The coupled problem of stress and temperature adjacent to a strike slip fault is solved for a steady state model. The fault is divided into two parts: an upper brittle zone and a lower plastic zone. A coefficient of friction is assumed to be applicable to the brittle zone, and motion on the plastic zone is assumed to take place by thermally activated creep. The transition from brittle to plastic behavior is assumed to occur at a depth where the shear stresses in the two zones are equal. The vertical distribition of stress and temperature on the fault and the surface heat flow are obtained for several values of the coefficient of friction. For a low value of the effective friction coefficient, near 0.15, the depth of the brittle zone is near 15 km, which is about the depth of the deepest earthquakes on the San Andreas fault; however, the predicted heat flow anomaly immediately adjacent to the fault exceeded the scatter in the measured values. Alternative explanations for this discrepancy are given.