Major Earthquake, Solomon Islands

A major earthquake struck the Solomon Islands at 8:40 this morning, New Zealand time.

The earthquake, which struck at 8:40 a.m. on Monday April 2nd 2007 NZ Standard Time, was located 45 km SSE of Gizo, New Georgia Islands, in the Solomon Islands at a depth of 10 km according to the US Geological Survey. Initial analysis of the quake which was 345 km WNW of the capital Honiara, put the quake’s magnitude at 7.6.

The Pacific Tsunami Warning Centre, which initially estimated the earthquake at magnitude 7.8 issued three bulletins on the tsunami threat to Hawaii and the Pacific. The latest bulletin, issued at 10.39 this morning, revised the quake’s magnitude to 7.6 (richter, 8.1 moment) and confirmed that a 15 cm wave was detected at Honiara at 9.37 a.m. New Zealand time.

The bulletin stated that a tsunami watch is still in effect for New Zealand, but the threat has reduced and the list of areas on watch was considerably reduced. Further data from wave gauges is awaited before the “tsunami watch” is lifted. Estimated arrival times for any wave that might have been generated are 1:38 p.m. for North Cape and 2:14 p.m. for East Cape, according to the PTWC.

Australia, which is closer to the epicentre, will provide valuable information on the tsunami risk as the estimated arrival time for a wave passes at 11:49 this morning at Cairns.

The earthquake struck undersea on the edge of the Pacific Plate close to the intersection with the Solomon microplate. Latest Richter magnitude estimates are 7.6 by the USGS, PTWC and IRIS. An estimate from Geoscience Australia is not available as their server has been blocked since the event.

A magnitude 6.7 earthquake at 8:48 a.m. followed the major event. This was located 100 km south of Arawa, Bougainville, Papua New Guinea.

The earthquakes have occurred after a busy week in the South Pacific. Since the pair of magnitude 7 quakes which struck Vanuatu on March 25th, eleven earthquakes with magnitudes between 4.4 and 5.7 have been reported in the area.

Four deep 4th magnitude quakes and one shallow 5th magnitude event have been reported near Fiji. A shallow 4th magnitude quake has been reported near Tonga and three have occurred near Vanuatu – one 4th magnitude and two 5th magnitude, all shallow. A 4th magnitude quake has been reported in the Santa Cruz Islands, with a larger 5th magnitude event striking near the Southern East Pacific Rise.

Earthquakes have also occurred between the Bay of Plenty and the southern Kermadec Islands, but data for these events is not available.

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