Splay Fault Branching Along the Nankai Subduction Zone

Park, Jin-Oh
Tsuru, Tetsuro
Kodaira, Shuichi
Cummins, Phil R.
Kaneda, Yoshiyuki

Institute for Frontier Research on Earth Evolution, Japan Marine Science and Technology Center, Yokosuka 237-0061, Japan.

*To whom correspondence should be addressed. E-mail: [email protected]

17 May 2002; accepted 1 July 2002

Science 297(5584):p 1157-1160, August 16, 2002.

Seismic reflection profiles reveal steeply landward-dipping splay faults in the rupture area of the magnitude (M) 8.1 Tonankai earthquake in the Nankai subduction zone. These splay faults branch upward from the plate-boundary interface (that is, the subduction zone) at a depth of ∼10 kilometers, ∼50 to 55 kilometers landward of the trough axis, breaking through the upper crustal plate. Slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion.