Fig. 13

Partial derivatives of pore fluid pressure field in the depth direction. The partial derivatives at depths of a 5 km, b 10 km, and c 15 km. Values are truncated outside the region from − 1 to 1 MPa/km. The squares and circles denote evaluation points of Groups 1 and 2 where we observed temporal increases in pore fluid pressure triggering events. The stars, grey lines, and rectangles are the same as in Fig. 2