ON THE RELATION BETWEEN TRANSFORM-FAULT RESISTANCE AND PLATE MOTION

A simple model for power dissipation due to friction along transform faults is used to examine the relations between relative velocity and power dissipation across transforms, transform lengths, and plate motions. Comparison is made between ridge transforms, i.e., those that are part of spreading systems, and major boundary transforms, such as the San Andreas fault. Power dissipation is calculated using velocity across the transform area above the 400-degrees-C (oceanic) or 350-degrees-C (continental) isotherm. Transform thermal structure is modeled by averaging the temperatures on either side of the transform. Whereas ridge transforms across which the relative plate velocity is slow can be of any length, fast relative velocities only appear across short transforms. When all transforms are used in this comparison, a maximum speed, as a function of transform length, is suggested. A minimum speed of approximately 13.5 mm/yr across ridge transforms was found. In a case study of the Pacific plate, the transform lengths were found to have varied with time which has minimized the total power dissipation across the plate's transforms.