Focal Mechanism and Stress Implication on the Surrounding Region of the Jishishan,Gansu Ms6.2 Earthquake on December 18,2023
In order to study the stress implication of the 2023 Ms6.2 earthquake in Jishis-han,Gansu on the surrounding areas,the central focal mechanism solution of the earth-quake is estimated based on the focal mechanism data provided by various institutes and scholars,with nodal plane Ⅰ:strike 159.08°,dip 40.57°,and rake 112.46°,and nodal plane Ⅱ:strike 310.52°,dip 53.05°,and rake 71.88°.It can be judged as a reverse focal mechanism type of this earthquake.Projecting the local tectonic stress tensor on the two nodal planes of the central focal mechanism,the resulted relative shear stress on the nodal plane are 0.797 and 0.951,respectively,which mean that the earthquake is a normal ener-gy release under the action of the local tectonic stress field.The NNW striking of the Lajishan Northern Margin fault is dipping SWW and dip angle of 45°～55° by geological field investigation,and nearly consistent with the nodal plane Ⅰ of the central focal mech-anism,we consider that the Lajishan Northern Margin fault is the seismogenic fault of the earthquake.Based on the rupture model and homogeneous elastic half-space model,we calculate the co-seismic displacement field and strain field generated by the earthquake in the surrounding areas.The volumetric strain at the epicenter area shows tensile tension,and the northeast and southwest sides far from the epicenter show slight tensile tension,and the periphery of the epicenter shows compression with strong compression on the east side.The horizontal displacement presents the outflow of material from the northwest and a small portion of the southeast side of the epicenter,while the material from the northeast and southwest sides of the epicenter is inflowed into the epicenter.Corresponding to the horizontal displacement field,the vertical displacement field is uplifted at the epicenter,while the surrounding area shows little subsidence.
The 2023 Jishishan Ms6.2 earthquakeCentral focal mechanism solutionDisplacement fieldStrain field
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万方数据
