Magnitude 4.9, Tue Apr 9 1974 7:49 PM


Download Event Information


Origin


PublicID 1555709
UTC Time 1974-04-09T07:49:46Z
Latitude -45.97 (± 0.0 km)
Longitude 170.52 (± 0.0 km)
Depth 12 km (± 0 km)
Depth Type operator assigned
Earth Model nz1d
Used Phase Count 15
Used Station Count 7
Standard Error 0.80 (s)
Azimuthal Gap 205.00 (degrees)
Minimum Distance 0.94 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (ML) 4.9 (± 0.2)  
ML 4.9 (± 0.2) 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


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

Station Magnitudes (ML)


0.01.02.03.04.05.06.0Magnitude0Distance (degrees)Station Magnitudes (ML)

Magnitude Residuals (ML)


-1.00.01.0Residual0Distance (degrees)Magnitude Residuals (ML)