Magnitude 2.5, Mon Nov 20 2017 7:31 PM



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Origin


PublicID 2017p873707
UTC Time 2017-11-20T06:31:16Z
Latitude -41.71 (± 3.0 km)
Longitude 174.12 (± 3.5 km)
Depth 6 km (± 5 km)
Depth Type free
Earth Model iasp91
Used Phase Count 16
Used Station Count 12
Standard Error 0.34 (s)
Azimuthal Gap 81.00 (degrees)
Minimum Distance 0.08 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (M) 2.5  
MLv 2.5 (± 0.3) 6
ML 2.7 (± 0.2) 9
M 2.5 6

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)01Distance (degrees)Pick Residuals

Station Magnitudes (MLv)


0.01.02.03.04.0Magnitude0Distance (degrees)Station Magnitudes (MLv)

Station Magnitudes (ML)


0.01.02.03.04.0Magnitude0Distance (degrees)Station Magnitudes (ML)

Magnitude Residuals (MLv)


-1.00.01.0Residual0Distance (degrees)Magnitude Residuals (MLv)

Magnitude Residuals (ML)


-1.00.01.0Residual0Distance (degrees)Magnitude Residuals (ML)