ABSTRACT This study presents an alternate site-response model to the existing ground-motion prediction equation (GMPE) from our previous study with some calibration to the magnitude term. We used a new site-response proxy TVH=4×max(30,HB)/VS30 that combines VS30 (the travel-time-averaged shear-wave velocity to 30 m depth) with the engineering bedrock depth HB. VS30 is available for many strong-motion recording stations. However, GMPEs using VS30 do not directly account for the response of the soil layers between 30 m and bedrock depth. Site period TS (four times the shear-wave travel time to the engineering bedrock depth) has also been used in recent GMPEs, with TS being considered a theoretically better parameter than a pseudosite period TVS30 (four times the shear-wave travel time to a depth of 30 m). Obtaining the shear-wave velocity profiles between 30 m and HB for a deep soil site can be expensive, whereas obtaining bedrock depth based on the geotechnical description of borehole data may be relatively easy. We used velocity profiles from the Kyoshin net and Kiban–Kyoshin net strong-motion networks and found that a pseudosite period TVH and TS have an excellent correlation with a small standard deviation at all spectral periods, suggesting that TVH is a suitable site-effect parameter. The poor correlations between TVS30 and TS and between TVS30 and TVH for sites with TS>0.4 s led to poor model performance at long spectral periods. We modified a GMPE by replacing TVS30 with TVH, and we made a minor modification to the moment magnitude term of the GMPE that was necessary for the new site term. The response spectra predicted by models using TVH, TS, and TVS30 at short spectral periods up to 0.6 s are generally similar. At long spectral periods, the spectra predicted by the TVS30 are much smaller than those from the other two GMPEs. For all spectral periods, TVH is an excellent substitute for TVS30.
{"title":"A Site-Response Model for the Vertical Component of Ground-Motion Prediction Equation Using a New Site-Response Parameter TVH","authors":"Shihong Bai, John X. Zhao","doi":"10.1785/0120220103","DOIUrl":"https://doi.org/10.1785/0120220103","url":null,"abstract":"ABSTRACT This study presents an alternate site-response model to the existing ground-motion prediction equation (GMPE) from our previous study with some calibration to the magnitude term. We used a new site-response proxy TVH=4×max(30,HB)/VS30 that combines VS30 (the travel-time-averaged shear-wave velocity to 30 m depth) with the engineering bedrock depth HB. VS30 is available for many strong-motion recording stations. However, GMPEs using VS30 do not directly account for the response of the soil layers between 30 m and bedrock depth. Site period TS (four times the shear-wave travel time to the engineering bedrock depth) has also been used in recent GMPEs, with TS being considered a theoretically better parameter than a pseudosite period TVS30 (four times the shear-wave travel time to a depth of 30 m). Obtaining the shear-wave velocity profiles between 30 m and HB for a deep soil site can be expensive, whereas obtaining bedrock depth based on the geotechnical description of borehole data may be relatively easy. We used velocity profiles from the Kyoshin net and Kiban–Kyoshin net strong-motion networks and found that a pseudosite period TVH and TS have an excellent correlation with a small standard deviation at all spectral periods, suggesting that TVH is a suitable site-effect parameter. The poor correlations between TVS30 and TS and between TVS30 and TVH for sites with TS>0.4 s led to poor model performance at long spectral periods. We modified a GMPE by replacing TVS30 with TVH, and we made a minor modification to the moment magnitude term of the GMPE that was necessary for the new site term. The response spectra predicted by models using TVH, TS, and TVS30 at short spectral periods up to 0.6 s are generally similar. At long spectral periods, the spectra predicted by the TVS30 are much smaller than those from the other two GMPEs. For all spectral periods, TVH is an excellent substitute for TVS30.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135878811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adam T. Ringler, Robert E. Anthony, Brian Shiro, Toshiro Tanimoto, David C. Wilson
ABSTRACT An increase in seismic stations also having microbarographs has led to increased interest in the field of seismoacoustics. A review of the recent advances in this field can be found in Dannemann Dugick et al. (2023). The goal of this note is to draw the attention of the readers of Dannemann Dugick et al. (2023) to several additional interactions between the solid Earth and atmosphere that have not been classically considered in the field of seismoacoustics. The 15 January 2022 Hunga Tonga–Hunga Ha‘api eruption produced acoustic gravity waves that were recorded globally. For example, the Lamb wave from this eruption produced early-arriving and long-lasting tsunami waves. This eruption also provided globally recorded coupling of atmospheric modes with solid Earth modes, providing another example of the complex interactions that can occur at the boundary between the atmosphere and the solid Earth. Even in the absence of large atmospheric signals, collocated pressure sensors at seismic stations can be a useful tool for estimating the local substructure, such at VS30, the average shear velocity of the upper 30 m. Finally, at low frequencies, it is possible to use pressure records to correct out atmospheric disturbances recorded on seismometers. We briefly review the aforementioned, nontraditional seismoacoustic topics that we feel are important to consider as part of the full suite of interactions occurring between the solid Earth and atmosphere.
