Ground Motion Attenuation Research Articles

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.

Design response spectrum based on shock-waveform decomposition method

This study applies the shock-waveform (SW) decomposition method, originally developed for mechanical shock analysis, to earthquake ground motions. It reveals a general shape similarity between the envelope of the Pseudo-Spectral Accelerations (PSAs) of SW decomposed components and the PSA of the corresponding ground motion. Based on this similarity, a novel method to determine the characteristic period Tg, the long-period transition period TD, the shape correction period Tβ, and the Design Response Spectrum (DRS) is proposed and evaluated. New methods to determine Tg, TD and Tβ from the signal decomposition perspective are integrated into the normalized DRS in Eurocode 8–2022, enabling the construction of the normalized DRS based on SW method (SWDRS). Furthermore, simple ground motion attenuation regression equations are derived to relate the parameters (Tg, TD, Tβ) and the corresponding spectral ordinates of the normalized SWDRS model with seismic magnitude and site conditions. The SWDRS model is validated by randomly selecting two sites in United States. For each site, the SWDRS is determined by using the attenuation regression equations and the DRS spectral plateau value from the official seismic hazard map. Comparisons between the SWDRS, the latest local DRS, and the severest historical PSA recorded at the specific site demonstrate that the SWDRS provides more accurate spectral values over intermediate- and long-period ranges for structural seismic design.

Three-dimensional path-effect model to simulate ground motion attenuation on the Korean Peninsula

In low-to-moderately active seismic regions such as the Korean Peninsula, it is difficult to analyze seismic hazards because only a limited number of strong ground motions have been recorded. To address this shortcoming in the data, ground motion simulation can be used to generate the strong ground motions associated with potentially large earthquakes, taking into account the attenuation that occurs as the distance from the source increases. To simulate this attenuation, the path effect, which is a component of the Fourier amplitude spectrum ( FAS), needs to be defined, along with the source and site effects. The path effect represents the propagation of seismic rays through a tectonic medium. In this study, a three-dimensional (3D) path effect model is developed for the Korean Peninsula, consisting of a 3D geometrical spreading factor, quality factor, and shear-wave velocity. The accuracy of the proposed model is verified by comparing the path-effect values obtained from the FAS of individual ground motions recorded on the Korean Peninsula and those calculated from the model. Examples that demonstrate the procedure to calculate the 3D path effect for the Korean Peninsula are also provided.

Site classification methodology using support vector machine: A study

The site effect is a crucial factor when analyzing seismic risk and establishing ground motion attenuation relationships. A number of countries have introduced building site classification into earthquake-resistant design codes to account for local site effects on ground motion. However, most site classification indicators rely on drilling data, which is often expensive and requires considerable manpower. As a result, the less detailed drilling data may lead to an undetermined site category of numerous stations. In this study, a Support Vector Machine (SVM) algorithm-based site classification model was trained to address this issue using strong ground motion data and site data from KiK-net and K-net. The classification model used the average HVSR curve of the labeled site and the combined inputs, including frequency, peak, “prominence, and “sharpness” extracted from the curve. The SVM classification model has an accuracy of 76.12% on the test set, with recall rates of 82.69%, 75%, and 63.64% for sites I, II, and III, respectively. The precision rates are 75.44%, 73.77%, and 87.50%, respectively, with F1 scores of 78.90%, 74.38%, and 73.68%. For sites without significant peaks in the HVSR curve, the HVSR curve value was used as the characteristic parameter (input), and the SVM-based site classification model was also trained. The accuracy of class I and II is 75.86%. The results of this study show higher recall and accuracy rates than those obtained using the spectral ratio curve matching method and GRNN method, indicating a better classification performance. Finally, the generalization ability of the model was verified using some basic stations in Xinjiang deployed by the “National Seismic Intensity Rapid Reporting and Early Warning Project”. The SVM-based site classification model that employs strong motion data can provide more reliable classification results for sites without detailed borehole information, and the site classification results can serve as a reference for probing ground motion attenuation relationships, ground motion simulation, and seismic fortification considering the site effect.

