The Watchers - by Adonai - August 17, 2013
A swarm of strong and shallow earthquakes is shaking Cook Strait, New Zealand again. After M 6.5 that struck on July 21, 2013, and hundreds of aftershocks that followed, another severe, damaging and shallow earthquake M 6.6 hit on August 16, 2013 at 02:31 UTC. Damage has been reported on both sides of Cook Strait. The earthquake sequence is generating hundreds of aftershocks, although most of them are not felt.
Epicenter was located 29 km (18 miles) SSE of Blenheim and 80 km (50 miles) SW of Wellington, New Zealand. There are about 427 156 people living within 100 km radius.
USGS measured depth at 10 km, EMSC at 2 km and GEONET at 8 km.
GEONET explains "The focal mechanism shows it to be a strike-slip earthquake, similar to the M6.5 earthquake in July. We have now had two similarly-sized earthquakes with the same sort of characteristics - they are termed a "doublet". This is not what we would usually expect."
Strike-slip faults are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally. If the block opposite an observer looking across the fault moves to the right, the slip style is termed right lateral; if the block moves to the left, the motion is termed left lateral.
