摘要
利用2009年姚安Ms6.0地震前滇西实验场流动重力网2005—2009年9期复测数据,给出了区域重力场差分和累积动态变化图像。分析研究表明:1)重力场动态演化图像大体反映出震前地壳物质运动状态,累积动态变化更能反映区域构造运动与断裂构造作用,差分动态变化有利于突出短期局部效应;2)姚安地震显著重力"前兆"标志为:震前约2年穿过震中的近南北向正负过渡重力梯级带和约半年的以震中区为中心重力场变化呈现局部相对上升与下降的对称四象限分布;3)震中西部震前约3年持续的正重力变化应有利于震源能量的积累;4)震中区相对变化四象限分布图像反映出孕震体先存剪应力,为此提出了"闭锁剪力"前兆模式。
From the repeted gravimetry data of Dianxi Experimental Field from 2005 to 2009,local differential and cumulate gravity change pictures have been obtained.The study results from the data are as follows.1）The dynamic evolvement pictures of gravity field can generally reflect the movement state of the crustal substance before earthquake.Short-term local effect is obviously reflected by the differential dynamic change,while local tectonic movement and fault structure effect by the cumulate dynamic change.2）A positive and negative transitional gravity gradient zone across the epicenter along almost north-south direction appeared two years before the earthquake,and a symmetrical four-quadrant distribution of the gravity change appeared too around the epicenter half year before the earthquake.They were the prominent gravity precursor marks of the Yaoan earthquake.3）Durative positive gravity change appeared in the west to the epicenter three years before the earthquake.It was helpfull for energy accumulation.4）The relatively high-low four-quadrant distribution picture may reflect that there exist a shearing stress.So we put forward a ’lock in shearing force mode’ for the precursor model.
出处
《大地测量与地球动力学》
CSCD
北大核心
2011年第2期17-22,47,共7页
Journal of Geodesy and Geodynamics
基金
国家社会公益项目(2005DIB3J120)
地震科学联合基金(A07030)
国家自然科学基金(40574012)
关键词
姚安地震
重力场
动态变化
前兆模式
闭锁剪力
Yaoan earthquake
gravity field
dynamic change
precursor model
lock in shearing force mode