Ground motion prediction model for shallow crustal earthquakes in Japan based on XGBoost with Bayesian optimization

Ground motion prediction is an important and complex research subject in earthquake engineering and traditional approaches based on statistical regression have much room for improvement in prediction accuracy. Utilizing the 67,164 ground motion records from KiK-net and K-Net for 777 shallow crustal earthquakes between 1997 and 2019 in Japan, this paper proposes a ground motion prediction model XGBoost-SC based on the machine learning algorithm of eXtreme Gradient Boosting (XGBoost) for Japan. Magnitude, focal depth, hypo-central distance, Vs30, site altitude, and focal mechanism were used as the feature parameters, and XGBoost, Random Forest, and Deep Neural Networks (DNN) algorithms were selected for model training while Bayesian optimization was used to search for optimized hyperparameters to improve the prediction accuracy. XGBoost algorithm was selected for further study based on the comparison of results from the three algorithms. Residual change with magnitude and hypo-central distance, the probability distribution of residuals, residual standard deviation (σ), residual mean squared error (MSE), and Pearson correlation coefficient (R) were used as the evaluation parameters, and a comparison study was performed against the ground motion prediction equation based on traditional approaches. Actual earthquake events were selected to compare the prediction results against the observation records. To further validate and explain the proposed model, SHapley Additive exPlanations (SHAP) analysis was performed to explain the impact of selected feature parameters on the proposed model. The results demonstrate that the proposed XGBoost-SC model has good prediction stability for all periods, and its residual errors are smaller than those of other models. Therefore, the proposed model can better reflect the ground motion attenuation for shallow crustal earthquakes in Japan and can serve as a better model for ground motion prediction in future aseismic design and earthquake disaster mitigation efforts.

Subregional Anelastic Attenuation Model for California

ABSTRACT Ground-motion models (GMMs) typically include a source-to-site path model that describes the attenuation of ground motion with distance due to geometric spreading and anelastic attenuation. In contemporary GMMs, the anelastic component is typically derived for use in one or more broad geographical regions such as California or Japan, which necessarily averages spatially variable path effects within those regions. We extend that path modeling framework to account for systematic variations of anelastic attenuation for ten physiographic subregions in California that are defined in consideration of geological differences. Using a large database that is approximately doubled in size for California relative to Next Generation Attenuation (NGA)-West2, we find relatively high attenuation in Coast Range areas (North Coast, Bay area, and Central Coast), relatively low attenuation in eastern California (Sierra Nevada, eastern California shear zone), and state-average attenuation elsewhere, including southern California. As part of these analyses, we find for the North Coast region relatively weak ground motions on average from induced events (from the Geysers), similar attenuation rates for induced and tectonic events, and higher levels of ground-motion dispersion than other portions of the state. The proposed subregional path model appreciably reduces within-event and single-station variability relative to an NGA-West2 GMM for ground motions at large distance (RJB>100 km). The approach presented here can readily be adapted for other GMMs and regions.

Dynamic Rupture Models, Fault Interaction and Ground Motion Simulations for the Segmented Húsavík‐Flatey Fault Zone, Northern Iceland

AbstractThe Húsavík‐Flatey Fault Zone (HFFZ) is the largest strike‐slip fault in Iceland and poses a high seismic risk to coastal communities. To investigate physics‐based constraints on earthquake hazards, we construct three fault system models of varying geometric complexity and model 79 3‐D multi‐fault dynamic rupture scenarios in the HFFZ. By assuming a simple regional prestress and varying hypocenter locations, we analyze the rupture dynamics, fault interactions, and the associated ground motions up to 2.5 Hz. All models account for regional seismotectonics, topo‐bathymetry, 3‐D subsurface velocity, viscoelastic attenuation, and off‐fault plasticity, and we explore the effect of fault roughness. The rupture scenarios obey earthquake scaling relations and predict magnitudes comparable to those of historical events. We show how fault system geometry and segmentation, hypocenter location, and prestress can affect the potential for rupture cascading, leading to varying slip distributions across different portions of the fault system. Our earthquake scenarios yield spatially heterogeneous near‐field ground motions modulated by geometric complexities, topography, and rupture directivity, particularly in the near‐field. The average ground motion attenuation characteristics of dynamic rupture scenarios of comparable magnitudes and mean stress drop are independent of variations in source complexity, magnitude‐consistent and in good agreement with the latest regional empirical ground motion models. However, physics‐based ground motion variability changes considerably with fault‐distance and increases for unilateral compared to bilateral ruptures. Systematic variations in physics‐based near‐fault ground motions provide important insights into the mechanics and potential earthquake hazard of large strike‐slip fault systems, such as the HFFZ.

