Shear deformation zones along major transform faults and subducting slabs

Narrow zones of intense shear deformation, i.e. viscous slip zones, are studied analytically with a one-dimensional time-dependent model of two half-spaces of identical or contrasting rheologies and ambient temperatures in relative motion. The rheologies of the half-spaces are strongly temperaturedependent and viscous heating maintains a thin zone of high temperature, low viscosity and large strain rate. The mathematical model is used to describe the structures of slip zones at ridge and plate-boundary transform faults, major continental strike-slip faults and at the top of subducting oceanic crust.