Strong Ground Motion Simulation Research Articles

Dynamic Rupture and Strong Ground-Motion Simulations of the 8 January 2022 Ms 6.9 Qinghai Menyuan Earthquake

Abstract The 2022 Ms 6.9 Qinghai Menyuan, China, earthquake is the most destructive earthquake to have occurred near the Lenglongling fault at the western segment of the Qilian–Haiyuan fault since 2016 Ms 6.4 Menyuan earthquake. The 2022 earthquake generated surface rupture measuring about 30 km with an unexpected maximum offset larger than 2.6 m in the epicentral area, and severely damaged the local infrastructure and transportation. To analyze the possible causes of the large surface slip and to reveal the rupture process, we modeled the dynamic rupture and strong ground motion of the 2022 Menyuan earthquake using the curved-grid finite-difference method. In the simulation, the geometry of the fault is constructed based on the observed trace of the surface ruptures. The background tectonic stress field is assumed to be uniform, and the slip-weakening law with the constant friction coefficients is adopted. Our modeling results showed that the rupture model with a focal depth of 6 km and a rupture width of 10 km provides a good fit to the observed surface slips and the field records. We also investigated the effects of the focal depth and the rupture size on the surface slips. It is found that under the same conditions, the dynamic rupture models with a larger rupture size generated greater coseismic slips at the surface. However, only the model with a relatively smaller rupture width produced an Mw∼6.7 event similar to the Menyuan earthquake. In contrast, the influence of the focal depth is less significant. The decrease of the focal depth only leads to a slight increase in surface slip. Our results illustrated that a surface-breaking rupture with a relatively narrow width may physically control the general characteristics of the earthquake. This study provides a new insight into the rupture dynamics of the 2022 Menyuan earthquake.

Unveiling the Mechanisms of the 1819 M 7.7 Kachchh Earthquake, India: Integrating Physics‐Based Simulation and Strong Ground Motion Estimates

AbstractThis study provided a comprehensive understanding of the source process of the 1819 M 7.7 Kachchh Indian earthquake using physics‐based dynamic rupture modeling and strong ground motion simulations. We successfully simulated the spontaneous dynamic rupture along a curved non‐planar fault using the 3‐D curved‐grid finite‐difference method (CGFDM). The estimated earthquake magnitude is around 7.6, consistent with previous estimations. Our simulations accurately replicated macroscopic rupture patterns and surface deformation, showing agreement with observed data along the Allah Bund fault (ABF) with a maximum displacement ∼5.5 m at the Earth's surface. The maximum modeled coseismic slip on the fault was approximately 7.5 m. Notably, the ABF exhibited characteristics of a weak barrier (leaky barrier) at the bending part, allowing the rupture to propagate further. Despite limitations in surface deformation calculations, the modeled values aligned with the trend of surface fault slip, with a slight deviation in the epicenter toward the east compared to earlier studies. We observed a homogeneous principal stress oriented N25°E, consistent with the present day Indian plate motion. The estimated horizontal peak ground velocities (PGVh) and the maximum value of Intensity X+ aligns well with observations. Furthermore, conducting thorough case studies on significant earthquakes and potential seismic scenarios in stable continental regions is crucial. Such studies play a vital role in validating and improving dynamic rupture models. When combined with statistical methods, this research holds great promise for advancing seismic hazard assessments, earthquake engineering, and strategies for disaster management.

Simulation of Strong Ground Motions From the October 30, 2020, Samos Earthquake and Validations Against Observed Records, Intensity Distributions, and Damages in Izmir, Türkiye

An earthquake of Mw = 7.0 occurred on October 30, 2020, in the Aegean Sea near Samos Island, which caused severe structural damage in Bayraklı, Izmir (Türkiye), located around 70 km from the epicenter. To investigate the source, path, and site effects, ground motions recorded in Western Anatolia are simulated using the stochastic finite-fault method based on a dynamic corner frequency approach. The input model parameters are calibrated using the recorded motions at selected 10 stations within an epicentral distance of less than 100 km. The soil amplifications are modeled using horizontal-to-vertical spectral ratios and generic amplification factors. At most stations, including a few within Izmir Bay, amplitudes and frequency contents are modeled closely. Minor discrepancies within particular frequency bands can be attributed to insufficient representation of the local site effects. Finally, distributions of observed and simulated felt intensities are found to be consistent.

