Magnitude 4.0, Fri Jul 28 2023 6:17 AM


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Origin


PublicID 2023p561523
UTC Time 2023-07-27T18:17:45Z
Latitude -27.87 (± 19.4 km)
Longitude -178.79 (± 64.9 km)
Depth 500 km (± 0 km)
Depth Type operator assigned
Earth Model iasp91
Used Phase Count 11
Used Station Count 8
Standard Error 0.70 (s)
Azimuthal Gap 345.11 (degrees)
Minimum Distance 10.27 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (Mw(mB)) 4.0 (± 0.4)  
mB 4.8 (± 0.1) 3
Mw(mB) 4.0 (± 0.4) 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


-4.0-3.0-2.0-1.00.01.02.03.04.0residual (s)024681012Distance (degrees)Pick Residuals

Station Magnitudes (mB)


0.01.02.03.04.05.0Magnitude11Distance (degrees)Station Magnitudes (mB)

Magnitude Residuals (mB)


-1.00.01.0Residual11Distance (degrees)Magnitude Residuals (mB)