青藏高原及其周边地区大地震震源过程成像

TOMOGRAPHY OF THE SOURCE PROCESS OF LARGE EARTHQUAKES IN THE TIBETAN PLATEAU AND ITS SURROUNDING REGION

青藏高原是世界上地震多发区之一。仅 1990年以来就有 4次强烈地震发生在青藏高原及其周边地区。发生于 1990年 4月 2 6日的青海省共和县MW 6 .4 (MS6 .9)地震位于青藏高原的东北缘 ,发生于 1997年 11月 8日的西藏自治区玛尼县MW 7.5 (MS7.9)地震和 2 0 0 1年 11月 14日的昆仑山口西MW7.8地震位于青藏高原的北部 ,发生于 1996年 2月 3日的云南省丽江县MW 6 .6 (MS7.0 )地震位于青藏高原的东缘。通过中国数字地震台网 (CDSN)和全球数字地震台网 (GDSN)记录的数字波形成像 ,分析研究了这些大地震的震源运动学和几何学特征。研究表明 ,这些地震的震源性质因震源所处位置的不同而不同 ,它们的发生与印度板块与欧亚板块的碰撞、青藏高原的运动与变形有着密切的关系。反过来 ,从地震波形资料中获得的关于这些地震的震源机制、震源运动学和几何学特征的进一步认识为青藏高原目前的运动状态提供了证据。

Tibetan plateau is one of the regions with high seismicity in the world. Just since 1990 four strong earthquakes have been occurred in the Tibetan plateau and its surrounding regions. The M W6.4( M S6.9) earthquake in Gonghe, Qinghai, on April 26, 1990, was in the northeastern margin of the Tibetan plateau. The M W 7.5 ( M S 7.9) earthquake in Mani, Tibet, on November 8, 1997, and the M W 7.8 earthquake in western pass of Kunlun Mountain, on November 14, 2001, were located in the northern Tibetan plateau. The M W6.6 ( M S 7.0) in Lijiang, Yunnan on February 3, 1996, earthquake was east of the Tibetan plateau. By inverting the digital waveform data from China Digital Seismograph Network (CDSN) and Global Digital Seismograph Network (GDSN), the kinematic and geometrical characteristics of these large earthquakes are analyzed. The results indicate that the characteristics of the sources vary with the locations of their hypocenters, and imply that their occurrence was closely related with the motion and deformation of Tibetan plateau caused by the collision of the Indian and the Eurasian plates. The knowledge about the focal mechanism and the kinematic and geometrical characteristics of the earthquake sources from the seismic waveform data further provides evidence for the kinematics of Tibetan plateau.