Abstract：In this paper, we use the amplitude ratio method to calculate the focal mechanism solution of the 2.5≤ML≤5.0 earthquakes in the northwest margin of the Ordos block, which occurred between the year of 2000 and 2018. Through the normalized frequency statistics of the parameters of focal mechanism solution, we find that the predominant orientation of stress axis is basically consistent with the tectonic stress field in this area. Using linear stress inversion bootstrap(LSIB) method, we retrieve the direction of stress field in Bayanhot basin and Hetao seismic belt in three periods. We find that 5 years before the April 15,2015 Alxa left banner MS5.8 earthquake, the direction of stress field in Bayanhot basin deflects largely, forming an angle with the Hetao seismic belt. The direction of principal compressive stress field of Bayanhot basin obtained by inversion is consistent with the P-axis direction of this earthquake, which shows that the MS5.8 earthquake is controlled by regional stress field. After the earthquake, the direction of principal compressive stress field in Bayanhot basin is inherited, the stress field of Hetao seismic belt is affected, and the direction of the principal compressive stress field deflects and is consistent with that of the former.
LI Juan,HAN Xiaoming,ZHANG Fan. Research on the Tectonic Stress Field before and after the April 15,2015 Alxa Left Banner MS5.8 Earthquake[J]. jgg, 2020, 40(9): 923-927.
