Shallow seismicity in New Zealand 1956–75

Abstract

The pattern of 20 years of shallow seismic activity indicates that the boundary between the Pacific and Indian plates in the New Zealand region is characterised by Eiby's three major seismic regions. The Main Seismic Region overlies subducted Pacific Plate and covers much of the North Island and northern part of the South Island, but smaller groupings can be distinguished within it and a major break in seismicity may be associated with a serpentinite belt. The Central Region, through which the Alpine Fault passes and which represents the appressing of two continental regions is only mildly seismic, requiring the expectation of a large event or that the deformation is mainly aseismic. The Fiordland Region, which lies over a small sliver of subducted Indian Plate, is the most active seismic area of New Zealand, but epicentral intensities are remarkably low.