Earthquake-induced landslides in Norway

Abstract. Norway is located in an intraplate setting with low-to-moderate seismicity. The mountainous landscape leads to a high level of landside activity throughout the country. Earthquake-induced landslides (EQILs) are common in seismically active areas, but there are only a few studies of EQILs in intraplate regions. We systematically analyse all earthquakes in Norway with magnitudes ≥ 4.5 in the time period 1800–2021 CE. For each event we search for reports of EQILs in the available macroseismic data and in the Norwegian landslide database. We furthermore consider precipitation data from the Norwegian Centre for Climate Services to evaluate the role of precipitation in the triggering of the identified potential EQILs. Through this approach, we identify 22 EQILs that have been triggered by eight earthquakes in the magnitude range 4.5–5.9. The events are widely distributed in northern and southern Norway. The maximum landslide distance limits and landslide-affected areas are much larger than those found in empirical studies of global datasets and are in agreement with data from other intraplate regions. For four of the earthquakes, it seems that landslide triggering was due to a combined effect of precipitation and earthquake ground shaking. Our observations confirm that intraplate earthquakes have the potential to trigger EQILs over large distances, most likely due to the low ground motion attenuation in such regions. Slope susceptibility seems to be another important factor in the triggering. Our conclusions demonstrate the importance of considering EQIL potential in earthquake risk management in intraplate regions.

Inferring the depth and magnitude of pre-instrumental earthquakes from intensity attenuation curves

Abstract. The Italian historical earthquake record is among the richest worldwide; as such it allows for the development of advanced techniques for retrieving quantitative information by calibration with recent earthquakes. Building on a pilot elaboration of northern Italian earthquakes, we developed a procedure for determining the hypocentral depth of all Italian earthquakes from macroseismic intensity data alone. In a second step the procedure calculates their magnitude, taking into account the inferred depth. Hypocentral depth exhibits substantial variability countrywide but has so far received little attention: pre-instrumental earthquakes were routinely “flattened” at the upper-crustal level (∼10 km), on the grounds that the calculation of hypocentral depth is heavily dependent on the largely unknown local propagation properties. We gathered a learning set of 42 earthquakes documented by reliable instrumental data and by numerous macroseismic intensity observations. We observe (1) that within 50 km from the epicenter the ground motion attenuation rate is primarily controlled by hypocentral depth and largely independent of magnitude, (2) that within this distance the fluctuations in crustal attenuation properties are negligible countrywide, and (3) that knowing both the depth and the expected epicentral intensity makes it possible to estimate a reliable magnitude.

Numerical Modeling of Air-Blast Suppression as a Function of Explosive-Charge Burial Depth

Abstract As a chemical explosion is buried, the mechanism for acoustic wave generation transitions from fully gas-generated at the surface to completely spall-induced at full containment depth. The fully gas-generated and completely spall-induced signals in the acoustic waveform are well described; however, the transition between these two end-members eludes numerical modeling because of the complex phenomena that are involved. The phenomena of crater formation and explosive cloud evolution are simulated using an Eulerian hydrocode that incorporates geomaterials with strength and porosity. Having accurately modeled these phenomena, we can confidently predict the propagation and relative strength of the gas-generated and spall-induced pulses in the recorded acoustic waveform. The numerical predictions agree with observations from the historical Stagecoach experiment as well as modern recordings from the Source Physics Experiment. In particular, the peak pressure p generated by an explosion is initially due to the gas-generated mechanism and decays with scaled depth of burial ds (depth d scaled by the cube-root of explosive yield w1/3) as exp(−ds) but then transitions near a scaled depth of 6 m/ton1/3 to the spall-generated mechanism in which the decay is ds−7/4. This decay form is related to the strong ground-motion attenuation relationship that affects spall strength. These results can improve seismoacoustic inverse models for the explosive source that need to account for the gas-generated and spall-induced signals and their effect on peak pressures and other acoustic signal features.

Rapid Near-Field Attenuation of Ground Motion from Shallow Induced Earthquakes, Case Study: Preston New Road, United Kingdom

Abstract Ground motions from shallow induced earthquakes and tectonic seismicity were investigated in this study by directly modeling the seismic attenuation quality factor (Q) using spectral fitting and coda envelope decay methods. We use data from the Preston New Road (PNR) shale gas induced seismicity sequences near Blackpool, United Kingdom, in 2018 and 2019, in addition to regional tectonic events in the United Kingdom. Our results show that the local Q obtained from the induced seismic sequences at PNR, attributed to shallower layers in the crust, leads to a rapid rate of near-field decay (sudden loss in amplitude of earthquake signal over a short distances), with significantly stronger attenuation than observed for regional events. We furthermore find that estimates of Q are nonunique to a given record, differing both with the method and the analysis windows used, particularly at high frequency. These differences can be attributed to the different modeling methodologies (e.g., different assumptions) or to fundamental differences in physical attenuation processes within the seismic wavefield itself, which traverses multiple ray paths and comprises various phases. Our results indicate that to model ground motions for shallow earthquakes, it is important to consider the composite Q along a specific path rather than an average regional Q. To this extent, a depth-dependent attenuation model is considered crucial to bridge the gap between shallow induced earthquakes and tectonic seismicity.

