中国中深源地震分布特征及其意义

DISTRIBUTION FEATURE OF INTERMEDIATE AND DEEP FOCUS EARTHQUAKES IN CHINA AND ITS SIGNIFICANCE

分析了中国 6 .0级以上中深源地震的分布特征及其与各主要地震活动区地震活动的关系 .深震集中分布在东北地区以 42°N ,1 30°E为中心的 2°× 2°范围内 ,震源深度平均约 5 6 0km .中源地震集中分布在东海经台湾到东沙群岛一线 ,形成NE～SW走向的条带 ,震源深度多在 2 5 0km以内 ,平均约 1 5 0km .中深源地震活动具有约 6 3年的周期 .中源地震活跃期紧接在深源地震活跃期之后 .中深源地震发生以后台湾地区出现 7.0级以上 ,青藏块体北部和东部出现 6 .0级以上的浅源地震活动 .青藏块体的地震活动总体上表现出自块体北部开始 ,然后沿块体东部逐步向南迁移的特征 .中深源地震及受东部应力场控制的浅源地震活动平静了近 2 0年 ,1 999年珲春 7.0级深震和台湾 7.

The distribution feature of intermediate and deep focus earthquakes(M≥6.0) in China and relationship between it and seismic activity in whole nation and the main seismic areas of China are analysed. The deep focus events are distributed in Northeast China, concentrated in a region of 2°×2° of which central point is 42° N, 130°E. Average depth of the events is about 560 km. The intermediate shocks are distributed along a zone of which strike is NE～SW from the East China Sea, through Taiwan to Dongsha Islands, with depth within 250 km and a mean value near 150 km. There is a period about 63 a in activity of the intermediate and deep focus earthquakes in China. The activity of the intermediate shocks of Southeast China comes after the deep focus shocks of Northeast China. After intermediate and deep focus earthquakes, M S≥7.0 shallow earthquakes of Taiwan region and M S≥6.0 shallow earthquakes of northeast Qinghai Xizang block may occur. The seismic activity of Qinghai Xizang block generally begins in northern part first, then migrates progressively southward along the eastern part of the block. After shallow earthquakes controlled by the eastern stress field and intermediate and deep focus earthquakes quieted for about 20 a,the Huichun M7.0 deep focus earthquake and the Taiwan M7.6 earthquake may be a signal of aggravation of action of the Pacific plate and beginning of relative seismic activity in China.