Earthquake doublet in an active shear zone, southwest Japan; Constraints from geophysical and geochemical findings

Umeda, Koji; Asamori, Koichi; Makuuchi, Ayumu; Kobori, Kazuo

The geophysical and geochemical observations are significant indications that the invasion of mantle fluids into the crust, driven by upwelling asthenosphere from the Okinawa trough, triggers the notable left-lateral shearing in the zone in the present-day subduction system. In addition, the existence of aqueous fluids in and below the seismogenic layer could change the strength of the zones, and alter the local stress regime, resulting in the occurrence of the 1997 earthquake doublet.