Another Matata Earthquake Swarm

Earthquake activity near Matata in the Bay of Plenty has reactivated overnight.

A dozen second and third magnitude earthquakes have been recorded off the coast near Matata since ten o’clock on Tuesday morning. Activity began in earnest just after 8 o’clock last night when the second quake was recorded.

GeoNet has published details for the four largest events, a magnitude 3.7 quake at 9:10 p.m. on Tuesday the 2nd of September 2008, a magnitude 3.6 quake at 10:12 p.m., a magnitude 3.2 quake at 00:51 this morning (Wednesday), and a magnitude 3.7 quake at 9:43 a.m. All of these quakes were located 10 km off-shore from Matata at depths between 1 and 7 km.

An examination of GeoNet’s database shows six quakes of magnitude 2 and six of magnitude 3 in a small area off-shore from Matata in just over 24 hours.

The activity appears to be a new earthquake swarm event. The last swarm, which began in December 2006, included earthquakes on-shore and off-shore near Matata. That swarm steadily increased until March 2007 when GeoNet reported 30 events near Matata, with 23 occurring during April and 18 during May. Activity declined to 15 events in June 2007 before virtually ceasing.

An abrupt increase in activity during September 2007 included four quakes of 4th magnitude, and GeoNet reported on 11 quakes of 3rd magnitude. Activity again declined during October and, after a relatively quiet spell during November, activity increased during December 2007. Of the 13 quakes reported felt that month, ten were magnitude 3 and two were magnitude 4. The biggest events were magnitude 4.1 quakes on December 14th and 19th.

Activity increased slightly during January 2008, with 17 quakes being reported felt. Thirteen were magnitude 3 and one was magnitude 4. The magnitude 4.3 quake on January 25th was somewhat disconcerting for many locals who felt two earthquakes in short succession, with a magnitude 3.4 quake striking 50 seconds later. Activity continued into February with quakes of magnitude 4.1 and 3.2 being felt 6 minutes apart early on the morning of Sunday the 3rd but activity again declined to 8 events in February and 5 or fewer events have been recorded each month through to August.

During 2005, three distinct swarms of earthquakes struck Matata between the 12th of February and 25th of August. Some of the 55 earthquakes plagued the town at the same time as a flash flood which caused considerable damage to the settlement.

In 2004, a swarm of 4 earthquakes struck the area on May 2nd.

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

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