Seismographs are used to measure accurately the magnitude, location and other characteristics of earthquakes. The New Zealand National Seismograph Network is made up of 51 backbone stations located throughout the country and offshore islands to provide a uniform location and data collection capability. The sites consists of:
- Guralp CMG3-ESP or Streckeisen STS-2 broadband seismometers;
- Kinemetrics Episensor strong-motion accelerometers;
- Quanterra Q330 24-bit data loggers;
- High-speed data connections using standard internet protocols (TCP/IP) to the data centres.
Regional seismograph networks provide enhanced volcano monitoring and improved depth control for subduction-related earthquakes along the Hikurangi margin. They use predominantly short-period seismometers, remote digitisers and spread-spectrum radio links to backbone stations or directly to the data centres.
Over 250 strong-motion recorders monitor how structures perform in earthquakes. The network of strong-motion recorders uses or facilitates:
- Kinemetrics Etna and Basalt/Obsidian, and CSI CUSP instrumentation for:
- free-field sites,
- near fault monitoring of major active faults, including the Alpine fault,
- urban and microzone monitoring;
- Structural arrays using CSI CUSP-M recorders triggered from a central point;
- Near real-time data links using cell phone or internet telemetry.
Seismic, geochemical, GPS survey and remote sensing techniques are used for early detection and monitoring of volcanic unrest. This is achieved through:
- Volcano seismic networks at selected volcanic centres in the North Island;
- A fluid and gas analytical laboratory and portable instruments for baseline monitoring and remote sensing (including InSAR);
- Digital cameras at major volcanic centres to provide a record of activity.
The Global Positioning System (GPS) network is used to pinpoint where strain is building up or being released in the earth's crust. There are:
- 36 nation-wide continuous GPS stations (also in collaboration with Land Information New Zealand) using Trimble NetR9 receivers;
- A densely-spaced GPS network along the east coast from East Cape to Marlborough, some co-located with the complementary regional seismograph network;
- An intensified GPS network in volcanic centres and 2 tiltmeters deployed around Ruapehu Volcano.