Magnitude 1.8, Mon Dec 21 2020 11:33 AM


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Origin


PublicID 2020p959297
UTC Time 2020-12-20T22:33:36Z
Latitude -37.87 (± 16.9 km)
Longitude 176.22 (± 10.3 km)
Depth 121 km (± 17 km)
Depth Type free
Earth Model iasp91
Used Phase Count 13
Used Station Count 8
Standard Error 0.38 (s)
Azimuthal Gap 256.72 (degrees)
Minimum Distance 0.75 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (M) 1.8  
MLv 1.8 (± 0.1) 4
M 1.8 4

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)012Distance (degrees)Pick Residuals

Station Magnitudes (MLv)


0.01.02.0Magnitude1Distance (degrees)Station Magnitudes (MLv)

Magnitude Residuals (MLv)


-1.00.01.0Residual1Distance (degrees)Magnitude Residuals (MLv)