Regional Finite-Fault Source Model for Development of Ground Motion Attenuation Relationship in Sichuan, China

The attenuation relationship of ground motion based on seismology has always been a front subject of engineering earthquake. Among them, the regional finite-fault source model is very important. In view of this point, the general characteristics of regional seism-tectonics, including the dip and depth of the fault plane, are emphasized. According to the statistics of regional seism-tectonics and focal mechanisms in Sichuan, China, and the sensitivity of estimated peak ground acceleration (PGA) attenuation is analyzed, and the dip angle is taken as an average of 70°. Based the statistics of the upper crustal structure and the focal depth of regional earthquakes, the bottom boundary of the sedimentary cover can be used as the upper limit for estimating the depth of upper-edge. The analysis shows that this value is sensitive to PGA. Based on the analysis of geometric relations, the corresponding calculation formula is used, and a set of concepts and steps for building the regional finite-fault source model is proposed. The estimation of source parameters takes into account the uncertainty, the geometric relationship among parameters and the total energy conservation. Meanwhile, a set of reasonable models is developed, which lay a foundation for the further study of regional ground motion attenuation based on seismology.

Preliminary Evaluation of Crustal Medium Parameters in Western China

The establishment of attenuation relation of ground motion is always an important research content in engineering earthquake field. In seismology-based ground motion attenuation relationship and ground motion simulation using the stochastic method, regional parameters are necessary. These parameters involve stress drop Δσ, two segmentation points R1 and R2 of the geometric spreading item, Q0 and η of the inelastic attenuation item and the near-surface high-frequency decay parameter κ0, which reflect the regional crustal medium and site characteristics and have little relation with the earthquake size. In this paper, we take Sichuan, Yunnan and Xinjiang regions in western China as examples and we inverse the parameters for each region by micro-genetic algorithm. The inversion ranges of crustal media parameters in the three regions were determined respectively. Finally, we get the inversion results of every parameters and find that the parameters of the three regions have a great difference.

Regional Spectral Characteristics Derived Using the Generalized Inversion Technique and Applications to Stochastic Simulation of the 2021 Mw 6.1 Yangbi Earthquake

ABSTRACTIn this study, 334 accelerograms of 42 small-to-moderate earthquakes recorded at 36 strong-motion stations were used to investigate the ground-motion characteristics of the southwestern margin of the Sichuan–Yunnan rhombic block (SWM-SYRB), one of the most active seismic regions in China. The high-frequency attenuation parameter was estimated using the spectral decay method, and the site component (κ0) was fitted. The κ0 estimates decrease with the increasing time-averaged S-wave velocity of the uppermost 30 m (VS30). Using the generalized inversion technique, the source spectra, quality factor (Q), and site amplification were derived from the Fourier amplitude spectra (FAS). The obtained average stress drop for earthquakes occurred in SWM-SYRB was the second largest among various boundary areas of SYRB. The inverted Q model was Q(f)=115.1f0.616. The low Q structure that extends southwestward from the Songpan–Garze block to SWM-SYRB could be responsible for the strong regional attenuation of ground motion with distance. At frequencies above 10 Hz, the average site amplifications were influenced by the high-frequency attenuation effect. The site amplification of site class D reached a factor of 6 at 0.7 Hz. Moreover, it was observed that site amplification factors can be even higher when peak ground acceleration is larger than 0.8 m/s2. Finally, the obtained parameters were used in the stochastic finite-fault simulation method to reproduce the FAS, 5%-damped pseudospectral acceleration, and time series of the 2021 Mw 6.1 Yangbi earthquake. The simulated spectra properly matched the observations in a broad frequency band of 0.1–25 Hz. Furthermore, the simulated time series could generally represent the amplitude of the S-wave portion of observed ones.

