J. Goltz, Katsuya Yamori, K. Nakayachi, Hideyuki Shiroshita, Takashi Sugiyama, Yu Matsubara
A team of social scientists from the United States and Japan has conducted a study exploring the extent to which municipal governments in Japan have developed plans for response to an operational earthquake forecast from the Japan Meteorological Agency (JMA), indicating that seismic activity in the Nankai trough region has elevated the short-term probability that a major earthquake may occur. Employing both survey research and in-depth interviews, the team explored various aspects of the history and science behind the alerting system, guidance from the national government of Japan, and planning by local jurisdictions for a possible future Nankai trough major earthquake. The survey included questions regarding planning actions included in response plans for receipt of “special earthquake warning information” as well as questions regarding challenges in the planning process, expectations that an earthquake would follow the issuance of an alert, and whether planning would reduce the number of fatalities and injuries. We also conducted in-depth interviews that explored the scientific basis for the alerting system and asked working disaster managers in the Nankai region what they had done to plan and the reasons for not planning if plans had not been developed. We received 469 responses from a total of 736 jurisdictions that comprise the Nankai region—a response rate of 63.7%. We conducted a total of 17 in-depth interviews. In general, we found that a majority of jurisdictions have response plans for receipt of an alert from the JMA; however, the plans lacked a number of planning elements considered important from a disaster management perspective. In addition, many smaller jurisdictions lacked the staffing, resources, and guidance to form comprehensive response plans. Our report identifies both the strengths and weaknesses of existing plans, and outlines a program for improving planning in the region.
{"title":"Operational Earthquake Forecasting in Japan: A Study of Municipal Government Planning for an Earthquake Advisory or Warning in the Nankai Region","authors":"J. Goltz, Katsuya Yamori, K. Nakayachi, Hideyuki Shiroshita, Takashi Sugiyama, Yu Matsubara","doi":"10.1785/0220230304","DOIUrl":"https://doi.org/10.1785/0220230304","url":null,"abstract":"\u0000 A team of social scientists from the United States and Japan has conducted a study exploring the extent to which municipal governments in Japan have developed plans for response to an operational earthquake forecast from the Japan Meteorological Agency (JMA), indicating that seismic activity in the Nankai trough region has elevated the short-term probability that a major earthquake may occur. Employing both survey research and in-depth interviews, the team explored various aspects of the history and science behind the alerting system, guidance from the national government of Japan, and planning by local jurisdictions for a possible future Nankai trough major earthquake. The survey included questions regarding planning actions included in response plans for receipt of “special earthquake warning information” as well as questions regarding challenges in the planning process, expectations that an earthquake would follow the issuance of an alert, and whether planning would reduce the number of fatalities and injuries. We also conducted in-depth interviews that explored the scientific basis for the alerting system and asked working disaster managers in the Nankai region what they had done to plan and the reasons for not planning if plans had not been developed. We received 469 responses from a total of 736 jurisdictions that comprise the Nankai region—a response rate of 63.7%. We conducted a total of 17 in-depth interviews. In general, we found that a majority of jurisdictions have response plans for receipt of an alert from the JMA; however, the plans lacked a number of planning elements considered important from a disaster management perspective. In addition, many smaller jurisdictions lacked the staffing, resources, and guidance to form comprehensive response plans. Our report identifies both the strengths and weaknesses of existing plans, and outlines a program for improving planning in the region.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140481562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lu Li, Baoshan Wang, Zhigang Peng, J. Hou, Fang Wang
The Chinese continent is seismically active and is an important region for analyzing statistical behaviors of large intraplate earthquake sequences. A systematic and detailed record of large earthquake sequences provides the basis for such analysis in a tectonically complex region. In this study, using a graphic processing units-accelerated matched filter technique, we detected up to five times more events than standard earthquake catalogs to generate newly detected catalogs for 32 Ms≥6.0 earthquakes on the Chinese continent from October 2008 to December 2019. The statistical analysis of the newly detected high-resolution catalogs showed that strike-slip mainshocks have higher potential to have anomalous foreshock sequences but are followed by fewer aftershocks than those with other faulting styles. We also provided an example for the 2014 Yingjiang, Yunnan, earthquake sequence, in which the b-value shows a reduction for foreshock sequences and is followed by a recovery in the aftershock period. Our detected catalogs can be used to further study statistical behaviors of earthquake sequences, which is essential for understanding earthquake interaction and improving seismic hazard assessment on the Chinese continent and around the world.
