Pub Date : 2025-09-02DOI: 10.1016/j.eqs.2025.06.003
Xianwei Zeng , Chunquan Yu
We present CrazyBeachball, a MATLAB-based graphical user interface (GUI) software package designed for focal mechanism inversion using P-wave first-motion polarity and S/P amplitude ratio data. CrazyBeachball integrates seismic waveform visualization, first-motion polarity picking, and focal mechanism inversion into a single, interactive platform. Unlike conventional methods that involve separate, independent steps, CrazyBeachball streamlines the process and eliminates the need for external data conversion. Its user-friendly interface allows for efficient focal mechanism determination, while its human-machine interaction facilitates enhanced quality control. We demonstrate its effectiveness by determining focal mechanisms for 21 aftershocks from the 2021 MS6.4 Yangbi earthquake sequence, with results aligning with the regional stress field and fault zone geometry. This open-source software package also allows for user customization, enabling adaptation for specific research needs.
{"title":"CrazyBeachball: A MATLAB GUI-based software package for focal mechanism inversion","authors":"Xianwei Zeng , Chunquan Yu","doi":"10.1016/j.eqs.2025.06.003","DOIUrl":"10.1016/j.eqs.2025.06.003","url":null,"abstract":"<div><div>We present CrazyBeachball, a MATLAB-based graphical user interface (GUI) software package designed for focal mechanism inversion using P-wave first-motion polarity and S/P amplitude ratio data. CrazyBeachball integrates seismic waveform visualization, first-motion polarity picking, and focal mechanism inversion into a single, interactive platform. Unlike conventional methods that involve separate, independent steps, CrazyBeachball streamlines the process and eliminates the need for external data conversion. Its user-friendly interface allows for efficient focal mechanism determination, while its human-machine interaction facilitates enhanced quality control. We demonstrate its effectiveness by determining focal mechanisms for 21 aftershocks from the 2021 <em>M</em><sub>S</sub>6.4 Yangbi earthquake sequence, with results aligning with the regional stress field and fault zone geometry. This open-source software package also allows for user customization, enabling adaptation for specific research needs.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 5","pages":"Pages 441-449"},"PeriodicalIF":4.1,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-02DOI: 10.1016/j.eqs.2025.06.001
Lanbo Liu
Dilatancy is referred to the phenomenon of volume increase that occurs when a material is deformed. Dilatancy theory originated in geomechanics for the study of the behavior of granular materials. Later it is expanded to the case of more brittle materials like rocks when it is subjected to the load of varying effective stress and starts to crack and deform, then named the dilatancy-diffusion hypothesis. This hypothesis was developed to explain the changes in rock volume and pore pressure that occur prior to and during fault slip, which can influence earthquake dynamics. Dilatancy-fluid diffusion is a significant concept in understanding the seismogenic process and has served as the major theoretical pillar for earthquake prediction by its classic definition. This paper starts with the recount of fundamental laboratory experiments on granular materials and rocks, then conducts review and examination of the history for using the dilatancy-diffusion hypothesis to interpret the ‘prediction’ of the 1975 Haicheng Earthquake and other events. The Haicheng Earthquake is the first significant event to be interpreted with the dilatancy-diffusion hypothesis in the world. As one pivotal figure in the development of the dilatancy-diffusion hypothesis for earthquake prediction Professor Amos Nur of Stanford University worked tirelessly to attract societal attention to this important scientific and humanistic issue. As a deterministic physical model the dilatancy-diffusion hypothesis intrinsically bears the deficit to interpret the stochastic seismogenic process. With the emergence of deep learning and its successful applications to many science and technology fields, we may see a possibility to overcome the shortcoming of the current state of the theory with the addition of empirical statistics to push the operational earthquake forecasting approach with the addition of the physically-informed neural networks which adopt the dilatancy-diffusion hypothesis as one of its embedded physical relations, to uplift the seismic risk reduction to a new level for saving lives and reducing the losses.
