The Enhancement of Seismicity before the 2004 MW9.0 Indonesia Sumatra Earthquake and Its Relation to the Earth Rotation
详细信息
- 责任者：Chen Xuezhong (Institute of Geophysics ; China Earthquake Administration ; Beijing 100081 ; China) ; Li Yane
- 刊名：Chinese Journal of Geophysics
- 出版年：2013
- 卷期：56(1)
- 关键词：苏门答腊地震2004 ; Sumatra earthquake 2004 ; 地震活动性 ; seismicity ; 印度尼西亚 ; Indonesia
- 页码：p.79-90
- 图表：illus., 26 refs.
- 分类号：0500
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
The region where the aftershocks of the December 26,2004 Indonesia Sumatra earthquake of MW9.0 are distributed is selected for research in this spaper.It is located in the central part of the Myanmar plate,with a latitude range from 2°N to 15°N.The data of the earthquake catalogue pubulished by the United States Geological Survey is used to study the temporal and spatial variations of the earthquake frequency before the 2004 MW9.0 Indonesia Sumatra earthquake,and to analyze the relationship between the seismicity and the earth rotation.The results are as follows: 1) A very clear gradually increasing variation of the earthquake frequency within the region of aftershocks began from 2000,reflecting the enhanceing process of the seismicity.The earthquake frequency decreased to a certain extent prior to the imminency of the main shock.2) Through the spacial mapping analyse of the earthquake frequency,it is found that a significant increasing region of seismic activity was located near the epicenter before the main shock.3) The rda value,defined as the ratio of earthquake number cuurring in a unit time in the deceleration period of the earth rotation to that in the acceleration period of the earth rotation,increased significantly before the MW9.0 earthquake.It increased slowly from 1998 to 2002,and reached to the maximum at the end of 2002,and then decreased until the occurrence of the main shock.4) The M≥5.5 earthquakes occurring in the region with latitude range from 1°N to 7°N near the epicenter almost all happened in the deceleration period of the seasonal change of the earth rotation.5) When it is in the deceleration period of the seasonal change of the earth rotation,ΔN,defined as the deference between the cumulative annual frequency of seismic activity and its mean,increases,which shows that the seismic activity enhanced.When it is in the acceleration period,ΔN decreases,and the seismic activity becomes weak.This phenomenon is not accidental,maybe reveals the relation of the MW9.0 Indonesia Sumatra earthquake to the deceleration of the earth rotation.These results are valuable to us for further understanding the process of earthquake pregnancy and researching earthquake prediction.
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