M 7.2 Darfield (Canterbury) Sat, Sep 4 2010

The Darfield earthquake caused severe building damage in mid-Canterbury, particularly to the city of Christchurch. It revealed the existence of a hidden west-east fault under the gravels of the Canterbury Plains.

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PublicID 3366146
UTC Time 2010-09-03T16:35:41Z
Latitude -43.53 (± 0.0 km)
Longitude 172.17 (± 0.0 km)
Depth 11 km (± 1 km)
Depth Type free
Earth Model nz1dr
Used Phase Count 21
Used Station Count 16
Standard Error 0.14 (s)
Azimuthal Gap 82.00 (degrees)
Minimum Distance 0.06 (degrees)


Type Magnitude Station Count
Preferred (Mw) 7.2  
ML 7.1 0
Mw 7.2 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

- (s)0Distance (degrees)Pick Residuals