Focal Mechanism Changing Character of Earthquake Sequence Induced by Water Injection:A Case Study of Changning Sequence,Sichuan Province
Zhu Hang
He Chang
Abstract：Earthquakes induced by water injection appeared in the border area of Changning,Xingwen and Gongxian counties, Sichuan Province since April,2006.Up to April 30,2013,1 6 ML ≥4.0 earthquakes occurred and the maximum is ML =5.2 on April 25,2013.In this paper,the earthquake focal mechanism changing process of Changning ML ≥3.0 earthquake sequence is studied by calculating correlation coefficient of body wave spectral amplitudes,and the results show that focal mechanisms of sequence events are scattering,furthermore,12 ML ≥4.0 earthquakes??focal mechanisms are calculated by CAP method and they are in disorder also.The following analyses believe that water injection causes the pore pressure of rock body increasing as well as the friction coefficients of pre-existing fault planes decreasing,and those 2 factors lead to Coulomb stress change Δσf in-creasing,thus induce earthquakes??occurrence.Therefore,the earthquakes induced by water injection occur without obvious en-hancement of regional tectonic stress intensity,and there are no obvious restraining effects on the rupture directions of the earthquakes.As a result,the focal mechanisms of those earthquakes appear scattering.
Keywords：earthquake induced by water injectionearthquake sequencefocal mechanismspectral amplitude correlation coef-ficientearthquake
Publication Date：2014-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：7( 1776-1782 )