门源6.4级地震的构造形变效应及其区域形变背景初析

PRELIMINARY ANALYSIS OF THE TECTONIC DEFORMATION EFFECTS AND THE REGIONAL DEFORMATION BACKGROUND OF MENYUAN M=6.4 EARTHQUAKE

一九八六年八月二十六日青海门源县北部发生的6.4级地震,是一九三二年昌马7.5级地震五十余年后,在昌马—俄博—古浪—海源巨型构造地震带上出现的第一次Ms<6级强震。无疑,这次地震的发生,对于北祁连构造带近期的震情趋势有着极为深刻的寓意。本文依据震前的形变测量资料和震后复测结果,对门源6.4级地震的构造形变效应及其区域形变背景作初步分析和探讨。

An earthquake of 6.4 occurred in the northern part of Menyuan in Qinhai province on Aug.26th,1986.The epifocus located on Leng Longling fracture zone which belongs to the North Qilian tectonic zone.Several observation methods have been set up along the zone with which the paper analysed all of the data,as well as the results of repetitive measurements within the month after the shock.It is showed that on the background of regional deformation trend,the leveling measures both across Lenglongling fracture zone and Biandukou fault had the characteristics of preseismic deformations and sudden changes during the occurrence.This quake is a sudden event under the background of intensified stress field.So the North Qilian tectonic zone,especially some large active fracture zones still exist the abilities of strong earthquakes over 6.0.