Magnitude 3.9, Thu Apr 20 2017 3:07 PM


Download Event Information


Origin


PublicID 2017p294948
UTC Time 2017-04-20T03:07:35Z
Latitude -35.40 (± 35.4 km)
Longitude 174.05 (± 36.5 km)
Depth 0 km (± 0 km)
Depth Type free
Earth Model iasp91
Used Phase Count 10
Used Station Count 9
Standard Error 1.40 (s)
Azimuthal Gap 342.14 (degrees)
Minimum Distance 3.76 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (M) 3.9  
ML 3.8 (± 0.2) 7
MLv 3.9 (± 0.1) 6
M 3.9 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


-13.0-11.0-9.0-7.0-5.0-3.0-1.01.03.05.07.09.011.013.0residual (s)01234Distance (degrees)Pick Residuals

Station Magnitudes (ML)


0.01.02.03.04.05.0Magnitude4Distance (degrees)Station Magnitudes (ML)

Station Magnitudes (MLv)


0.01.02.03.04.05.0Magnitude4Distance (degrees)Station Magnitudes (MLv)

Magnitude Residuals (ML)


-1.00.01.0Residual4Distance (degrees)Magnitude Residuals (ML)

Magnitude Residuals (MLv)


-1.00.01.0Residual4Distance (degrees)Magnitude Residuals (MLv)