{"title":"The dilatancy-diffusion hypothesis, earthquake prediction, and operational earthquake forecasting: In memory of Professor Amos Nur on the 50th Anniversary of the 1975 Haicheng Earthquake","authors":"Lanbo Liu","doi":"10.1016/j.eqs.2025.06.001","DOIUrl":"10.1016/j.eqs.2025.06.001","url":null,"abstract":"<div><div>Dilatancy is referred to the phenomenon of volume increase that occurs when a material is deformed. Dilatancy theory originated in geomechanics for the study of the behavior of granular materials. Later it is expanded to the case of more brittle materials like rocks when it is subjected to the load of varying effective stress and starts to crack and deform, then named the dilatancy-diffusion hypothesis. This hypothesis was developed to explain the changes in rock volume and pore pressure that occur prior to and during fault slip, which can influence earthquake dynamics. Dilatancy-fluid diffusion is a significant concept in understanding the seismogenic process and has served as the major theoretical pillar for earthquake prediction by its classic definition. This paper starts with the recount of fundamental laboratory experiments on granular materials and rocks, then conducts review and examination of the history for using the dilatancy-diffusion hypothesis to interpret the ‘prediction’ of the 1975 Haicheng Earthquake and other events. The Haicheng Earthquake is the first significant event to be interpreted with the dilatancy-diffusion hypothesis in the world. As one pivotal figure in the development of the dilatancy-diffusion hypothesis for earthquake prediction Professor Amos Nur of Stanford University worked tirelessly to attract societal attention to this important scientific and humanistic issue. As a deterministic physical model the dilatancy-diffusion hypothesis intrinsically bears the deficit to interpret the stochastic seismogenic process. With the emergence of deep learning and its successful applications to many science and technology fields, we may see a possibility to overcome the shortcoming of the current state of the theory with the addition of empirical statistics to push the operational earthquake forecasting approach with the addition of the physically-informed neural networks which adopt the dilatancy-diffusion hypothesis as one of its embedded physical relations, to uplift the seismic risk reduction to a new level for saving lives and reducing the losses.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 5","pages":"Pages 465-484"},"PeriodicalIF":4.1,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-02DOI: 10.1016/j.eqs.2025.02.001
Suli Yao , Zhigao Yang , Hongfeng Yang
Determining the rupture directivity for small earthquakes is challenging due to the small source dimension and limited resolution of far-field observations. In recent years, the burst of near-source observations provides great opportunities to study earthquake rupture. Here we present the rapid determination of the rupture directivity for the 2024 Feidong M4.7 earthquake using only one strong motion station located 4 km from the epicenter. We find that the polarization of S waves evolves during the rupture, indicating an azimuth change during the rupture propagation. Through comparing the data with the synthetic waveforms, we infer that the M4.7 event propagated dominantly to the southwest on the dextral Tanlu fault. Our inference is further validated through comparing the data with records at local stations for M3 earthquakes in the Feidong sequence. Our study highlights the superior application of near-source observations in earthquake source studies.
