{"title":"Analysis of spatiotemporal variations in b-values before the 6.8-magnitude earthquake in Luding, Sichuan, China, on September 5, 2022","authors":"Qidong Li, Zhuojuan Xie","doi":"10.1007/s11600-024-01369-5","DOIUrl":null,"url":null,"abstract":"<div><p>Using the earthquake catalog provided by the Sichuan Earthquake Network Center, spatial and temporal <i>b</i>-value variations were calculated for in regional and local scales based on assessing the completeness of the earthquake catalog and declustering. The results show that (1) <i>b</i>-value temporal variations in regional scale ranged from 0.689 to 1.169, with a mean value of 0.928; while, the local-scale temporal variations ranged from 0.694 to 1.223, with a mean value of 0.925. The <i>b</i>-values in the study area were below the mean value before the moderate and large earthquakes occurrence, and all <i>b</i>-values exhibited the anomalous feature of a sudden decrease before the earthquake low peak rise after the earthquake. (2) The seismotectonic characteristic of the area is the higher value of slip rate of the NW section of Xianshui River Fault Zone; therefore, a large amount of stress was accumulated in the Moxi section of the SE section, leading to a <i>M</i> = 6.8 earthquake in Luding. Before the earthquake, the study area has a low <i>b</i>-value area. The <i>b</i>-value decreased within a short period after the earthquake, dividing the area into asperity. This area still has a future risk of moderate to strong earthquakes. (3) The error in the <i>b</i>-values for most of the earthquakes in the regional and local scales regions is between 0.05 and 0.15, and only individual grid points have larger <i>b</i>-value errors (> 0.2), indicating high confidence in the information. In addition, when conducting a <i>b</i>-value study, choosing a suitable study area is important to avoid missing the <i>b</i>-value anomaly area.</p><h3>Graphical abstract</h3>\n<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":6988,"journal":{"name":"Acta Geophysica","volume":"72 6","pages":"3957 - 3974"},"PeriodicalIF":2.3000,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Acta Geophysica","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s11600-024-01369-5","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
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Abstract
Using the earthquake catalog provided by the Sichuan Earthquake Network Center, spatial and temporal b-value variations were calculated for in regional and local scales based on assessing the completeness of the earthquake catalog and declustering. The results show that (1) b-value temporal variations in regional scale ranged from 0.689 to 1.169, with a mean value of 0.928; while, the local-scale temporal variations ranged from 0.694 to 1.223, with a mean value of 0.925. The b-values in the study area were below the mean value before the moderate and large earthquakes occurrence, and all b-values exhibited the anomalous feature of a sudden decrease before the earthquake low peak rise after the earthquake. (2) The seismotectonic characteristic of the area is the higher value of slip rate of the NW section of Xianshui River Fault Zone; therefore, a large amount of stress was accumulated in the Moxi section of the SE section, leading to a M = 6.8 earthquake in Luding. Before the earthquake, the study area has a low b-value area. The b-value decreased within a short period after the earthquake, dividing the area into asperity. This area still has a future risk of moderate to strong earthquakes. (3) The error in the b-values for most of the earthquakes in the regional and local scales regions is between 0.05 and 0.15, and only individual grid points have larger b-value errors (> 0.2), indicating high confidence in the information. In addition, when conducting a b-value study, choosing a suitable study area is important to avoid missing the b-value anomaly area.
利用四川省地震台网中心提供的地震目录，在评估地震目录完整性和解簇的基础上，计算了区域和地方尺度的b值时空变化。结果表明：（1）区域尺度的 b 值时空变化范围为 0.689 至 1.169，平均值为 0.928；地方尺度的 b 值时空变化范围为 0.694 至 1.223，平均值为 0.925。研究区的 b 值在中震和大震发生前均低于平均值，且所有 b 值均表现出震前骤降、震后低峰上升的异常特征。(2）该地区的地震构造特点是咸水江断裂带西北段的滑动速率值较高，因此东南段墨溪段积累了大量应力，导致了泸定 M=6.8 地震的发生。地震前，研究区为低 b 值区。地震发生后，b 值在短时间内下降，将该区域划分为浅表区。该地区未来仍有发生中强地震的危险。(3）区域和局部尺度区域内大部分地震的 b 值误差在 0.05 至 0.15 之间，只有个别网格点的 b 值误差较大（> 0.2），说明信息的可信度较高。此外，在进行 b 值研究时，选择合适的研究区域对避免遗漏 b 值异常区非常重要。
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Acta Geophysica is open to all kinds of manuscripts including research and review articles, short communications, comments to published papers, letters to the Editor as well as book reviews. Some of the issues are fully devoted to particular topics; we do encourage proposals for such topical issues. We accept submissions from scientists world-wide, offering high scientific and editorial standard and comprehensive treatment of the discussed topics.
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