{"title":"Statistical Features of Seismicity Associated with Large Earthquakes on the Chinese Continent between 2008 and 2019 Based on Newly Detected Catalogs","authors":"Lu Li, Baoshan Wang, Zhigang Peng, J. Hou, Fang Wang","doi":"10.1785/0220230189","DOIUrl":"https://doi.org/10.1785/0220230189","url":null,"abstract":"\u0000 The Chinese continent is seismically active and is an important region for analyzing statistical behaviors of large intraplate earthquake sequences. A systematic and detailed record of large earthquake sequences provides the basis for such analysis in a tectonically complex region. In this study, using a graphic processing units-accelerated matched filter technique, we detected up to five times more events than standard earthquake catalogs to generate newly detected catalogs for 32 Ms≥6.0 earthquakes on the Chinese continent from October 2008 to December 2019. The statistical analysis of the newly detected high-resolution catalogs showed that strike-slip mainshocks have higher potential to have anomalous foreshock sequences but are followed by fewer aftershocks than those with other faulting styles. We also provided an example for the 2014 Yingjiang, Yunnan, earthquake sequence, in which the b-value shows a reduction for foreshock sequences and is followed by a recovery in the aftershock period. Our detected catalogs can be used to further study statistical behaviors of earthquake sequences, which is essential for understanding earthquake interaction and improving seismic hazard assessment on the Chinese continent and around the world.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"69 19","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140486511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Earthquake activities in areas across the Midland basin and the Central Basin Platform of West Texas have significantly increased since mid-2019 because of continuing industrial activities involving wastewater injection. The induced seismicity has allowed us to discover previously unknown seismogenic structures. This article presents a study focusing on seismotectonic characteristics of the Midland basin. For this purpose, we first delineated seismicity to identify seismogenic structures. In addition, we performed waveform moment tensor inversion to determine earthquake source mechanisms; subsequently, we inverted for the regional stress field using the obtained source mechanisms. As a result, we have obtained 150 focal mechanisms (from 2017 to November 2023). Based on the seismicity distribution and source mechanism patterns, we have identified 15 distinctive seismogenic zones. A vast majority of seismicity are located in the crystalline basement. Most of the 15 seismicity zones contain seismogenic structures commonly presenting linear geometry but with various orientation. Although the inverted focal mechanisms are a mix of strike-slip and normal faulting, the inverted stress field contains the least compression axes (S3) commonly oriented in 330° azimuth across the 15 identified seismogenic zones. A combination of all seismogenic features has demonstrated that the Midland basin contains fault architectures resulting from the latest extensional tectonic activities, creating a series of basement-rooted strike-slip and normal faults. The two types of basement-rooted faults coexist in our study area, where a presumed basement-rooted rift system transects the Midland basin. They are reactivated by the current fluid injection.
{"title":"Complex Seismotectonic Characteristics in the Midland Basin of Texas: Constrained by Seismicity and Earthquake Source Mechanisms","authors":"Guo-chin Dino Huang, Yangkang Chen, Alexandras Savvaidis","doi":"10.1785/0220230269","DOIUrl":"https://doi.org/10.1785/0220230269","url":null,"abstract":"\u0000 Earthquake activities in areas across the Midland basin and the Central Basin Platform of West Texas have significantly increased since mid-2019 because of continuing industrial activities involving wastewater injection. The induced seismicity has allowed us to discover previously unknown seismogenic structures. This article presents a study focusing on seismotectonic characteristics of the Midland basin. For this purpose, we first delineated seismicity to identify seismogenic structures. In addition, we performed waveform moment tensor inversion to determine earthquake source mechanisms; subsequently, we inverted for the regional stress field using the obtained source mechanisms. As a result, we have obtained 150 focal mechanisms (from 2017 to November 2023). Based on the seismicity distribution and source mechanism patterns, we have identified 15 distinctive seismogenic zones. A vast majority of seismicity are located in the crystalline basement. Most of the 15 seismicity zones contain seismogenic structures commonly presenting linear geometry but with various orientation. Although the inverted focal mechanisms are a mix of strike-slip and normal faulting, the inverted stress field contains the least compression axes (S3) commonly oriented in 330° azimuth across the 15 identified seismogenic zones. A combination of all seismogenic features has demonstrated that the Midland basin contains fault architectures resulting from the latest extensional tectonic activities, creating a series of basement-rooted strike-slip and normal faults. The two types of basement-rooted faults coexist in our study area, where a presumed basement-rooted rift system transects the Midland basin. They are reactivated by the current fluid injection.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"6 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140489827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The global ergodic GK17 (Graizer, 2018) ground-motion model developed using the Next Generation Attenuation-West2 database (Ancheta et al., 2014) for the active crustal regions (ACRs) was applied to the dataset of recordings from the two largest moment magnitude Mw 7.8 and 7.5 earthquakes in Türkiye (Buckreis et al., 2023a). The GK17 model demonstrates acceptable performance while mostly underpredicting spectral accelerations (SAs) at near-fault up to ∼100 km and far-field more than ∼400 km rupture distances for periods T < 1 s. The GK17 model was modified by applying additional Rrup distance and VS30 residuals corrections, creating an updated GK nonergodic model tuned for Türkiye called the GK_T model. After varying anelastic attenuation of SAs QSA, it was concluded that the average for the ACRs value of QSA=120 produces the best results. Comparisons of the model site amplification functions (SAFs) show that the GK_T SAFs are lower compared to the GK17 model. The Türkiye-specific GK_T partially nonergodic model shows better agreement with the recorded data than the ergodic GK17 model, especially at short periods and short rupture distances. As expected, application of the Türkiye-specific model results in a lower sigma. It is also lower than the within-event sigma of the GK17 model, except for the period range of 1.5 < T < 3 s. Improvements to the GK_T model can be expected with an addition of deep sediment (basin depth) information to the current dataset and other earthquakes in the region.
