Intraplate seismicity and stresses in young oceanic lithosphere

A systematic study has been conducted of oceanic intraplate seismicity in the 1964-1983 period occurring in lithosphere younger than 35 million years. Detailed findings are presented on the stress in young lithosphere, depth of seismicity, intraplate events in fracture zones, seismicity distributions, and regional concentrations of seismicity. It is concluded that there is no evidence of a general transition from tensional to compressive stresses at any particular age of the lithosphere. Extensional events are located mostly in the Indian Ocean and have tensional axes oriented at large angles to the spreading direction. Compressional axes of thrust faulting events show a weak preferred orientation parallel to the spreading direction. Normal faulting events occur at greater depths and temperatures than thrust faulting events. Differential thermal contraction along fracture zones is not a significant source of intraplate seismicity.