Thermal model of oceanic transform faults

A thennal model of the oceanic transform fault which includes effects of the lateral heat conduction across the fault and the shear heating along the fault has been developed. The results show that shear heating along the transform fault significantly raises the temperature along the fault. The depths to isotherms of the thermal model were compared to the depths of earthquakes along transform faults. By including the shear heating, the limiting isotherm of the focal depths of Atlantic transform earthquakes is 700°C (600°C if not including the shear heating), which is close to the limiting temperature of the intraplate oceanic earthquakes. If the transform earthquakes are limited by the 750°C isotherm, then the transform earthquakes should be shallow events as predicted by our thermal model. The model predicts the maximum depth of the 750°C isotherm increases with the length of the transform fault and decreases with the half-slip rate. Both the effects of the lateral heat conduction across the transform fault and the shear heating along the fault generate topographic and geoid anomalies in a 30 to 60-km-wide zone at the fault with magnitudes of the order of a few hundred meters and tens of centimeters, respectively. Given the thermal structure of the transform fault, the shear traction along the fault can be estimated. The average shear traction per unit length of the transform fault is of the order of 1012 N/m which is comparable to the magnitude of the major plate-driving forces.