Moderate Ml 5.8 Earthquake Strikes North Island, New Zealand
A local magnitude 5.8 (GNS, New Zealand; moment magnitude 5.4 - GFZ, Germany) earthquake has struck the North Island of New Zealand, about 10 kilometres east of the small village of Pongaroa. The earthquake was the result of a shallow-dip reverse fault.
This earthquake was preceded by several foreshocks, the largest of which was a M3.8 six hours prior to the mainshock. A smattering of aftershocks have followed this moderate-size earthquake, the largest 74 minutes after the mainshock with a magnitude of 4.1.
The earthquake was felt across most of the lower and central North Island, gaining at least 4990 felt reports (likely to exceed 5000 soon). The M4.1 aftershock has gained only 50 felt reports.
It is my expectation that the M4.1 aftershock may only be exceeded by one or two earthquakes hereafter; the maximum is a M4.6, but my preferential forecast is for an aftershock to reach ~M4.3 at maximum. This would agree with Bath's Law for mainshock-aftershock relationship.
This earthquake (or more strictly true, an earthquake of similar magnitude in New Zealand) was anticipated by myself, but only on the basis of a comparative lack of such events in the past 4-6 months. The chances of this Pongaroa earthquake being a foreshock are small, but not impossible; if any further large earthquakes are to follow, it would be in a swarm-like manner, much like the Weber Earthquakes of 1990-1992.
Addendum: Whilst writing, a M4.4 aftershock struck, fulfilling my prediction:
For more information:
http://geonet.org.nz/quakes/region/newzealand/2015p768477
http://geonet.org.nz/quakes/region/newzealand/2015p768477
 |
| Moment Tensor Solution for the Pongaroa Ml 5.8 Earthquake, as given by the GEOFON Program, GFZ Potsdam, Germany. It shows shallow-dip reverse faulting, corresponding well with the tectonic regime of the eastern North Island.Written by J H Gurney, 11:03 BST (23:03 NZDT), 12th October 2015. |
