Yara Rossi, K. Tatsis, J. Clinton, E. Chatzi, M. Rothacher
In this article, we demonstrate that a single station can be used to measure the dynamic properties of a structure. The station includes a collocated accelerometer and rotational sensor, hence, can record both three-component translation and three-component rotation and is referred to as the 6C-station within this study. The key advantage of this approach is to provide a fast and simple path to a comprehensive structural health monitoring characterization that is comparable to the use of a traditional approach using a horizontal array of three-component accelerometers. The deployment of newly developed high-quality rotational sensors allows the direct measurement of structural rotations, facilitating the extraction of structural mode shapes. In this work, we show how an established system identification tool, stochastic subspace identification, can be applied to the 6C-station data and characterize modal properties and structural response. Our results are verified and contrasted against standard horizontal and vertical array configurations. The Prime Tower, a high-rise structure in Zürich, serves as a case study. A structural characterization of this building is presented for the first time. We show that a 6C-station is capable of defining the frequencies of this stiff high-rise building with a fidelity that is on par with a five-sensor horizontal array. The mode shapes of the roof can be precisely determined with a confidence margin that is comparable to conventional sensing array solutions. However, the effectiveness of using only a 6C-station is determined by the noise level of the sensors—in particular, the rotational seismometer needs to be of high quality. The results indicate that, owing to the collocation measurement of translation and rotation, a 6C-station can deliver a comprehensive structural monitoring solution with minimum time, effort, and footprint.
{"title":"A New Paradigm for Structural Characterization, including Rotational Measurements at a Single Site","authors":"Yara Rossi, K. Tatsis, J. Clinton, E. Chatzi, M. Rothacher","doi":"10.1785/0120230026","DOIUrl":"https://doi.org/10.1785/0120230026","url":null,"abstract":"\u0000 In this article, we demonstrate that a single station can be used to measure the dynamic properties of a structure. The station includes a collocated accelerometer and rotational sensor, hence, can record both three-component translation and three-component rotation and is referred to as the 6C-station within this study. The key advantage of this approach is to provide a fast and simple path to a comprehensive structural health monitoring characterization that is comparable to the use of a traditional approach using a horizontal array of three-component accelerometers. The deployment of newly developed high-quality rotational sensors allows the direct measurement of structural rotations, facilitating the extraction of structural mode shapes. In this work, we show how an established system identification tool, stochastic subspace identification, can be applied to the 6C-station data and characterize modal properties and structural response. Our results are verified and contrasted against standard horizontal and vertical array configurations. The Prime Tower, a high-rise structure in Zürich, serves as a case study. A structural characterization of this building is presented for the first time. We show that a 6C-station is capable of defining the frequencies of this stiff high-rise building with a fidelity that is on par with a five-sensor horizontal array. The mode shapes of the roof can be precisely determined with a confidence margin that is comparable to conventional sensing array solutions. However, the effectiveness of using only a 6C-station is determined by the noise level of the sensors—in particular, the rotational seismometer needs to be of high quality. The results indicate that, owing to the collocation measurement of translation and rotation, a 6C-station can deliver a comprehensive structural monitoring solution with minimum time, effort, and footprint.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"3 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75677149","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}
T. Buckreis, J. Stewart, S. Brandenberg, Pengfei Wang
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.
{"title":"Subregional Anelastic Attenuation Model for California","authors":"T. Buckreis, J. Stewart, S. Brandenberg, Pengfei Wang","doi":"10.1785/0120220173","DOIUrl":"https://doi.org/10.1785/0120220173","url":null,"abstract":"\u0000 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.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"13 6","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72536886","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}
Declustering a seismicity catalog to obtain a background seismicity model for probabilistic seismic hazard analysis is not a uniquely defined process. Zaliapin and Ben-Zion (2020) present a method for randomly thinning a complete catalog by removing nearest-neighbor earthquakes. The number of events in the residual catalog depends on a continuous parameter, α0, called the “cluster threshold.” Varying α0 results in a family of residual catalogs, and when enough events are removed the catalog is nearly Poissonian and can be considered declustered. This family of thinned catalogs is used to generate a corresponding family of background seismicity models, which in turn are used to find the probabilistic seismic hazard on an east–west profile across California. Additional models are developed by renormalizing the thinned Zaliapin and Ben-Zion (2020) catalogs to the catalog rate of earthquakes with moment magnitude Mw≥5 and from the maximum shaking earthquake catalog of Anderson et al. (2021). Adding fault contributions, the simplified estimate of the hazards with probability of exceedance of 2% in 50 yr are comparable to the 2018 National Seismic Hazard Model (NSHM). Where faults dominate the hazard, the method of thinning has little effect. The range of hazard estimates from the set of background models alone illustrate the range of effects of catalog thinning for any location where faults do not dominate. The spread of background hazard estimates at most sites is generally within a multiplicative factor of ∼2 of the hazard estimated from a catalog declustered for the 2018 NSHM. However, the spread in the estimates is very large in the vicinity of aftershock zones of large earthquakes. The family of randomly thinned catalogs, including alternative smoothing parameters and optional rescaling, may span the body and range of background hazard that can be inferred from the known history of earthquakes.
