Broadband Ground Research Articles

A View of the Linkup Between the Neodeterministic and the Probabilistic Seismic Hazard Assessments

Abstract In this article, with a focus on improving the framework of seismic hazard assessment (SHA), we propose a link-up procedure between the neodeterministic seismic hazard assessment (NDSHA) and the widely adopted probabilistic seismic hazard assessment (PSHA). We discussed why NDSHA should be linked with PSHA if the former is to play a role in the framework of the existing multilevel fortification strategy against earthquake disasters. The link-up procedure was illustrated by a case study in which scenario earthquake (SE) was the bridge between the two SHAs. Some potential issues related to the proposed procedure, such as the determination of SE, modeling of finite-fault source, and synthesis method of broadband ground motion, were further discussed. The final result is a set of hazard maps with multiple parameters and multiple fortification levels, which is appropriate for application to the seismic design of engineering structures. The improved hazard map highlights the hazards from future large earthquakes near big cities.

Stochastic Green’s Function Method Considering Non-Uniform Rise Time Distribution to Simulate 3D Broadband Ground Motion

The stochastic Green’s function method has been widely used in the field of ground motion simulation in recent years. It is generally assumed that the rise time of each subfault is the same in this method. Since the rise time significantly influences the amplitude of simulation results in the intermediate frequency band, to improve the accuracy of stochastic Green’s function method for near-fault broadband ground motion simulation, referring to the numerical simulation results of Day, the rise time is assumed to be non-uniformly distributed on the fault, and an improved approximate expression of rise time on a rectangular fault considering that the rupture starting point may be at any position and the aspect ratio may be arbitrary is proposed. Additionally, the contributions of P, SV and SH wave are considered, respectively, and an improved stochastic Green’s function method is proposed for 3D broadband ground motion simulation. Taking the 1994 Northridge earthquake in America and 2013 Lushan earthquake in China as examples, under different subfault division numbers, the synthesized source spectra are compared with the omega-squared theoretical source spectra of the large earthquake, and the simulated ground motions at observation points are compared with observed records to verify the effectiveness of the improved method. The results show that when the Northridge earthquake fault and Lushan earthquake fault are divided into 9 × 10 subfaults and 11 × 7 subfaults, respectively, the simulation results obtained using the improved method are close to the observed records in the broadband frequency range. Therefore, the improved method can effectively simulate the 3D ground motion in near-fault regions.

Kinematic rupture modeling of broadband ground motion from the 2022 MS6.9 Menyuan earthquake

AbstractWe propose a novel kinematic rupture modeling procedure for synthesizing broadband ground motions derived from the frequency-wavenumber integration algorithm. This procedure addresses two key issues in characterizing the rupture processes relevant to broadband seismic radiation: an accurate Green's function and a well-constrained kinematic source model. For the first issue, we derive the theoretical Green's function based on an improved dynamic stiffness matrix approach that effectively handles wave propagation in a 1D crustal velocity structure across a broad frequency band. For the second issue, we generate the hybrid source model that combines asperity slip and random slip over the fault plane to effectively implement constraints on the radiated energy during the whole rupture process. The accuracy and effectiveness of the proposed methodology are verified by comparing with the surface acceleration traces and Fourier spectra calculated by spectral element method. With the hybrid source model and crustal velocity structure applicable to the target area, the broadband (0–10 Hz) ground motion of the 2022 MS6.9 Menyuan earthquake is synthesized. The amplitude, duration, and frequency content of the synthetic motions are systematically compared with those of the available observed records and ground motion attenuation relationships, as well as the spatial distribution characteristics of the near-field ground motions from the earthquake scenarios are presented. In conclusion, the case study of the Menyuan MS6.9 earthquake demonstrates that the presented modeling procedure can estimate broadband ground motions rapidly and reliably from a physics-based kinematic rupture perspective.

