青藏高原北部与东缘地震波特征对比及其地球物理意义

COMPARISON BETWEEN SEISMIC WAVE CHARACTERS ALONG BOTH NORTHERN AND EASTERN MARGINS OF QINGHAI-XIZANG PLATEAU AND ITS GEOPHYSICAL MEANINGS

摘要:

藏北与滇南均是地震多发区,甘肃台网记录的该两区地震波有明显差异。滇南地震波途经青藏高原东缘到兰州,其体波波列以短周期成分为主。短周期面波L(_g1)和L(_g2)非常显著,起始尖锐。藏北地震波途经青藏高原东北部到兰州,传播介质对地震体波的短周期部分吸收相当强,体波和面波均有一定的衰减,L(_g1)不明显或缺失,L(_g2)起始缓慢,周期长。对两区地震波的对比研究表明,由于两传播路径中的上地幔与地壳上部构造差异显著,介质密度和分层不同,对地震波的吸收也就不同,从而造成两地区地震记录上的差别。

Abstract:

The berth Xizang and south Yunnan the regions where earthquakes often occur. The seismic waves of the regions recorded by Gansu networks are obviously different from each other. The seismic wares in south Yunnan travel to lanzhou by way of the eastern margin of Qinghai -Xizang Plateau,their body wave trains mainly comprise short period compositions,and surface waves L_g1, and L_g2, are very remarkable and start sharply. The seismic waves in north Xizang travel to Lanzhou by way of the northeastern margin of Qinghai-Xizang Plateau, the short period part of seismic body waves is strongly absorbed by propagation medium, body wave and surface wave have some attenuation, L_g1, is not obvious or absent and L_g2, starts slowly and has a long period. The comparison results show that there are very different upper mantle and upper crust structures as well as different media and stratifications along the two propagation paths,so the absorptions to seismic waves are also different, resulting in differences of seismic records.