{"title":"Effects on Probabilistic Seismic Hazard Estimates That Result from Nonuniqueness in Declustering an Earthquake Catalog","authors":"John G. Anderson, I. Zaliapin","doi":"10.1785/0120220239","DOIUrl":"https://doi.org/10.1785/0120220239","url":null,"abstract":"\u0000 Declustering a seismicity catalog to obtain a background seismicity model for probabilistic seismic hazard analysis is not a uniquely defined process. Zaliapin and Ben-Zion (2020) present a method for randomly thinning a complete catalog by removing nearest-neighbor earthquakes. The number of events in the residual catalog depends on a continuous parameter, α0, called the “cluster threshold.” Varying α0 results in a family of residual catalogs, and when enough events are removed the catalog is nearly Poissonian and can be considered declustered. This family of thinned catalogs is used to generate a corresponding family of background seismicity models, which in turn are used to find the probabilistic seismic hazard on an east–west profile across California. Additional models are developed by renormalizing the thinned Zaliapin and Ben-Zion (2020) catalogs to the catalog rate of earthquakes with moment magnitude Mw≥5 and from the maximum shaking earthquake catalog of Anderson et al. (2021). Adding fault contributions, the simplified estimate of the hazards with probability of exceedance of 2% in 50 yr are comparable to the 2018 National Seismic Hazard Model (NSHM). Where faults dominate the hazard, the method of thinning has little effect. The range of hazard estimates from the set of background models alone illustrate the range of effects of catalog thinning for any location where faults do not dominate. The spread of background hazard estimates at most sites is generally within a multiplicative factor of ∼2 of the hazard estimated from a catalog declustered for the 2018 NSHM. However, the spread in the estimates is very large in the vicinity of aftershock zones of large earthquakes. The family of randomly thinned catalogs, including alternative smoothing parameters and optional rescaling, may span the body and range of background hazard that can be inferred from the known history of earthquakes.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"29 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84370910","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}
We demonstrate the effects of soil–structure interaction (SSI) for three idealized building typologies on a regional scale, using a simulated earthquake scenario of the 2008 Mw 5.4 Chino Hills mainshock in southern California as an example. All the three buildings lie on shallow foundations, and they are subject to three-component simulated ground motions. To carry out this task, we develop a reduced order model (ROM) for each building typology that accounts for the effects of SSI on the building system in the time domain. We specifically use ensemble Kalman inversion (EnKI) to extract the soil impedance values from fully coupled soil–foundation–structure interaction simulations; and we interpolate the EnKI results to derive analytical functions that span the range of applicability of the soil impedance model. We then verify our ROMs by comparing results to fully coupled soil–foundation–structure interaction simulations, also known as direct modeling methods. We finally populate the simulation grid across southern California with the verified building ROMs, and interpret the responses in the form of maps that represent urban-scale effects of SSI on the seismic demand parameters such as maximum displacement, acceleration, and interstory drift. We also identify areas where the effects of SSI, given the resonant characteristics of a specific building, the foundation typology, and the local site conditions, lead to higher seismic demand relative to the fixed-base response.
