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地震 ›› 2020, Vol. 40 ›› Issue (3): 1-14.doi: 10.12196/j.issn.1000-3274.2020.03.001

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2019年6月17日长宁MS6.0地震前后b值时空变化分析

曾宪伟1, 龙锋2, 任家琪1, 蔡新华1, 李文君1   

  1. 1.宁夏回族自治区地震局, 宁夏 银川 750001;
    2.四川省地震局, 四川 成都 610041
  • 收稿日期:2019-11-25 出版日期:2020-07-31 发布日期:2020-07-28
  • 作者简介:曾宪伟(1982-),男,山东菏泽人,高级工程师,主要从事地震活动性及震源机制方面的研究。
  • 基金资助:
    地震科技星火计划项目(XH18053Y);宁夏自然科学基金项目(NZ17221);国家自然科学基金(41604015);强震危险性研究创新团队(CX2019-4)

Spatial and Temporal Variation of b value before and after the Changning MS6.0 Earthquake on June 17, 2019

ZENG Xian-wei1, LONG Feng2, REN Jia-qi1, CAI Xin-hua1, LI Wen-jun1   

  1. 1. Earthquake Agency of Ningxia Hui Autonomous Region, Yinchuan 750001, China;
    2. Sichuan Earthquake Agency, Chengdu 610041, China
  • Received:2019-11-25 Online:2020-07-31 Published:2020-07-28

摘要: 选取2014年1月至2019年8月宜宾地区(28.0°N~28.5°N, 104.6°E~105.1°E)记录的地震资料, 利用最大似然法估算b值, 得到了宜宾地区b值的时空变化特征。结果显示: ① 2019年长宁MS6.0地震前5个月, b值出现加速下降变化, 震后快速回升。这一现象很可能反映了地震孕育中的应力积累集中到地震发生后的应力释放过程。② 长宁地震前震中区及附近地区一直存在低b值异常(≤0.85), 震前5个月, 震中附近出现了b值下降, 尤其是长宁地震西偏北方向出现了b值显著下降, 后续珙县发生的3次MS5地震正位于该异常区及边缘。③ b值空间低值异常可用于判定未来中强地震发生的危险区域, 而b值的下降可用于判定强余震的可能发生地点。④ 分析地震危险性时, 更应关注低b值背景下的b值下降, 即高应力集中区域的地震危险性增强。

关键词: 长宁地震, b值, 最大似然法, 地震危险性

Abstract: Based on the earthquakes recorded in Yibin area (28.0°N~28.5°N, 104.6°E~105.1°E), Sichuan Province, from January 2014 to August 2019, we estimated the b values in the studied area by the maximum likelihood method and obtained their temporal and spatial characteristics. The results show that, firstly, the b value decreased rapidly five months before the Changning MS6.0 earthquake and recovered quickly after that. This phenomenon is likely to reflect the process of stress accumulation during earthquake preparation and stress release after the earthquake. Secondly, before the Changning earthquake, there was always a low b value anomaly (≤0.85) in the epicenter and its vicinity. Five months before the earthquake, a further decrease of b value occurred near the epicenter, especially in the northwest of Changning, where following three MS5 earthquakes taking place in Gongxian were just located in this abnormal region and its edge area. Thirdly, the spatial distribution of low b value anomalies indicates the risk area of medium and strong earthquakes in the future. And, the fast decrease region in b value can be used to determine the possible location of strong aftershocks. Fourthly, when analyzing the seismic risk, we should pay more attention to the b value decrease under the background of long-term low b value, which illustrates the increasing seismic risk in high stress concentration area.

Key words: 2019 Changning MS6.0 earthquake, b value, the Maximum Likelihood Method, Seismic risk

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