RAPID: Near-trench Deformation and Tsunami Runup from the Jan 3, 2010 Solomon Islands Earthquake

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

On January 3, 2010 a moment magnitude, MW 7.1 earthquake occurred along a portion of the Solomon Islands, causing substantial strong shaking and triggering local landslides and a tsunami that impacted several of the islands, most notably Tetepare and Rendova. The event was likely triggered by, and occurred very near the southeastern terminus of the massive MW 8.1 earthquake of April 1, 2007, which itself caused a substantial local tsunami that devastated many coastal areas. This most recent event was unique in that it caused a notable tsunami that was identifiable on two ocean-bottom pressure sensors nearly 1000 km away, even though it was only a moderately large MW 7.1 event. Such disproportionate tsunami excitation is observed with moderately larger (MW 7.5-7.8) rare tsunami earthquakes, yet this exhibits only a modestly slow character. Two main possibilities are proposed to explain the tsunami excitation of the 2010 event: 1) The earthquake was a "partial tsunami earthquake" in that it ruptured both a fast and slow component, giving it a mostly normal energy-moment ratio (a now well established tsunami earthquake discriminant; or 2) Strong shaking from the event triggered a submarine landslide that generated the tsunami. It is likely that this event ruptured similarly to the 2007 event, with slip occurring primarily in discrete patches along the shallowest portion of the trench, much like slip observed in tsunami earthquakes. We will use the extreme proximity of coastal environments to the rupture area and trench to conduct a postseismic tsunami inundation and near-source geodetic deformation survey along the two most proximal islands to the event to identify the magnitude and distribution of both parameters. Geodetic measurements will include short-term static and kinematic GPS of uplifted and exposed coral communities and subsidence and submergence of anthropogenic structures. SAR scenes will also be evaluated for usable interferograms covering the affected islands. This information will be invaluable at assessing whether the coseismic slip alone was responsible for generating the observed tsunami, and will yield new insight into the potential for tsunami excitation from even low-magnitude 7 events occurring within the shallow trench. The tsunami run-up data will be modeled (in collaboration with researchers from NOAA) using the resultant coseismic interface slip model constrained from the combined geodetic techniques. This RAPID award was supported by the Geophysics, Marine Geology & Geophysics, and Geotechnical Engineering Programs.