Offshore Quakes Near Seddon

Four earthquakes have been reported near Seddon in the upper South Island during June 2008.

The first event was a magnitude 3.4 earthquake which struck at 2:47 p.m. on the afternoon of Friday June 20th. The quake was located 40 km south-east of Seddon at a depth of 30 km.

Two more quakes were recorded on Wednesday 25th, the first being a magnitude 3.3 event at a depth of 3 km located 10 km east of Seddon at 7:53 a.m. The event was felt in Seddon and Ward and some Wellington suburbs. That night a magnitude 3.6 quake, 15 km deep, struck 20 km east of Seddon at 9:56 p.m. This event was felt at Seddon, Ward and Blenheim.

On the afternoon of Sunday June 29th a magnitude 3.3 quake struck 30 km east of Seddon at a depth of 50 km. The 1:43 p.m. quake struck while a southerly storm was battering the area, and only 2 felt reports have been filed.

In 2003 a series of ten earthquakes with magnitudes between 2.7 and 5.0 was reported near Seddon. The quakes, which struck between May 25th and July 31st ranged in depth between 5 and 25 km, with the epicentres within 40 km of Seddon.

A more tightly located swarm of quakes struck the area during November of 2005, when 9 earthquakes located 10 km east of Seddon were reported. The quakes ranged between magnitude 3.2 and 4.8 and were felt in conjunction with another 7 events nearby, the largest of which was also magnitude 4.8. Most of the quakes were only 5 km deep, the deepest of the series occurring at 40 km.

Most of the activity occurred over a period of three days between the 1st and 3rd and seemed to have run its course by November 20th. However, a magnitude 4.2 quake on the 29th was followed by another 3 events located 10 km east of Seddon on December 18th and 19th. These quakes of magnitude 3.6 to 3.9 signalled the end of the swarm as 2005 drew to a close..

In 2007, another swarm of 5 quakes with magnitudes between 3.8 and 4.1 occurred between June 3rd and 24th. All of the events were within 10 km of Seddon at varying depths of 10 to 40 km.

[Compiled from data provided by the GeoNet project and its sponsors EQC, GNS Science and FRST.]

Leave a Reply