Local magnitude measurement of small-micro earthquakes in the Changning-Zhaotong Shale Gas Demonstration Zone

Based on the high-density broadband mobile seismic observation array deployed in the Changning-Zhaotong Shale Gas Demonstration Zone, we obtained a precise location catalog of 108727 small-micro earthquakes with magnitudes ranging from -0. 1 to 5. 2 from April to October 2021 using the LOCFLOW workflow. In view of the systematic deviation between the magnitude measured by the LOCFLOW built-in algorithm and the magnitude published by the China Earthquake Networks Center (CENC), we developed local magnitude formulas suitable for the study area. According to the definition of Richter magnitude, these formulas were derived using two methods: gauge function parameter fitting inversion considering reference magnitude correction and station base correction. These new gauge functions can more accurately represent amplitude attenuation characteristics of small-micro seismic events in the study area in the southern Sichuan Basin. They enable more precise local magnitude assessments for small-micro earthquake events, facilitating research into magnitude-frequency relationships and related studies in shale gas development areas.