越来越多的地震台站也配备了微型气压计，这增加了人们对地震声学领域的兴趣。对该领域最新进展的回顾可以在Dannemann Dugick等人(2023)中找到。本说明的目的是提请Dannemann Dugick等人(2023)的读者注意固体地球和大气之间的几个额外的相互作用，这些相互作用在地震声学领域中没有被经典地考虑过。2022年1月15日，Hunga Tonga-Hunga Ha 'api火山爆发产生了声波重力波，全球都有记录。例如，这次喷发产生的兰姆波产生了早到达且持续时间长的海啸波。这次喷发还提供了全球记录的大气模式与固体地球模式的耦合，为大气和固体地球之间的边界可能发生的复杂相互作用提供了另一个例子。即使在没有大的大气信号的情况下，地震台站配置的压力传感器也可以成为估计当地子结构的有用工具，例如在VS30，上层30米的平均剪切速度。最后，在低频率下，可以使用压力记录来校正地震仪上记录的大气扰动。我们简要回顾了上述非传统的地震声学主题，我们认为这些主题作为固体地球和大气之间发生的全套相互作用的一部分是重要的。
{"title":"Comment on “A New Decade in Seismoacoustics (2010–2022)” by Fransiska Dannemann Dugick, Clinton Koch, Elizabeth Berg, Stephen Arrowsmith, and Sarah Albert","authors":"Adam T. Ringler, Robert E. Anthony, Brian Shiro, Toshiro Tanimoto, David C. Wilson","doi":"10.1785/0120230111","DOIUrl":"https://doi.org/10.1785/0120230111","url":null,"abstract":"ABSTRACT An increase in seismic stations also having microbarographs has led to increased interest in the field of seismoacoustics. A review of the recent advances in this field can be found in Dannemann Dugick et al. (2023). The goal of this note is to draw the attention of the readers of Dannemann Dugick et al. (2023) to several additional interactions between the solid Earth and atmosphere that have not been classically considered in the field of seismoacoustics. The 15 January 2022 Hunga Tonga–Hunga Ha‘api eruption produced acoustic gravity waves that were recorded globally. For example, the Lamb wave from this eruption produced early-arriving and long-lasting tsunami waves. This eruption also provided globally recorded coupling of atmospheric modes with solid Earth modes, providing another example of the complex interactions that can occur at the boundary between the atmosphere and the solid Earth. Even in the absence of large atmospheric signals, collocated pressure sensors at seismic stations can be a useful tool for estimating the local substructure, such at VS30, the average shear velocity of the upper 30 m. Finally, at low frequencies, it is possible to use pressure records to correct out atmospheric disturbances recorded on seismometers. We briefly review the aforementioned, nontraditional seismoacoustic topics that we feel are important to consider as part of the full suite of interactions occurring between the solid Earth and atmosphere.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135879945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A model to estimate the 5% damped response spectra of horizontal components at specific orientations is presented. The model, which explicitly accounts for directionality, is based on prior research by the authors that identified that the orientation of maximum horizontal spectral response at a site in strike-slip earthquakes tends to occur at or close to the transverse orientation with respect to the epicenter. Using a database of 1962 ground motions recorded in shallow crustal earthquakes with strike-slip faulting, it is shown that there is a significantly larger probability of exceeding orientation-independent RotD50 intensities in the transverse orientation than in the radial orientation. Furthermore, the results indicate that, on average, spectral responses in the transverse orientation are significantly larger than those in the radial orientation and that these differences become more significant as the period of the oscillator increases. For example, spectral responses in the transverse orientation are, on average, 12% larger than those in the radial orientation for 1 s oscillators and 78% larger for 10 s oscillators. A period- and orientation-dependent model is developed and calibrated to estimate 5% damped response spectral ordinates at specific orientations by modifying orientation-independent RotD50 intensities. The proposed orientation-dependent model can explicitly account for directionality by modifying the means and standard deviations of any ground-motion model that estimates RotD50 response spectral ordinates for strike-slip earthquakes to obtain probability distributions of response spectral ordinates but now at specific horizontal orientations.
