Magnitude 1.6, Thu Sep 16 2021 3:40 AM

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PublicID 2021p696358
UTC Time 2021-09-15T15:40:04Z
Latitude -40.67 (± 2.5 km)
Longitude 175.86 (± 2.7 km)
Depth 20 km (± 4 km)
Depth Type free
Earth Model iasp91
Used Phase Count 27
Used Station Count 16
Standard Error 0.40 (s)
Azimuthal Gap 77.13 (degrees)
Minimum Distance 0.11 (degrees)


Type Magnitude Station Count
Preferred (M) 1.6  
ML 1.5 (± 0.2) 13
MLv 1.6 (± 0.6) 5
M 1.6 5

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

-2.0- (s)0Distance (degrees)Pick Residuals

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

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

Magnitude Residuals (ML)

- (degrees)Magnitude Residuals (ML)

Magnitude Residuals (MLv)

-2.0- (degrees)Magnitude Residuals (MLv)