The Swarm of shallow earthquakes occurring 10 km East of Seddon in Marlborough seems to have run its course. The swarm of 9 earthquakes, all 5 km deep, commenced on November 1st and the last event was reported by the Geonet site on November 11th. The earthquakes ranged between magnitude 3.2 and 4.8, with the largest two events (magnitudes 4.6 and 4.8) shaking goods off shelves in Blenheim.
The swarm occurred amidst a cluster of deeper earthquakes in the Picton, Blenheim and Seddon area that commenced on October 18th, bringing the total number of earthquakes reported in the area by Geonet to 17. Fifteen of the earthquakes were within a 20 km radius of Seddon, with only the October 18th event near Picton and the November 20th event which was offshore from Blenheim being further away.
A similar cluster of 10 earthquakes occurred in this area between May 25th and July 31st of 2003, but it lacked the tight swarm component that characterised this year’s sequence. The 2003 earthquakes ranged between magnitude 2.7 and 5.0 (4 were magnitude 4.1 or greater) and were located between 5 and 25 km deep. The epicentres on that occasion were all within 40 km of Seddon.
I see “they’re back”! Missed the one that was supposedly felt in Wellington.