2019年甘肃夏河MS5.7地震前重力场变化

doi:10.12196/j.issn.1000-3274.2021.01.006

摘要/Abstract

摘要： 本文对2017年以来中国地震局在南北地震带采集到的5期相对重力测网数据进行了平差计算, 简要分析了甘东南研究区内测点平差精度, 进而分析了2019年10月28日甘肃夏河M_S5.7地震前的区域重力场变化。结果表明: ① 研究区内90%测点平差后重力值精度小于10×10^-8 m·s^-2, 与绝对重力观测结果符合性也较好, 表明观测质量较高, 数据可靠; ② 2017年 4月至2018年4月, 临潭—宕昌断裂南西侧重力正变化、北东侧重力负变化, 与2017年8月8日九寨沟M_S7.0地震前重力变化反向, 断裂西段夏河、合作附近出现显著的重力差异变化; ③ 2018年4月至2019年4月, 临潭—宕昌断裂南西侧重力变化-10×10^-8～-30×10^-8 m·s^-2、北东侧重力变化+20×10^-8～+30×10^-8 m·s^-2, 夏河M_S5.7震中附近重力变化不明显, 呈现出围绕夏河县、泽库县和碌曲县等三县交界地区准四象限分布的特征; ④ 强震易发生在重力变化四象限分布中心地带或正、负异常区过渡的高梯度带上, 九寨沟M_S7.0地震后, 我们曾基于流动重力异常变化在夏河M_S5.7地震前做过一定程度的中期预测, 尤其是地点预测。

关键词: 2019年夏河M_S5.7地震, 重力变化, 临潭—宕昌断裂, 前兆

Abstract: The relative gravity data were calculated by the of classic adjustment from 2017 to 2019 in the North-South seismic belt. We analyzed the precision of gravity value at sites in the study area of south-east of Gansu province, and studied the variation of the regional gravity field before Xiahe Gansu M_S5.7 earthquake. The results show that ① Gravity value precision of 90% gravity sites is less than 10×10^-8 m·s^-2 after adjustment calculation in our study area, and the gravity value at absolute gravity sites is well accordance with absolute gravity observation. ② Between April 2017 and April 2018, gravity variation is positive in the south-west side of the Lintan-Dangchang fault, and it is negative in the north-east side of the fault. It is opposite to the gravity variation before Jiuzhaigou M_S7.0 on August 8, 2017. There are violent difference gravity variation in the area near the Hezuo city and Xiahe county. ③ Between April 2018 and April 2019, gravity variation is negative in the south-west side of the Lintan-Dangchang fault, about -10×10^-8～-30×10^-8 m·s^-2, and it is positive in the north-east side of the fault, about +20×10^-8～+30×10^-8 m·s^-2. The gravity variation is not obvious near the epicenter of Xiahe M_S5.7 earthquake, which indicated that the area near epicenter was possible to be in locked during the time. While there is a unconspicuous four quadrant distribution of gravity change centered on the junction of Xiahe county, Luqu county and Zeku county. ④ Strong earthquakes are prone to occur in four quadrant distribution center of gravity change of high gradient belt of positive and negative anomalies. We made a medium-term forecast about Xiahe M_S5.7 earthquake based on relative gravity changes, especially forecasting localities of potential earthquake.

Key words: 2019 Xiahe M_S5.7 earthquake, Gravity changes, Lintan-Dangchang fault, Precursor

中图分类号:

P315.7

赵云峰, 祝意青, 刘芳, 徐云马, 张国庆, 毛经伦, 朱辉. 2019年甘肃夏河M_S5.7地震前重力场变化[J]. 地震, 2021, 41(1): 67-77.

ZHAO Yun-feng, ZHU Yi-qing, LIU Fang, XU Yun-ma, ZHANG Guo-qing, MAO Jing-lun, ZHU Hui. Gravity Changes Before the 2019 Xiahe Gansu M_S5.7 Earthquake[J]. EARTHQUAKE, 2021, 41(1): 67-77.

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