Accessing Near-Field Strong Ground Motions Using a Multi-Scheme Method in the Kalawenguquan Fault, Xinjiang, China

The middle segment of the Kalawenguquan fault has been active since the Holocene, with a maximum credible earthquake magnitude of MS 7.5. We established two source models based on empirical relationships, as well as geological, geomorphological, and seismic characteristics. Taking into account the uncertainties of simulation parameters, we adopted the stochastic finite-fault method to calculate all combinations of a multi-scheme simulation. The effects of different source models, initial rupture points, and site locations on the prediction of ground motion parameters were analyzed. The results indicate that when a site is located on a smaller asperity and is a certain distance from the largest asperity, the simulation results are higher. For different sites, when the initial rupture point is located near the smaller rather than the larger asperity, the acceleration response spectra are higher. Our results show that the relationships between the initial rupture points, asperities, and sites have a significant impact on the simulation results. Therefore, our study highlights the relevance of determining the initial rupture point and source model to obtain a reasonable evaluation for near-field strong ground motion simulations at major infrastructures.

A Physics-Based Seismic Risk Assessment of the Qujiang Fault: From Dynamic Rupture to Disaster Estimation

This study achieved the construction of earthquake disaster scenarios based on physics-based methods—from fault dynamic rupture to seismic wave propagation—and then population and economic loss estimations. The physics-based dynamic rupture and strong ground motion simulations can fully consider the three-dimensional complexity of physical parameters such as fault geometry, stress field, rock properties, and terrain. Quantitative analysis of multiple seismic disaster scenarios along the Qujiang Fault in western Yunnan Province in southwestern China based on different nucleation locations was achieved. The results indicate that the northwestern segment of the Qujiang Fault is expected to experience significantly higher levels of damage compared to the southeastern segment. Additionally, there are significant variations in human losses, even though the economic losses are similar across different scenarios. Dali Bai Autonomous Prefecture, Chuxiong Yi Autonomous Prefecture, Yuxi City, Honghe Hani and Yi Autonomous Prefecture, and Wenshan Zhuang and Miao Autonomous Prefecture were identified as at medium to high seismic risks, with Yuxi and Honghe being particularly vulnerable. Implementing targeted earthquake prevention measures in Yuxi and Honghe will significantly mitigate the potential risks posed by the Qujiang Fault. Notably, although the fault is within Yuxi, Honghe is likely to suffer the most severe damage. These findings emphasize the importance of considering rupture directivity and its influence on ground motion distribution when assessing seismic risk.

Simulation of strong ground motions from 2016 Kumamoto (Mw 7.1), Japan, earthquake using modified hybrid technique

Simulation of strong ground motions from 2016 Kumamoto (Mw 7.1), Japan, earthquake using modified hybrid technique

Stochastic strong-ground motion simulation in the Santiago metropolitan region considering an Mw 7.8 intraplate intermediate-depth earthquake

Large intraplate intermediate-depth (IID) events are the most destructive to Chilean structures and they occurred throughout the country. Cities located above the hypocenters of these large earthquakes have been completely destroyed. In recent years, only small- and moderate-magnitude IID events have been reported below Santiago, the most populated Chilean city; however, the occurrence of large-magnitude IID events cannot be ruled out. In this study, we investigated the strong-ground motion generated by large-magnitude earthquakes occurring below the Santiago metropolitan region. We used a stochastic methodology to simulate synthetic records, considering IID events of magnitude Mw 7.8. To validate this method, we simulated intermediate-depth events of magnitudes Mw ∼5-6 that occurred near Santiago. We further calibrate our results by reproducing the strong-ground motion data recorded during the 2005 Tarapacá Mw 7.8 Northern Chile IID earthquake. We observe that in some areas of the Santiago Basin, high PGA values can reach values close to 1 g, in which, in addition to directivity effects and takeoff angles, the rupture distances (∼100 km) and soil type (C) play a key role in amplifying strong-ground motion. Finally, our findings highlight the importance of reproducing high-frequency time histories as a proxy to re-evaluate the seismic hazard due to large IID earthquakes.

