剪张型微地震震源机制与振幅分布特征  

Focal mechanism of shear-tensile microseismic and amplitude distribution characteristics

作　　者：唐杰[1,2] 王浩 温雷[1,2] 张文征 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,山东青岛266071

出　　处：《石油地球物理勘探》2018年第3期502-510,共9页Oil Geophysical Prospecting

基　　金：国家自然科学基金项目(41504097;41374123);国家科技重大专项(2016ZX05006-002)联合资助

摘　　要：水力压裂诱发的微地震事件中有很多为非双力偶源,表明岩石可能发生了剪张破裂。与纯剪切型震源相比,剪张型震源在震源特征以及记录振幅方面存在诸多差异。本文研究了剪张源微地震震源机制,分析了剪张源微地震信号的辐射花样和能量传播特征,通过数值计算获得了地表接收的不同震相的振幅分布。主要内容包括:(1)水力压裂微地震中剪张破裂被认为是较为合理的震源模型,可以采用走向角、倾角、滑动角和张裂角表示其源张量,结合介质参数可获得矩张量;(2)剪张源包含双力偶(DC)成分和非双力偶(Non-DC)成分,非DC成分包括补偿线性偶极子(CLVD)和各向同性(ISO)成分,各成分的百分比可采用Hudson图和钻石图等进行研究;(3)剪张型震源辐射能量会随张裂角而发生变化,地面接收的信号振幅分布与震源机制、模型参数和检波器位置等有关。研究剪张型微地震震源机制与振幅分布特征,可以更清楚地认识微地震震源特征及其信号分布规律。Microseismic events induced by hydraulic fracturing contain many non-double couple types,shear tensile rupture may occur in rocks.Shear-tensile type microseismic show many differences in source and amplitude characteristics compared with shear type earthquake.We study in this paper the sheartensile mechanism,and analyze shear-tensile source microseismic radiation pattern and energy propagation characteristics.The main understandings are included:A.Shear-tensile sources generate shear and tensile motions and the source tensor can be described with strike,dip,rake,and tensile angle;B.Moment tensors of shear-tensile source can be decomposed to double-couple(DC)and non-double-couple(Non-DC)components.Non-double-couple components comprise the compensated linear vector dipole(CLVD)and the isotropic(ISO)component;C.Radiation energy of shear-tensile source will change with the tensile angle,the amplitude distribution at surface receivers is relative to focal mechanism,model parameters,and sensor positions.Based on study of the focal mechanism and amplitude distribution characteristics of sheartensile microseismic,we can get a better understanding of the source characteristics and signal distribution.

关 键 词：微地震 源张量 矩张量 辐射花样 剪张源 张裂角 

分 类 号：P631[天文地球—地质矿产勘探]