{"title":"Modification of Ground-Motion Models to Estimate Orientation-Dependent Horizontal Response Spectra in Strike-Slip Earthquakes","authors":"A. Poulos, Eduardo Miranda","doi":"10.1785/0120230084","DOIUrl":"https://doi.org/10.1785/0120230084","url":null,"abstract":"\u0000 A model to estimate the 5% damped response spectra of horizontal components at specific orientations is presented. The model, which explicitly accounts for directionality, is based on prior research by the authors that identified that the orientation of maximum horizontal spectral response at a site in strike-slip earthquakes tends to occur at or close to the transverse orientation with respect to the epicenter. Using a database of 1962 ground motions recorded in shallow crustal earthquakes with strike-slip faulting, it is shown that there is a significantly larger probability of exceeding orientation-independent RotD50 intensities in the transverse orientation than in the radial orientation. Furthermore, the results indicate that, on average, spectral responses in the transverse orientation are significantly larger than those in the radial orientation and that these differences become more significant as the period of the oscillator increases. For example, spectral responses in the transverse orientation are, on average, 12% larger than those in the radial orientation for 1 s oscillators and 78% larger for 10 s oscillators. A period- and orientation-dependent model is developed and calibrated to estimate 5% damped response spectral ordinates at specific orientations by modifying orientation-independent RotD50 intensities. The proposed orientation-dependent model can explicitly account for directionality by modifying the means and standard deviations of any ground-motion model that estimates RotD50 response spectral ordinates for strike-slip earthquakes to obtain probability distributions of response spectral ordinates but now at specific horizontal orientations.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"21 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86364675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Latchman, F. Dondin, R. Robertson, Roderick Stewart, Paddy Smith, Lloyd L. Lynch, C. Ramsingh, N. Nath, H. Ramsingh, Ian Juman, Stacey Edwards, C. Ash
{"title":"Erratum to Contrasting T-Phase and P-Wave Patterns from the 2015 and 2017 Eruptions of the Submarine Volcano Kick-‘em-Jenny: Influence of Cardinal Direction on Recorded First-Phase Arrival","authors":"J. Latchman, F. Dondin, R. Robertson, Roderick Stewart, Paddy Smith, Lloyd L. Lynch, C. Ramsingh, N. Nath, H. Ramsingh, Ian Juman, Stacey Edwards, C. Ash","doi":"10.1785/0120230132","DOIUrl":"https://doi.org/10.1785/0120230132","url":null,"abstract":"","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"78 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79125172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Roten, Te-Yang Yeh, Kim B. Olsen, Steven M. Day, Yifeng Cui
We have implemented and verified a parallel-series Iwan-type nonlinear model in a 3D fourth-order staggered-grid velocity–stress finite-difference method. The Masing unloading and reloading behavior is simulated by tracking an overlay of concentric von Mises yield surfaces. Lamé parameters and failure stresses pertaining to each surface are calibrated to reproduce the stress–strain backbone curve, which is controlled by the reference strain assigned to a given depth level. The implementation is successfully verified against established codes for 1D and 2D SH-wave benchmarks. The capabilities of the method for large-scale nonlinear earthquake modeling are demonstrated for an Mw 7.8 dynamic rupture ShakeOut scenario on the southern San Andreas fault. Although ShakeOut simulations with a single yield surface reduces long-period ground-motion amplitudes by about 25% inside a waveguide in greater Los Angeles, Iwan nonlinearity further reduces the values by a factor of 2. For example, inside the Whittier Narrows corridor spectral accelerations at a period of 3 s are reduced from 1g in the linear case to about 0.8 in the bilinear case and to 0.3–0.4g in the multisurface Iwan nonlinear case, depending on the choice of reference strain. Normalized shear modulus reductions reach values of up to 50% in the waveguide and up to 75% in the San Bernardino basin at the San Andreas fault. We expect the implementation to be a valuable tool for future nonlinear 3D dynamic rupture and ground-motion simulations in models with coupled source, path, and site effects.
