Study on the crustal stress field of the Tengchong volcanic area using composite focal mechanism method
Sheng Shu-zhong 1, Wan Yong-ge♦2,3, Jiang Chang-sheng 4, Wang Xiao-shan 5,Liang Shan-shan 6, Xiao Gen-ru 7, and Hu Xiao-hui 2
1. School of Geophysics and Measurement-control Technology, East China University of Technology, Nanchang 330013, China.
2. Institute of Disaster Prevention, Sanhe 065201, Hebei, China.
3. Hebei Key Laboratory of Earthquake Dynamics, Sanhe 065201, Hebei, China.
4. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China.
5. Earthquake Administration of Hebei Province, Shijiazhuang 050021, China.
6. China Earthquake Networks Center, Beijing 100045, China.
7. School of Geomatics, East China University of Technology, Nanchang 330013, China.
Abstract：
We calculated the crustal stress field using the composite focal mechanism method based on the P-wave initial motion polarity data of the Tengchong volcanic area from January 2011 to April 2019 obtained from the Bulletin of Seismological Observations of Chinese stations. The magnitude range of earthquakes used in this study is 0–4, and their magnitudes are mainly approximately 1.0. To investigate the influence of the source location on the stress fi eld and obtain reliable stress fi elds of the study area, we applied the double-difference algorithm to relocate the seismic events, obtaining more accurate and reliable relative positions of seismic events with a clearer seismic belt. On the basis of relocation results, the study on the stress fi eld along the fault zone was conducted, and the influence of seismic event position on the stress fi eld was analyzed. Results show that, first, the current stress regime in the shallow crust of the Tengchong volcanic area is strike-slip faulting, the orientation of the principal compressive stress axis is NE–SW, the orientation of the principal extension stress axis is SE–NW, the principal compressive and extension stress axes are nearly horizontal, and the dip angle of intermediate principal stress axis is relatively large. This reflects that the volcanic and seismic activities in the Tengchong volcanic area are mainly controlled by the collision and squeezing effect of the Indian–Eurasian plate. It also reflects that the current tensile action caused by deep magma activity has little influence on the shallow crustal stress field. Second, the stress field along fault zones reveals that there exist local stress fi elds, such as the thrust stress regime at the strike-slip fault terminal area, which is consistent with the compressional area at the intersection of conjugate strike-slip faults indicated by previous study. Third, the stress fi eld results are consistent, regardless of using the original location in the bulletin or the relocated location, indicating that the influence of the event location error can be neglected when there are sufficient data and reflecting the stability of the composite focal mechanism method. The findings can serve as a reference for investigating geological structure movement, seismic activities, and volcanic activities in the Tengchong volcanic area.
. Study on the crustal stress field of the Tengchong volcanic area using composite focal mechanism method[J]. APPLIED GEOPHYSICS, 2021, 18(2): 239-252.
2021, Vol. 18 
