Relevant migration characteristics of strong earthquakes between the North-South Seismic Belt and North China block

Cao Fengjuan; Wang Liang; Li Jun; Wang Xilong; Yang Muping; Zhang Bo

doi:10.11939/jass.2015.04.003

Abstract：The focal mechanism solutions of earthquakes and in-situ stress mea-surement results showed that there was a regional stress field in nearly radial pattern in Chinese mainland,and the radiation center was located in the eastern Qinghai-Xizang (Tibet)block.In this paper we defined the approximate radia-tion center (35°N,100°E)in Chinese mainland as the dynamic source point and then calculated the distance between the dynamic source point and the locationof 34 earthquakes with MS ≥6 .0 since the year 1 900 in eastern part of Chinesemainland (30°N—44°N, 1 04°E—1 2 5°E ) so as to analyze the relationshipbetween the distance and earthquake occurrence time.The results showed that aseries of MS ≥ 6 .0 earthquakes occurred in North China block after an earthquakewith MS ≥7 .0 occurred in North-South Seismic Belt in the 20th century,and they generally migrated eastward from North-South Seismic Belt with time.This also suggested that the earthquakes occurred in North China block shouldbe mainly controlled by the influence of the Qinghai-Xizang (Tibet)block’ssqueezing to the eastern Chinese mainland under the action of Indian Plate,causing the MS ≥6 .0 earthquakes eastward migrating in the North China block.There were four distinct groups of migrations with velocity about 80 km/a.Theinterval between the first MS ≥ 6 .0 earthquake in North China block and thelatest MS ≥7 .0 earthquake in North-South Seismic Belt was about 1 month to1 1 .8 years,and 60% of the MS ≥6 .0 earthquakes were located in the area closeto (3 9°N±1 .5°).Therefore it could be inferred that the MS ≥6 .0 earthquakesprobably occur in North China block in recent years after the Wenchuan MS 8.0earthquake in 2008 and Lushan MS 7 .0 earthquake in 20 1 3 .Accordingly,weshould focus on the j unction areas of Shanxi,Hebei,Inner Mongolia,and thecircum-Bohai and their surrounding areas.