Magnitude 4.0, Sun Aug 15 2021 9:46 AM


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Origin


PublicID 2021p610562
UTC Time 2021-08-14T21:46:39Z
Latitude -32.59 (± 41.7 km)
Longitude 178.77 (± 101.2 km)
Depth 412 km (± 90 km)
Depth Type free
Earth Model iasp91
Used Phase Count 7
Used Station Count 6
Standard Error 0.61 (s)
Azimuthal Gap 350.10 (degrees)
Minimum Distance 5.22 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (mB) 4.0  
mB 4.0 1

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


-3.0-2.0-1.00.01.02.03.0residual (s)01234567Distance (degrees)Pick Residuals

Station Magnitudes (mB)


0.01.02.03.04.05.0MagnitudeDistance (degrees)Station Magnitudes (mB)

Magnitude Residuals (mB)


-1.00.01.0ResidualDistance (degrees)Magnitude Residuals (mB)