The Study On Modern Tectonic Stress Field In Myanmar Arc Subduction Zone

The Myanmar arc subduction zone is located between the Indian plate and the Eurasian plate,and it is one of the most active plate areas in south-east Asia.It is of great significance to know the stress field around the region for understanding the mechanism of earthquakes and the developing trend of subsequent earthquakes.We collect the data of focal mechanism from previous studies and Global CMT in the Myanmar and its adjacent areas to calculate and sort out the central focal mechanism solutions.Then we use MSATSI to invert the tectonic stress field of plane and the tectonic stress field in different depth,and calculate the fault plane parameters of the typical semi-arcuate seismic belt by using the Gauss-Newton combined with simulated annealing method to determine fault plane in the Myanmar arc area under different depths and zones.Finally,we analyze the characteristics of tectonic stress field in this area in detail and analyze the geodynamic.The result shows that:?1?The compressive stress axis??₁ axis?is mainly and nearly in the direction of WE and NW-SE,it is consistent with the phenomenon that study area is controlled by the east-west convergence of the Indian plate.?2?The plunge angles of tensile stress axis??₃axis?are big in study area and it close to vertical in the range of depth greater than120km.?3?The region with smaller R value is basically distributed in the central lowland of the Myanmar arc area.Along with the depth increases,the R value decreases,and combined with the results of plunge angles of stress axis,we speculate that it probably caused by the lithosphere of the study area driving downward under the plate convergence boundary.?4?By fitting parameters of fault plane in half-arc seismic area,we analyze the trend of dip angle of fault becomes larger with increasing depth.According to combining the analysis of the inversion results of the structural stress field in different depths and the local geological background,the Indian plate is in an active subduction rate model.Compared with previous work,this study has collected and arranged more accurate and detailed focal mechanism solution data and acquired a more detailed image of the tectonic stress field distribution in the Myanmar arc and its adjacent area by using the MSATSI.And combined with the fault plane fitting results of the half-arc seismic area,it shows the tectonic stress field characteristics of Myanmar arc subduction area and the geodynamic analysis of the subduction zone.This study provides basic information for the research of seismogenic background and seismic dynamics of Myanmar arc subduction area.