The Tasman Sea earthquake of 25 November 1983 and stress in the Australian plate

The Tasman Sea earthquake of 25 November 1983 was large enough (M₀ ≈ 1.1× 10¹⁸ Nm) to be recorded world-wide and provide information on the state of intraplate stress in the lithosphere beneath the Tasman Sea. The earthquake occurred beneath the abyssal plain at a depth of about 25 km and was associated with almost pure dip-slip faulting. The direction of the pressure axis of the focal mechanism is similar (139 degrees E of N) to those observed from the nearby Australian mainland. Hence both the oceanic Tasman Sea and continental Australia appear to be part of the same stress regime. However, the direction of stress in this part of the Australian plate does not coincide with the north-south direction of motion of the plate and therefore forces other than the ridge push must be invoked to generate the stresses observed.