{"title":"Soil–Structure Interaction Effects on a Regional Scale through Ground-Motion Simulations and Reduced Order Models: A Case Study from the 2008 Mw 5.4 Chino Hills Mainshock","authors":"D. Kusanovic, R. Taborda, D. Asimaki","doi":"10.1785/0120220241","DOIUrl":"https://doi.org/10.1785/0120220241","url":null,"abstract":"\u0000 We demonstrate the effects of soil–structure interaction (SSI) for three idealized building typologies on a regional scale, using a simulated earthquake scenario of the 2008 Mw 5.4 Chino Hills mainshock in southern California as an example. All the three buildings lie on shallow foundations, and they are subject to three-component simulated ground motions. To carry out this task, we develop a reduced order model (ROM) for each building typology that accounts for the effects of SSI on the building system in the time domain. We specifically use ensemble Kalman inversion (EnKI) to extract the soil impedance values from fully coupled soil–foundation–structure interaction simulations; and we interpolate the EnKI results to derive analytical functions that span the range of applicability of the soil impedance model. We then verify our ROMs by comparing results to fully coupled soil–foundation–structure interaction simulations, also known as direct modeling methods. We finally populate the simulation grid across southern California with the verified building ROMs, and interpret the responses in the form of maps that represent urban-scale effects of SSI on the seismic demand parameters such as maximum displacement, acceleration, and interstory drift. We also identify areas where the effects of SSI, given the resonant characteristics of a specific building, the foundation typology, and the local site conditions, lead to higher seismic demand relative to the fixed-base response.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"82 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78069084","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}
The 1923 Taisho Kanto earthquake—an interplate event along the Sagami trough where the Philippine Sea plate subducts beneath the Kanto region—produced ground shaking, crustal deformation, landslides, and tsunamis, and caused the worst earthquake disaster in Japan. Based on seismological and geodetic data, many fault models have been proposed, extending ∼100 km from the epicenter, with a moment magnitude (Mw) of 7.8–8.2, and large slips of ∼8 m located near the epicenter and beneath the Miura Peninsula. The penultimate 1703 Genroku Kanto earthquake produced similar macroseismic effects around Sagami Bay and the Miura Peninsula, but larger coastal uplift and tsunami in the Boso Peninsula. The proposed fault models extend off the Boso Peninsula with Mw of 8.1–8.5. In 2004, the Earthquake Research Committee (ERC) classified the Kanto earthquakes as “Taisho type” and “Genroku type” with recurrence intervals of 200–400 yr and 2300 yr, respectively. In 2014, the ERC revised the long-term evaluation to a recurrence interval of 180–590 yr and a 30 yr probability of 0%–5% based on the Brownian passage time model. With the Cabinet Office, the ERC considered the source area of the maximum possible earthquake of Mw 8.6–8.7. The recent historiographical and paleoseismological studies have identified other candidates for the past Kanto earthquakes in 1495, 1433, 1293, and 878. Various combinations of these candidates give a mean recurrence interval of 210–315 yr, an aperiodicity parameter of 0.04–0.76, and a 30 yr probability of 0.0%–19%. The Cabinet Office has calculated the seismic intensity and tsunami heights of various types of Kanto earthquakes. National and local governments estimate the damage from these hazards. For the Tokyo metropolitan area, the estimated damage and occurrence probability are more significant for M ∼7 earthquakes with various types and depths, and most mitigation efforts are directed at such events.
{"title":"Recurrence and Long-Term Evaluation of Kanto Earthquakes","authors":"K. Satake","doi":"10.1785/0120230072","DOIUrl":"https://doi.org/10.1785/0120230072","url":null,"abstract":"\u0000 The 1923 Taisho Kanto earthquake—an interplate event along the Sagami trough where the Philippine Sea plate subducts beneath the Kanto region—produced ground shaking, crustal deformation, landslides, and tsunamis, and caused the worst earthquake disaster in Japan. Based on seismological and geodetic data, many fault models have been proposed, extending ∼100 km from the epicenter, with a moment magnitude (Mw) of 7.8–8.2, and large slips of ∼8 m located near the epicenter and beneath the Miura Peninsula. The penultimate 1703 Genroku Kanto earthquake produced similar macroseismic effects around Sagami Bay and the Miura Peninsula, but larger coastal uplift and tsunami in the Boso Peninsula. The proposed fault models extend off the Boso Peninsula with Mw of 8.1–8.5. In 2004, the Earthquake Research Committee (ERC) classified the Kanto earthquakes as “Taisho type” and “Genroku type” with recurrence intervals of 200–400 yr and 2300 yr, respectively. In 2014, the ERC revised the long-term evaluation to a recurrence interval of 180–590 yr and a 30 yr probability of 0%–5% based on the Brownian passage time model. With the Cabinet Office, the ERC considered the source area of the maximum possible earthquake of Mw 8.6–8.7. The recent historiographical and paleoseismological studies have identified other candidates for the past Kanto earthquakes in 1495, 1433, 1293, and 878. Various combinations of these candidates give a mean recurrence interval of 210–315 yr, an aperiodicity parameter of 0.04–0.76, and a 30 yr probability of 0.0%–19%. The Cabinet Office has calculated the seismic intensity and tsunami heights of various types of Kanto earthquakes. National and local governments estimate the damage from these hazards. For the Tokyo metropolitan area, the estimated damage and occurrence probability are more significant for M ∼7 earthquakes with various types and depths, and most mitigation efforts are directed at such events.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":" 28","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72381982","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}
Yumi Nakadai, Y. Tanioka, Y. Yamanaka, Tatsuya Nakagaki
The 1923 Kanto earthquake generated not only strong motions that caused a devastating disaster around the metropolitan Tokyo area but also a large tsunami. Although the slip distribution of the 1923 Kanto earthquake has been estimated by several researchers, tsunami waveforms observed at tide gauges near the source have never been used. In this study, the slip distribution of the 1923 Kanto earthquake was estimated using joint inversion of tsunami waveforms and vertical crustal deformations reported in historical documents. The estimated slip distribution was generally consistent with those estimated in the previous studies except for a large slip of 9 m along the western portion of the plate interface, up-dip near the Sagami trough. The east coast of the Izu Peninsula was inundated by the tsunami and surveyed after the tsunami to determine tsunami heights in the inundation areas. The tsunami inundation computed from the estimated slip distribution explained the tsunami heights, and the large slip played an important role in large inundation. These results indicate that the large slip west of the Sagami trough is essential for explaining the observed tsunami caused by the 1923 Kanto earthquake.
