Magnitude 4.0, Fri Dec 10 2021 2:17 PM


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Origin


PublicID 2021p927174
UTC Time 2021-12-10T01:17:37Z
Latitude -32.47 (± 38.3 km)
Longitude 178.87 (± 64.0 km)
Depth 306 km (± 76 km)
Depth Type free
Earth Model iasp91
Used Phase Count 10
Used Station Count 7
Standard Error 0.71 (s)
Azimuthal Gap 349.51 (degrees)
Minimum Distance 5.35 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (mB) 4.0 (± 0.3)  
mB 4.0 (± 0.3) 2

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


-5.0-3.0-1.01.03.05.0residual (s)01234567Distance (degrees)Pick Residuals

Station Magnitudes (mB)


0.01.02.03.04.05.0Magnitude6Distance (degrees)Station Magnitudes (mB)

Magnitude Residuals (mB)


-1.00.01.0Residual6Distance (degrees)Magnitude Residuals (mB)