Earth Planets Space, Vol. 58 (No. 2), pp. 195-201, 2006
Kenji Hirata1, Kenji Satake2, Yuichiro Tanioka3, Tsurane Kuragano4, Yohei Hasegawa5, Yutaka Hayashi5, and Nobuo Hamada6
1Program for Deep Sea Research, IFREE, Japan Agency for Marine-Earth Science and Technology, Natsushima 2-15, Yokosuka 237-0061, Japan
2Active Fault Research Center, National Institute of Advanced Industrial Science and Technology, Site C7 1-1-1 Higashi, Tsukuba 305-8567, Japan
3Institute of Seismology and Volcanology, Hokkaido University, N10W8 Kita-ku, Sapporo 060-0810, Japan
4Global Environment and Marine Department, Japan Meteorological Agency, Otemachi 1-3-4, Chiyoda-ku, Tokyo 100-8122, Japan
5Seismilogy and Volcanology Research Department, Meteorological Research Institute, 1-1 Nagamine, Tsukuba 305-005, Japan
6Sapporo District Meteorological Observatory, N2W18-2, Chuo-ku, Sapporo 060-0002, Japan
(Received July 8, 2005; Revised October 14, 2005; Accepted October 21, 2005; Online published February 17, 2006)
Satellite altimetry measurements of sea surface heights for the first-time captured the Indian Ocean tsunami generated from the December 2004 great Sumatra earthquake. Analysis of the sea surface height profile suggests that the tsunami source, or the seafloor deformation, of the great earthquake propagated to the north at an extremely slow speed of less than 1 km/sec on average for the entire 1300-km-long segment along the northern Sumatra-Nicobar-Andaman Trench. The extremely slow propagation speed produces a very long duration of tens minutes, longer than earthquake source duration estimated (480-500 sec) from short-period P-wave radiation. The satellite altimetry data requires a total seismic moment of 9.86 × 1022 Nm (Mw=9.3). This estimate is approximately 2.5 times larger than the value from long-period surface wave analysis but nearly the same as that from the ultra-long-period normal mode study. The maximum amount of slip (~30 m) is identified in an offshore region closest to the northern most part of Sumatra where the largest tsunami run-up heights were observed.
Key words: 2004 Sumatra earthquake, tsunami, source model, satellite, Indian Ocean.