{"title":"Determination of rupture directivity of the 2024 Feidong M4.7 earthquake using one single near-source station","authors":"Suli Yao , Zhigao Yang , Hongfeng Yang","doi":"10.1016/j.eqs.2025.02.001","DOIUrl":"10.1016/j.eqs.2025.02.001","url":null,"abstract":"<div><div>Determining the rupture directivity for small earthquakes is challenging due to the small source dimension and limited resolution of far-field observations. In recent years, the burst of near-source observations provides great opportunities to study earthquake rupture. Here we present the rapid determination of the rupture directivity for the 2024 Feidong <em>M</em>4.7 earthquake using only one strong motion station located 4 km from the epicenter. We find that the polarization of S waves evolves during the rupture, indicating an azimuth change during the rupture propagation. Through comparing the data with the synthetic waveforms, we infer that the <em>M</em>4.7 event propagated dominantly to the southwest on the dextral Tanlu fault. Our inference is further validated through comparing the data with records at local stations for <em>M</em>3 earthquakes in the Feidong sequence. Our study highlights the superior application of near-source observations in earthquake source studies.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 5","pages":"Pages 399-407"},"PeriodicalIF":4.1,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-02DOI: 10.1016/j.eqs.2025.06.005
Wang-Ping Chen
{"title":"Science knows no borders: Memories of Professor Rong-Sheng Zeng, a pioneering figure of modern geophysics in China","authors":"Wang-Ping Chen","doi":"10.1016/j.eqs.2025.06.005","DOIUrl":"10.1016/j.eqs.2025.06.005","url":null,"abstract":"","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 5","pages":"Pages 461-464"},"PeriodicalIF":4.1,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.1016/j.eqs.2025.03.002
Zixin Chen , Lei Gao , Haijiang Zhang , Shaobo Yang , Ying Liu , Diana Comte
The Chilean subduction zone is one of the most seismically active regions globally, characterized by extensive intermediate-depth seismicity in the slab. In this study, we construct a new earthquake catalog for northern Chile using seismic waveforms assembled for the period of 2014−2019, from which 320,070 P-wave and 232,907 S-wave first arrivals are obtained for 25,763 earthquakes. Grid search location method NonLinLoc is applied to determine initial earthquake locations and double-difference location method is used to improve relative event locations. The distribution of earthquakes exhibits distinct patterns to the north and south of 21°S. There are many more earthquakes deeper than ∼150 km to the south of 21°S, while relatively fewer to the north. The intraslab earthquakes shallower than ∼80 km generally reveal a distinct double seismic zone, and the gap between the two seismic planes disappears at a depth of approximately ∼80 km, followed by a concentration of seismicity in the depth range of ∼80−150 km. In the deeper slab, there exist several seismicity clusters with distinct earthquake activities down to ∼300 km. These characteristics shown in slab seismicity are likely caused by different mechanisms and can be helpful for understanding the subduction process.
{"title":"Intraslab seismicity characteristics of northern Chile","authors":"Zixin Chen , Lei Gao , Haijiang Zhang , Shaobo Yang , Ying Liu , Diana Comte","doi":"10.1016/j.eqs.2025.03.002","DOIUrl":"10.1016/j.eqs.2025.03.002","url":null,"abstract":"<div><div>The Chilean subduction zone is one of the most seismically active regions globally, characterized by extensive intermediate-depth seismicity in the slab. In this study, we construct a new earthquake catalog for northern Chile using seismic waveforms assembled for the period of 2014−2019, from which 320,070 P-wave and 232,907 S-wave first arrivals are obtained for 25,763 earthquakes. Grid search location method NonLinLoc is applied to determine initial earthquake locations and double-difference location method is used to improve relative event locations. The distribution of earthquakes exhibits distinct patterns to the north and south of 21°S. There are many more earthquakes deeper than ∼150 km to the south of 21°S, while relatively fewer to the north. The intraslab earthquakes shallower than ∼80 km generally reveal a distinct double seismic zone, and the gap between the two seismic planes disappears at a depth of approximately ∼80 km, followed by a concentration of seismicity in the depth range of ∼80−150 km. In the deeper slab, there exist several seismicity clusters with distinct earthquake activities down to ∼300 km. These characteristics shown in slab seismicity are likely caused by different mechanisms and can be helpful for understanding the subduction process.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 4","pages":"Pages 273-287"},"PeriodicalIF":1.2,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.1016/j.eqs.2025.03.001
Qinghui Cui , Yuanze Zhou , Yuan Gao , Ran Cui
The structures of the mantle transition zone (MTZ) are of great significance for studying interactions of the subducted slab and deep mantle and related slab dynamics beneath subduction zones. Here by dense near-source SdP sampling from a large global dataset, we image topographies of transition zone discontinuities such as the 410-km and 660-km discontinuities (410 and 660) beneath the Kamchatka and conduct cross-section comparisons with the seismicity. Compared with the IASP91 model, the 410 exhibits apparent uplifts of 45−65 km with an average of 55 km in a horizontal width of ∼130 km, corresponding to low-temperature anomalies of 750−1083 K with an average of 916 K. In contrast, the 660 shows depressions of 15−37 km with an average of 25 km together with downward deflections in a width of ∼260 km, implying low-temperature anomalies of 161−397 K with an average of 268 K. Thus, we confirm a thickened MTZ with a thickness of 325−345 km around the cold descending Pacific slab. We suggest that topographic patterns of transition zone discontinuities imply a Pacific slab that has been significantly heated in the MTZ with broadened thermal effects on the 660. When considered along with other studies, we infer that the slab is possibly heated by hot mantle flows around the torn slab window extended to at least the MTZ range, thus inducing variations in thermal and rheological properties of the slab. Our seismic results can provide more insight into slab dynamics in the northwestern Pacific.