Structure of the Gonghe Sedimentary Basin in the northeastern Tibetan Plateau: evidence from teleseismicPwaves recorded by a dense seismic array

SUMMARYThe Gonghe Basin in the northeast Tibetan Plateau presents significant potential for hot dry rock (HDR) geothermal resources. A 1990 Mw 6.4 earthquake in the basin furthers the need for an improved understanding of its sedimentary structure. In this study, we utilize data from a dense seismic array of 88 short-period seismometers deployed at an interstation spacing of approximately 3 km to scrutinize the sedimentary structure of the Gonghe Basin. By analysing teleseismic P waveforms, we identify P-to-S converted waves (Ps wave) originating from the sedimentary basement. We then determine the delay time between the Ps waves and the direct P waves (P wave) through waveform cross-correlation. By integrating this delay time with empirical velocity structure models, HDR borehole data and results from teleseismic receiver function analysis, we derive a sediment thickness model of the Gonghe Basin for the Qabqa geothermal area. Our findings reveal a gradual increase in sediment thickness from around 500 m in the east to approximately 3000 m in the west, which is consistent with other geophysical surveys and borehole data. The thick sediments in the basin could potentially serve as an excellent thermal storage cover for HDR. The strong ground motion simulation using our sediment thickness model shows that thick sediments can amplify seismic waves, increasing the risk of seismic hazards. Moreover, our study indicates that the clear Ps waves can be effectively extracted to construct a dependable sediment thickness model using teleseismic P waves recorded by a short-period dense seismic array.

Simulation of strong ground motions of 1991 Uttarkashi (M 7) and 1999 Chamoli (M 6.6) earthquakes using modified hybrid technique

Simulation of strong ground motions of 1991 Uttarkashi (M 7) and 1999 Chamoli (M 6.6) earthquakes using modified hybrid technique

Broadband Strong Ground Motion Modeling Using Planar Dynamic Rupture With Fractal Parameters

AbstractDynamic rupture modeling represents a promising physics‐based approach to strong ground motion simulations. However, its application in a broad frequency range (0–10 Hz), interesting for engineering studies, is challenging. The main reason is that widely used and relatively simple planar fault models with smooth distributions of initial stress and frictional parameters, or even self‐similar initial stress, result in ground motions depleted in high‐frequency content. Here we propose an efficient approach for the linear slip‐weakening friction model on a planar fault based on the Ide and Aochi (2005, https://doi.org/10.1029/2004jb003591) multiscale model with a small‐scale random fractal distribution of the slip‐weakening distance Dc. We propose a way to combine these variations with a large‐scale deterministic dynamic model. We illustrate the approach on an elliptical model and a smooth model of the 2016 Mw 6.2 Amatrice, Italy, earthquake from low‐frequency dynamic rupture inversion. To intensify the incoherence of the rupture propagation, we also include a variation of the strength and initial stress, both correlated with Dc. These additions result in sustained high‐frequency radiation during the whole rupture propagation and omega‐square source time functions. The new model of the Amatrice earthquake generates synthetics that agree with the local ground motion model up to 5 Hz in terms of spectral accelerations while preserving the average and integral dynamic rupture parameters (e.g., stress drop, fracture and radiated energy). The fractal dynamic model can be easily implemented in any dynamic rupture propagation code and is thus readily applicable in broadband physics‐based ground motion predictions for earthquake scenarios in seismic hazard assessment.

The 3-D shallow velocity structure and sedimentary structure of 2017 Ms6.6 Jinghe earthquake source area derived from dense array observations of ambient noise

To understand the shallow structure and complex sedimentary environment of the 2017 Jinghe Ms6.6 earthquake focal area, we used one mouth of continuous sesimic data from a dense seismic array of 208 short period stations around the earthquake focal area, and applied the ambient noise tomography (ANT) method to image the three-dimensional Shear wave velocity structure at the depth less than 4 km. The shear wave velocity shown clear lateral variations and vertical variations from the surface to the deeper regions and has a tight correlation with surface geological and tectonic features in the study area. Obvious low-velocity anomalies has been presented throughout most of the Jinghe depression, whereas the Borokonu Mountains presented high-velocity anomalies. The thickness of the Cenozoic sedimentary basement in the study area is approximately 1–4 km, and the distribution of thickness is highly uneven. The crystalline basement in the study area has strong bending deformation, and the non-uniform Cenozoic sediments are related to the strong bending deformation of the crystalline basement. The Kusongmuchik piedmont fault is a high-angle thrust fault cutting through the base. There are also many medium low-angle faults, which do not penetrate the surface, which has indicated that they are in a concealed state at present. The results have provided a shallow high-resolution 3D velocity model that can be used in the simulation of strong ground motion and for evaluating potential seismic hazards.

