“Double Door” Opening of the Japan Sea Inferred by Pn Attenuation Tomography

The extension of back-arc basins and formation marginal seas following the subduction oceanic lithosphere are usually attributed to rollback subducting slabs distorted mantle convection. However, for Japan Sea, largest sea in northwestern Pacific, its opening is unlikely only resulted from Pacific plate because coeval Philippine arcuate arc volcanic zone. Therefore, present-day thermal structure uppermost mantle, which can be directly constrained by strong Pn-wave attenuation, plays a vital role understanding Sea opening. Here, we observe two belts Pn attenuation beneath Sea; their strikes generally consistent with local anisotropy retreat directions trenches. Hence, there seem divergent flows pushing “double door”