{"title":"Re-Estimating a Source Model for the 1923 Kanto Earthquake by Joint Inversion of Tsunami Waveforms and Coseismic Deformation Data","authors":"Yumi Nakadai, Y. Tanioka, Y. Yamanaka, Tatsuya Nakagaki","doi":"10.1785/0120230050","DOIUrl":"https://doi.org/10.1785/0120230050","url":null,"abstract":"\u0000 The 1923 Kanto earthquake generated not only strong motions that caused a devastating disaster around the metropolitan Tokyo area but also a large tsunami. Although the slip distribution of the 1923 Kanto earthquake has been estimated by several researchers, tsunami waveforms observed at tide gauges near the source have never been used. In this study, the slip distribution of the 1923 Kanto earthquake was estimated using joint inversion of tsunami waveforms and vertical crustal deformations reported in historical documents. The estimated slip distribution was generally consistent with those estimated in the previous studies except for a large slip of 9 m along the western portion of the plate interface, up-dip near the Sagami trough. The east coast of the Izu Peninsula was inundated by the tsunami and surveyed after the tsunami to determine tsunami heights in the inundation areas. The tsunami inundation computed from the estimated slip distribution explained the tsunami heights, and the large slip played an important role in large inundation. These results indicate that the large slip west of the Sagami trough is essential for explaining the observed tsunami caused by the 1923 Kanto earthquake.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"315 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76280045","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}
The fore-arc of the southern Cascadia subduction zone (CSZ), north of the Mendocino triple junction (MTJ), is home to a network of Quaternary-active crustal faults that accumulate strain due to the interaction of the North American, Juan de Fuca (Gorda), and Pacific plates. These faults, including the Little Salmon and Mad River fault (LSF and MRF) zones, are located near the most populated parts of California’s north coast and show paleoseismic evidence for three slip events of several-meter scale in the past 1700 yr. However, the geodetic slip rates of these faults are poorly constrained. In this work, we analyze a new compilation of interseismic geodetic velocities from Global Navigation Satellite Systems, leveling, and tide gauge data near the MTJ to constrain present-day slip deficit rates on upper-plate faults and coupling on the megathrust. We construct Green’s functions for interseismic slip deficit for discrete faults embedded in an elastic plate overlying a viscoelastic mantle. We then use a constrained least-squares inversion to determine best-fitting slip rates on the major faults and investigate slip rate trade-offs between faults. Results indicate that the LSF and MRF systems together accumulate 4–5 mm/yr of reverse-slip deficit, although their separate slip rates cannot be determined independently. Modeling of the horizontal and vertical velocities suggests that the southernmost CSZ is coupled interseismically to deeper than 25 km depth. We also find that 6–17 mm/yr of right-lateral slip deficit extends north of the MTJ and into the southern Cascadia fore-arc. These results reinforce the notion that both the southernmost Cascadia megathrust and the smaller fore-arc faults above it contribute to regional seismic hazard.