Improvements to EXSIM in Ground Motion Simulation for Earthquakes Explained by Double‐Corner‐Frequency Source Model

AbstractThe stochastic EXtended finite‐fault ground‐motion SIMulation algorithm (EXSIM) has been widely applied in simulating and predicting broadband strong ground‐motion. However, an increasingly number of researchers have found that EXSIM may overestimate ground‐motions at low frequencies for some large‐magnitude earthquakes and/or thrust earthquakes, for which the far‐field source model has been explained by a double‐corner‐frequency model. Despite controversy, the double‐corner‐frequency model is now being accepted as one of the main categories of the far‐field source model. This study demonstrated the limited applicability of EXSIM to earthquakes explained by the double‐corner‐frequency source model, by presenting the equivalence between motions generated by EXSIM and those generated by EXSIM's point‐source version, SMSIM, which adopts the ω‐square single‐corner‐frequency model. Furthermore, two improvements to EXSIM have been proposed: (a) the incorporation of the asperity‐distributed stress‐drop compound faults model and (b) the hybrid application of EXSIM with the proposed model. The effects of the two improvements have been verified by comparing EXSIM‐generating motions with recorded ground‐motions for the 2013 Mw 6.7 Lushan thrust earthquake. Significantly, consistent simulation accuracy has been achieved across high‐ and low‐frequency bands as well as in far‐ and near‐fields. The consistent accuracy of the improved EXSIM in simulating high‐ and low‐frequency ground motions enables its direct and independent application to broadband ground motion simulations. Moreover, the first validation of this consistent accuracy in both near‐ and far‐field scenarios further enhances its application in earthquake engineering practices.

Revisiting the 1934Mw 8.2 Bihar–Nepal earthquake—Simulation of broadband ground motions

SUMMARYThe 1934 Mw 8.2 Bihar–Nepal earthquake was one of the devastating earthquakes, which made seismologists realize the importance of proper seismic hazard analysis and design aspects in India. The event occurred way before proper seismic networks were implemented and hence there are no recorded ground motions available for this event. This study, thus aims to generate possible ground motions for the 1934 Mw 8.2 Bihar–Nepal event. The complex geographical features, ambiguous source information and lack of ground motion data make the simulation and validation of ground motions very difficult. In this regard, the broad-band (BB) ground motions are simulated and validated for the most recent well-documented Himalayan event, that is, the 2015 Mw 7.9 Nepal earthquake in order to calibrate the model and simulation methodology. For this purpose, the computational model is presented for a region of 1000 km × 670 km (longitude 80–89 °E and latitude 23–30 °N) in the Indo-Gangetic Basin to simulate the low-frequency (LF) ground motions using spectral element method. These deterministically simulated LF ground motions are combined with stochastically simulated high-frequency (HF) ground motions based on an improved seismological model . The seismic moment and dimensions of the rupture plane are used to generate ten samples for the finite fault source model having different slip distribution along the rupture plane as a random field. The BB ground motions (0.01–25 Hz) are obtained by merging LF and HF ground motions in the time domain by matching them at a frequency of ∼0.3 Hz. Such BB results are simulated at a grid of stations and at locations where modified Mercalli intensity (MMI) values are available. The estimated MMI values and the observed MMI values are compared to emphasize the efficacy of the model. The maximum PGA estimated from the simulated ground motions in horizontal and vertical directions are observed to be 0.48 g and 0.4 g. Further, 5 per cent damped response spectra and spectral amplification are analysed concerning the sediment depth of the Indo-Gangetic Basin. The results from the study can serve as inputs for dynamic analysis and the design of earthquake-resistant structures across different locations in the Indo-Gangetic Basin.

