The New Zealand National Seismograph Network

Abstract

### Tectonic Settings & Seismicity in New Zealand New Zealand's active tectonics are dominated by the oblique convergence of the Pacific plate and the Australian plate, which produces earthquakes, volcanoes, active geological deformation, and steep terrain. The tectonic setting (Figure 1) makes New Zealand one of the most seismically active countries in the world with more than 15,000 earthquakes ( ML ≥ 2) located per year (http://www.geonet.org.nz/earthquake/). Shallow earthquakes (depth <40 km) cluster in a band that extends along the east coast of the North Island above the Hikurangi subduction zone, through the western South Island in proximity to the Alpine fault, to the southernmost tip of the South Island above the Puysegur subduction zone (Figure 2A). Another band of shallow seismicity maps the Taupo volcanic zone (TVZ), and the cluster beneath the western part of the central North Island is associated with the Cape Egmont fault zone and Egmont Volcano (Mount Taranaki). Figure 2B shows the deep seismicity (≥40 km) of New Zealand. The deep earthquakes beneath the North Island and the upper part of the South Island define the dipping Benioff zone within the subducting Pacific plate. In the Fiordland region the deep seismicity is associated with the subduction of the Australian plate beneath the Pacific plate. Detailed overviews of the seismicity of New Zealand can be found in Robinson (1986), Reyners (1989), Anderson and Webb (1994), and Eberhart-Phillips (1995). ### The GeoNet Project The New Zealand GeoNet is a strongly integrated data collection and analysis system consisting of national and regional-scale sensor networks. In 2001, GNS Science, a New Zealand government-owned research institute, received funding from the New Zealand Earthquake Commission (EQC), a New Zealand government mandated natural disasters insurer, to develop GeoNet as a non-profit “public good” initiative to enhance New Zealand's ability to respond to and prepare for natural hazards such as earthquakes, volcanic eruptions, tsunamis, …