TEMPERATURES, HEAT-FLUX, AND FRICTIONAL STRESS NEAR MAJOR THRUST FAULTS

The two-dimensional advective and conductive transport of heat in a region of thrust faulting was examined. Both simple theoretical considerations and numerical experiments show that the steady state temperatures near the fault are reduced by a divisor, below what they would be with the same heat sources but in the absence of advection. An equation is given for initial changes in temperature near the fault. Two time constants govern the transition from the initial change in temperature to steady state. An application of the formulae to measurements of conductive heat flow at island arcs implies that shear stresses approach 100 MPa and are greater than 30 MPa. Calculations of temperatures appropriate for the Himalaya suggest that shear stresses of 100 MPa on the Main Central Thrust probably are required to account for the Tertiary granites of the region, if melting took place after slip began on the thrust. Similarly, the cut-off in seismicity at a depth of about 15 km in the Himalaya, if due to temperatures exceeding 350° to 450°C, implies a deviatoric stress close to 100 MPa. -after Authors