropic models of seismic compressional and shear wavespeeds, Vp and Vs, respectively, their ratio, Vp/Vs, and a catalog of relocated earthquakes for Southern California from more than 10 million P‐ and S‐wave arrivals associated with over 0.3 million earthquakes that occurred between 2000 and 2020. We augment high‐quality analyst‐reviewed phase arrival picks from the Southern California Earthquake Data Center with S‐wave arrival picks obtained with an automated algorithm, and we derive new wavespeed models via traveltime tomography formulated using Poisson‐Voronoi cells (Fang et al., 2020, https://doi.org/10.1785/0220190141). The results contribute to improved regional wavespeed models, particularly the Vp/Vs model, and absolute event locations. The obtained models correlate well with regional geological features and yield more accurate synthetic waveforms than other regional models do for waves with periods shorter than 5 s in much of the modeled region. The derived event catalog exhibits tighter spatial clustering than the standard regional catalog, thereby helping to characterize subsurface features of major faults. The regional 1D averaged Vp/Vs ratio shows high values at shallow depths, decreases to a minimum at about 10 km, then increases again at greater depths below 15 km. Deep seismicity correlates well with regions of Vp/Vs ratio lower than 1.75, which may indicate an increased brittle‐to‐ductile transition depth with an important influence on crustal mechanics. The new wavespeed models and seismic catalog can be useful for various studies including analyses of seismicity patterns and simulations of crustal deformation and ground motion.

On Computational Costs for Monte Carlo Regional-Scale Simulation for Reliable Estimate of City and Urban Area Earthquake Disaster

Regional-scale simulation in high spatial and temporal resolutions is being developed for a more reliable estimate of earthquake disasters in city and urban areas. Monte Carlo simulation is used to account for various uncertainties in analysis models. Since one regional-scale simulation needs a large amount of computation, it is important to estimate computational costs for the Monte Carlo simulation. In this paper, we first clarify uncertainties involved in the simulation of ground motion, structural seismic response, traffic flow, and economic recoveries. We then evaluate computational costs that are required for the reliable estimate using Tokyo Metropolis Earthquake as an example. The reliability of the Monte Carlo regional-scale simulation is discussed, considering the future trends of digital information about city and urban areas and monetized computational cost as well as the uncertainty of an earthquake scenario which is input to the regional-scale earthquake simulation.

Ground motion variability in Israel from 3-D simulations of <i>M</i> 6 and <i>M</i> 7 earthquakes

Abstract. In Israel, due to low seismicity rates and a sparse seismic network, the temporal and spatial coverage of ground motion data is insufficient to estimate the variability in moderate–strong (M>6) ground motions required to construct a local ground motion model (GMM). To fill this data gap and to study the ground motion variability in M>6 events, we performed a series of 3-D numerical simulations of M 6 and M 7 earthquakes. Based on the results of the simulations, we developed a parametric attenuation model (AM) and studied the residuals between simulated and AM peak ground velocities (PGVs) and the single station variability. We also compared the simulated ground motions with a global GMM in terms of PGV and significant duration (Ds 595). Our results suggested that the AM was unable to fully capture the simulated ground motion variability mainly due to the incorporation of super-shear rupture and effects of local sedimentary structures. We also showed that an imported GMM considerably deviates from simulated ground motions. This work sets the basis for future development of a comprehensive GMM for Israel, accounting for local source, path, and site effects.

Seismic response analysis of single-pylon suspension bridge under random ground motion

The finite element model of suspension bridge was established according to the actual bridge engineering in Southwest area of China. In order to simulate the random ground motion model accurately and efficiently, the orthogonal random function ground motion modeling method based on Priestley evolution spectrum theory is adopted. The dimensionality reduction simulation of random ground motion is realized, and the simulated ground motion samples are input into the finite element model to carry out the time history analysis. Finally, the seismic response of the bearing and pylon is analyzed and important conclusions are drawn.

CGFDM3D-EQR: A Platform for Rapid Response to Earthquake Disasters in 3D Complex Media

AbstractEarthquake disasters cause serious losses of human life and property. A rapid response platform for earthquake disasters can provide scientific suggestions for real-time postearthquake rescue deployment, reducing losses. We developed an earthquake response platform named CGFDM3D-EQR that quickly provides earthquake intensity for evaluating complex earthquake disasters. The intensity evaluations are derived from strong ground motion simulations that couple 3D complexities in elevation, medium structure, and earthquake source. The curved grid finite difference method (CG-FDM), which can accurately resolve 3D complexities during earthquake simulation, is adopted in this platform. We developed a CG-FDM parallel algorithm for strong ground motion simulation based on central processing unit (CPU) and graphical processing unit (GPU) heterogeneous architectures. With these characteristics, the platform can simulate strong earthquake ground motions and provide seismic intensity assessments in less than 30 min using our cluster. To verify the platform, we performed four simulations, and the results show that our platform is reliable and efficient. Owing to its user-friendly features and high efficiency, the CGFDM3D-EQR platform can play essential roles in seismic hazards responses, scenario earthquake evaluations, and related applications.

Wavelet-Based Stochastic Model for Jointly Simulating Three-Component Ground Motions

ABSTRACTA large number of ground motions are needed in performance-based earthquake engineering. To date, most existing stochastic models are limited to simulating a single horizontal component of earthquake motions. This study proposes a wavelet-based stochastic method for jointly simulating three-component accelerograms using earthquake magnitudes, source-to-site distances, and site conditions as input. Based on the Pacific Earthquake Engineering Research Center Next Generation Attenuation (NGA)-West2 database, prediction equations are developed for wavelet-packet parameters of two horizontal and one vertical components. Correlations among these components are obtained to jointly simulate three-component motions based on earthquake scenarios. The simulated ground motions are systematically compared with existing ground-motion attenuation equations. The model has the capability to simulate the different frequency content of horizontal and vertical motions. The simulated vertical-to-horizontal spectral ratios are found to be consistent with observed strong-motion data. The model is applicable to shallow crustal earthquakes in an active tectonic region with a moment magnitude between 5 and 8, source-to-site distance from 0 to 100 km, and shear-wave velocity in the top 30 m (VS30) in the range of 150–1000 m/s. It can find important applications in 3D time-history analyses in performance-based earthquake engineering.