中国南北地震带磁性层构造特征

CHARACTERISTICS OF THE STRUCTURE OF MAGNETIC LAYER IN THE NORTH-SOUTH SEISMIC BELT IN CHINA

本文首先给出磁性层下界面反演的等效模型和其在球坐标系下变地磁倾角的二维反演方法,利用航磁资料研究了南北地震带的磁性层结构构造及其与地震活动性的关系为:1.磁性层南北两端厚,中间薄;2.下界面呈南北向的宽隆起带,北浅南深;3.磁性层所处的层位温压条件适于积累应力能量产生粘滑错动,地震多发生在磁性层内,往往位于磁性层由厚变薄的过渡处,并多伴有断裂、温泉、岩浆活动。

An equivalent model of the bottom of magnetic layer and a two-dimensional inversion method with variable magnetic inclination in polar coordinate system are developed in this paper. By using the model and method, the structure of the magnetic layer and its relation to seismicity in North-South Seismic Belt are discussed in detail on the basis of the magnetic data in the region. The following conclusions can be drawn from the result:1. Both the northern and southern parts of the magnetic layer in the belt are thicker than the central part with their demarcati, on lines through 28°N and 34°N, respectively;2. The bottom of the magnetic layer appears as a N-S-trending broad uplift zone in an area from 100°E to 106°E, getting shallower from south to north, with its shallowest part at 103°E;3. The P, T condition of the magnetic, layer is suitable for the accumulation of stress energy, and thus the magnetic layer is a seismogenic layer. Most of the earthquakes occurred within the magnetic layer, especially in the transition zone from its thick to thin parts. The seismicity is usually accompanied by faulting, hot spring and magmatism.