Strong Quakes, Solomon Islands

Two strong earthquakes struck the Solomon Islands less than an hour apart earlier today.

Monday 4th January 2010

Two earthquakes of magnitude 7.2 and 6.5 struck the Solomon Islands late this morning, New Zealand time.

The first event, a 10 km-deep magnitude 6.5 foreshock which struck at 10:48 a.m. New Zealand time, was located 90 km south-south-east of Gizo, New Georgia Islands, in the Solomons group, according to the U.S. Geological Survey. Geoscience Australia reports the quake as magnitude 6.7, at a depth of 45 km.

The Pacific Tsunami Warning Centre issued a bulletin for this event at 11:04 a.m. NZDT, advising that a tsunami threat to coastlines in the Pacific did not exist.

Forty-nine minutes after the foreshock struck, at 11:37 a.m. New Zealand time, a magnitude 7.2 earthquake struck 105 km south-south-east of Gizo, New Georgia Islands at a depth of 31 km. Geoscience Australia reports this event as magnitude 7.0 at a depth of 50 km.

The Pacific Tsunami Warning Centre issued a bulletin at 12:03 p.m. advising that a threat to coastlines in the Pacific did not exist as a result of the second quake. A further bulletin issued at 1:10 p.m. NZDT reported that a 6 cm wave had been detected at Honiara, about 150 km from the earthquake epicentre. Early news reports suggest that larger sea disturbances have been observed near the epicentre but details are vague at this stage, and indications are that a catastrophic wave was not experienced.

The U.S. Geological Survey issued a report on the event, noting that the main earthquake had occurred at the boundary of the Pacific and Australian plates, in an area where the Australian Plate subducts (slides under) the Pacific tectonic plate at the rate of about 95 mm per year.

The report also said, “The Solomon Islands arc as a whole experiences a very high level of earthquake activity, and many shocks of magnitude 7 and larger have been recorded since the early decades of the twentieth century. The January 3rd, 2010 earthquake nucleated approximately 50 km to the south-east of a M8.1 earthquake in April 2007, which with an associated tsunami caused at least 50 fatalities and detstrroyed several coastal villages on nearby islands.”

Aftershocks of magnitude 5.3 and 5.2 struck at 2:47 and 3:08 p.m. respectively.

Earthquakes have struck nearby areas from Papua, Indonesia to the Santa Cruz Islands in the past 24 hours. A shallow magnitude 5.5 quake struck the Santa Cruz Islands this morning at 4:14 a.m. New Zealand time. At 3:14 a.m. a shallow magnitude 5.2 event occurred near the north coast of Papua, Indonesia. Yesterday, a deep magnitude 5.0 earthquake struck Vanuatu at 10:11 p.m. and a deep quake of magnitude 5.8 was recorded 10 km south of Madang, New Guinea at 5:12 p.m.

[Compiled from data supplied by the U.S. Geological Survey and its contributing agencies; the U.S. National Oceanic & Atmospheric Administration’s Pacific Tsunami Warning Centre, and Geoscience Australia.]

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