Estimation high-frequency energy radiation of the 2013 Lushan Mw6.6 earthquake by envelope inversion

This study uses the envelope inversion method to investigate the characteristics of high-frequency energy radiation of the 2013 M _w 6.6 Lushan earthquake. We selected near field acceleration records from two small earthquakes as empirical Green’s functions and applied the differential evolution algorithm to perform the inversion. We determined an appropriate subfault size through checkerboard test to ensure stable and reliable results. The results indicate that nearly half of the fault plane generated high-frequency radiation, which is primarily concentrated around asperity and along the edges of the fault. Around the asperity, there are two major regions of high-frequency radiation areas. The first is located 10 km northeast of the initial rupture point at a depth of 6.2 km, with an area of approximately 400 km², extending from 10 km depth to the surface. This region exhibits the strongest and most extensive high-frequency radiation on the fault. The second region is situated directly below the initial rupture point at a depth of 24.6 km, covering an area of about 200 km². Additional high-frequency radiation areas are concentrated along the fault edges: near the southwestern shallow section, the deep southwestern section, and the deep northeastern section, with 200 km², 100 km², and 200 km², respectively. The distribution of high-frequency radiation of the Lushan earthquake is consistent with theoretical studies suggesting that abrupt changes in slip or arrest of rupture propagation excite high-frequency energy.