HR: 0800h
AN: U11A-0824    [Abstracts]
TI: Source Study of the Aceh-Sumatra 2004 and the Sumatra 2005 Earthquakes From Very Long Period Earth Free Oscillations
AU: * Lambotte, S
EM: Sophie.Lambotte@eost.u-strasbg.fr
AF: EOST-IPGS, CNRS-ULP, 5 rue Rene Descartes, Strasbourg, 67084 France
AU: Rivera, L
EM: luis@sismo.u-strasbg.fr
AF: EOST-IPGS, CNRS-ULP, 5 rue Rene Descartes, Strasbourg, 67084 France
AU: Hinderer, J
EM: Jacques.Hinderer@eost.u-strasbg.fr
AF: EOST-IPGS, CNRS-ULP, 5 rue Rene Descartes, Strasbourg, 67084 France
AB: The giant Aceh-Sumatra 2004 earthquake strongly excited the free oscillations of the earth including some usually elusive very long period modes which are conspicuous in the Fourier spectra. Several source models, published in the first days after the event, obtained from teleseismic body waves, show a rupture length of 400-500 km with a source duration of 200 sec approximately. On the other hand additional observations from long period data, GPS data, as well as some short period data, support a longer rupture over 1200-1300 km. This is consistent with the size of the aftershocks area which extends more than 1000 km northward from the epicenter. Well-separated split multiplets can provide useful information on the source of such huge earthquakes: phases of split singlets carry information on location, duration, length of the rupture and consequently mean rupture velocity. Singlet amplitude is linearly related to the seismic moment. We study some of the gravest modes (_0S_2, _0S_3, _0S_0 and _1S_0) recorded at several Very Long Period, worldwide distributed, permanent stations (Geoscope, IRIS, GGP) for recovering individual singlet parameters: excitation amplitudes and phases, quality factors and frequencies. Then we exploit amplitudes and phases (mostly from vertical components but also from horizontal ones when detectable) to constrain the spatio-temporal finiteness of the source as well as seismic moment for the Aceh-Sumatra 2004 earthquake and the Sumatra 2005 earthquake. On the basis of the initial phase measurements we present here, we obtain, for the main event, a fault length of about 1200 km and a duration of about 500 sec.
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7255 Surface waves and free oscillations
DE: 7260 Theory
SC: Union [U]
MN: Fall Meeting 2005