Estimating Seismic Intensity Maps of the 2021 M w 7.3 Madoi, Qinghai and M w 6.1 Yangbi, Yunnan, China Earthquakes

This study focuses on rapidly determining seismic intensity maps of earthquakes because it offers fundamental information for effective emergency rescue and subsequent scientific research, and remains challenging to accurately determine seismic intensity map in regions with sparse instrumental observations. Here we applied a novel method that consisted of array technology (back-projection), ground-motion prediction equations, and site corrections, to estimate the seismic intensity maps of the 2021 M w 7.3 Madoi, Qinghai and the M w 6.1 Yangbi, Yunnan, China earthquakes. We used seismic data recorded at European stations to back-project the source processes of the 2021 M w 7.3 Madoi, Qinghai and the M w 6.1 Yangbi, Yunnan, China earthquakes. The back-projected energy radiations were then used as subevents or used to define the fault geometry. Summing the contributions of each subevent or estimating the shortest distances from each site to the rupture fault, we obtained the ground motion (PGA and PGV) for each site under rock site conditions. The estimated ground motions were corrected at each site for local site amplification according to the Vs30 database. Our estimated seismic intensity maps and field reports showed high similarity, which further validated the effectiveness of the novel approach, and pushed the limit of earthquake size down to ∼ M 6. Such efforts would substantially help in the fast and accurate evaluation of earthquake damage, and precise rescue efforts.