HR: 14:10h
AN: S13F-03    [Abstracts]
TI: LOCAL AND DISTANT RECORDING OF THE KALAPANA, HAWAII BENCH COLLAPSE OF 16 AUGUST 2007
AU: * Hyvernaud, O
EM: hyvernaud@labogeo.pf
AF: Laboratoire de Geophysique, CEA, Boite Postale 12, F-98713 Papeete, Tahiti, French Polynesia
AU: Reymond, D
EM: reymond.d@labogeo.pf
AF: Laboratoire de Geophysique, CEA, Boite Postale 12, F-98713 Papeete, Tahiti, French Polynesia
AU: Okal, E A
EM: emile@earth.northwestern.edu
AF: Northwestern, University, Evanston, IL 60208, United States
AB: On 16 August 2007 at 01:24 GMT, a small event took place on the Southeastern shore of the Big Island of Hawaii, with an initially assigned HVO duration magnitude of 1.7. It followed two larger earthquakes at essentially the same location, on 13 and 15 August. This epicentral location was the site of a documented, but untimed, bench collapse reported on the HVO web site. In a preliminary study, we analyzed both seismic waves recorded at the local IRIS station POHA located on the Big Island, 75 km from the epicenter, and hydroacoustic signals recorded at Christmas Island and in Polynesia. The local signal at POHA for the 16 August event is dominated by a 4-minute long signal peaked at about 3 Hz starting 1.5 minutes after the P wave, which is absent from the 13 and 15 August records. Similarly, hydroacoustic records at XMAS and in Polynesia show T waves of long duration and relatively low amplitudes, with a Duration-Amplitude discriminant [Talandier and Okal, 2001] D = -4.95 at XMAS. This value is lower than observed for most earthquake sources, and also than computed at Wake for the 1998 PNG landslide. These properties identify the 16 August 2004 as a bench collapse, with the event at 01:24 probably representing a small earthquake nucleating the process. The combination of the seismic and hydroacoustic records provides a unique opportunity for the detailed study of this phenomenon, which until now had been caught only rarely on distant instruments. A full report based on a more comprehensive dataset will be presented. ~
DE: 3025 Marine seismics (0935, 7294)
DE: 3070 Submarine landslides
DE: 7200 SEISMOLOGY
DE: 9355 Pacific Ocean
SC: Seismology [S]
MN: 2007 Fall Meeting