利用下一代衰减-West2数据库（Ancheta等人，2014年）为活动地壳区域（ACRs）开发的全球遍历GK17（Graizer，2018年）地动模型被应用于图尔基耶两次最大矩级Mw 7.8和7.5地震的记录数据集（Buckreis等人，2023年a）。GK17 模型的性能是可以接受的，但在 T < 1 秒的情况下，它对 100 km 以下近断层和 400 km 以上远场破裂距离的频谱加速度（SAs）预测不足。在改变 SAs QSA 的无弹性衰减后，得出的结论是 QSA=120 的 ACRs 平均值产生了最佳结果。对模型位点放大函数（SAFs）的比较表明，GK_T 的 SAFs 比 GK17 模型低。图尔基耶特有的 GK_T 部分非啮合模型比啮合 GK17 模型显示出与记录数据更好的一致性，尤其是在短周期和短破裂距离时。正如预期的那样，应用图尔基耶特定模型的结果是较低的西格玛。除了 1.5 < T < 3 s 的周期范围外，它也低于 GK17 模型的事件内西格玛。随着当前数据集和该地区其他地震的深层沉积（盆地深度）信息的增加，GK_T 模型有望得到改进。
{"title":"Application of GK17 Ground-Motion Model to Preliminary Processed Turkish Ground-Motion Recordings Dataset and GK Model Adjustment to the Turkish Environment by Developing Partially Nonergodic Model","authors":"V. Graizer","doi":"10.1785/0220230291","DOIUrl":"https://doi.org/10.1785/0220230291","url":null,"abstract":"\u0000 The global ergodic GK17 (Graizer, 2018) ground-motion model developed using the Next Generation Attenuation-West2 database (Ancheta et al., 2014) for the active crustal regions (ACRs) was applied to the dataset of recordings from the two largest moment magnitude Mw 7.8 and 7.5 earthquakes in Türkiye (Buckreis et al., 2023a). The GK17 model demonstrates acceptable performance while mostly underpredicting spectral accelerations (SAs) at near-fault up to ∼100 km and far-field more than ∼400 km rupture distances for periods T < 1 s. The GK17 model was modified by applying additional Rrup distance and VS30 residuals corrections, creating an updated GK nonergodic model tuned for Türkiye called the GK_T model. After varying anelastic attenuation of SAs QSA, it was concluded that the average for the ACRs value of QSA=120 produces the best results. Comparisons of the model site amplification functions (SAFs) show that the GK_T SAFs are lower compared to the GK17 model. The Türkiye-specific GK_T partially nonergodic model shows better agreement with the recorded data than the ergodic GK17 model, especially at short periods and short rupture distances. As expected, application of the Türkiye-specific model results in a lower sigma. It is also lower than the within-event sigma of the GK17 model, except for the period range of 1.5 < T < 3 s. Improvements to the GK_T model can be expected with an addition of deep sediment (basin depth) information to the current dataset and other earthquakes in the region.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"24 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139597922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adel Asadi, Christina Sanon, E. Cakir, Weiwei Zhan, Hooman Shirzadi, Laurie Gaskins Baise, K. Onder Cetin, Babak Moaveni
A global geospatial liquefaction model (GGLM-2017) was previously developed (Zhu et al., 2017) using logistic regression (LR) and is currently used by the U.S. Geological Survey as the preferred liquefaction model to map liquefaction probability immediately after the occurrence of earthquake events. This research proposes an ensemble modeling approach to improve the performance of the GGLM-2017 for geospatial liquefaction modeling of the 2023 Türkiye earthquakes using an updated inventory of liquefaction occurrence locations in Europe (the OpenLIQ database, which includes prior events occurring in Türkiye) and a new inventory from the 2023 Türkiye earthquakes (gathered from multiple sources). Using the same geospatial proxies for soil saturation, soil density, and earthquake loading, and the same non-liquefaction sampling strategy used to develop GGLM-2017, the proposed ensemble method is validated on the data of the 2023 Türkiye earthquakes by integrating four models, including global (GGLM-2017), continental (LR model trained on eight European events), regional (LR model trained on three historical events in Türkiye), and event-specific (LR model trained on partially available data from the 2023 Türkiye earthquakes) models. The inventory from the 2023 Türkiye earthquakes is split into two batches, in which the first batch (163 liquefaction occurrences) resulted from the preliminary reconnaissance and is used for training the event-specific model, and the second batch (284 liquefaction occurrences) resulted from a more complete reconnaissance (which was made available later) and is used for validating all models. The rationale for using the first batch for training the event-specific model is to exploit the information as they become available to optimize the performance of global model in liquefaction prediction. The final ensemble probability assignment is done by averaging the probabilities derived by the four individual models, and a 50% threshold is used for classification accuracy evaluations. Comparative analysis of the ensemble model’s performance with the GGLM-2017 showed improved predictive accuracy, resulting in higher liquefaction detection for the specific event under study (the 2023 Türkiye earthquakes). The ensemble model also provides an estimate of model uncertainty.