{"title":"Implementation of Iwan-Type Nonlinear Rheology in a 3D High-Order Staggered-Grid Finite-Difference Method","authors":"D. Roten, Te-Yang Yeh, Kim B. Olsen, Steven M. Day, Yifeng Cui","doi":"10.1785/0120230011","DOIUrl":"https://doi.org/10.1785/0120230011","url":null,"abstract":"\u0000 We have implemented and verified a parallel-series Iwan-type nonlinear model in a 3D fourth-order staggered-grid velocity–stress finite-difference method. The Masing unloading and reloading behavior is simulated by tracking an overlay of concentric von Mises yield surfaces. Lamé parameters and failure stresses pertaining to each surface are calibrated to reproduce the stress–strain backbone curve, which is controlled by the reference strain assigned to a given depth level. The implementation is successfully verified against established codes for 1D and 2D SH-wave benchmarks. The capabilities of the method for large-scale nonlinear earthquake modeling are demonstrated for an Mw 7.8 dynamic rupture ShakeOut scenario on the southern San Andreas fault. Although ShakeOut simulations with a single yield surface reduces long-period ground-motion amplitudes by about 25% inside a waveguide in greater Los Angeles, Iwan nonlinearity further reduces the values by a factor of 2. For example, inside the Whittier Narrows corridor spectral accelerations at a period of 3 s are reduced from 1g in the linear case to about 0.8 in the bilinear case and to 0.3–0.4g in the multisurface Iwan nonlinear case, depending on the choice of reference strain. Normalized shear modulus reductions reach values of up to 50% in the waveguide and up to 75% in the San Bernardino basin at the San Andreas fault. We expect the implementation to be a valuable tool for future nonlinear 3D dynamic rupture and ground-motion simulations in models with coupled source, path, and site effects.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"1 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90207702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ting Yang, Ke Jia, Aiyu Zhu, Shiguang Wang, L. Fang
Within four hours on 10 June 2022, three consecutive earthquakes of Ms≥5.0 with a maximum magnitude up to Ms 6.0 struck Maerkang, Sichuan, where is supposedly less prone to earthquakes. This article uses seismic observations recorded by the Sichuan Seismic Network to relocate the earthquake sequences and refine velocity models in Maerkang using a double-difference seismic tomography method. The results show that the aftershocks align along northwest and north-northwest directions with a V-shaped pattern, and the Ms 5.8 and 6.0 earthquakes are located in the center of the sequences. The seismogenic faults of the Maerkang earthquake are the two intersecting secondary faults on the east side of the Songgang fault that dip to the northeast and southwest, respectively, with dip angles of about 80°. Analysis of the seismicity parameters and Coulomb stress changes revealed that the Ms 5.8 and 6.0 earthquakes occurred on two separate faults, and the Ms 5.8 earthquake triggered the Ms 6.0 earthquake, while the Ms 6.0 earthquake prevented the rupture of the Ms 5.8 earthquake. The apparent high-velocity anomaly in the upper crust and the low-velocity and high-conductivity layer in the middle-lower crust of the source region suggest that drag forces exerted by the ductile middle-lower crust may have caused the brittle upper crust to move under the eastward extrusion of the Tibetan plateau, leading to the stresses accumulate and release on the causative faults. The Maerkang earthquake highlighted the lateral movement of deep materials and energy redistribution in the intrablock deformation of the Bayan Har block.