Application of MEMS Data to Fast Inversion of Rupture Process: Tests with Recordings from the IRREEW Network

AbstractThe China Earthquake Administration established a network for intensity rapid report and earthquake early warning (IRREEW) in 2016–2020, which consists of approximately 5000 conventional strong-motion and approximately 10,000 low-cost micro-electro-mechanical system (MEMS) seismometers. These seismographs, particularly MEMS stations, can provide a large amount of near-field waveform data suitable for rapid source inversion. Compared with conventional strong-motion data, MEMS recordings have rarely been used in the previous source inversions, because the MEMS technology is newly applied in earthquake monitoring, and the seismograph has a relatively lower signal-to-noise ratio and more severe baseline shifts. However, from waveform comparisons at collocated MEMS and strong-motion stations, we find that they are highly consistent with each other, particularly at frequencies above 0.04 Hz. To explore the application prospect of MEMS data to source inversion, we inverted both MEMS and strong-motion data for three strong earthquakes recorded by the IRREEW network during 2021–2022 to determine their rupture processes. In applications to the 2021 Mw 6.1 Yangbi earthquake, the 2022 Mw 6.6 Menyuan earthquake, and the 2022 Mw 6.6 Luding earthquake, the MEMS data equally well constrain the rupture model. The resulting source information, including the moment magnitude, rupture direction, and rupture dimension, are consistent with those obtained from the strong-motion inversions. Because the low-cost MEMS instruments can be deployed densely around seismically active regions, they can provide urgent waveform data for rapid determination of rupture process, which is crucial for simulation of strong ground motions, and assessments of earthquake and related disasters.

Strong ground motion simulations of the 2016 Kumamoto earthquakes using corrected empirical Green’s functions: methods and results for ESG6 blind prediction Steps 2 and 3 with improved parameters

This paper describes the methods and results of the strong ground motion simulations for three earthquakes from the 2016 Kumamoto earthquake sequence using corrected empirical Green’s functions. The target earthquakes were an aftershock (Mw 5.5), the largest foreshock of the sequence (Mw 6.1), and the mainshock (Mw 7.1). The corrected empirical Green’s function method was used in the simulations. This simulation method combines simple source and path factors with empirical site amplification and phase factors to generate realistic site-specific strong motions. Simulations were originally conducted to participate in blind prediction exercises in ESG6. Although the simulations performed in this study were based on the models submitted to the blind prediction committee, several modifications were made after the blind prediction exercise. First, the observed records at the target site of the blind prediction called KUMA were used to compare observed and synthetic strong ground motions. In addition, a regional spectral inversion was conducted to obtain a more appropriate Q-value and site amplification factor. Synthetic strong motions were found to explain the observed strong ground motions at KUMA and other stations. Comparisons with predictions by other methods and the sensitivity to the rupture scenario were also discussed. These results provide useful information for applying the corrected Green’s function method to strong ground motion simulations.Graphical

Probabilistic and Scenario-Based Seismic Hazard Assessment on the Western Gulf of Corinth (Central Greece)

The Gulf of Corinth (Central Greece) is one of the most rapidly extending rifts worldwide, with its western part being the most seismically active, hosting numerous strong (M ≥ 6.0) earthquakes that have caused significant damage. The main objective of this study was the evaluation of seismic hazard through a probabilistic and stochastic methodology. The implementation of three seismotectonic models in the form of area source zones via a logic tree framework revealed the expected level of peak ground acceleration and velocity for return periods of 475 and 950 years. Moreover, PGA values were obtained through the stochastic simulation of strong ground motion by adopting worst-case seismic scenarios of potential earthquake occurrences for known active faults in the area. Site-specific analysis of the most populated urban areas (Patras, Aigion, Nafpaktos) was performed by constructing uniform hazard spectra in terms of spectral acceleration. The relative contribution of each selected fault segment to the seismic hazard characterizing each site was evaluated through response spectra obtained for the adopted scenarios. Almost all parts of the study area were found to exceed the reference value proposed by the current Greek National Building Code; however, the three urban areas are covered by the Eurocode 8 regulations.

