April 1, 2007 Earthquake: Solomon Islands

On April 1 at 20:39:58.7 UTC (April 2, 2007 at 7:39:56 AM local time) an earthquake occurred about 40 km (25 miles) SSE of Gizo, New Georgia Islands, Solomon Islands or about 345 km (215 miles) WNW of Honiara, Guadalcanal. Fifty-two people killed and several villages destroyed by the earthquake and tsunami. About 300 homes, schools and a hospital were destroyed at Sasamunga and about 500 houses were damaged at Gizo. Tsunami damage also occurred on Lefung and Taro. Two people were killed by landslides on Ranongga, where uplift was also observed. Felt (IV) at Honiara. A 3.5-meter tsunami was measured at Unumatana and a 2 meter tsunami was observed at Kelau, Woodlark Island, Papua New Guinea, where 17 houses were destroyed, a church was damaged and the tsunami ran inland up to 1 km. The tsunami also caused damage on Rossel Island and Bougainville. (reference #1053)

This Solomon Island earthquake represents a unique

opportunity to characterize the tsunamigenic seafloor displacements

as numerous islands were within proximity on

both sides of the rupture. Uplift was measured on uplifted

corals based on high tide water lines, while subsidence was

determined based on boat docks, disappeared navigation

obstacles and engulfed trees. The southern part of Ranongga

Island was uplifted by up to 3.6 m decreasing towards the

north with only 1.5 m uplift (Figure 3d). Less than 1 m

uplift was determined on the northwest tip of Vella Lavella

and Vonavona Islands. The islands were uplifted during the

earthquake prior to tsunami arrival significantly reducing

the tsunami impact. In the course of a few minutes,

Ranongga Island acquired significant new land, mostly

uplifted corals. (reference #3759)

Link to NGDC

tsunami information

for tide gauge data and tsunami damage reports.

Interactive Map displays significant tsunami events and related hazard layers.

USGS National Earthquake Information Center, reference #1053, http://earthquake.usgs.gov/eqcenter/eqinthenews/2007/us2007aqbk/

Tectonic Summary

The Solomon Islands earthquake of April 1, 2007, occurred along the boundary of the Pacific plate with, respectively, the Australia, Woodlark, and Solomon Sea plates. The latter three plates converge to the east-northeast or northeast against the Pacific plate with velocities of 90-105 mm/y. Along much of the plate boundary between the Pacific plate and the Australia/Woodlark/Solomon Sea plates, relative plate-motion is accomplished principally by subduction of the Australia/Woodlark/Solomon Sea plates beneath the Pacific plate. The April 1 earthquake's location and focal mechanism are consistent with the earthquake having occurred as underthrusting of the Australia/Woodlark/Solomon Sea plate beneath the Pacific plate, as part of the broader northeast-directed subduction process.

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 April 1 earthquake, however, nucleated in a 250-long segment of the arc that had produced no shocks of magnitude 7 or larger since the early 20th century

Earthquake Summary Poster from the USGS National Earthquake Information Center.

Additional USGS Analysis of the Geologic/Tectonic background where the earthquake occurred.