Research on Regional Stress Field Dynamics before the Wenchuan Ms8.0 Earthquake
详细信息
- 责任者：Cheng Wanzheng (Earthquake Prediction Institute ; Earthquake Administration of Sichuan Province ; Chengdu 610041 ; China) ; Zhang Yongjiu
- 刊名：Earthquake Research in China
- 出版年：2011
- 卷期：27(3)
- 关键词：汶川地震2008 ; Wenchuan earthquake 2008 ; 构造应力场 ; tectonic stress field ; 龙门山断裂带 ; Longmenshan Fault Zone
- 页码：p.215-225
- 图表：illus., 37 refs.
- 分类号：0500
- issnNo：ISSN1001-4683
- isbnNo：CN11-2008/P
摘要
This article uses the telemetry digital seismic waveform data from Chengdu and Kunming to study the focal mechanism solutions and the apparent stress values of a large number of small earthquakes, and analyzes the regional stress field dynamics and the spatio-temporal distribution of apparent stress values. The temporal variation of the average stress field azimuth in Sichuan-Qinghai block is given. The average principal stress field azimuth of Sichuan-Qinghai block had obvious disturbances before the Wenchuan MS8.0 earthquake. This may be related to status change of block stress field between the Sumatra Ms9.0 earthquake on December 26, 2004 in Indonesia and the Wenchuan MS8.0 earthquake in 2008. The ratio of thrust-type earthquake in the Sichuan-Qinghai block was high from 2006 to 2007. The variations of the earthquake dislocation type of regional moderate and small earthquakes before the Wenchuan Ms8.0 earthquake are consistent with the state change of block displacement field revealed by GPS data, and also identical with analysis results of crustal shortening velocity change which is vertical to Longmenshan fault zone. The apparent stress value is determined on the basis of the whole band of the seismic waveform to calculate radiation energy. The fluctuation shape of the fitting trend of the apparent stress line is related to strong and weak of regional seismicity. It reveals that the micro-dynamic fluctuation process of regional stress value is similar to the azimuth transition of regional principal compressive stress field, which can be used to grope for pregnant physical process. The higher value areas of apparent stress are the possible areas of potential seismic risk. It can be seen from the spatial distribution of the medium-and short-term apparent stress before the Wenchuan Ms8.0 earthquake that the Longmenshan fault zone is low stress distribution area, and the relatively high apparent stress is in peripheral area. These images may show the lock phenomenon near the medium and short Wenchuan MS8.0 earthquake, for example, the focal parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces changed with time, the thrust-type earthquakes in Sichuan-Qinghai block continually increased, the spatial distribution areas of the high apparent stress were discovered, and so on. The authors’ continuous work in this aspect after the Wenchuan Ms8.0 earthquake may further reveal the relationship between these phenomena and future great earthquake.