Magnitude 5.4, Wed Aug 18 2021 5:24 AM


Download Event Information


Origin


PublicID 2021p618182
UTC Time 2021-08-17T17:24:49Z
Latitude -23.04 (± 0.0 km)
Longitude -177.04 (± 0.0 km)
Depth 157 km (± 0 km)
Depth Type free
Earth Model
Used Phase Count 0
Used Station Count 0
Standard Error 5.34 (s)
Azimuthal Gap 0.00 (degrees)
Minimum Distance 0.00 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (mB) 5.4 (± 0.2)  
mB 5.4 (± 0.2) 9

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


-21.0-19.0-17.0-15.0-13.0-11.0-9.0-7.0-5.0-3.0-1.01.03.05.07.09.011.013.015.017.019.021.0residual (s)024681012141618202224262830323436384042444648505254Distance (degrees)Pick Residuals

Station Magnitudes (mB)


0.01.02.03.04.05.06.07.0Magnitude79111315Distance (degrees)Station Magnitudes (mB)

Magnitude Residuals (mB)


-2.0-1.00.01.02.0Residual79111315Distance (degrees)Magnitude Residuals (mB)