A Near-Vertical Slab Tear in the Southeastern Solomon Islands

The Solomon Islands is one of the most seismically active areas in the southern Pacific with high earthquake hazard potential. The regional seismic network, equipped with six broadband seismic stations, was constructed as late as October 2018. On January 27 and 29, 2020, two moderate earthquakes, Mw 6.3 and 6.0, respectively, occurred in the southeastern Solomon Islands. The entire foreshock-main-shock-aftershock sequence was recorded by this seismic network for exploring the seismogenic structures. Based on the spacial distribution of the foreshock-aftershock sequence, the interaction of the subduction and transform zones between the Pacific and the Australia plates could lead to the near-vertical dip-slip tear slab. Confirmed with PREM and the new 1D velocity model for testing the robustness of the earthquake locations, a seismic gap at depths from 25 to 35 km is observed as the “jelly sandwich” rheology of the continental crust of the Australia plate.