{"title":"Geospatial Liquefaction Modeling of the 2023 Türkiye Earthquake Sequence by an Ensemble of Global, Continental, Regional, and Event-Specific Models","authors":"Adel Asadi, Christina Sanon, E. Cakir, Weiwei Zhan, Hooman Shirzadi, Laurie Gaskins Baise, K. Onder Cetin, Babak Moaveni","doi":"10.1785/0220230287","DOIUrl":"https://doi.org/10.1785/0220230287","url":null,"abstract":"\u0000 A global geospatial liquefaction model (GGLM-2017) was previously developed (Zhu et al., 2017) using logistic regression (LR) and is currently used by the U.S. Geological Survey as the preferred liquefaction model to map liquefaction probability immediately after the occurrence of earthquake events. This research proposes an ensemble modeling approach to improve the performance of the GGLM-2017 for geospatial liquefaction modeling of the 2023 Türkiye earthquakes using an updated inventory of liquefaction occurrence locations in Europe (the OpenLIQ database, which includes prior events occurring in Türkiye) and a new inventory from the 2023 Türkiye earthquakes (gathered from multiple sources). Using the same geospatial proxies for soil saturation, soil density, and earthquake loading, and the same non-liquefaction sampling strategy used to develop GGLM-2017, the proposed ensemble method is validated on the data of the 2023 Türkiye earthquakes by integrating four models, including global (GGLM-2017), continental (LR model trained on eight European events), regional (LR model trained on three historical events in Türkiye), and event-specific (LR model trained on partially available data from the 2023 Türkiye earthquakes) models. The inventory from the 2023 Türkiye earthquakes is split into two batches, in which the first batch (163 liquefaction occurrences) resulted from the preliminary reconnaissance and is used for training the event-specific model, and the second batch (284 liquefaction occurrences) resulted from a more complete reconnaissance (which was made available later) and is used for validating all models. The rationale for using the first batch for training the event-specific model is to exploit the information as they become available to optimize the performance of global model in liquefaction prediction. The final ensemble probability assignment is done by averaging the probabilities derived by the four individual models, and a 50% threshold is used for classification accuracy evaluations. Comparative analysis of the ensemble model’s performance with the GGLM-2017 showed improved predictive accuracy, resulting in higher liquefaction detection for the specific event under study (the 2023 Türkiye earthquakes). The ensemble model also provides an estimate of model uncertainty.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"42 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139598014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hongwu Yang, Yingmin Li, Lei Hu, Weihao Pan, Shuyan Ji
On 6 February 2023, a magnitude 7.8 earthquake struck south-central Türkiye. It was followed by many aftershocks, the largest of which was a magnitude 7.5 aftershock. This earthquake caused considerable loss of life and property. Numerous near-fault ground-motion records were collected during the 2023 Türkiye earthquake. Most existing baseline correction methods for near-fault ground motions disregard the commonly used filtering techniques due to their potential elimination of actual permanent displacement. To address this, a new automatic baseline correction method is proposed based on the continuous wavelet transform, which incorporates filtering while preserving permanent displacement. This method is compatible with existing filtering techniques and demonstrates good applicability. In this approach, the raw record is decomposed into a pulse signal containing permanent displacement and a nonpulse signal. The nonpulse signal is high-pass filtered to obtain the corrected nonpulse signal, and then the true ground motion is obtained by combining the pulse signal with the corrected nonpulse signal. The effectiveness of the proposed method is evaluated across five aspects using the 1999 Chi-Chi earthquake records: time histories, baseline offsets, response spectra, peak ground velocities, and peak ground displacements. Furthermore, the method is applied to 36 station records (108 components) of the 2023 Türkiye earthquake. The analysis results indicate that the corrected displacement time histories exhibit sustained flatness in their tails and demonstrate a closer agreement with the Global Navigation Satellite System (GNSS) measurements than the previous methods. This method can also incorporate static GNSS offsets to accurately determine true ground motions with precise permanent displacements. The corrected results can be utilized for nonlinear seismic calculations and structural damage analysis of fault-crossing structures such as bridges and tunnels.