{"title":"Seismic evidence for a thickened mantle transition zone beneath the Kamchatka subduction zone","authors":"Qinghui Cui , Yuanze Zhou , Yuan Gao , Ran Cui","doi":"10.1016/j.eqs.2025.03.001","DOIUrl":"10.1016/j.eqs.2025.03.001","url":null,"abstract":"<div><div>The structures of the mantle transition zone (MTZ) are of great significance for studying interactions of the subducted slab and deep mantle and related slab dynamics beneath subduction zones. Here by dense near-source SdP sampling from a large global dataset, we image topographies of transition zone discontinuities such as the 410-km and 660-km discontinuities (410 and 660) beneath the Kamchatka and conduct cross-section comparisons with the seismicity. Compared with the IASP91 model, the 410 exhibits apparent uplifts of 45−65 km with an average of 55 km in a horizontal width of ∼130 km, corresponding to low-temperature anomalies of 750−1083 K with an average of 916 K. In contrast, the 660 shows depressions of 15−37 km with an average of 25 km together with downward deflections in a width of ∼260 km, implying low-temperature anomalies of 161−397 K with an average of 268 K. Thus, we confirm a thickened MTZ with a thickness of 325−345 km around the cold descending Pacific slab. We suggest that topographic patterns of transition zone discontinuities imply a Pacific slab that has been significantly heated in the MTZ with broadened thermal effects on the 660. When considered along with other studies, we infer that the slab is possibly heated by hot mantle flows around the torn slab window extended to at least the MTZ range, thus inducing variations in thermal and rheological properties of the slab. Our seismic results can provide more insight into slab dynamics in the northwestern Pacific.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 4","pages":"Pages 288-303"},"PeriodicalIF":1.2,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.1016/j.eqs.2025.03.003
Gaohua Zhu , Hongfeng Yang , Yingying Zhang
Monitoring the evolution of foreshocks can be a valuable way to analyze the nucleation process. Foreshocks accompanying moderate mainshocks have been recorded in the west of Yunnan Province, China. We obtain the earthquake catalog and source parameters of the 2016 Yunlong foreshocks, and discuss the implications for the nucleation processes of the earthquake in western Yunnan, China. By using the matched filter detection, we identify 343 foreshocks with a magnitude of −0.8−4.5, starting with a magnitude 1.0 foreshock approximately 3 months before the 2016 MS5.1 Yunlong mainshock. The spatial distribution of foreshocks doesn’t show localization or directional migration towards the mainshock. Coulomb stress analysis suggests a positive stress perturbation at the mainshock nucleate area. These observations indicate a cascade-triggering mechanism of the 2016 Yunlong earthquakes. We further collect published catalogs of 2021 Yangbi and 2017 Yangbi foreshocks in the adjacent area, and analyze the temporal changes in b values. The temporal changes in b values reveal precursory drops before the mainshocks.