Earthquake Risk Probability Evaluation for Najin Lhasa in Southern Tibet

The probabilistic seismic hazard analysis (PSHA) method is effectively used in an earthquake risk probability evaluation in seismogenic regions with active faults. In this study, by focusing on the potential seismic source area in Najin Lhasa, southern Tibet, and by incorporating the PSHA method, we determined the seismic activity parameters and discussed the relationship of ground motion attenuation, the seismic hazard probability, and the horizontal bedrock ground motion acceleration peak value under different transcendence probabilities in this area. The calculation results show that the PSHA method divides the potential source area via specific tectonic scales and detailed tectonic markers, which reduces the scale of the potential source area and better reflects the uneven spatial distribution of seismic activity in the vicinity of Najin. The corrected attenuation relationship is also in line with the actual work requirements and is suitable for earthquake risk analysis. In addition, the major influences on the peak acceleration of ground motion in the study area are mainly in the potential source areas of Qushui (M7.5), Dangxiong (M8.5), and Kangma (M7.5). The peak horizontal ground motion acceleration (PGA) with a transcendence probability of 10% in 50 years is 185.9 cm/s2, and that with a transcendence probability of 2% in 50 years is 265.9 cm/s2.

Predictive kappa (κ) models for Turkey: Regional effects and uncertainty analysis

High-frequency attenuation of ground motions is commonly characterized by the κ parameter. κ and its value at zero distance, [Formula: see text], are critical parameters for site characterization, ground motion simulations, and adjustment of ground motion models for different site conditions. In this study, we derive regional κ models for Eastern, Western, and Northwestern Turkey, using a ground motion data set of 3212 strong ground motion records with 9636 components from 1053 earthquakes, recorded at 178 stations with varying site conditions. Initially, models with linear functional forms are derived with distance and site conditions as predictor variables. Residual analyses showed that these models have non-normal residuals with heterogeneous variances (heteroscedasticity). Box–Cox transformations on κ values are performed to address these two issues. Models using these transformations resulted in normal residuals with homogeneous variances (homoscedasticity). Effects of earthquake magnitude on the κ value are also investigated, and a linear adjustment for magnitudes is proposed. A constant vertical-to-horizontal ratio of 0.78 is proposed to estimate the vertical κ values instead of deriving separate models for the vertical component. This approach does not result in significant decreases in accuracy and is preferred due to its simplicity. Next, the physical implications of logarithmic transformations for the κ values are discussed. Finally, regional differences in κ models are highlighted.

Attenuation Characteristics of High-Frequency Ground Motions from Local Sources Caused by Great Subduction Zone Earthquakes in Northeast Japan

AbstractGround-motion attenuation characteristics are examined for the peak ground accelerations (PGAs) and peak ground velocities (PGVs) from strong-motion generation areas (SMGAs), which emit strong high-frequency waves during great subduction zone earthquakes. A conventional ground-motion prediction equation (GMPE) for earthquakes is designed based on the magnitude and distance from the source fault to predict the peak ground motion amplitude. For great subduction zone earthquakes, significant wavetrains of high-frequency ground motions are often separately observed in seismograms, and the corresponding rupture areas are estimated as SMGAs along the plate interface. In this case, although the advantages of using the shortest distances measured from the closest SMGAs rather than the shortest fault distance have been confirmed in previous studies, it is more physically reasonable to examine the ground-motion attenuation characteristics of individual SMGAs based on their magnitudes and locations. Therefore, we examine the attenuation characteristics of the PGAs and PGVs of individual SMGAs of the 2003 Mw 8.2 Tokachi–Oki earthquake and 2011 Mw 9.1 Tohoku earthquake in the Japan subduction zone considering data at stations within an SMGA distance of 300 km and the SMGA moment magnitude. The model, exhibiting the same functional form as a conventional GMPE, is fitted to the PGA and PGV data pertaining to each SMGA that are normalized to a bedrock site with VS30=760 m/s at any distance. The uncertainties in the obtained PGAs and PGVs are 3.6% and 13.5% lower, respectively, in terms of the residual in logarithmic units than those in the results of previous approaches considering only the SMGA distance. This result could help develop GMPEs for SMGAs to more appropriately predict the strong motions generated during great subduction zone earthquakes.

