闽台震源机制和区域应力场

本文系统地汇集、修订了1933年至1969年台湾及其东部海域6级以上强震的震源机制资料,并重新测定了1970年至1978年台湾6级以上地震,福建省和台湾海峡部份地震以及1604年泉州海外8级强震的震源机制,分析了闽、台两省震源机制特征,指出:(1)由震源机制求出的断层面解与源深处的现代构造运动紧密相关;(2)大部份主压应力轴方向与主要断裂带垂直;(3)在台湾东部海中,中强地震组成三个互相平行的椭圆形空区,空区周围83%的6.0——6.9级地震的主 P 轴方向近似与空区边线垂直,7级以上强震都发生在空区边缘;(4)以巴士海峡为中心,面向福建大陆,应力场呈现向西北展开的扇形分布. 

ON THE FOCAL MECHANISMS OF EARTHQUAKES AND REGIONAL STRESS FIELD OF THE FUJIAN-TAIWAN REGION

In this paper, the focal mechanisms of the earthquakes of M 6, occurred in Taiwan Province and on the sea east of it, from 1933 to 1969 have been critically collected and compiled. In addition, the focal mechanisms of the earthquakes M 6 occurred in Taiwan and Fujian provinces, and in the Strait of Taiwan from 1970 to 1978 and of the earthquake of Magnitude 8 of 1604 are reexamined. After analyzing all these focal mechanism data of the two provinces, it is pointed out that: (1) the focal plane solutions obtained are closely related to the recent crustal movement at depth; (2) most of the directions of principal axis of compressive stress are perpendicular to the major fault zone; (3) on the sea east of Taiwan province, earthquakes moderate in size form three parallel seismic gaps elliptical in shape. Around the gaps, about 83% of the earthquakes of magnitude 6.0-6.9 have their major P axis nearly at right angles to the periphery of the gaps on which most earthquakes of magnitudes equal or greater than 7 occurred; (4) taking the Bashi strait as the center, facing Fujian province, the stress field consists of fan-like pattern toward NW.