{"title":"Foreshocks of the 2016 MS5.1 Yunlong earthquake in Western Yunnan, China, and implications for earthquake nucleation","authors":"Gaohua Zhu , Hongfeng Yang , Yingying Zhang","doi":"10.1016/j.eqs.2025.03.003","DOIUrl":"10.1016/j.eqs.2025.03.003","url":null,"abstract":"<div><div>Monitoring the evolution of foreshocks can be a valuable way to analyze the nucleation process. Foreshocks accompanying moderate mainshocks have been recorded in the west of Yunnan Province, China. We obtain the earthquake catalog and source parameters of the 2016 Yunlong foreshocks, and discuss the implications for the nucleation processes of the earthquake in western Yunnan, China. By using the matched filter detection, we identify 343 foreshocks with a magnitude of −0.8−4.5, starting with a magnitude 1.0 foreshock approximately 3 months before the 2016 <em>M</em><sub>S</sub>5.1 Yunlong mainshock. The spatial distribution of foreshocks doesn’t show localization or directional migration towards the mainshock. Coulomb stress analysis suggests a positive stress perturbation at the mainshock nucleate area. These observations indicate a cascade-triggering mechanism of the 2016 Yunlong earthquakes. We further collect published catalogs of 2021 Yangbi and 2017 Yangbi foreshocks in the adjacent area, and analyze the temporal changes in <em>b</em> values. The temporal changes in <em>b</em> values reveal precursory drops before the mainshocks.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 4","pages":"Pages 363-374"},"PeriodicalIF":1.2,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.1016/j.eqs.2025.03.004
Jing Huang , Shi Chen , Zhongliang Wu
Given the complexity of earthquake forecast and the current limitations in the application of artificial intelligence (AI), we propose a conceptual framework for a novel AI system, HuiShangGPT, intended to act as an expert in discussion on the trend of seismicity. This system, still in the conceptual stage, aims to integrate AI into the empirical approaches traditionally used in earthquake forecasting. The proposed HuiShangGPT system would not only assist in the comprehensive analysis of seismic data but also contribute to the expert panel discussions, enhancing the decision-making process. We outline the envisioned functionalities and potential benefits of such a system, while acknowledging the technical and practical challenges that need to be addressed for its future implementation.
{"title":"HuiShangGPT in the discussion on the trend of seismicity?.","authors":"Jing Huang , Shi Chen , Zhongliang Wu","doi":"10.1016/j.eqs.2025.03.004","DOIUrl":"10.1016/j.eqs.2025.03.004","url":null,"abstract":"<div><div>Given the complexity of earthquake forecast and the current limitations in the application of artificial intelligence (AI), we propose a conceptual framework for a novel AI system, HuiShangGPT, intended to act as an expert in discussion on the trend of seismicity. This system, still in the conceptual stage, aims to integrate AI into the empirical approaches traditionally used in earthquake forecasting. The proposed HuiShangGPT system would not only assist in the comprehensive analysis of seismic data but also contribute to the expert panel discussions, enhancing the decision-making process. We outline the envisioned functionalities and potential benefits of such a system, while acknowledging the technical and practical challenges that need to be addressed for its future implementation.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 4","pages":"Pages 391-398"},"PeriodicalIF":1.2,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.1016/j.eqs.2025.03.006
Weimin Xu , Shi Chen , Yongbo Li , Jiangpei Huang , Bing Zheng , Yufei Han , Zhaohui Chen , Qiuyue Zheng , Hongyan Lu , Linhai Wang , Honglei Li , Dong Liu
Since the 1975 MS7.3 Haicheng earthquake, spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors. Recent technical advances in terrestrial gravity observation, along with the construction of a high-precision mobile gravity network covering Chinese mainland, have positioned temporal gravity variations (GVs) as an important tool for clarifying the signal characteristics and dynamic mechanisms of crustal sources. Reportedly, crustal mass transfer, which is affected by stress state and structural environment, alters the characteristics of the regional gravity field, thus serving as an indicator for locations of moderate to strong earthquakes and a seismology-independent predictor for regions at risk for strong earthquakes. Therefore, quantitatively tracking time-varying gravity is of paramount importance to enhance the effectiveness of earthquake prediction. In this study, we divided the areas effectively covered by the terrestrial mobile gravity network in the Sichuan-Yunnan region into small grids based on the latest observational data (since 2018) from the network. Next, we calculated the 1- and 3-year GVs and gravity gradient indicators (amplitude of analytic signal, AAS; total horizontal derivative, THD; and amplitude of vertical gradient, AVG) to quantitatively characterize variations in regional time-varying gravity field. Next, we assessed the effectiveness of gravity field variations in predicting earthquakes in the Sichuan-Yunnan region using Molchan diagrams constructed for gravity signals of 13 earthquakes (M ≥ 5.0; occurred between 2021 and 2024) within the terrestrial mobile gravity network. The results reveal a certain correspondence between gravity field variations and the locations of moderate and strong earthquakes in the Sichuan-Yunnan region. Furthermore, the 3-year AAS and AVG outperform the 3-year THD in predicting subsequent seismic events. Notably, the AAS and AVG showed large probability gains prior to the MS6.8 Luding earthquake, indicating their potential for earthquake prediction.
