Magnitude 4.4, Fri Sep 3 2021 10:18 AM


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Origin


PublicID 2021p661975
UTC Time 2021-09-02T22:18:35Z
Latitude -31.35 (± 10.9 km)
Longitude 177.59 (± 41.7 km)
Depth 33 km (± 0 km)
Depth Type operator assigned
Earth Model iasp91
Used Phase Count 10
Used Station Count 8
Standard Error 1.08 (s)
Azimuthal Gap 343.32 (degrees)
Minimum Distance 6.39 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (mB) 4.4 (± 0.3)  
mB 4.4 (± 0.3) 3
ML 4.3 (± 0.2) 5
Mw(mB) 3.5 (± 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)0246810Distance (degrees)Pick Residuals

Station Magnitudes (mB)


0.01.02.03.04.05.0MagnitudeDistance (degrees)Station Magnitudes (mB)

Station Magnitudes (ML)


0.01.02.03.04.05.0Magnitude7Distance (degrees)Station Magnitudes (ML)

Magnitude Residuals (mB)


-1.00.01.0ResidualDistance (degrees)Magnitude Residuals (mB)

Magnitude Residuals (ML)


-1.00.01.0Residual7Distance (degrees)Magnitude Residuals (ML)