论文部分内容阅读
2008年5月12日汶川发生的MS 8.0地震使四川、甘肃和陕西等省遭受重大人员伤亡及财产损失,本文通过震前完成的穿过龙门山构造带中段的松潘-中江大地电磁测深剖面的反演解释,揭示了龙门山构造带及其两侧松潘-甘孜褶皱带、川西前陆盆地地壳内部30km深处电性结构。龙门山构造带东侧四川盆地为上部较厚低阻沉积盖层之下存在连续稳定高阻的扬子基底特征,而以西的松潘-甘孜褶皱带分上部和下部两部分,上部为高阻古生界夹低阻中新生界,下部(中下地壳)呈连续低阻层,推测可能存在一个连续稳定的壳内高导层。而龙门山恰好是青藏高原与扬子地台联合作用的结果,形成了上部高阻及下部基底高阻,中间夹西倾低阻带,低阻带最厚10km,其深度从地表10km连续向西延伸至20km深处,与松潘-甘孜褶皱带15～20km的低阻层相连。这个异常低阻带可能是松潘-甘孜地块向东向上移动的传输带,北川-映秀断层逆冲分量显然大于右行走滑分量,因此汶川地震属于右行平移-逆冲断裂型地震。
The MS 8.0 earthquake in Wenchuan on May 12, 2008, caused heavy casualties and property losses in Sichuan, Gansu and Shaanxi provinces. This paper passes the Songpan-Zhongjiang Electromagnetic Deep-Sounding Profile that was completed in the middle of the Longmen Shan tectonic belt , Revealing the Longmen Shan tectonic belt and its Songpan-Ganzi fold belt on both sides and the electrical structure within 30 km deep in the crust of the western Sichuan foreland basin. The Sichuan Basin, on the east side of the Longmen Shan tectonic belt, is characterized by a continuous stable high-resistance Yangtze basement under the upper thick-low-resistance sedimentary caprock. The upper Songpan-Ganzi fold belt in the west is divided into upper and lower parts, Boundary clip low resistivity Mesozoic, the lower (middle and lower crust) was a continuous low resistivity layer, suggesting that there may be a continuous and stable high-conductivity shell. The Longmenshan happens to be the result of the combined action of the Qinghai-Xizang Plateau and the Yangtze platform. The upper high resistance and the lower high resistance of the basement are formed. The middle of the Longmen Shan is the westward low resistance zone. The low resistance zone is thickest 10km. The depth ranges from 10km to the west It extends to the depth of 20km and connects with the low resistivity layer of 15 ~ 20km in Songpan-Ganzi fold belt. This anomalous low-resistivity zone may be the belt moving eastwards of the Songpan-Garzê block. The component of the Beichuan-Yingxiu fault thrust is obviously larger than the right-hand slip component, so the Wenchuan earthquake is a right-lateral translation-thrust earthquake.