At 8:28 a.m., on Friday 5 March 2021 NZDT, a magnitude 8.1 earthquake struck the Kermadec Islands, 1025 km north-east of Whangarei.
| PublicID | 2021p169764 |
| UTC Time | 2021-03-04T19:28:32Z |
| Latitude | -29.73 (± 0.0 km) |
| Longitude | -177.28 (± 0.0 km) |
| Depth | 26 km (± 0 km) |
| Depth Type | free |
| Earth Model | |
| Used Phase Count | 0 |
| Used Station Count | 0 |
| Standard Error | 7.99 (s) |
| Azimuthal Gap | 0.00 (degrees) |
| Minimum Distance | 0.00 (degrees) |
| Type | Magnitude | Station Count |
| Preferred (Mw(mB)) | 8.1 (± 0.4) | |
| Mw(mB) | 8.1 (± 0.4) | 5 |
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.