Magnitude 2.4, Sat Sep 18 2021 1:28 AM


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Origin


PublicID 2021p701517
UTC Time 2021-09-17T13:28:31Z
Latitude -36.10 (± 40.6 km)
Longitude 178.11 (± 30.9 km)
Depth 200 km (± 41 km)
Depth Type free
Earth Model iasp91
Used Phase Count 13
Used Station Count 7
Standard Error 0.24 (s)
Azimuthal Gap 328.07 (degrees)
Minimum Distance 1.67 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (MLv) 2.4 (± 0.5)  
MLv 2.4 (± 0.5) 3
ML 2.7 (± 0.3) 7
M 2.4 3

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


-2.0-1.00.01.02.0residual (s)01234Distance (degrees)Pick Residuals

Station Magnitudes (MLv)


0.01.02.03.0Magnitude2Distance (degrees)Station Magnitudes (MLv)

Station Magnitudes (ML)


0.01.02.03.04.0Magnitude2Distance (degrees)Station Magnitudes (ML)

Magnitude Residuals (MLv)


-1.00.01.0Residual2Distance (degrees)Magnitude Residuals (MLv)

Magnitude Residuals (ML)


-1.00.01.0Residual2Distance (degrees)Magnitude Residuals (ML)