{"title":"Slip Deficit Rates on Southern Cascadia Faults Resolved with Viscoelastic Earthquake Cycle Modeling of Geodetic Deformation","authors":"K. Materna, J. Murray, F. Pollitz, J. Patton","doi":"10.1785/0120230007","DOIUrl":"https://doi.org/10.1785/0120230007","url":null,"abstract":"\u0000 The fore-arc of the southern Cascadia subduction zone (CSZ), north of the Mendocino triple junction (MTJ), is home to a network of Quaternary-active crustal faults that accumulate strain due to the interaction of the North American, Juan de Fuca (Gorda), and Pacific plates. These faults, including the Little Salmon and Mad River fault (LSF and MRF) zones, are located near the most populated parts of California’s north coast and show paleoseismic evidence for three slip events of several-meter scale in the past 1700 yr. However, the geodetic slip rates of these faults are poorly constrained. In this work, we analyze a new compilation of interseismic geodetic velocities from Global Navigation Satellite Systems, leveling, and tide gauge data near the MTJ to constrain present-day slip deficit rates on upper-plate faults and coupling on the megathrust. We construct Green’s functions for interseismic slip deficit for discrete faults embedded in an elastic plate overlying a viscoelastic mantle. We then use a constrained least-squares inversion to determine best-fitting slip rates on the major faults and investigate slip rate trade-offs between faults. Results indicate that the LSF and MRF systems together accumulate 4–5 mm/yr of reverse-slip deficit, although their separate slip rates cannot be determined independently. Modeling of the horizontal and vertical velocities suggests that the southernmost CSZ is coupled interseismically to deeper than 25 km depth. We also find that 6–17 mm/yr of right-lateral slip deficit extends north of the MTJ and into the southern Cascadia fore-arc. These results reinforce the notion that both the southernmost Cascadia megathrust and the smaller fore-arc faults above it contribute to regional seismic hazard.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"5 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87685920","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}
F. D. Dannemann Dugick, J. Bishop, L. Martire, A. Iezzi, J. Assink, Q. Brissaud, S. Arrowsmith
{"title":"Introduction to the Special Section on Seismoacoustics and Seismoacoustic Data Fusion","authors":"F. D. Dannemann Dugick, J. Bishop, L. Martire, A. Iezzi, J. Assink, Q. Brissaud, S. Arrowsmith","doi":"10.1785/0120230049","DOIUrl":"https://doi.org/10.1785/0120230049","url":null,"abstract":"","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"43 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76289860","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}
C. Yoon, E. Cochran, E. Vanacore, V. Huerfano, G. Báez-Sánchez, John P H Wilding, Jonathan D. Smith
The 2020–2023 southwestern Puerto Rico seismic sequence, still ongoing in 2023, is remarkable for its multiple-fault rupture complexity and elevated aftershock productivity. We applied an automatic workflow to continuous data from 43 seismic stations in Puerto Rico to build an enhanced earthquake catalog with ∼180,000 events for the 3+ yr sequence from 28 December 2019 to 1 January 2023. This workflow contained the EQTransformer (EQT) deep learning model for event detection and phase picking, the EikoNet-Hypocenter Inversion with Stein Variational Inference probabilistic earthquake location approach with a neural network trained to solve the eikonal wave equation, and relocation with event-pair waveform cross correlation. EQT increased the number of catalog events in the sequence by about seven times, though its performance was not quite as good as thorough analyst review. The enhanced catalog revealed new structural details of the sequence space–time evolution, including sudden changes in activity, on a complex system of many small normal and strike-slip faults. This sequence started on 28 December 2019 with an M 4.7 strike-slip earthquake followed by 10 days of shallow strike-slip foreshocks, including several M 5+ earthquakes, in a compact region. The oblique normal fault Mw 6.4 mainshock then happened on 7 January 2020. Early aftershocks in January 2020, with several M 5+ earthquakes, quickly expanded into two intersecting fault zones with diffuse seismicity: one extending ∼35 km on a northward-dipping normal fault and the other ∼60-km-long and oriented west-northwest–east-southeast on strike-slip faults. Months to years later, aftershocks moved westward, deeper, and to outer reaches of the active fault zones, with abrupt rapid seismicity migration following larger M 4.7+ aftershocks in May, July, and December 2020. The observed seismicity evolution indicates cascading failure from stress transfer on multiple critically stressed faults. High aftershock productivity results from the complex multiple-fault network hosting the sequence, which is characteristic of an immature fault system in the diffuse deformation zone around Puerto Rico, at the complicated North American–Caribbean plate boundary region.
