Earthquake focal mechanisms in the central Taupo Volcanic Zone and their relation to faulting and deformation

Abstract The New Zealand Taupo Volcanic Zone (TVZ) is an area with considerable crustal seismicity, but the shallowness of the seismicity has made it difficult to determine good focal mechanisms from the permanent seismic stations. Within the central TVZ, the only focal mechanisms previously available were composite ones derived from earthquake swarms. These mechanisms were dominantly strike‐slip, rather than the normal mechanisms that might be expected from the dominant southeast‐northwest extension seen from deformation measurements and geology. The 1987 ML 6.3 Edgecumbe earthquake near the northern end of the zone had a normal mechanism consistent with the deformation, as did some large earthquakes just offshore. We present focal mechanisms obtained from a 6 month (Jan‐Jun 1995) seismometer deployment consisting of 64 short‐period and 23 broadband seismometers together with the 15 permanent stations within the TVZ. This close‐spaced network enabled us to get focal mechanisms for a considerable number o...