M 6.9 Gisborne, Sat May 17 1947

There were two severe earthquakes off the coast of Gisborne in March and May 1947, each generating large tsunamis in the surrounding area.



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Origin


PublicID 1543047
UTC Time 1947-05-17T07:06:23Z
Latitude -38.42 (± 0.0 km)
Longitude 178.87 (± 0.0 km)
Depth 12 km (± 0 km)
Depth Type operator assigned
Earth Model nz1dr
Used Phase Count 5
Used Station Count 4
Standard Error 0.17 (s)
Azimuthal Gap 309.00 (degrees)
Minimum Distance 1.40 (degrees)

Magnitudes


Type Magnitude Station Count
Preferred (Mw) 6.9  
ML 5.6 (± 0.1) 4
Mw 6.9 0
MS 7.2 0

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


-1.00.01.0residual (s)01234Distance (degrees)Pick Residuals