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地震

地震 ›› 2000, Vol. 20 ›› Issue (z1): 135-142.

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热物质上涌与震前重力异常关系初探

张永仙1, 石耀霖2, 刘桂萍1   

  1. 1.中国地震局分析预报中心, 北京 100036;
    2.中国科学院研究生院 ,北京 100039
  • 收稿日期:2000-06-05 修回日期:2000-06-09 出版日期:2000-09-30 发布日期:2022-09-23
  • 作者简介:张永仙 (1965-), 女, 云南东川人 ,副研究员, 1999年获博士学位 ,主要从事孕震过程的物理力学模式、前兆机理和地震综合预报的研究。
  • 基金资助:
    国家科技攻关项目 (96-913-04-03-02)

Preliminary study on the relationship between upwelling of hot material and gravity anomaly before earthquake

Zhang Yong-xian1, Shi Yao-lin2, Liu Gui-ping1   

  1. 1. Cen ter for Analysis and Prediction, CSB, Beijing 100036, China;
    2. Graduate School, China Academic Sinica, Beijing 100039, China
  • Received:2000-06-05 Revised:2000-06-09 Online:2000-09-30 Published:2022-09-23

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摘要： 根据震前近震中地区重力上升 - 下降 - 上升的异常特征 ,提出一种可能机制。地震孕育中短期阶段 ,由于岩石的扩容膨胀引起扩容区孔隙压的锐减 ,当裂隙逐渐贯通时, 扩容区外围相对高压的流体渗入扩容区 ,尤其来自于深大断裂的高压热物质上涌到扩容区, 引起地表重力值的升高过程。同时, 热物质迁入扩容区的结果是使扩容区成为一个温度正异常区, 其力学效应是在浅部产生张性活动 ,从而引起浅部密度的降低过程 ,即重力的降低过程, 而浅部的张性活动有利于深部流体的上涌及周围流体的流入, 从而使重力值从前一阶段的下降转为上升。根据这一物理过程 ,反演了唐山 7. 8级地震和张北 6. 2级地震前地壳扩容部位和地壳浅部密度的变化量。

关键词: 热物质上涌, 震前, 重力异常

Abstract: A possible mechanism of gravity anomaly before earthquake is put forward based on the up-down-up feature of gravity variation near the epicenter. Firstly, pore pressure in the dilatant region would drop down quickly during the medium -short term of earthquake preparation, and fluids around the dilatant region, especially the high-pressure and hot fluids from the deeper crust would intrude into it, hence cause the increase of gravity on the g round. Secondly, the ho t fluids would heat up the dilatant region gradually, subjoining an extensional stress to the shallow crust, which would decrease the density of the shallow crust. Thirdly, the process of fluids intruding into the extensional region of the shallow crust would make the gravity growup again. Some parameters of Tangshan and Zhangbei earthquake, such as density variation, the size of dilatant regionetc, are developed according to the observatory data before the earthquakes.

Key words: Upwelling of hot material, Before earthquake, Gravity anomaly

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