鲜水河断裂带深部情况及其与地震的关系

THE CONDITION IN THE DEPTH OF XIANSHUIHE FRACTURE BELT AND RELATIONSHIP BETWEEN IT AND EARTHQUAKES

摘要:

本文根据重力、航磁、地壳视厚度、地震活动性及震源深度等资料,对鲜水河断裂带形成的深部状况及其与地震发生的关系进行了初步分析和讨论。结果表明:
1.该断裂带在上地幔顶部的壳幔界面上並未得到清晰和直观的反映,因此推测它可能未切穿岩石圈,而属一条壳内区域大断裂。
2.该断裂是在前海西期构造隆起背景上发育起来的。
3.从地壳剖面上看,古生代变质岩系底板以下到磁性居里等温面之间的带状空间,是该断裂带的孕震和发震的层位。
4.磁性居里等温面的隆起或高点部位,因岩浆或高温流体的侵入,往往是孕震断层的根部,根部增温,上部锁住,故有利于应力的集中,最易产生错动,而成为强震孕育、发生的重要场所。

Abstract:

On the basis of data on the gravity, the aeromagnetic survey, the apparent crustal thickness, the seismicity and the depth of focus, the author preliminarily studied and discussed the condition of formation of the Xianshuihe fracture and relationship between it and occurrence of earthquakes. Results were showed as follows:
1. As there was no clear and direct reflection of the Xianshuihe fracture on boundary surface between the crust and the mantle at the top of the mantle, this fracture may not pass through the lithosphere and was a strong regional fracture inside the crust.
2. This fracture had developed on the tectonic background of upheaval of the crust before the Variscian period.
3. It will be seen on the section of the crust that the belt between the bottom of metamorphic rock of the Palaeozoic era and magnetic Curie isothermal surface is place of occurrence and brewing of earthquakes of the fracture belt.
4. Because of irruption of magmas or fluids with high temperature, upheaval and higher temperature sites on magnetic Curie isothermal surface usually are the bottom of fractures brewing earthquake. Because temperature of the bottom is raised and the upside is caught here, the stress is concentrated easily and movement of the fracture easily is caused, therefore it is principal place where strong earthquakes brew and occur.