Magnitude 3.9, Mon Sep 18 2023 4:23 AM

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PublicID 2023p701845
UTC Time 2023-09-17T16:23:23Z
Latitude -36.53 (± 9.1 km)
Longitude 177.47 (± 9.4 km)
Depth 227 km (± 11 km)
Depth Type free
Earth Model iasp91
Used Phase Count 29
Used Station Count 22
Standard Error 0.47 (s)
Azimuthal Gap 216.37 (degrees)
Minimum Distance 1.23 (degrees)


Type Magnitude Station Count
Preferred (MLv) 3.9 (± 0.4)  
ML 3.2 (± 0.4) 13
MLv 3.9 (± 0.4) 31

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

-7.0-5.0-3.0- (s)0246810Distance (degrees)Pick Residuals

Station Magnitudes (ML) (degrees)Station Magnitudes (ML)

Station Magnitudes (MLv) (degrees)Station Magnitudes (MLv)

Magnitude Residuals (ML)

-2.0- (degrees)Magnitude Residuals (ML)

Magnitude Residuals (MLv)

-2.0- (degrees)Magnitude Residuals (MLv)