Fast 1-D Velocity Optimization Inversion to 3D Velocity Imaging: A Case Study of Sichuan Maerkang Earthquake Swarm in 2022

To obtain an accurate one-dimensional velocity model, we developed the EA_VELEST method based on evolutionary algorithm and VELEST program. This can quickly generate a suitable 1D model finally input it into 3D inversion process using TomoDD method. We adopt methods to inverse high-resolution three-dimension structure relative earthquake hypocenters for this sequence. system processing flow was applied Sichuan Maerkang swarm in 2022. By collecting seismic phase data of area between 1 January 2009 15 June 2022, relocated historical earthquakes obtained imaging results. The reveal SE-trending secondary fault, which is located ~5 km NW Songgang fault. In first ten-hour sequence, events clearly down-dip migrated toward SE direction. inverted indicates that majority during sequence occurred along boundaries high low-velocity zones or low-VP/VS anomalies. Especially both two largest earthquakes, MS 5.8 6.0, at discontinuities zones. proposed paper novel has played very good enlightenment role optimization geophysics certain reference significance. results analysis tectonic significance provide seismogenic environment deep Ganzi block.