{"title":"New Baseline Correction Method for Near-Fault Ground-Motion Records Based on Continuous Wavelet Transform","authors":"Hongwu Yang, Yingmin Li, Lei Hu, Weihao Pan, Shuyan Ji","doi":"10.1785/0220230184","DOIUrl":"https://doi.org/10.1785/0220230184","url":null,"abstract":"\u0000 On 6 February 2023, a magnitude 7.8 earthquake struck south-central Türkiye. It was followed by many aftershocks, the largest of which was a magnitude 7.5 aftershock. This earthquake caused considerable loss of life and property. Numerous near-fault ground-motion records were collected during the 2023 Türkiye earthquake. Most existing baseline correction methods for near-fault ground motions disregard the commonly used filtering techniques due to their potential elimination of actual permanent displacement. To address this, a new automatic baseline correction method is proposed based on the continuous wavelet transform, which incorporates filtering while preserving permanent displacement. This method is compatible with existing filtering techniques and demonstrates good applicability. In this approach, the raw record is decomposed into a pulse signal containing permanent displacement and a nonpulse signal. The nonpulse signal is high-pass filtered to obtain the corrected nonpulse signal, and then the true ground motion is obtained by combining the pulse signal with the corrected nonpulse signal. The effectiveness of the proposed method is evaluated across five aspects using the 1999 Chi-Chi earthquake records: time histories, baseline offsets, response spectra, peak ground velocities, and peak ground displacements. Furthermore, the method is applied to 36 station records (108 components) of the 2023 Türkiye earthquake. The analysis results indicate that the corrected displacement time histories exhibit sustained flatness in their tails and demonstrate a closer agreement with the Global Navigation Satellite System (GNSS) measurements than the previous methods. This method can also incorporate static GNSS offsets to accurately determine true ground motions with precise permanent displacements. The corrected results can be utilized for nonlinear seismic calculations and structural damage analysis of fault-crossing structures such as bridges and tunnels.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"111 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139596605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuji Yagi, R. Okuwaki, S. Hirano, Bogdan Enescu, Masataro Chikamori, Ryo Yamaguchi
Seismic waveforms, including teleseismic body waves, contain information about the irregular behavior of rupture propagation, which is essential for understanding the evolution process of large earthquakes. Here, a high-degree-of-freedom source inversion is applied to the teleseismic P waves of the 2023 moment magnitude 6.8 Morocco earthquake to reveal the irregular rupture behavior during earthquake growth. The resulting total moment tensor solution is an oblique focal mechanism that exhibits reverse faulting with a strike-slip component. There are two distinct peaks at 2 and 4 s in the moment rate function. The reverse fault component dominates at the beginning of the rupture, but then the strike-slip component increases to the second peak and then decreases. The main rupture propagates first in an east-northeast direction, then both up- and down-dip. The down-dip propagating rupture diminishes shortly, whereas the up-dip propagating rupture becomes dominant. The main rupture propagating in the up-dip direction is temporarily suppressed around a point located at 19 km depth and 10 km east-northeast of the hypocenter (region B). After the rupture propagates surrounding region B, the rupture propagates into region B, where a relatively fast slip rate is observed. It is confirmed that the irregular rupture propagation associated with region B is reproduced even when the model settings and the data sampling interval are slightly changed. The irregular rupture propagation obtained in this study suggests that a barrier with high apparent strength (e.g., high fracture surface energy) can cause the rupture to be initially suppressed within the barrier region, followed by delayed rupture propagation through the apparent barrier. The high-frequency seismic motions caused by such an irregular rupture propagation may have contributed to the increase in earthquake-related damage.