Spatial correlation assessment of multiple earthquake intensity measures using physics-based simulated ground motions

Predictive models for spatial correlation play an effective role in the assessment of seismic risk associated with distributed infrastructure and building portfolios. However, existing models often rely on simplified approaches, assuming isotropy and stationarity. This paper verifies these assumptions by presenting a comprehensive study using a database of 3D physics-based simulated broadband ground motions for Istanbul, generated by the SPEED software. The results reveal significant event-to-event variability and nonstationary and anisotropic characteristics of spatial correlation influenced by source, path, and site effects. The development of nonstationary correlation models requires exploring influential metrics beyond spatial proximity and gaining a deep understanding of their impact, which is the focus of this study. Analysis of the spatial correlations of peak ground displacement, peak ground velocity, peak ground acceleration, and response spectral accelerations at different periods, employing both stationary and nonstationary correlation modelling methods and considering the finite fault model, indicates that the slip distribution pattern, direction and distance of station pairs relative to earthquake rupture, soil softness, and homogeneity of soil properties significantly influence the spatial correlations of near-field earthquake ground motions. Implementation of the introduced parameters in predictive spatial correlation models enhances the precision of regional seismic hazard assessments.

Prediction of Regional Broadband Strong Ground Motions Using a Teleseismic Source Model of the 18 April 2014 Mw 7.3 Papanoa, Mexico, Earthquake

ABSTRACT To estimate predicted ground motion from a teleseismic slip model, we use a low- and high-frequency hybrid method to simulate the regional, strong ground motions observed following the 18 April 2014 moment magnitude (Mw) 7.3 Papanoa, Mexico, earthquake. To generate the regional ground motion at low frequencies (<1 Hz), a teleseismically derived, finite-fault, kinematic model is used to define the earthquake source, taking into account slip-model variations identified with a parameter sampling approach that considers possible errors in the fault geometry, the hypocenter depth, and the rupture velocity. A 3D crustal model is used to calculate the low-frequency ground motions using a finite-element calculation that includes topography and considers variations in the source model to estimate the uncertainty in the calculations. High frequencies (>1 Hz) are added using a 1D full-wave propagation code that estimates uncertainties by considering multiple random distributions of slip with different spatial correlation lengths. The synthetic, broadband (0.05–10.0 Hz) ground motions are obtained by combining the low- and high-frequency portions match filtered at 1 Hz. These synthetic ground motions are compared with the regional observations using velocity records, peak ground acceleration, and medians of the orientation-independent response spectra of the horizontal components (RotD50) calculated at periods of 0.2, 0.3, 0.5, 1.0, 2.0, 3.0, 5.0, 7.5, and 10.0 s. The results indicate that ground motions estimated at these periods using our hybrid approach based primarily on a teleseismically derived source model are comparable to the values observed for the 2014 Papanoa earthquake at regional distances. The approach could be used to estimate strong-motion spectral levels expected for regions with limited local and regional recordings and could also fill in magnitude or distance gaps in ground-motion prediction relations utilized in the assessment of seismic hazard.

A future scenario earthquake and ground motion hazards for Kathmandu, Nepal

Since Nepal is an earthquake-prone country due to the collision of the Indian and Eurasian plates, it is crucial for its capital of Kathmandu to evaluate ground motion hazards from a future large earthquake. For this purpose, we constructed a realistic scenario earthquake with realistic rupture parameters in a likely location. To obtain the location, a new distribution of the rupture zones of large historical earthquakes along the Main Himalayan Thrust (MHT) was obtained by integrating the distribution from a previous study and the results of trench surveys. Global Navigation Satellite System observations indicated that the plate boundary is strongly coupled from the southern boundary of the MHT to a depth of approximately 10 km and there is almost no lateral change in the coupling. This implies that all regions along the MHT have similar rates of strain increase. Therefore, it is most probable that the rupture zone of the oldest previous event will rupture as a scenario earthquake. In the new distribution, the 1255 earthquake is the oldest. However, large earthquakes occurred in 1934 and 2015 within its rupture zone. Thus, we adopted the area obtained by removing the 1934 and 2015 rupture zones from the western part of the 1255 rupture zone. The relationship between the rupture area size and seismic moment of the 2015 earthquake lies between the scaling formulas for crustal earthquakes and plate-boundary earthquakes, but is closer to the former. Therefore, using this and the scheme for characterized source models, we determined realistic rupture parameters. We then simulated broadband ground motions in Kathmandu using these rupture parameters, our 3-D velocity structure models, and a hybrid method combining the finite-difference method and the stochastic Green’s function method. We obtained the peak ground accelerations (PGAs) of simulated ground motions, and calculated the seismic intensities in the Modified Mercalli intensity scale from the PGAs as indexes of hazards for Kathmandu. Intensities IX coincide with the center of the Kathmandu Valley, and intensities VIII and VII are found in the area surrounded by the sedimentary boundary and the southernmost part of the valley.Graphical abstract

