Oct 10 2009 - Wellington earthquake

Focal mechanism for the earthquake in Wellington.

The quake's epicentre was 40 km deep and was felt from the middle of the North island to the top of the South Island, with the GeoNet website receiving 2,338 felt reports to date.

The earthquake was located within the top part of the subducted Pacific plate. The interface between the subducted Pacific plate and overlying Australian plate lies at 30 km depth in this region. The earthquake was caused by bending of the Pacific plate as it subducts. The reason why such a relatively small magnitude earthquake was felt widely in the southern North Island and Marlborough is that the rocks in both the subducted Pacific plate and overlying Australian plate are very competent (strong) in this region. This means that seismic waves from the earthquake to the surface travel very efficiently, with little loss of energy.

The earthquake was a normal faulting mechanism located within the Pacific plate as it pushes (subducts) beneath the Australian plate beneath the North Island and is a typical mechanism for earthquakes like these. It is a similar type of earthquake as the one which occurred in Cook Strait in late August.