青藏块体及邻区强震活动特征分析*
屠泓为1,杨丽萍1,罗国富2,姚家骏1

(1.青海省地震局,青海 西宁 810001; 2.宁夏回族自治区地震局,宁夏 银川 750001)

青藏块体; 强震活动; 发生频率; 迁移特征; b值

Analysis on Characteristics of Strong Earthquake Activities in Qinghai-Tibet Block and its Adjacent Area
TU Hong-wei1,YANG Li-ping1,LUO Guo-fu2,YAO Jia-jun1

(1. Earthquake Administration of Qinghai Province,Xining 810001,Qinghai,China)(2. Ningxia Earthquake Administration of Hui Autonomous Region,Yingchuan 750001,Ningxia,China)

Qinghai-Tibet Block; strong earthquake activity; earthquake frequency; migration characteristics; b-value

备注

结合1900～2013年的历史地震目录,对青藏块体及其邻区不同震级段地震的发生频率进行计算分析,得出如下结论:1900年以来,青藏块体及邻区仅5年未发生M≥5.5地震,有16年未发生M≥6.0地震,有36年未发生M≥6.5地震,即M≥5.5、M≥6.0及M≥6.5地震年发生概率分别为0.956、0.86及0.68。对该区域历史有记载的地震进行分震级段的b值计算,得出5.5≤M≤7.0震级段地震的b最低为0.59,最高为0.899,M≥7.1震级段的b值均大于1.0,M≥7.5震级段的b值明显低于相邻震级段,表明未来存在发生7.5级左右地震的可能。最后对2000年以来研究区M≥6.5地震的空间迁移规律进行分析,得出青藏块体内部地震存在顺时针迁移的特征的结论。

Using the history earthquakes catalogue from 1900 to 2013,we analyze the frequency of earthquake occurrence in different magnitude section,and get the following conclusions:there were not occurred M≥5.5 earthquakes in 5 years,M≥6.0 earthquakes in 16 years,and M≥6.5 earthquakes in 36 years in Qinghai-Tibet Block and its adjacent area since 1900. The annual occurrence probability of M≥5.5,M≥6.0 and M≥6.5 earthquakes were close to 0.956,0.86 and 0.68 respectively. Furthermore,we calculated b-value of each magnitude section of the earthquake recorded in history,and obtained that the b-value of 5.5≤M≤7.0 earthquakes was from 0.59 to 0.899,the b-value of M≥7.1 earthquakes is greater than 1.0,and the b-value of M≥7.5 earthquakes was significantly lower than the adjacent magnitude section. It shows that there may occur M7.5 earthquake in the future. Finally,we analyzed the space migration patterns of M≥6.5 earthquakes since 2000,and got that the characteristic of earthquake exist the regular of clockwise migration.