包括远震体波在内的地震波形包含破裂传播的不规则行为信息，这对于理解大地震的演化过程至关重要。本文对 2023 年摩洛哥 6.8 级地震的远震 P 波进行了高自由度震源反演，以揭示地震发展过程中的不规则破裂行为。由此得出的总力矩张量解决方案是一种斜焦机制，表现出带有走向滑动成分的反向断层。力矩速率函数在 2 秒和 4 秒处有两个明显的峰值。在断裂开始时，反向断层分量占主导地位，但随后走向滑动分量增加到第二个峰值，然后减小。主断裂首先向东-东北方向传播，然后向上和向下传播。向下倾斜传播的断裂很快减弱，而向上倾斜传播的断裂则占主导地位。沿上倾方向传播的主破裂暂时被压制在位于下中心东北偏东 10 公里、深度为 19 公里的一个点（区域 B）周围。在断裂向 B 区域周围传播后，断裂向 B 区域传播，在该区域观察到相对较快的滑动速率。结果证实，即使模型设置和数据采样间隔稍有改变，与区域 B 相关的不规则破裂传播也会重现。本研究获得的不规则破裂传播表明，表观强度高（如断裂面能量高）的屏障可导致破裂最初在屏障区域内受到抑制，随后破裂延迟传播穿过表观屏障。这种不规则的破裂传播所引起的高频地震运动可能是造成地震相关破坏增加的原因。
{"title":"Barrier-Induced Rupture Front Disturbances during the 2023 Morocco Earthquake","authors":"Yuji Yagi, R. Okuwaki, S. Hirano, Bogdan Enescu, Masataro Chikamori, Ryo Yamaguchi","doi":"10.1785/0220230357","DOIUrl":"https://doi.org/10.1785/0220230357","url":null,"abstract":"\u0000 Seismic waveforms, including teleseismic body waves, contain information about the irregular behavior of rupture propagation, which is essential for understanding the evolution process of large earthquakes. Here, a high-degree-of-freedom source inversion is applied to the teleseismic P waves of the 2023 moment magnitude 6.8 Morocco earthquake to reveal the irregular rupture behavior during earthquake growth. The resulting total moment tensor solution is an oblique focal mechanism that exhibits reverse faulting with a strike-slip component. There are two distinct peaks at 2 and 4 s in the moment rate function. The reverse fault component dominates at the beginning of the rupture, but then the strike-slip component increases to the second peak and then decreases. The main rupture propagates first in an east-northeast direction, then both up- and down-dip. The down-dip propagating rupture diminishes shortly, whereas the up-dip propagating rupture becomes dominant. The main rupture propagating in the up-dip direction is temporarily suppressed around a point located at 19 km depth and 10 km east-northeast of the hypocenter (region B). After the rupture propagates surrounding region B, the rupture propagates into region B, where a relatively fast slip rate is observed. It is confirmed that the irregular rupture propagation associated with region B is reproduced even when the model settings and the data sampling interval are slightly changed. The irregular rupture propagation obtained in this study suggests that a barrier with high apparent strength (e.g., high fracture surface energy) can cause the rupture to be initially suppressed within the barrier region, followed by delayed rupture propagation through the apparent barrier. The high-frequency seismic motions caused by such an irregular rupture propagation may have contributed to the increase in earthquake-related damage.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"117 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139596680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yangkang Chen, Alexandras Savvaidis, O.M. Saad, Guo-Chin Dino Huang, Daniel Siervo, Vincent O’Sullivan, Cooper McCabe, Bede Uku, Preston Fleck, Grace Burke, Natalie L. Alvarez, Jessica Domino, I. Grigoratos
Machine-learning (ML) seismology relies on large datasets with high-fidelity labels from humans to train generalized models. Among the seismological applications of ML, earthquake detection, and P- and S-wave arrival picking are the most widely studied, with capabilities that can exceed humans. Here, we present a regional artificial intelligence (AI) earthquake dataset (TXED) compiled for the state of Texas. The TXED dataset is composed of earthquake signals with manually picked P- and S-wave arrival times and manually picked noise waveforms corresponding to more than 20,000 earthquake events spanning from the beginning of the Texas seismological network (TexNet) (1 January 2017) to date. These data are a supplement to the existing worldwide open-access seismological AI datasets and represent the signal and noise characteristics of Texas. Direct applications of the TXED datasets include improving the performance of a global picking model in Texas by transfer learning using the new dataset. This dataset will also serve as a benchmark dataset for fundamental AI research like designing seismology-oriented deep-learning architectures. We plan to continue to expand the TXED dataset as more observations are made by TexNet analysts.
