In this study,8071 focal parameters of small and moderate earthquakes from January 2019 to December 2023 in the Sichuan-Yunnan region were calculated.The tempo-ral and spatial variation trends of stress drop in the focal areas of the May 21,2021 Yangbi MS6.4 earthquake,the September 5,2022 Luding MS6.8 earthquake,and key observation areas(Longmenshan fault zone and the intersection area of the Honghe fault and Xiaojiang fault)were analyzed.According to the variation trends of stress drop,significant precur-sor changes were observed in the 2021 Yangbi MS6.4 focal area one year before the earth-quake.The stress drop time series of the 2022 Luding MS6.8 earthquake shows a rapid rise and decline in the short term after the main earthquake;meanwhile,the stress drop has no obvious upward trends at present.The stress drops in the intersection area of the Honghe fault and Xiaojiang fault at the southern end of the Sichuan-Yunnan rhombohedral block and the northeast section of the Longmenshan fault zone are relatively high.Conse-quently,the future risk of strong earthquakes deserves attention,and the stress drop changes in these two areas should be continuously observed.
维普
万方数据