{"title":"The 2022 Ms 5.8 and 6.0 Maerkang Earthquakes: Two Strike-Slip Events Occurred on V-Shaped Faults","authors":"Ting Yang, Ke Jia, Aiyu Zhu, Shiguang Wang, L. Fang","doi":"10.1785/0120220206","DOIUrl":"https://doi.org/10.1785/0120220206","url":null,"abstract":"\u0000 Within four hours on 10 June 2022, three consecutive earthquakes of Ms≥5.0 with a maximum magnitude up to Ms 6.0 struck Maerkang, Sichuan, where is supposedly less prone to earthquakes. This article uses seismic observations recorded by the Sichuan Seismic Network to relocate the earthquake sequences and refine velocity models in Maerkang using a double-difference seismic tomography method. The results show that the aftershocks align along northwest and north-northwest directions with a V-shaped pattern, and the Ms 5.8 and 6.0 earthquakes are located in the center of the sequences. The seismogenic faults of the Maerkang earthquake are the two intersecting secondary faults on the east side of the Songgang fault that dip to the northeast and southwest, respectively, with dip angles of about 80°. Analysis of the seismicity parameters and Coulomb stress changes revealed that the Ms 5.8 and 6.0 earthquakes occurred on two separate faults, and the Ms 5.8 earthquake triggered the Ms 6.0 earthquake, while the Ms 6.0 earthquake prevented the rupture of the Ms 5.8 earthquake. The apparent high-velocity anomaly in the upper crust and the low-velocity and high-conductivity layer in the middle-lower crust of the source region suggest that drag forces exerted by the ductile middle-lower crust may have caused the brittle upper crust to move under the eastward extrusion of the Tibetan plateau, leading to the stresses accumulate and release on the causative faults. The Maerkang earthquake highlighted the lateral movement of deep materials and energy redistribution in the intrablock deformation of the Bayan Har block.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"25 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86909909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ian Stone, E. Wirth, Alex Grant, Arthur D. Frankel
We simulate shaking in Tacoma, Washington, and surrounding areas from Mw 6.5 and 7.0 earthquakes on the Tacoma fault. Ground motions are directly modeled up to 2.5 Hz using kinematic, finite-fault sources; a 3D seismic velocity model considering regional geology; and a model mesh with 30 m sampling at the ground surface. In addition, we explore how adjustments to the seismic velocity model affect predicted shaking over a range of periods. These adjustments include the addition of a region-specific geotechnical gradient, surface topography, and a fault damage zone. We find that the simulated shaking tends to be near estimates from empirical ground-motion models (GMMs). However, long-period (T = 5.0 s) shaking within the Tacoma basin is typically underpredicted by the GMMs. The fit between simulated and GMM-derived short-period (T = 0.5 s) shaking is significantly improved with the addition of the geotechnical gradient. From comparing different Mw 6.5 earthquake scenarios, we also find that the response of the Tacoma basin is sensitive to the azimuth of incoming seismic waves. In adding surface topography to the simulation, we find that average ground motion is similar to that produced from the nontopography model. However, shaking is often amplified at topographic highs and deamplified at topographic lows, and the wavefield undergoes extensive scattering. Adding a fault damage zone has the effect of amplifying short-period shaking adjacent to the fault, while reducing far-field shaking. Intermediate-period shaking is amplified within the Tacoma basin, likely due to enhanced surface-wave generation attributable to the fault damage zone waveguide. When applied in the same model, the topography and fault damage zone adjustments often enhance or reduce the effects of one another, adding further complexity to the wavefield. These results emphasize the importance of improving near-surface velocity model resolution as waveform simulations progress toward higher frequencies.
{"title":"3D Wave Propagation Simulations of Mw 6.5+ Earthquakes on the Tacoma Fault, Washington State, Considering the Effects of Topography, a Geotechnical Gradient, and a Fault Damage Zone","authors":"Ian Stone, E. Wirth, Alex Grant, Arthur D. Frankel","doi":"10.1785/0120230083","DOIUrl":"https://doi.org/10.1785/0120230083","url":null,"abstract":"\u0000 We simulate shaking in Tacoma, Washington, and surrounding areas from Mw 6.5 and 7.0 earthquakes on the Tacoma fault. Ground motions are directly modeled up to 2.5 Hz using kinematic, finite-fault sources; a 3D seismic velocity model considering regional geology; and a model mesh with 30 m sampling at the ground surface. In addition, we explore how adjustments to the seismic velocity model affect predicted shaking over a range of periods. These adjustments include the addition of a region-specific geotechnical gradient, surface topography, and a fault damage zone. We find that the simulated shaking tends to be near estimates from empirical ground-motion models (GMMs). However, long-period (T = 5.0 s) shaking within the Tacoma basin is typically underpredicted by the GMMs. The fit between simulated and GMM-derived short-period (T = 0.5 s) shaking is significantly improved with the addition of the geotechnical gradient. From comparing different Mw 6.5 earthquake scenarios, we also find that the response of the Tacoma basin is sensitive to the azimuth of incoming seismic waves. In adding surface topography to the simulation, we find that average ground motion is similar to that produced from the nontopography model. However, shaking is often amplified at topographic highs and deamplified at topographic lows, and the wavefield undergoes extensive scattering. Adding a fault damage zone has the effect of amplifying short-period shaking adjacent to the fault, while reducing far-field shaking. Intermediate-period shaking is amplified within the Tacoma basin, likely due to enhanced surface-wave generation attributable to the fault damage zone waveguide. When applied in the same model, the topography and fault damage zone adjustments often enhance or reduce the effects of one another, adding further complexity to the wavefield. These results emphasize the importance of improving near-surface velocity model resolution as waveform simulations progress toward higher frequencies.