地震走时层析成像方法在研究强震孕震、发生机制中的应用

Advances in the study of seismogenic and occurrence mechanism of strong earthquakes by using seismic tomography

选取1950年以来中国大陆内部发生的数十次6.0级以上强震的孕震、发震机制研究实例,本文回顾总结了近年来国内外学者对强震的发生与地壳介质结构不均匀性关系的研究进展情况,分析了不同研究方法的优点和存在的问题.相对定位方法获取精确的余震震源位置和地震层析成像方法,获得震源区高分辨率的三维速度结构是目前研究强震孕震构造和发震机制的主要手段.与流体触发俯冲带强震机制不同,大陆强震多发生于易于积累应力的高速块体内部或高低速块体过渡区域,中下地壳的低速高导层的弱化作用是触发强震的主要因素.深入了解发震地区的地壳介质结构、发震构造和地震活动的关系,可以为预测地震的发生和防震减灾提供重要的参考数据.

In this paper, we review the research progress of domestic and foreign scientists on the relationship between the occurrence of strong earthquakes and crustal heterogeneity, and analyze the advantages and problems of the main research methods. Further analysis shows that the main methods to study the structure of the focal region and seismogenic mechanism of strong earthquakes are as follows: relocating the high-precision focal location of aftershocks by the relative localization method and obtaining the high-resolution seismic wave velocity structure in the focal area by seismic tomography. Different from the mechanism of strong earthquakes in fluid-triggered subduction zones, strong earthquakes occur in or at the boundary of high-velocity anomaly that is easy to accumulate stress, and the weakening of the low-velocity and high-conductivity layer in the middle and lower crust is the main factor that triggers strong earthquakes. Insights into the crustal heterogeneity, seismogenic structure, and seismicity in seismogenic areas can provide important data for earthquake prevention and disaster reduction.