On Wednesday, 17 October 2007, seismologists recorded a large tremor measuring 6.7 on the Richter scale at 1.29am in the morning. The epicenter was 60km west of Milford Sound, at a depth of 24km. There has been scarcely any damage that's been reported following this quake but the residents from the lower North Island felt the movement too along with shaking that was felt widely across the immediate Southland area. Our scientists are planning an in depth study of the after shocks.
Photo: Fiordland Travel
This is the biggest quake in New Zealand since August 2003. The last quake measured 7.2 and hit Secretary Island, which is located off the Fiordland coast. GNS Scientists have moved quickly this time to install portable equipment that will better record the aftershocks. So far, they have recorded aftershocks with a magnitude of 6.2, this immediately followed the main tremor.
In 2003, as many as 5000 aftershocks had been recorded over several months. These aftershocks happen because the Earth's crust is adjusting to stresses caused by the main shock and Mr Field stated that, “No two aftershock stresses are the same.”
This information is crucial and critical in the study of the seismologist's field of expertise. It allows them to ascertain the size and orientation of the “fault-break” in the earths crust, helping to indicate if the main shock had any effects on faults nearby and if it could possibly have more effects on us.
The battery-powered seismometers could pinpoint the size, depth, and location of the aftershocks with greater accuracy than before. Bryan Field said that the sequences of these aftershocks should yield some useful information.