Stochastic Model to Characterize High-Frequency Ground Motion at Depth Validated by KiK-Net Vertical Array Data

ABSTRACTThe design of important structures for earthquake resistance requires an assessment of the local seismic hazard. One of its essential components is a site response that evaluates the amplification and attenuation of ground motion on a local scale. The shaking on the ground surface (in which it is generally measured) differs from the one at a depth; therefore, there is a need to characterize the ground motion at depth for important underground structures and buildings with deep foundations. In this study, we introduce a method to characterize the high-frequency (>1 Hz) ground motion at depth. The method makes use of a novel stochastic model (SM) that relates the ground motion at depth and on the surface in the Fourier domain. The SM is physics-based, its spectral amplification resembles an empirical 1D site response, and it allows reliable full-waveform ground-motion predictions. The method is validated through the comparison with empirical surface-to-borehole amplification curves observed in 144 selected KiK-net vertical arrays in Japan. Using a frequency range of 0.1–50 Hz, we identified 36 and 83 sites with a good and partially good mutual fit of theoretical and empirical amplification curves, respectively. Finally, we demonstrate the performance of the method in two diverse applications. First, we design a Bayesian inversion of the empirical surface-to-borehole amplification to retrieve the S-wave velocity model and an effective value of t* (the path-integrated effect of the quality factor). This inversion is applied to all selected KiK-net sites. Second, we perform a full-waveform prediction of the ground motion at depth from surface recordings of the 2018 northern Osaka Mw 5.6 earthquake. Both of these applications demonstrate a good performance of our SM in a broad frequency range.

Site-specific Investigations of the Earthquake Activities and Hazards for Some Caves in Thailand

The seismicity for 35 natural caves in Thailand was investigated probabilistically in order to provide information on their potential earthquake situation. All values representing the earthquake activities within a 300-km radius and the seismic hazard level at each cave were clarified. Seismotectonically, 28 of the 35 caves are situated within previously proposed seismic source zones and most of the seismogenic faults nearby each cave is presently still active, as determined by seismicity and paleoseismological evidence. For the present-day seismicity, the Pla cave in northwest Thailand (situated 0.3[Formula: see text]km from the Mae Hong Son-Tak fault) showed a comparatively high [Formula: see text]-value (4.16) suggesting a high entire seismicity rate, but a relatively high [Formula: see text]-value of 0.82. With respect to the [Formula: see text]-value, which inversely represents the accumulated seismotectonic stress, the caves at Pha Puang, Lom-Wang, Naresuan and Fha Mue Daeng in the Central-North regions had a comparatively low [Formula: see text]-value ([Formula: see text]), indicating a high accumulated stress. Based on the recognized earthquake sources and the utilized strong ground-motion attenuation model, the seismic hazard analyses revealed that the caves at Daowadeung, Phra Thart and Lawa in Western Thailand were in the highest seismic hazard areas. This new study contributes to important information for geotourism (e.g. mitigation planning) and selecting/prioritizing speleoseismological investigation sites.

Ground motion prediction equation for the average horizontal component of PGA, PGV, and 5% damped acceleration response spectra at periods ranging from 0.033 to 8.0s in southwest China

In this paper, we collect and process free-field strong motion recordings from 70 earthquakes for 4.2 ≤ MW ≤ 7.9 at 0 < Rrup < 300 km between 2008 and 2018 in the active tectonic regions of southwest China, and then establish a dataset containing 1324 average horizontal ground motion (ROTD50) and corresponding metadata such as parameters of the earthquake source, distance, and site. A new ground motion prediction equation (GMPE) for the average horizontal component of peak ground acceleration (PGA), peak ground velocity (PGV), and 5% damped acceleration response spectra at periods ranging from 0.033 to 8.0 s (SA (T = 0.033–8.0 s)) is introduced. This GMPE considers multiple influencing factors such as magnitude and distance saturation effect, geometric attenuation, style-of-faulting, hanging-wall effect, linear/nonlinear site response, and anelastic attenuation. The residual evaluation and median ground motion are presented. The predicted ground motions using the new GMPE are compared with predictions from the GMPE in western China and five NGA-West2 GMPEs, and the observed ground motions of strong earthquakes which occurred in southwest China. The results show that the proposed GMPE can better reflect the influence of the earthquake source characteristic, propagation media, site effect on the ground motion attenuation characteristic in southwest China, and works well versus independent strong motion data of earthquakes in southwest China, and well reflects the general feature of ground motions for the Wenchuan and Lushan earthquakes that is rich at short-period and weak at long-period. The new GMPE shows outstanding performance estimating the horizontal ground motion of the earthquakes in southwest China for MW 4.2–7.9 (related to style-of-faulting) and Rrup = 10–200 km, at sites with VS30 = 140–1130 m/s.