GeoNet Equipment

Seismograph Stations

Far West (FWVZ) seismic station on Mount Ruapehu, part of the Tongariro National Park Volcanic Seismic Network. Mount Ngauruhoe is in the background above the clouds.

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.

Strong-Motion Instrumentation

Tsunami gauge at Lottin Point (LOTT), East Cape.

Over 250 strong-motion recorders monitor how structures perform in earthquakes. The network of strong-motion recorders uses or facilitates:

• Kinemetrics Etna 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.

Volcano Surveillance

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.

Tsunami Detection

In addition to seismometers capable of characterising tsunami-causing earthquakes, a network of 17 tsunami gauges (plus 2 will be Australian installations) was established in collaboration with Land Information New Zealand. These use:

The continuous GPS installation at Hicks Bay (HIKB).

• Quanterra Q330 24-bit data loggers;
• Druck pressure sensors.

Geodetic Monitoring

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.

Data Management Centres

The Data Management Centres perform round the clock operation of the monitoring system:

• The National and Regional network seismographs telemeter data continuously to two independent Data Management Centres (at Avalon and Wairakei), providing backup in the event of a large earthquake in Wellington or an eruption near Taupo;
• The telemetry uses both satellite (VSAT) and terrestrial broadband links, as well as high-speed ethernet radios, to provide robustness through diversity;
• Dell servers store the incoming data and forward detected earthquakes to the New Zealand version of the CUSP analysis system running on Compaq Alpha servers, thus providing real-time event data for auto-location and detailed analysis;
• The strong-motion data stream is fully integrated and analysed with the existing seismograph data;
• GPS data are telemetered on shared links where possible and are archived as Rinex files in the data centre.