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"13 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84520028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O.M. Saad, Yunfeng Chen, A. Savvaidis, Sergey Fomel, Xiuxuan Jiang, Dino Huang, Y. A. S. I. Oboué, Shan-shan Yong, Xin'an Wang, Xing Zhang, Y. Chen
Earthquake forecasting is one of the most challenging tasks in the field of seismology that aims to save human life and mitigate catastrophic damages. We have designed a real-time earthquake forecasting framework to forecast earthquakes and tested it in seismogenic regions in southwestern China. The input data are the features provided by the multicomponent seismic monitoring system acoustic electromagnetic to AI (AETA), in which the data are recorded using two types of sensors per station: electromagnetic (EM) and geo-acoustic (GA) sensors. The target is to forecast the location and magnitude of the earthquake that may occur next week, given the data of the current week. The proposed method is based on dimension reduction from massive EM and GA data using principal component analysis, which is followed by random-forest-based classification. The proposed algorithm is trained using the available data from 2016 to 2020 and evaluated using real-time data during 2021. As a result, the testing accuracy reaches 70%, whereas the precision, recall, and F1-score are 63.63%, 93.33%, and 75.66%, respectively. The mean absolute error of the distance and the predicted magnitude using the proposed method compared to the catalog solution are 381 km and 0.49, respectively.
{"title":"Earthquake Forecasting Using Big Data and Artificial Intelligence: A 30-Week Real-Time Case Study in China","authors":"O.M. Saad, Yunfeng Chen, A. Savvaidis, Sergey Fomel, Xiuxuan Jiang, Dino Huang, Y. A. S. I. Oboué, Shan-shan Yong, Xin'an Wang, Xing Zhang, Y. Chen","doi":"10.1785/0120230031","DOIUrl":"https://doi.org/10.1785/0120230031","url":null,"abstract":"\u0000 Earthquake forecasting is one of the most challenging tasks in the field of seismology that aims to save human life and mitigate catastrophic damages. We have designed a real-time earthquake forecasting framework to forecast earthquakes and tested it in seismogenic regions in southwestern China. The input data are the features provided by the multicomponent seismic monitoring system acoustic electromagnetic to AI (AETA), in which the data are recorded using two types of sensors per station: electromagnetic (EM) and geo-acoustic (GA) sensors. The target is to forecast the location and magnitude of the earthquake that may occur next week, given the data of the current week. The proposed method is based on dimension reduction from massive EM and GA data using principal component analysis, which is followed by random-forest-based classification. The proposed algorithm is trained using the available data from 2016 to 2020 and evaluated using real-time data during 2021. As a result, the testing accuracy reaches 70%, whereas the precision, recall, and F1-score are 63.63%, 93.33%, and 75.66%, respectively. The mean absolute error of the distance and the predicted magnitude using the proposed method compared to the catalog solution are 381 km and 0.49, respectively.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"360 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76462121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To determine the P- and S-wave velocities (VP and VS, respectively) of the sedimentary layers in the Shimousa region of the Kanto basin, Japan, the autocorrelations of P and S waves and the receiver function (RF) for the local earthquakes at the strong-motion stations in the region were jointly analyzed. Because the autocorrelations and RF were insensitive to the event location, the stacked functions for various events captured clear P and S reflections and the Ps phase at the bedrock of the basin. The PpPs phase was also clearly observed at some stations in the region. The arrival times of the P and S reflections and the Ps phase depended on the station. These phases arrived earlier at the northern and eastern parts of the region, and later at the southern and western parts. This trend shows good agreement with that expected from the 3D velocity structure model developed by the Japan Seismic Hazard Information Station. The VP, VS, and thickness (H) values were then estimated from the histogram of the H–V stack for the P and S autocorrelations and the Ps and PpPs phases in the RF. VP, which is less sensitive than VS and H, was not always well determined at some stations, whereas VS and H were well estimated with high resolution. It was found that the resolution depends on the station location in the region. This dependence could be caused by the appearance of clear phases in the functions.
