Magnitude 2.3, Wed Apr 19 2023 7:48 AM


Download Event Information


Origin


PublicID 2023p291420
UTC Time 2023-04-18T19:48:45Z
Latitude -37.78 (± 21.2 km)
Longitude 176.72 (± 37.2 km)
Depth 138 km (± 21 km)
Depth Type free
Earth Model iasp91
Used Phase Count 10
Used Station Count 8
Standard Error 0.50 (s)
Azimuthal Gap 238.53 (degrees)
Minimum Distance 0.57 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (M) 2.3  
MLv 2.3 (± 0.4) 4
M 2.3 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


-2.0-1.00.01.02.0residual (s)012Distance (degrees)Pick Residuals

Station Magnitudes (MLv)


0.01.02.03.0Magnitude1Distance (degrees)Station Magnitudes (MLv)

Magnitude Residuals (MLv)


-1.00.01.0Residual1Distance (degrees)Magnitude Residuals (MLv)