The city of Christchurch experienced a major earthquake centred south of the city; severe damage and casualties occurred.
| PublicID | 3468575 |
| UTC Time | 2011-02-21T23:51:42Z |
| Latitude | -43.58 (± 0.0 km) |
| Longitude | 172.68 (± 0.0 km) |
| Depth | 5 km (± 1 km) |
| Depth Type | free |
| Earth Model | nz1dr |
| Used Phase Count | 40 |
| Used Station Count | 36 |
| Standard Error | 0.26 (s) |
| Azimuthal Gap | 72.00 (degrees) |
| Minimum Distance | 0.02 (degrees) |
| Type | Magnitude | Station Count |
| Preferred (Mw) | 6.2 | |
| ML | 6.3 (± 0.3) | 114 |
| Mw | 6.2 | 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).
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.