M7.8 Dusky Sound Wed, Jul 15 2009

The earthquake which struck the Fiordland region in the evening of Wednesday 15 July was the biggest since the Buller and Hawke's Bay earthquakes of 1929 and 1931.

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PublicID 3124785
UTC Time 2009-07-15T09:22:29Z
Latitude -45.77 (± 0.0 km)
Longitude 166.59 (± 0.0 km)
Depth 12 km (± 0 km)
Depth Type operator assigned
Earth Model nz1dr
Used Phase Count 19
Used Station Count 17
Standard Error 0.16 (s)
Azimuthal Gap 230.00 (degrees)
Minimum Distance 0.40 (degrees)


Type Magnitude Station Count
Preferred (Mw) 7.8  
Mw 7.8 0

GeoNet combines magnitudes into a summary magnitude, M, which consists of a weighted average of the individual magnitudes and attempts to be a best possible compromise between all magnitudes for a range of earthquake sizes. Summary magnitude for GeoNet is then defined as:

M = (2 * MLv + (0.4 * number_of stations(Mw(mB)) - 1) * Mw(mB)) / (2 + (0.4 * number_of_stations(Mw(mB)) - 1))

Where MLv is local magnitude calculated on the vertical component and Mw(mB) is a Mw estimation based of mB by Bormann and Saul (2008).

Origin Map

Map of New Zealand.

Map showing stations with picks used to locate the earthquake. Stations with picks that have a zero weight in the solution are shown as small grey circles. Those with a higher weight are shown as larger circles. The quake is shown by the largest circle.

Pick Residuals

-2.0- (s)0123456789Distance (degrees)Pick Residuals