{"title":"Quantifying of spatio-temporal variations in the regional gravity field and the effectiveness of earthquake prediction: A case study of MS ≥ 5.0 earthquakes in the Sichuan-Yunnan region during 2021–2024","authors":"Weimin Xu , Shi Chen , Yongbo Li , Jiangpei Huang , Bing Zheng , Yufei Han , Zhaohui Chen , Qiuyue Zheng , Hongyan Lu , Linhai Wang , Honglei Li , Dong Liu","doi":"10.1016/j.eqs.2025.03.006","DOIUrl":"10.1016/j.eqs.2025.03.006","url":null,"abstract":"<div><div>Since the 1975 <em>M</em><sub>S</sub>7.3 Haicheng earthquake, spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors. Recent technical advances in terrestrial gravity observation, along with the construction of a high-precision mobile gravity network covering Chinese mainland, have positioned temporal gravity variations (GVs) as an important tool for clarifying the signal characteristics and dynamic mechanisms of crustal sources. Reportedly, crustal mass transfer, which is affected by stress state and structural environment, alters the characteristics of the regional gravity field, thus serving as an indicator for locations of moderate to strong earthquakes and a seismology-independent predictor for regions at risk for strong earthquakes. Therefore, quantitatively tracking time-varying gravity is of paramount importance to enhance the effectiveness of earthquake prediction. In this study, we divided the areas effectively covered by the terrestrial mobile gravity network in the Sichuan-Yunnan region into small grids based on the latest observational data (since 2018) from the network. Next, we calculated the 1- and 3-year GVs and gravity gradient indicators (amplitude of analytic signal, AAS; total horizontal derivative, THD; and amplitude of vertical gradient, AVG) to quantitatively characterize variations in regional time-varying gravity field. Next, we assessed the effectiveness of gravity field variations in predicting earthquakes in the Sichuan-Yunnan region using Molchan diagrams constructed for gravity signals of 13 earthquakes (<em>M</em> ≥ 5.0; occurred between 2021 and 2024) within the terrestrial mobile gravity network. The results reveal a certain correspondence between gravity field variations and the locations of moderate and strong earthquakes in the Sichuan-Yunnan region. Furthermore, the 3-year AAS and AVG outperform the 3-year THD in predicting subsequent seismic events. Notably, the AAS and AVG showed large probability gains prior to the <em>M</em><sub>S</sub>6.8 Luding earthquake, indicating their potential for earthquake prediction.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 4","pages":"Pages 375-390"},"PeriodicalIF":1.2,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.1016/j.eqs.2025.03.007
Zemin Liu , Weitao Wang , Lu Li , Zihao Li , Ziye Yu , Songyong Yuan , Lanshu Bai
The aftershocks of the 1975 MS7.3 Haicheng and 1999 MS5.4 Xiuyan earthquakes have persisted for a long time. The ChinArray-III dense stations, deployed in eastern North China from 2018 to 2020, increased seismic monitoring capability in the Haicheng-Xiuyan region, which can facilitate the construction of high-precision earthquake catalogs to better clarify the fault structures and seismogenic mechanisms of the two earthquakes. In this study, we selected 15 permanent stations and 37 ChinArray-III stations within 150 km of the epicenter of the Haicheng Earthquake. Next, we used deep learning methods to pick P- and S-wave phases from continuous waveforms recorded at these stations from January 2018 to July 2020. Based on these picks, we constructed an automatic earthquake catalog of the Haicheng-Xiuyan region. Compared with the routine manual catalog by China Earthquake Networks Center (CENC), our catalog contains 9.7 times more seismic events, including 98.3% of the seismic events in the CENC catalog, and has a lower magnitude