| 东昆仑大地震的深部构造背景 |
| |
| 关键词:deep seismic sounding crust structure earthquake Tibetan Plateau East Kunlun |
| 基金项目:国家重点基础研究发展规划项目(编号:G1998040800) |
|
| 摘要点击次数: 5571 |
| 全文下载次数: 5851 |
| 摘要: |
| Deep Tectonic Background of the 8.1 Ms Earthquake in the East Kunlun |
| This paper has discussed the deep background of East Kunlun Ms 8.1 earthquake through the crust structure derived from the deep seismic sounding profile. Along a 500 km profile from Tuotuohe to Xiaochaidan, there exist two large Moho offsets under the transitional belt from East Kunlun Mountains to Qaidam basin and under Jinshajiang suture respectively. The crustal thickness is 61 to 75 km beneath the northern Tibet plateau. Moho with weak reflectivity remains continuously dipping southward and gets dee pened. The low crust has been thickened with no obvious decrease of velocity. In the upper crust, thrust and slide faults are developed, and the lower velocity layer appears between the upper and the lower crust. The Qaidam basin has a thickness of 52±2 km, being more rigid than the northern Tibet plateau. The special structure of the crust and the upper mantle beneath the East Kunlun Mountain and its surrounding areas is favorable for the formation of violent (great) earthquakes. In the regional stress field where the India plate pushes northward and the Qaidam block underthrusts southward, the relatively weak low crust beneath the northern Tibet plateau has been shortened and thickened. The creep slide movement in the process of deformation has enlarged the stress in the shallow part of the crust. Nevertheless, the formation of a great earthquake is related not only to the northeastern main compresso stress but also to the lateral movement of the blocks in the northern Tibet plateau. The differences in velocity and magnitude of the lateral movement between various terrenes of northern Tibet have resulted in the stress accumulation along the boundaries of the blocks and reactivated boundary faults. The existence of the low velocity layer is the prerequisite for the formation of such local stress setting as 'viaduct' which is the favorable site for violent (great) earthquake. |
| LI Qiu-sheng,PENG Su-ping,GAO Rui,GUAN Hua,FAN Jing-yi.2004.Deep Tectonic Background of the 8.1 Ms Earthquake in the East Kunlun[J].Acta Geoscientica Sinica,25(1):11-16. |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|