Abstract:
(Objective) In order to understand the aftershock sequence and intensity distribution of the Dingri
Ms 6.8 earthquake in 2025, (Method) the double-difference location method has been utilized to relocate the aftershocks within 72 hours and the standard deviation ellipse weighted by magnitude has been used to analyze the relocated aftershocks. Meanwhile, the instrumental intensities have been calculated with the strong-motion data within 150 km away from the epicenter. (Results) The relocated aftershocks distribute in a north-south direction, and the distribution of aftershocks within 2 hours shows consistence with that of the 72 hours. The aftershock center and macroseismic epicenter are both located to the north of the epicenter, and the major-axis direction of the aftershock area is 5° different from that of the intensity Ⅸ of the isoseismal lines. The distribution length of the aftershocks along the major axis is 71 km. There are few strong motion stations around the epicenter, therefore only 4 calculated intensity values have been obtained in areas of intensity VI and above, 2 of which show agreement with the macroseismic intensities. (Conclusions) Based on the spatial distribution of aftershocks and the focal mechanism solution, it is inferred that the nodal parameters of the seismogenic fault of the Dingri
Ms 6.8 earthquake are strike 181°/51°/-81° for strike/dip/rake angles. This earthquake shows a significant upper/lower wall effect, with greater high-intensity areas and a concentrated distribution of aftershocks in the upper wall.