Source parameters and rupture characteristics of the M6.2 Jishishan earthquake in Gansu Province on December 18, 2023

At 23:59 on December 18, 2023 (Beijing time), a M6.2 earthquake occurred in the Gansu Province of Jishishan. The Institute of Geophysics, China Earthquake Administration initiated the response mechanism after this earthquake and organized geophysics researchers to estimate the source parameters, focal mechanism, rupture process, earthquake radiation energy and earthquake relocation of this earthquake. Based on the source model, the Shakemap and the coseismic deformation field simulation are carried out. The results demonstrate that the earthquake is of dominant thrusting mechanism. The energy was concentrated and released in the first 8 seconds. The earthquake intensity in the extreme seismic area possibly exceeded Ⅷ, resulting in an estimated disaster range of approximately 6000 km². This earthquake caused apparent horizontal coseismic displacement with maximum displacements reaching 7.8 cm and 15.8 cm.