Simulation of Broadband Ground Motions for the 2016 Mw 6.8 Chauk Earthquake

Simulation of Broadband Ground Motions for the 2016 Mw 6.8 Chauk Earthquake

Broadband Ground-Motion Synthesis via Generative Adversarial Neural Operators: Development and Validation

ABSTRACT We present a data-driven framework for ground-motion synthesis that generates three-component acceleration time histories conditioned on moment magnitude (M), rupture distance (Rrup), time-average shear-wave velocity at the top 30 m (VS30), and style of faulting. We use a Generative Adversarial Neural Operator (GANO)—a resolution invariant architecture that guarantees model training independent of the data sampling frequency. We first present the conditional ground-motion synthesis algorithm (cGM-GANO) and discuss its advantages compared to the previous work. We next train cGM-GANO on simulated ground motions generated by the Southern California Earthquake Center Broadband Platform (BBP) and on recorded the Kiban–Kyoshin network (KiK-net) data, and show that the model can learn the overall magnitude, distance, and VS30 scaling of effective amplitude spectra (EAS) ordinates and pseudospectral accelerations (PSA). Results specifically show that cGM-GANO produces consistent median scaling with the training data for the corresponding tectonic environments over a wide range of frequencies for scenarios with sufficient data coverage. For the BBP dataset, cGM-GANO cannot learn the ground-motion scaling of the stochastic frequency components (f > 1 Hz); for the KiK-net dataset, the largest misfit is observed at short distances (Rrup<50 km) and for soft-soil conditions (VS30<200 m/s) due to the scarcity of such data. Except for these conditions, the aleatory variability of EAS and PSA are captured reasonably well. Finally, cGM-GANO produces similar median scaling to traditional ground-motion models (GMMs) for frequencies greater than 1 Hz for both PSA and EAS but underestimates the aleatory variability of EAS. Discrepancies in the comparisons between the synthetic ground motions and GMMs are attributed to inconsistencies between the training dataset and the datasets used in GMM development. Our pilot study demonstrates GANO’s potential for efficient synthesis of broadband ground motions.

GA-BPNN Prediction Model of Broadband Ground Motion Parameters in Tianjin Area Driven by Synthetic Database Based on Hybrid Simulated Method

GA-BPNN Prediction Model of Broadband Ground Motion Parameters in Tianjin Area Driven by Synthetic Database Based on Hybrid Simulated Method

Pseudo-dynamic rupture implementation in 3D viscoelastic finite-difference code for physics based broadband ground motion synthetics

Pseudo-dynamic rupture implementation in 3D viscoelastic finite-difference code for physics based broadband ground motion synthetics

City-scale buildings damage estimation based on broadband physics-based ground motion simulation of 2021 Ms 6.4 Yangbi, China, earthquake

This article proposed a computational workflow for city-scale building damage estimation based on broadband physics-based ground motion simulation. The dynamic stiffness matrix method in frequency-wavenumber domain is employed for broadband physics-based ground motion simulation of finite fault along with site response correction using equivalent-linear site response analysis approach. With simulated ground motion, seismic response of buildings, using multi-degree of freedom model, is simulated using nonlinear time history analysis, and building damage is evaluated based on a trilinear backbone curve of story’s nonlinear force-drift model. Main advantage of the framework lies in the employed dynamic stiffness matrix method for ground motion simulation, which can efficiently generate broadband ground motions in perfect parallel and naturally capture the physics of finite fault source, propagation path, and spatial variability characteristics of ground motion. To demonstrate the salient features of proposed workflow, the 2021 Ms 6.4 Yangbi earthquake is simulated with frequency resolution up to 20 Hz, and seismic damage of buildings in Yangbi county are estimated. Results show that most traditional wood-adobe structures suffer moderate to severe damage, and engineered seismic buildings (mostly RC frame) in Yangbi county suffer minor damage, which agrees with field investigation results.