{"title":"Sedimentary P- and S-Wave Velocity Structures in Shimousa Region of Kanto Basin Determined from Joint Autocorrelation and Receiver Function Analysis","authors":"K. Chimoto","doi":"10.1785/0120230058","DOIUrl":"https://doi.org/10.1785/0120230058","url":null,"abstract":"\u0000 To determine the P- and S-wave velocities (VP and VS, respectively) of the sedimentary layers in the Shimousa region of the Kanto basin, Japan, the autocorrelations of P and S waves and the receiver function (RF) for the local earthquakes at the strong-motion stations in the region were jointly analyzed. Because the autocorrelations and RF were insensitive to the event location, the stacked functions for various events captured clear P and S reflections and the Ps phase at the bedrock of the basin. The PpPs phase was also clearly observed at some stations in the region. The arrival times of the P and S reflections and the Ps phase depended on the station. These phases arrived earlier at the northern and eastern parts of the region, and later at the southern and western parts. This trend shows good agreement with that expected from the 3D velocity structure model developed by the Japan Seismic Hazard Information Station. The VP, VS, and thickness (H) values were then estimated from the histogram of the H–V stack for the P and S autocorrelations and the Ps and PpPs phases in the RF. VP, which is less sensitive than VS and H, was not always well determined at some stations, whereas VS and H were well estimated with high resolution. It was found that the resolution depends on the station location in the region. This dependence could be caused by the appearance of clear phases in the functions.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"18 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88271922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Serious damage to near-fault structures is caused mainly by velocity pulses in a ground motion, hence, the necessity to develop a pulse-related definition of strong-motion duration to adequately describe the intensity of near-fault ground motion. For a multipulse record, an ideal-pulse-based strong-motion duration, which is defined as the time interval between the beginning of the first pulse and the end of the last pulse in an ideal-pulse signal, is proposed. This strong-motion duration corresponds with the time interval of the occurrence of strong vibrations and energy accumulations in the original record. For near-fault records, pulselike characteristics can be completely presented within this duration. Meanwhile, the ideal-pulse-based strong-motion duration shows good performance in the estimation of structural responses. The elastic and inelastic displacement spectra of the original records agree well with those of the records shortened according to the proposed duration. The validity of applying the proposed duration to structural analysis is further verified by the nonlinear time history analyses of 3-, 9-, and 20-story steel moment-resisting frame structures. The proposed strong-motion duration accurately estimates nonlinear structural responses. It is proven that the ideal-pulse-based strong-motion duration can adequately describe the intensity of near-fault ground motions, both from the perspective of the energy accumulation process in a ground-motion record and that of the structural analyses subjected to these ground motions.
{"title":"Ideal-Pulse-Based Strong-Motion Duration for Multi-Pulse Near-Fault Records","authors":"Xiao-yu Chen, Dong-sheng Wang, Rui Zhang, Zhi-guo Sun, Wei Guo, Binbin Li","doi":"10.1785/0120220261","DOIUrl":"https://doi.org/10.1785/0120220261","url":null,"abstract":"\u0000 Serious damage to near-fault structures is caused mainly by velocity pulses in a ground motion, hence, the necessity to develop a pulse-related definition of strong-motion duration to adequately describe the intensity of near-fault ground motion. For a multipulse record, an ideal-pulse-based strong-motion duration, which is defined as the time interval between the beginning of the first pulse and the end of the last pulse in an ideal-pulse signal, is proposed. This strong-motion duration corresponds with the time interval of the occurrence of strong vibrations and energy accumulations in the original record. For near-fault records, pulselike characteristics can be completely presented within this duration. Meanwhile, the ideal-pulse-based strong-motion duration shows good performance in the estimation of structural responses. The elastic and inelastic displacement spectra of the original records agree well with those of the records shortened according to the proposed duration. The validity of applying the proposed duration to structural analysis is further verified by the nonlinear time history analyses of 3-, 9-, and 20-story steel moment-resisting frame structures. The proposed strong-motion duration accurately estimates nonlinear structural responses. It is proven that the ideal-pulse-based strong-motion duration can adequately describe the intensity of near-fault ground motions, both from the perspective of the energy accumulation process in a ground-motion record and that of the structural analyses subjected to these ground motions.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"9 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81678872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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