Simulation of Dynamic Rupture Process and Near-Field Strong Ground Motion for the Wenchuan Earthquake

ABSTRACT The 2008 Wenchuan earthquake that occurred in the Longmenshan thrust zone is the most serious natural disaster recorded in China’s densely populated areas over the past few decades. Its northeast-trending principal fault—the Yingxiu–Beichuan fault (YXBCF), has a complex, segmentary-cascaded geometry and was dominated by the thrust slip in the southwest section, while the right-lateral slip in the northeast section. Some previous works believe that there may have occurred a supershear rupture in the strike-slip-dominated northeast section. Here we revisited this earthquake by exploring the dynamic rupture mechanism of the principal fault and showed a hypothetical scenario with supershear rupture occurring in its northeast section. We utilized a 3D curve grid finite-difference method to simulate the spontaneous rupture process of the YXBCF and corresponding near-field strong ground motion. An appropriate focal process is obtained using the trial-and-error method within reasonable parameters, and its related responses are validated by geological investigations and geophysical inversions. Besides, a large hypothetical oblique propagating supershear rupture is shown between Beichuan and Nanba in the northeast section of the YXBCF. Its transition mechanism is related to the Gaochuan–Beichuan conjugated fault from the fault geometry perspective, and belongs to the joint action of fault barrier and free surface. Such a supershear scenario is not rejected by observations and could increase the credibility of the occurrence of supershear rupture in the northeast section of the YXBCF during the Wenchuan earthquake.

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).

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.

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.

Preliminary strong ground motion simulation at seismic stations within nuclear power plant sites in South Korea by a scenario earthquake on the causative fault of 2016 Gyeongju earthquake

Stochastic and an empirical Green's function (EGF) methods are preliminarily applied to simulate strong ground motions (SGMs) at seismic stations within nuclear power plant (NPP) sites in South Korea by an assumed large earthquake with MW6.5 (scenario earthquake) on the causative fault of the 2016 Gyeongju earthquake with MW5.5 (mainshock). In the stochastic method, a ratio of spectral amplitudes of observed and simulated waveforms for the mainshock is assumed to be an adjustment factor. In the EGF method, SGMs by the mainshock are simulated assuming SGMs by the 2016 Gyeongju earthquake with MW5.0 (foreshock) as the EGF. To simulate SGMs by the scenario earthquake, a ratio of fault length to width is assumed to be 2:1 in the stochastic method, and SGMs by the mainshock are assumed to be EGF in the EGF method. The results are similar based on a bias of the simulated response spectra by the two methods, and the simulated response spectra by the two methods exceeded commonly standard design response spectra anchored at 0.3 g of NPP sites slightly at a frequency band above 4 Hz, but considerable attention to interpretation is required since it is an indirect comparison.

Stochastic Simulation of Strong Ground Motions From Two M > 5 Uttarakhand Earthquakes

Many studies based on the geodetic data and statistical analysis of seismicity have pointed out that sufficient amount of stress accumulated in the Himalayan plate boundary may host a big earthquake. Consequently, high seismic activities and infrastructural developments in the major cities around Himalayan regions are always of major concern. The ground motion parameter estimation plays a vital role in the near real time evaluation of potentially damaged areas and helps in mitigating the seismic hazard. Therefore, keeping in mind the importance of estimation of ground motion parameters, we targeted two moderate-size earthquakes that occurred recently within a gap of 10 months in Uttarakhand region with M > 5.0 on 06/02/2017 and 06/12/2017. The ground motions are simulated by adopting a stochastic modeling technique. The source is assumed as ω−2, a circular point source (Brune’s model). The average value of reported anelastic attenuation from various studies, the quality factor, Qs= 130.4*(f0.996), and stress drop values obtained through iterative procedure are considered for simulations. The stochastic spectra are generated between 0.1 and 10 Hz of frequency range. The site effect is also estimated by using the H/V method in the same frequency range. The synthetic spectra are compared with the observed Fourier amplitude spectra obtained from the recorded waveform data and converted back to the time histories. The stochastic time histories are compared with the observed waveforms and discussed in terms of amplitude (PGA). The simulated and observed response spectra at different structural periods are also discussed. The mismatch between the observed and simulated PGA values along with the GMPE existing for shallow crustal earthquakes is also discussed in the present work.