HR: 16:00h
AN: U14A-01 INVITED     [Abstracts]
TI: The Simeulue saddle: evidence for a barrier to rupture for both the 2004 and 2005 Sumatran megathrust failures
AU: * Sieh, K
EM: Sieh@gps.caltech.edu
AF: Tetonics Observatory - California Institue of Technology, 1200 E. California Blvd ms 100-23, Pasadena, CA 91125 United States
AU: Briggs, R
U14A-01 AF: Tetonics Observatory - California Institue of Technology, 1200 E. California Blvd ms 100-23, Pasadena, CA 91125 United States
AU: Meltzner, A
U14A-01 AF: Tetonics Observatory - California Institue of Technology, 1200 E. California Blvd ms 100-23, Pasadena, CA 91125 United States
AU: Natawidjaja, D
U14A-01 AF: Research Center for Geotechnology, Indonesian institute of Sciences (LIPI), Komplek LIPI Gedung #70LIPI, Bullet JI. Sangkuriang-Cisitu 21/154D, Badung, 40135 Indonesia
AU: Hananto, N
U14A-01 AF: Research Center for Geotechnology, Indonesian institute of Sciences (LIPI), Komplek LIPI Gedung #70LIPI, Bullet JI. Sangkuriang-Cisitu 21/154D, Badung, 40135 Indonesia
AU: Suprihanto, I
U14A-01 AF: Research Center for Geotechnology, Indonesian institute of Sciences (LIPI), Komplek LIPI Gedung #70LIPI, Bullet JI. Sangkuriang-Cisitu 21/154D, Badung, 40135 Indonesia
AB: Uplifts above the 2004 and 2005 Sunda megathrust ruptures overlap slightly on Simeulue island, at about 2.5° N. Measurement of emerged corals show that uplift during the 2004 event was as high as 1.5 m on the northwestern flank of the island and tapered toward the southeast to zero. Conversely, uplift during the 2005 event was as high as 1.65 m on the southeastern part of the island and tapered toward the northwest to zero. Summing uplifts from the two earthquakes yields a 70-km long saddle along the middle of the island. At the center of the saddle, uplift was only about 0.5 m, a meter less than to the northwest and southeast. The corals also show that uplift associated with the M 7.3 earthquake of 2002 was centered squarely in the center of this saddle and had a maximum value of only about 0.2 m. We speculate that between giant-earthquake sequences, the portion of the megathrust beneath central Simeulue is characterized by moderate earthquakes such as occurred in 2002 and aseismic slip. If this were a persistent characteristic of the Simeulue saddle, it would be a permanent impediment to rupture from the northwest and from the southeast, because it would not store large strains. Such behavior would be analogous to what has been documented for the section of the Sunda megathrust at the Equator. The Equatorial section was flanked on the northwest by the giant ruptures of 1861 and 2005 and on the southeast by the giant earthquake rupture of 1797. For at least the past 250 years, the only large seismic rupture of the 70-km-long Equatorial section occurred during the M 7.7 earthquake of 1935.
DE: 1209 Tectonic deformation (6924)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8199 General or miscellaneous
SC: Union [U]
MN: Fall Meeting 2005