Strong South Pacific Quakes Continue

After a day when an extraordinary series of strong earthquakes played back and forth on the tectonic plate boundary between Vanuatu and the Santa Cruz Islands, earthquake activity in the South Pacific continues apace.

Friday 9th October 2009

A magnitude 7.8 earthquake located 260 km south of Lata in the Santa Cruz Islands heralded the beginning of an extraordinary series of very strong, shallow earthquakes yesterday. The shallow earthquake (35 km deep), which struck at 11:03 a.m. yesterday morning New Zealand Daylight time was initially thought to be about magnitude 8 and triggered tsunami warnings for much of the South Pacific.

Just 15 minutes later a magnitude 7.7 earthquake struck 210 km south-south-east of Lata, again at 35 km depth.

At 14 minutes after midday, New Zealand time, another magnitude 7 quake struck the area. This quake, at magnitude 7.3, was located 275 km south of Lata at a depth of 33 km. Later in the afternoon, a magnitude 6.6 event occurred 110 km south-south-east of Lata also at a depth of 35 km.

Fifth magnitude aftershocks followed each of these events until mid-evening New Zealand time when another pair of strong quakes struck the area. A magnitude 6.8 earthquake struck 285 km south of Lata at 9:29 p.m. NZDT and a magnitude 6.5 event was recorded 185 km south-south-east of Lata at 9:35 p.m.

The earthquakes are occurring near the edge of what is known as the Fiji Microplates, a tongue-shaped outcrop of the Pacific Plate where the Australian Plate is sliding underneath creating a drawn-down area known as the North New Hebrides Trench. The activity has oscillated back and forth close to the plate boundary, sometimes striking close to the Santa Cruz Islands, sometimes striking within Vanuatu territory. Most of the quakes have been in the Fiji Microplate, except for the 9:29 p.m. event which was centred in the Australian Plate.

Meanwhile, a pair of 4th magnitude earthquakes struck Fiordland just before midnight. The quakes of magnitude 4.7 and 4.8 struck at 11:16 and 11:35 p.m. and were centred 80 km west of Te Anau at 7 or 8 km depth.

[Compiled from data provided by the U.S. Geological Survey and its contributing agencies; and the GeoNet project and its sponsors EQC, GNS Science and FRST.]

One Response to “Strong South Pacific Quakes Continue”

  1. Darren says:

    Op – the first quake up near the Solomon Trench (5.3 – 18km).
    It has been fascinating watching these events walk their way northwards!
    Sticking my neck out – I’m still expecting another biggie to the north of the first few major events.

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