of completeness (Mc = 1.1 vs Mc = 1.8 for the CENC catalog). The relocated events indicate that the strike of the Haichenghe-Dayanghe fault varies considerably from northwest to southeast, indicating that the fault bends slightly around the hypocenter of the 1975 MS7.3 Haicheng earthquake which may act as a channel for fluid migration. The weak seismicity in the area between Haicheng and Xiuyan indicates that the fault section may be locked. Furthermore, the 1999 MS5.4 Xiuyan earthquake and its aftershock sequence occurred on the Kangjialing fault and its ENE-trending conjugate fault, and the intersection of the two faults coincides with the source areas of the 1999 MS5.4 and 2000 MS5.1 Xiuyan earthquakes. Therefore, the Xiuyan earthquake sequence may be controlled by the Kangjialing fault and its conjugate fault. This study shows that the automatic earthquake catalog, obtained by deep learning methods and dense seismic array, can provide valuable information for fault structures and the seismogenic mechanisms of moderate-to-strong earthquakes.
{"title":"Analysis of seismicity in the Haicheng-Xiuyan region based on dense array data and deep learning methods","authors":"Zemin Liu , Weitao Wang , Lu Li , Zihao Li , Ziye Yu , Songyong Yuan , Lanshu Bai","doi":"10.1016/j.eqs.2025.03.007","DOIUrl":"10.1016/j.eqs.2025.03.007","url":null,"abstract":"<div><div>The aftershocks of the 1975 <em>M</em><sub>S</sub>7.3 Haicheng and 1999 <em>M</em><sub>S</sub>5.4 Xiuyan earthquakes have persisted for a long time. The ChinArray-III dense stations, deployed in eastern North China from 2018 to 2020, increased seismic monitoring capability in the Haicheng-Xiuyan region, which can facilitate the construction of high-precision earthquake catalogs to better clarify the fault structures and seismogenic mechanisms of the two earthquakes. In this study, we selected 15 permanent stations and 37 ChinArray-III stations within 150 km of the epicenter of the Haicheng Earthquake. Next, we used deep learning methods to pick P- and S-wave phases from continuous waveforms recorded at these stations from January 2018 to July 2020. Based on these picks, we constructed an automatic earthquake catalog of the Haicheng-Xiuyan region. Compared with the routine manual catalog by China Earthquake Networks Center (CENC), our catalog contains 9.7 times more seismic events, including 98.3% of the seismic events in the CENC catalog, and has a lower magnitude of completeness (<em>M</em><sub>c</sub> = 1.1 <em>vs M</em><sub>c</sub> = 1.8 for the CENC catalog). The relocated events indicate that the strike of the Haichenghe-Dayanghe fault varies considerably from northwest to southeast, indicating that the fault bends slightly around the hypocenter of the 1975 <em>M</em><sub>S</sub>7.3 Haicheng earthquake which may act as a channel for fluid migration. The weak seismicity in the area between Haicheng and Xiuyan indicates that the fault section may be locked. Furthermore, the 1999 <em>M</em><sub>S</sub>5.4 Xiuyan earthquake and its aftershock sequence occurred on the Kangjialing fault and its ENE-trending conjugate fault, and the intersection of the two faults coincides with the source areas of the 1999 <em>M</em><sub>S</sub>5.4 and 2000 <em>M</em><sub>S</sub>5.1 Xiuyan earthquakes. Therefore, the Xiuyan earthquake sequence may be controlled by the Kangjialing fault and its conjugate fault. This study shows that the automatic earthquake catalog, obtained by deep learning methods and dense seismic array, can provide valuable information for fault structures and the seismogenic mechanisms of moderate-to-strong earthquakes.</div></div>","PeriodicalId":46333,"journal":{"name":"Earthquake Science","volume":"38 4","pages":"Pages 346-362"},"PeriodicalIF":1.2,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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