Magnitude 3.9, Mon Aug 21 2023 12:50 AM


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Origin


PublicID 2023p625772
UTC Time 2023-08-20T12:50:53Z
Latitude -32.73 (± 44.1 km)
Longitude -179.21 (± 34.1 km)
Depth 222 km (± 119 km)
Depth Type free
Earth Model iasp91
Used Phase Count 11
Used Station Count 8
Standard Error 1.00 (s)
Azimuthal Gap 335.42 (degrees)
Minimum Distance 5.59 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (Mw(mB)) 3.9 (± 0.4)  
mB 4.7 (± 0.4) 4
ML 4.2 (± 0.0) 2
Mw(mB) 3.9 (± 0.4) 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).

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


-8.0-6.0-4.0-2.00.02.04.06.08.0residual (s)024681012Distance (degrees)Pick Residuals

Station Magnitudes (mB)


0.01.02.03.04.05.06.0Magnitude78Distance (degrees)Station Magnitudes (mB)

Station Magnitudes (ML)


0.01.02.03.04.05.0Magnitude6Distance (degrees)Station Magnitudes (ML)

Magnitude Residuals (mB)


-1.00.01.0Residual78Distance (degrees)Magnitude Residuals (mB)

Magnitude Residuals (ML)


-1.00.01.0Residual6Distance (degrees)Magnitude Residuals (ML)