两次大震的视电阻率各向异性特征

Anisotropic characteristics of earth apparent resistivity during the two strong Earthquakes

对1976年松潘7 1级和唐山7 8级地震的地电阻率变化及各向异性特征作了较全面的分析,并从理论上作了一定程度的解释。结果表明,震前地电阻率变化的各向异性是客观存在的,各向异性主要有两种表现,一是不同台站的方位性差异;二是同台不同测向的差异。这种各向异性主要外观因素是台站的震中距、方位、测向、介质的力学因素和地震本身的机制;内在因素主要是原生裂隙的膨胀、闭合和排列、新生裂隙或破裂的发育、贯通、排列受应力场的作用。

In this paper the earth apparent resistivity variations and anisotropy characteristics during the two strong earthquakes,Songpan Earthquake MS7.1 in 1976 and Tangshan Earthquake MS7.8 in 1976,are analyzed completely.Theoretical interpretations are given in some extent.It indicates that the anisotropy phenomenon was objective and demonstrates in two aspects,one was the azimuth difference among different stations and the other was the measuring orientation difference in the same station.The outer factors for such anisotropy mainly include epicenter distance,station azimuth,measuring direction,media dynamic features under station and earthquake mechanism;the inner factors include the dilatancy,closure and alignment of original cracks as well as the development,connection and alignment of newly developed cracks under the affect of stress