2004年12月26日印度尼西亚M_W9.0大震前后震源机制一致性变化特征研究

A study on forecast method of focal mechanism consistency before the MW_9.0 Indonesia earthquake on December 26,2004

本文选取2004年12月26日发生在印度尼西亚西北近海、震中位于巽他海沟的东侧的M_W9.0地震的余震分布空间范围为研究区域,分析了该区域震源机制,并利用震源机制和构造应力场的一致性参数a进行了地震检验。研究结果表明,M_W≥7.5地震之前,都有参数a降低的现象,M_W9.0地震前,a值都有动荡起伏的情况。该研究区长达数千千米,而连续发生的M_W≥5.0地震的震源机制与构造应力场一致,应当不是随机现象,似可视为具某种前兆意义的现象。

The Indonesia region is one of the most seismically active zones of the earth. On December 26, 2004 an Mw9.0 earthquake occurred off the west coast of northern Sumatra Indonesia, and is also the largest earthquake in recent forty years. The epicenter is located in the east Sunda trough. The trough is the boundary of the Australian plate and the India plate. This paper selects the earthquake aftershock distribution range space as the study area,which is divided into two parts of north and south. The south latitude is 11°S-5°N,and the north is 5°N- 15°N. Based on the global focal mechanism directory of the China Earthquake Information Network, we analyze the focal mechanism of the area, and use the consistency parameter a of focal mechanism and tectonic stress field to conduct the earthquake test. The research results show that before the Mw ≥ 7.5 earthquake, there was a lower consistency parameter a. Before the Mw9.0 earthquake, the a value is in a turbulent state. The study region is thousands of kilometers, and focal mechanism and tectonic stress field of the continuous occurrence earthquake of Mw ≥ 5.0 is consistent which are not random phenomena, but with the precursory phenomena to be of some prediction significance.