Geoscientists have said that the 2007 Solomon Island earthquake may point to previously unknown increased earthquake and tsunami risks because of the unusual tectonic plate geography and the sudden change in direction of the earthquake.
On April 1, 2007, a tsunami-generating earthquake of magnitude 8.1 occurred East of Papua New Guinea off the coast of the Solomon Islands.
The subsequent tsunami killed about 52 people, destroyed much property and was larger than expected.
"This area has some of the fastest moving plates on Earth," said Kevin P. Furlong, professor of geoscience, Penn State. "It also has some of the youngest oceanic crust subducting anywhere," he added.
Subduction occurs when one tectonic plate moves beneath another plate. In this area, there are actually three plates involved, two of them subducting beneath the third while sliding past each other.
The Australia Plate and the Solomon Sea/Woodlark Basin Plate are both moving beneath the Pacific Plate.
At the same time, the Australia and Solomon Sea/Woodlark Basin Plates are sliding past each other.
The Australia Plate moves beneath the Pacific Plate at about 4 inches a year and the Solomon Sea Plate moves beneath the Pacific Plate at about 5.5 inches per year.
As if this were not complicated enough, the Australia and Solomon Sea plates are also moving in slightly different directions.
The researchers found that the earthquake crossed from one plate boundary - the Australia-Pacific boundary - into another - the Solomon/Woodlark-Pacific boundary.
The event began in the Australia Plate and moved across into the Solomon Sea Plate and had two centers of energy separated by lower energy areas.
"Normally we think earthquakes should stop at the plate boundaries," said Furlong.
According to Furlong, seismologists do not expect young sections of the Earths crust to be locations of major earthquakes, so the Solomon Island earthquake was unusual from the beginning.
He also believes that similar areas exist or existed.
"Other places along subduction zones had this type of geography in the past and might show up geologically," said Furlong. "At present, there are locations along the margins of Central America and southern South America that could potentially host similar earthquakes," he added.
A better understanding of earthquakes zones like the Solomon Islands may help residents along other complex plate boundaries to better prepare for localized regions of unusually large uplift and tsunami hazards.