地震迁移的类型、特征及机制讨论

地震活动的迁移是指地震沿着某一方向循序地发生，是地震活动总体无序中局部出现的有序结构。通过系统分析区域上典型的地震迁移现象可以发现，迁移可划分为沿断裂走向的纵向迁移、垂直断裂走向的横向迁移与岩石圈尺度的深源迁移三大类。结合具体的实例分析，可初步归纳出纵向迁移（包括单向、双向、反复和跳跃式迁移等常见形式）、横向迁移和深源地震迁移的主要特征，并初步估算出了不同类型迁移的速度值，其中沿全球板块边界纵向迁移平均速度约为V=569 km/a，沿亚板块边界的平均速度约为V=120 km/a，沿大陆内部断裂带平均速度约为V=50 km/a。横向迁移相对比较复杂，初步发现在东亚存在两种速度分别为约20 km/a、50 km/a的迁移现象。而深源地震迁移速度的全球平均值大约为360 km/a。地震的纵向与横向迁移都存在不同层次和级别，也存在多种不同频率、能量与速度的形变波与迁移现象，这很可能是区域上大地震丛集活动过程中断层相互作用、地震应力触发和岩石圈尺度的形变波传播等因素共同作用的结果，而这种大空间尺度上的地震迁移现象的存在及其所具有的规律性特征，显然可为开展区域地震危险性分析提供新的思路和方法参考。 

The types, characteristics and mechanism of seismic migration

The migration of seismicity refers to the sequential occurrence of earthquakes in a certain direction, which is the ordered structure in the local area in the overall disorder of seismicity. Through the systematic analysis of the typical seismic migration phenomena in the region, it can be found that the migrations can be divided into three categories:longitudinal migration along the fault strike, transverse migration along the vertical fault strike and deep source migration on the lithosphere scale. Combined with the analysis of specific examples, the main characteristics of vertical migration (including one-way, two-way, repeated and jumping migration), horizontal migration and deep source earthquake migration can be preliminarily summarized, and the velocity values of different types of migrations can be preliminarily estimated, among which the average velocity of vertical migration along the global plate boundary is about 569 km/a, the average velocity along the sub plate boundary is about 120 km/a, and the average velocity along the continental internal fault zone is about 34 km/a. The horizontal migration is relatively complex. It is found that there are two kinds of migration phenomena in East Asia, one is about 20 km/a, the other is about 50 km/a. The global average migration velocity of deep source earthquakes is about 360 km/a. There are different levels and grades of vertical and horizontal migration of earthquakes, and there are also many kinds of deformation waves and migration phenomena with different frequencies, energy and velocities, which may be the result of the interaction of interruption layers in the process of large earthquake clustering activity, the triggering of seismic stress and the propagation of deformation waves on the scale of lithosphere, and it is obvious that the existence and regularity of this kind of earthquake migration phenomenon on the scale of large space can provide new ideas and method reference for regional seismic risk analysis.