Magnitude 4.6, Wed Jan 20 2021 6:17 PM


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Origin


PublicID 2021p051951
UTC Time 2021-01-20T05:17:53Z
Latitude -29.10 (± 31.1 km)
Longitude 179.95 (± 93.7 km)
Depth 238 km (± 77 km)
Depth Type free
Earth Model iasp91
Used Phase Count 13
Used Station Count 8
Standard Error 0.92 (s)
Azimuthal Gap 261.40 (degrees)
Minimum Distance 1.87 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (mB) 4.6 (± 0.3)  
mB 4.6 (± 0.3) 3
Mw(mB) 3.8 (± 0.4) 3
M 3.8 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


-3.0-2.0-1.00.01.02.03.0residual (s)0246810Distance (degrees)Pick Residuals

Station Magnitudes (mB)


0.01.02.03.04.05.0Magnitude10Distance (degrees)Station Magnitudes (mB)

Magnitude Residuals (mB)


-1.00.01.0Residual10Distance (degrees)Magnitude Residuals (mB)