GeoNet's rapid response seismic team responds
At 4:35am on September the 4th 2010, a 7.1 magnitude quake hits the Canterbury region. It's the most damaging since the Hawkes Bay earthquake in 1931. By 7am plans are already well underway for a crew from GeoNet's Lower Hutt base to head down to Christchurch and deploy their seismic equipment.
4:35am: Saturday 4th September
A 7.1 magnitude quake hits the Canterbury region. Its the most damaging earthquake since the Hawkes Bay quake in 1931.
7:00am: Saturday 4th September
Staff are woken up and asked to come into work to prepare to deploy seismic equipment in Canterbury.
7:30am: Saturday 4th September
Arrived at work and helped organising two utes for a team of four to drive down to Christchurch. Included were 10 seismographs and 3 accelerometers, 750kg of batteries, and containers of diesel for the vehicles in case there was a fuel shortage. Spent the day in discussion with seismologists deciding where the instruments should be placed.
6:30pm: Saturday 4th September
Catch the ferry to Picton.
12:00am: Sunday 5th September
Arrive at our accommodation in Kaikoura.
The plan:
Install the instruments ASAP to record the aftershock sequence. We have two different types of instruments. The seismographs record data continuously and can record earthquakes smaller than are able to be felt. These instruments are to be evenly distributed around the zone of aftershocks, and placed in 0.5m holes on a paving slab cemented to the ground. The accelerometers can record strong ground shaking, and they are triggered to record data when there is sufficient shaking - around the level of a felt earthquake. These instruments are to be placed on or near the fault rupture, and need to be installed on a concrete slab, such as in a garage or shed.
6:30am: Sunday 5th and Monday 6th September
We are on the road again at 6:30am, and by nightfall have installed 9 seismographs and 1 accelerometer. All the instruments are installed by 1pm on Monday and will likely be left out for around 1 month to record the aftershocks.
6:30am: Tuesday 7th September
We are on the ferry at 6:30am and heading back to work at Avalon Lower Hutt.
Andrew Cowie installing an accelerometer in a shed east of Rolleston. The fault has come through the middle of the shed, cracking the concrete. Image by Nora Gale.
The installed seismograph sensor, which is placed on top of a paving slab cemented to the ground at the bottom of the hole. The sensor has been orientated to true north and levelled. Image by Andrew Cowie.
Nora Gale installing the seismograph at station LNSD south of Lincoln. Image by Andrew Cowie.
Seismograph display showing status (top half) and sensor traces (bottom half) - the large spikes on the right of the sensor traces are from someone jumping, our test to check that the sensor is recording. Image by Caroline Ashenden.
Daniel Whitaker installing the seismograph station ESND south of Darfield. Image by Caroline Ashenden.
The installed seismograph CARD east of Sheffield, with an electric fence for protection from animals. Image by Caroline Ashenden.