机器学习（ML）地震学依赖于带有人类高保真标签的大型数据集来训练通用模型。在机器学习的地震学应用中，地震探测、P 波和 S 波到达采样是研究最广泛的，其能力可以超过人类。在此，我们介绍一个为德克萨斯州编制的地区人工智能（AI）地震数据集（TXED）。TXED 数据集由人工选取的 P 波和 S 波到达时间以及人工选取的噪声波形的地震信号组成，对应于从德克萨斯地震学网络（TexNet）开始（2017 年 1 月 1 日）至今的 20,000 多个地震事件。这些数据是对现有的全球开放式地震人工影响数据集的补充，代表了德克萨斯州的信号和噪声特征。TXED 数据集的直接应用包括通过使用新数据集进行迁移学习，提高德克萨斯州全球采样模型的性能。该数据集还将作为基础人工智能研究的基准数据集，如设计面向地震学的深度学习架构。我们计划随着 TexNet 分析师进行更多观测，继续扩展 TXED 数据集。
{"title":"TXED: The Texas Earthquake Dataset for AI","authors":"Yangkang Chen, Alexandras Savvaidis, O.M. Saad, Guo-Chin Dino Huang, Daniel Siervo, Vincent O’Sullivan, Cooper McCabe, Bede Uku, Preston Fleck, Grace Burke, Natalie L. Alvarez, Jessica Domino, I. Grigoratos","doi":"10.1785/0220230327","DOIUrl":"https://doi.org/10.1785/0220230327","url":null,"abstract":"\u0000 Machine-learning (ML) seismology relies on large datasets with high-fidelity labels from humans to train generalized models. Among the seismological applications of ML, earthquake detection, and P- and S-wave arrival picking are the most widely studied, with capabilities that can exceed humans. Here, we present a regional artificial intelligence (AI) earthquake dataset (TXED) compiled for the state of Texas. The TXED dataset is composed of earthquake signals with manually picked P- and S-wave arrival times and manually picked noise waveforms corresponding to more than 20,000 earthquake events spanning from the beginning of the Texas seismological network (TexNet) (1 January 2017) to date. These data are a supplement to the existing worldwide open-access seismological AI datasets and represent the signal and noise characteristics of Texas. Direct applications of the TXED datasets include improving the performance of a global picking model in Texas by transfer learning using the new dataset. This dataset will also serve as a benchmark dataset for fundamental AI research like designing seismology-oriented deep-learning architectures. We plan to continue to expand the TXED dataset as more observations are made by TexNet analysts.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"38 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139599425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yohai Magen, G. Baer, A. Ziv, A. Inbal, R. N. Nof, Yarriv Hamiel, Oksana Piatibratova, Gökhan Gürbüz
Two devastating earthquakes struck southeastern Türkiye and northwestern Syria on 6 February 2023: an Mw 7.8 mainshock, followed 9 hr later by an Mw 7.6 aftershock. To recover and separate the subsurface geometry and slip distributions along the two earthquake faults, we jointly invert Interferometric Synthetic Aperture Radar, Synthetic Aperture Radar pixel offset tracking, burst overlap interferometry (BOI), Global Navigation Satellite System, and aftershock datasets. We introduce a new Kalman filter-based approach for merging spatially dense azimuth offset (AZO) data with the more precise yet spatially sparse BOI data. This procedure yields improved measurements of the displacements parallel to the near north-south satellite tracks, which are critical for resolving slip along most of the Mw 7.8 fault segments. We optimize the inversion using a new metric for assessing the degree of spatial correlation between the coseismic slip gradients and early aftershocks, resulting in a stable solution honoring the complementarity between the geodetic and aftershock datasets. The analysis suggests that the Mw 7.8 rupture consisted of three large segments and two short fault branches, covering about 300 km along the East Anatolian fault (EAF), whereas the Mw 7.6 rupture consisted of three segments extending for about 160 km along the nearby Sürgü fault (SF). On the basis of moment-to-stress-drop scaling relations, we show that the Mw 7.6 stress drop is four times larger than the Mw 7.8 stress drop, consistent with the larger recurrence intervals for Mw > 7 earthquakes on the SF than on the EAF. The moment released during the 2023 Mw 7.8 earthquake is 2–4 times larger than the sum of the moments released during individual historical Mw > 7 earthquakes along the three segments of the 2023 Mw 7.8 earthquake. Thus, when considering moment release for multisegment earthquakes, one should note that the final moment of fault coalescence is likely larger than the arithmetic sum of individual segment ruptures.