{"title":"A Detailed View of the 2020–2023 Southwestern Puerto Rico Seismic Sequence with Deep Learning","authors":"C. Yoon, E. Cochran, E. Vanacore, V. Huerfano, G. Báez-Sánchez, John P H Wilding, Jonathan D. Smith","doi":"10.1785/0120220229","DOIUrl":"https://doi.org/10.1785/0120220229","url":null,"abstract":"\u0000 The 2020–2023 southwestern Puerto Rico seismic sequence, still ongoing in 2023, is remarkable for its multiple-fault rupture complexity and elevated aftershock productivity. We applied an automatic workflow to continuous data from 43 seismic stations in Puerto Rico to build an enhanced earthquake catalog with ∼180,000 events for the 3+ yr sequence from 28 December 2019 to 1 January 2023. This workflow contained the EQTransformer (EQT) deep learning model for event detection and phase picking, the EikoNet-Hypocenter Inversion with Stein Variational Inference probabilistic earthquake location approach with a neural network trained to solve the eikonal wave equation, and relocation with event-pair waveform cross correlation. EQT increased the number of catalog events in the sequence by about seven times, though its performance was not quite as good as thorough analyst review. The enhanced catalog revealed new structural details of the sequence space–time evolution, including sudden changes in activity, on a complex system of many small normal and strike-slip faults. This sequence started on 28 December 2019 with an M 4.7 strike-slip earthquake followed by 10 days of shallow strike-slip foreshocks, including several M 5+ earthquakes, in a compact region. The oblique normal fault Mw 6.4 mainshock then happened on 7 January 2020. Early aftershocks in January 2020, with several M 5+ earthquakes, quickly expanded into two intersecting fault zones with diffuse seismicity: one extending ∼35 km on a northward-dipping normal fault and the other ∼60-km-long and oriented west-northwest–east-southeast on strike-slip faults. Months to years later, aftershocks moved westward, deeper, and to outer reaches of the active fault zones, with abrupt rapid seismicity migration following larger M 4.7+ aftershocks in May, July, and December 2020. The observed seismicity evolution indicates cascading failure from stress transfer on multiple critically stressed faults. High aftershock productivity results from the complex multiple-fault network hosting the sequence, which is characteristic of an immature fault system in the diffuse deformation zone around Puerto Rico, at the complicated North American–Caribbean plate boundary region.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"1 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82107196","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}
Changwei Yang, Kaiwen Zhang, Dongsheng Wu, Zhifang Zhang, Ke Su, Li-ming Qu, Liang Zhang
Automatic P-wave arrival detection is the first task in an earthquake early warning systems. This study proposes a novel detection method for this based on a fractal slope (FS). We improved the calculation method of the fractal dimension to increase the calculation speed and proposed a continuous algorithm. Furthermore, we applied FS in conjunction with the short-term average over the long-term average (STA/LTA), named STA/LTA + FS. We designed orthogonal experiments with different parameters and selected a total of 40,020 sets of seismic waves from the Japanese dataset to test the best parameters. A total of 45,302 sets of seismic waves from the STanford EArthquake dataset and the Chinese dataset were selected to test the generality of the proposed method. The results show that the mean error in detection time of the proposed method is +0.042 s for different datasets. In addition, STA/LTA + FS is robust over a wide range of signal-to-noise ratio, epicentral distance, and magnitude, with the percentage of timing errors below 0.5 s higher than 95%.
{"title":"Fractal Slope-Based Seismic Wave Detection Method","authors":"Changwei Yang, Kaiwen Zhang, Dongsheng Wu, Zhifang Zhang, Ke Su, Li-ming Qu, Liang Zhang","doi":"10.1785/0120220220","DOIUrl":"https://doi.org/10.1785/0120220220","url":null,"abstract":"\u0000 Automatic P-wave arrival detection is the first task in an earthquake early warning systems. This study proposes a novel detection method for this based on a fractal slope (FS). We improved the calculation method of the fractal dimension to increase the calculation speed and proposed a continuous algorithm. Furthermore, we applied FS in conjunction with the short-term average over the long-term average (STA/LTA), named STA/LTA + FS. We designed orthogonal experiments with different parameters and selected a total of 40,020 sets of seismic waves from the Japanese dataset to test the best parameters. A total of 45,302 sets of seismic waves from the STanford EArthquake dataset and the Chinese dataset were selected to test the generality of the proposed method. The results show that the mean error in detection time of the proposed method is +0.042 s for different datasets. In addition, STA/LTA + FS is robust over a wide range of signal-to-noise ratio, epicentral distance, and magnitude, with the percentage of timing errors below 0.5 s higher than 95%.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"2 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87537249","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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