Broadband ground motion simulation using a hybrid approach of the May 21, 2021 M7.4 earthquake in Maduo, Qinghai, China

In this study, the broadband ground motions of the 2021 M7.4 Maduo earthquake were simulated to overcome the scarcity of ground motion recordings and the low resolution of macroseismic intensity map in sparsely populated high-altitude regions. The simulation was conducted with a hybrid methodology, combining a stochastic high-frequency simulation with a low-frequency ground motion simulation, from the regional 1-D velocity structure model and the Wang WM et al. (2022) source rupture model, respectively. We found that the three-component waveforms simulated for specific stations matched the waveforms recorded at those stations, in terms of amplitude, duration, and frequency content. The validation results demonstrate the ability of the hybrid simulation method to reproduce the main characteristics of the observed ground motions for the 2021 Maduo earthquake over a broad frequency range. Our simulations suggest that the official map of macroseismic intensity tends to overestimate shaking by one intensity unit. Comparisons of simulations with empirical ground motion models indicate generally good consistency between the simulated and empirically predicted intensity measures. The high-frequency components of ground motions were found to be more prominent, while the low-frequency components were not, which is unexpected for large earthquakes. Our simulations provide valuable insight into the effects of source complexity on the level and variability of the resulting ground motions. The acceleration and velocity time histories and corresponding response spectra were provided for selected representative sites where no records were available. The simulated results have important implications for evaluating the performance of engineering structures in the epicentral regions of this earthquake and for estimating seismic hazards in the Tibetan regions where no strong ground motion records are available for large earthquakes.

A physics‐based spectral matching (PBSM) method for generating fully site‐related ground motions

AbstractThe response spectrum is generally adopted in the seismic design to represent the seismic fortification level, but the structural dynamic analysis requires the ground motions as an input. However, ground motions generated by the traditional spectral matching methods do not have site‐related physical backgrounds for the target site. In this study, a physics‐based spectral matching (PBSM) method is developed to generate fully site‐related broadband ground motions (i.e., the generated ground motions have real physical backgrounds for the target site, including the source process, propagation path, and local site conditions) that are compatible to the target spectrum. In this method, the three‐dimensional (3D) numerical model around the target site is constructed to calculate the strain Green's tensors of all potential source locations using adjoint simulations. The variable space dimension of the seismic source is significantly reduced by applying the self‐similar feature of the multidimension source model, so that the optimization algorithm can be used to search for the rupture process that generates the physics‐based and spectrum‐matched ground motions (abbreviated to PBSM ground motions). The proposed method is applied to the Xiluodu dam in China. Compared with the traditional techniques, the generated ground motions have fully site‐related physical backgrounds and are compatible to the target spectrum. Additionally, as this method generates broadband ground motions based on the deterministic rupture process, any features of ground motions, such as large velocity pulses, can be taken into account throughout the optimization process. This study introduces the deterministic physical backgrounds of earthquakes to performance‐based seismic design and analysis. The proposed method may have a significant application potential in earthquake engineering.

Solid Earth-atmosphere interaction forces during the 15 January 2022 Tonga eruption.

Rapid venting of volcanic material during the 15 January 2022 Tonga eruption generated impulsive downward reaction forces on the Earth of ~2.0 × 1013 N that radiated seismic waves observed throughout the planet, with ~25 s source bursts persisting for ~4.5hours. The force time history is determined by analysis of teleseismic P waves and Rayleigh waves with periods approximately <50 s, providing insight into the overall volcanic eruption process. The atmospheric acoustic-gravity Lamb wave expanding from the eruption produced broadband ground motions when transiting land, along with driven and conventional tsunami waves. Atmospheric standing acoustic waves near the source produced oscillatory peak forces as large as 4 × 1012 N, exciting resonant solid Earth Rayleigh wave motions at frequencies of 3.7 and 4.6 mHz.

