A magnitude 6.7 earthquake struck at 8:55 pm on Thursday 20 December. Located offshore, it caused damage to chimneys and buildings at several places along the East Coast, particularly in the Gisborne CBD.
| PublicID | 2839343 |
| UTC Time | 2007-12-20T07:55:16Z |
| Latitude | -38.89 (± 0.0 km) |
| Longitude | 178.54 (± 0.0 km) |
| Depth | 33 km (± 0 km) |
| Depth Type | operator assigned |
| Earth Model | nz1dr |
| Used Phase Count | 48 |
| Used Station Count | 43 |
| Standard Error | 0.21 (s) |
| Azimuthal Gap | 236.00 (degrees) |
| Minimum Distance | 0.46 (degrees) |
| Type | Magnitude | Station Count |
| Preferred (Mw) | 6.7 | |
| ML | 6.7 (± 0.2) | 74 |
| Mw | 6.7 | 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.