{"title":"Fault Coalescence, Slip Distribution, and Stress Drop of the February 2023 Southeast Türkiye Earthquakes from Joint Inversion of SAR, GNSS, and Burst Overlap Interferometry","authors":"Yohai Magen, G. Baer, A. Ziv, A. Inbal, R. N. Nof, Yarriv Hamiel, Oksana Piatibratova, Gökhan Gürbüz","doi":"10.1785/0220230271","DOIUrl":"https://doi.org/10.1785/0220230271","url":null,"abstract":"\u0000 Two devastating earthquakes struck southeastern Türkiye and northwestern Syria on 6 February 2023: an Mw 7.8 mainshock, followed 9 hr later by an Mw 7.6 aftershock. To recover and separate the subsurface geometry and slip distributions along the two earthquake faults, we jointly invert Interferometric Synthetic Aperture Radar, Synthetic Aperture Radar pixel offset tracking, burst overlap interferometry (BOI), Global Navigation Satellite System, and aftershock datasets. We introduce a new Kalman filter-based approach for merging spatially dense azimuth offset (AZO) data with the more precise yet spatially sparse BOI data. This procedure yields improved measurements of the displacements parallel to the near north-south satellite tracks, which are critical for resolving slip along most of the Mw 7.8 fault segments. We optimize the inversion using a new metric for assessing the degree of spatial correlation between the coseismic slip gradients and early aftershocks, resulting in a stable solution honoring the complementarity between the geodetic and aftershock datasets. The analysis suggests that the Mw 7.8 rupture consisted of three large segments and two short fault branches, covering about 300 km along the East Anatolian fault (EAF), whereas the Mw 7.6 rupture consisted of three segments extending for about 160 km along the nearby Sürgü fault (SF). On the basis of moment-to-stress-drop scaling relations, we show that the Mw 7.6 stress drop is four times larger than the Mw 7.8 stress drop, consistent with the larger recurrence intervals for Mw > 7 earthquakes on the SF than on the EAF. The moment released during the 2023 Mw 7.8 earthquake is 2–4 times larger than the sum of the moments released during individual historical Mw > 7 earthquakes along the three segments of the 2023 Mw 7.8 earthquake. Thus, when considering moment release for multisegment earthquakes, one should note that the final moment of fault coalescence is likely larger than the arithmetic sum of individual segment ruptures.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"8 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139609467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The seismograms recorded at a total of 71 strong ground-motion stations (SGMS) located within 100 km of the fault rupture were used to investigate the durational variability observed during the 6 February 2023 M 7.8 Pazarcık, Kahramanmaraş, Türkiye, earthquake. More specifically, significant duration (D) and equivalent number of uniform stress cycles (N) estimated using these accelerograms were compared with the ones predicted by Cetin et al. (2021) and Davatgari-Tafreshi and Bora (2023) models, respectively. To facilitate the comparisons, residuals were estimated and presented with reference to (1) SGMS’ geographical locations; (2) recorded peak ground acceleration (PGA) intensities; (3) distance to the fault rupture, or RJB; (4) site stiffness; and (5) angular orientation of the stations relative to the fault rupture. The assessment results reveal that during the Pazarcık event the duration parameters of D5−75, D5−95, and N were recorded as 23 s, 40 s, and 25 cycles, respectively, on average. Hatay and Kahramanmaraş emerge as the metropolitan cities with the highest PGA intensities, coupled with above-the-average significant durations. A negative correlation is evident between the duration and PGA intensity levels for stations located on the Anatolian side of the rupture, particularly pronounced for the significant duration parameters. The N, D5−75, and D5−95 values appear to be unaffected by RJB distances within 10 km, after which they exhibit an increasing trend. The significant durations were evaluated to be longer at softer soil sites. As the azimuth angle θ increases, D and N were observed to increase.
{"title":"Duration Characteristics of Strong Ground Motions Recorded during the 6 February 2023 M 7.8 Pazarcık, Kahramanmaraş, Türkiye, Earthquake","authors":"A. Elsaid, K. Onder Cetin","doi":"10.1785/0220230300","DOIUrl":"https://doi.org/10.1785/0220230300","url":null,"abstract":"\u0000 The seismograms recorded at a total of 71 strong ground-motion stations (SGMS) located within 100 km of the fault rupture were used to investigate the durational variability observed during the 6 February 2023 M 7.8 Pazarcık, Kahramanmaraş, Türkiye, earthquake. More specifically, significant duration (D) and equivalent number of uniform stress cycles (N) estimated using these accelerograms were compared with the ones predicted by Cetin et al. (2021) and Davatgari-Tafreshi and Bora (2023) models, respectively. To facilitate the comparisons, residuals were estimated and presented with reference to (1) SGMS’ geographical locations; (2) recorded peak ground acceleration (PGA) intensities; (3) distance to the fault rupture, or RJB; (4) site stiffness; and (5) angular orientation of the stations relative to the fault rupture. The assessment results reveal that during the Pazarcık event the duration parameters of D5−75, D5−95, and N were recorded as 23 s, 40 s, and 25 cycles, respectively, on average. Hatay and Kahramanmaraş emerge as the metropolitan cities with the highest PGA intensities, coupled with above-the-average significant durations. A negative correlation is evident between the duration and PGA intensity levels for stations located on the Anatolian side of the rupture, particularly pronounced for the significant duration parameters. The N, D5−75, and D5−95 values appear to be unaffected by RJB distances within 10 km, after which they exhibit an increasing trend. The significant durations were evaluated to be longer at softer soil sites. As the azimuth angle θ increases, D and N were observed to increase.","PeriodicalId":508466,"journal":{"name":"Seismological Research Letters","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139608302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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