Estimation of broadband ground motion characteristics considering source parameter uncertainty and undetermined site condition in densely populated areas of Pingwu

Three destructive earthquakes occurred in Pingwu and Songpan, Sichuan Province, China, between August 16 and 23, 1976. Due to the seismic monitoring capability at that time, the ground motion characteristics of these earthquakes are very vague. Realistc and reliable strong ground motion input plays an important role in seismic building design and urban-scale earthquake damage simulation. This study reproduces the main broadband ground motion characteristics of the 1976 Ms7.2 Songpan earthquake in densely populated areas of Pingwu. The empirical Green’s function method and finite difference method are used to simulate high-frequency and low-frequency ground motion, respectively, and the broadband ground motion is obtained by superposition within the frequency range. In addition, in combination with the “Recipe” source parameter scheme, various uncertainties in the source parameters are considered, including the source mechanism, source depth, asperity parameters, etc. We obtain 36 kinds of broadband ground motion at six typical locations in the Pingwu area. Moreover, we test the rationality of the obtained broadband ground motion by ground motion prediction equations(GMPEs), and the broadband ground motions are consistent with the local ground motion characteristics. The results show broadband ground motions obtained from the scenario earthquake in this paper can meet the destructive capacity of earthquakes of this magnitude. The hybrid method can effectively compensate for the lack of long-period components of the original empirical Green function method. This research also proves that the peak ground acceleration (PGA) of ground motion is mainly contributed by high-frequency ground motion components. Long-period ground motion contributes most to the peak ground velocity (PGV), and about twice the contribution of high-frequency ground motion. Concerning the Chinese seismic intensity scale (GB/T 17742-2020) and China Seismic Ground Motion Parameter Zoning Map (GB18306-2015), the basic fortification intensity in the Pingwu area is VIII. In this paper, the seismic intensity of PWN is VI-VII, indicating that the buildings at this location are less likely to be damaged after the earthquake. The seismic intensity of other regions is VII-IX and buildings are more likely to be damaged during the earthquake at these locations. There are many mountains and valleys in the Pingwu area, and the probability of landslides, debris flows, and other disasters after an earthquake is very high, and we should give special attention to the impact of secondary disasters caused by earthquakes. It is necessary to prevent dammed lakes and other disasters caused by landslides and debris flows.

New generalized ANN-based hybrid broadband response spectra generator using physics-based simulations

Estimation of the seismic risk associated with infrastructures requires site-specific seismic hazard studies. Further, for nonlinear time history analysis, one requires broadband ground motion. In modern times, physics-based simulations (PBS) for deriving the ground motion for future earthquakes have been considered. The PBS helps decrease the uncertainties related to hazard estimation compared to ground motion prediction equations. The PBS methods have a specific frequency threshold limit resulting from high computational demand. Hence, hybrid methods are required to attain broadband spectra for the simulated ground motion. This study uses a new artificial neural network (ANN)-based model to generate broadband ground motion spectra using the low-frequency spectral acceleration from PBS, source, path, and site parameters as input variables. A detailed parametric study and performance evaluation was made to identify the optimal input parameters in conjunction with the best-suited ANN architecture. The performance of the ANN model is demonstrated for Iwate (\(M_w\) 6.9, 2008) earthquake. We found that the predicted values from the developed ANN model agree with the recorded data. Furthermore, time histories are generated using the spectral ordinate matching technique from the estimated broadband spectra.

