背景应力场差应力约束研究 -以Landers地震和Hecter Mine地震为例

本项目是以1992年Landers7.4级地震和1999年Hecter Mine7.1级地震为例，利用主震引起的应力变化和主震前后应力场对背景应力场差应力進行约束研究。目标是利用这两次地震研究程度高、数据丰富质量高的优势，建立一套完整、可靠、成熟的差应力约束方法。经过两年多的预研究，我们已经得到了1992年Landers7.4级地震背景应力场差应力初步约束结果。差应力约束结果，加上常规应力场反演参数，就能计算出不同断层面上绝对剪应力大小，而剪应力是断层上地震发生的直接动力源，这在应力场强度研究问题上是前進了一步。

Taking the 1992 M=7.4 Landers earthquake and the 1999 M=7.1 Hecter Mine earthquake as examples in this project,we will constrain the differential stress of background stress field from stress changes due to main shock and stress fields before and after main shock.The goal is to establish a complete, reliable and mature constraint method for differential stress by taking advantages of the high degree of seismic research and high data quality in these two earthquakes. After more than two years of pre-research, we have obtained the preliminary differential stress of background stress field for the 1992 M=7.4 Landers earthquake. From differential stress together with the stress field parameters by conventional inversion, we can give the absolute magnitude of shear stress on different fault planes. The shear stress is the direct power source for earthquakes on the fault plane. This is a real progress in the study of the strength of stress field.