The neglected Istanbul earthquakes in the North Anatolian Shear Zone: tectonic implications and broad-band ground motion simulations for a future moderate event

SUMMARYİstanbul (Marmara Region, NW Turkey) is one of the megacities in the world and suffered from destructive earthquakes on the North Anatolian Fault, a member of the North Anatolian Shear Zone, throughout history. The 1999 Kocaeli and Düzce earthquakes emphasize the earthquake potential of the fault, crossing the Sea of Marmara, and the importance of seismic hazards in the region. The studies in the last 20 yr have concentrated on the main fault and its future destructive earthquake potential. In this study, unlike the previous ones, we focus on the two main topics about the earthquakes not interested previously in İstanbul: (1) Investigating recent earthquake activity masked by the blasts in the metropolitan area and its tectonic implications, (2) revealing their effects in İstanbul utilizing numerical ground motion simulations for a future moderate event (Mw 5). First, the 386 earthquakes from 2006 to 2016 are relocated with the double-difference method using the dense seismic network operated in the same period. The source mechanisms of the events (ML ≥ 3), including the most recent 2021 Kartal–İstanbul earthquake (ML 4.1), are determined. In addition to the analysis of the recent seismic activity, the location of the two moderate and pre-instrumental-period İstanbul earthquakes, which occurred in 1923 (Mw 5.5) and 1929 (Mw 5.1), are revised. Using the relocated epicentres outside of the principal deformation zone and the fault plane solutions, the roles of the earthquakes in the stress regime of the Marmara region are explained. The epicentres on the Cenozoic or Palaeozoic formation in the Istanbul–Zonguldak Zone are interpreted as the re-activation of the palaeo-structures under the recent tectonic stresses, and their fault plane solutions agree with the synthetic/antithetic shears of a transtensional regime corresponding to the right lateral strike-slip system with mainly N–S extension in the Marmara Region. In the second part, we investigate the effects of moderate scenario events (Mw 5) considering the current earthquake epicentres in the İstanbul metropolitan area, using characterized earthquake source model and 1-D velocity structure verified with the broad-band (0.1–10 Hz) numerical ground motion simulation of the 2021 Kartal–İstanbul earthquake. The simulated PGAs agree with the ground-motion prediction equations for short epicentral distances (&amp;lt;30 km). Furthermore, according to the empirical relation for Turkish earthquakes, the maximum PGA value of the synthetic models (∼0.3 g) corresponds to the felt intensity of MMI IX. The simulated spectral accelerations for the Mw 5 earthquake scenarios may exceed the design spectrum between 0.2 and 0.6 s given in the Turkish Building Earthquake Code (2018). In addition, certain models also generate spectral accelerations close to the design-level spectrum between 0.4 and 1 s, leading to resonance phenomena. The results indicate that a moderate event (Mw 5) in the İstanbul metropolitan area is capable of damage potential for the mid-rise buildings (4–10 stories) because of the site condition with resonance phenomena and poor construction quality.

Broadband Dynamic Rupture Modeling With Fractal Fault Roughness, Frictional Heterogeneity, Viscoelasticity and Topography: The 2016 Mw 6.2 Amatrice, Italy Earthquake

AbstractAdvances in physics‐based earthquake simulations, utilizing high‐performance computing, have been exploited to better understand the generation and characteristics of the high‐frequency seismic wavefield. However, direct comparison to ground motion observations of a specific earthquake is challenging. We here propose a new approach to simulate data‐fused broadband ground motion synthetics using 3D dynamic rupture modeling of the 2016 Mw 6.2 Amatrice, Italy earthquake. We augment a smooth, best‐fitting model from Bayesian dynamic rupture source inversion of strong‐motion data (&lt;1 Hz) with fractal fault roughness, frictional heterogeneities, viscoelastic attenuation, and topography. The required consistency to match long periods allows us to quantify the role of small‐scale dynamic source heterogeneities, such as the 3D roughness drag, from observational broadband seismic waveforms. We demonstrate that 3D data‐constrained fully dynamic rupture synthetics show good agreement with various observed ground‐motion metrics up to ∼5 Hz and are an important avenue toward non‐ergodic, physics‐based seismic hazard assessment.