HR: 08:45h
AN: T41E-04    [Abstracts]
TI: A Tale of Two Cataclysmic Earthquakes: 39 and 52 kyr BP, Dead Sea Transform, Israel; a Multi-archive Study
AU: * Kagan, E J
EM: elisa.kagan@mail.huji.ac.il
AF: Institute of Earth Sciences, Hebrew University, Givat Ram, Jerusalem, 91904, Israel
AU: * Kagan, E J
EM: elisa.kagan@mail.huji.ac.il
AF: Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501, Israel
AU: Stein, M
EM: motis@vms.huji.ac.i
AF: Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501, Israel
AU: Bar-Matthews, M
EM: matthews@gsi.gov.il
AF: Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501, Israel
AU: Agnon, A
EM: amotz@cc.huji.ac.il
AF: Institute of Earth Sciences, Hebrew University, Givat Ram, Jerusalem, 91904, Israel
AB: We have documented earthquake histories in four lacustrine sites and a cave in the Dead Sea Transform region in central Israel. The lacustrine Lake Lisan (last Glacial paleo-Dead Sea) sites include: Massada Plain (M1b), Perazim (PZ1), Tovlan (NT), and Tamar (TM). They are up to 110 kms apart, along the Dead Sea Basin. These lacustrine sites have a variety of deformed marls (e.g. brecciated, homogenated, folded, and/or faulted). Except for the more fluvial NT site, where there is only one breccia layer, the sites show numerous (up to 29) earthquake events. Brecciated marls have been shown to be valuable earthquake markers by correlation with historical earthquakes and by their relationship to intraformational fault scarps (Agnon et al., 2006). The Soreq Cave, a carbonate cave richly decorated with speleothems, is 40 km west of the Dead Sea Basin, near the town Bet Shemesh. Earthquake damage in the cave includes collapsed stalactites and ceilings and severed stalagmites. During the last Glacial time period the cave, more distant from the Transform than the lake sites, experienced ~7 damaging events, documented by tens of dated collapses. The Soreq cave collapses have been shown to be viable earthquake markers by correlation to lacustrine documented seismic events and by absence of potential non-seismic sources of damage in the cave (Kagan et al., 2005). All the earthquake evidence, speleological and lacustrine, was rigorously dated by high resolution mass spectrometry by MC-ICP-MS at the Geological Survey of Israel. Both the Soreq cave and the Lisan sediments have been studied intensely for paleo- climate purposes in other studies. From these different and distant paleoseismic sites two events stand out. At ~39±1 ka and ~52±2 ka there is paleoseismic evidence at 5 and 3 sites, respectively. The later event, ~39±1 ka, has left evidence of brecciated marls at all four Lisan sites (with extremely thick seismites at the PZ1 site and the only breccia at the NT site) as well as five well-constrained collapses in different areas of the Soreq cave. The ~52±2 ka seismic event has left evidence at M1b (a closely spaced doublet of seismites), at PZ1 (followed by a period with numerous (8) and very thick (up to 48 cm) seismites) and at the cave site (3 collapses). We suggest that these seismic events are large-earthquakes, sufficiently strong to cause cave collapses and lake bottom brecciation in numerous and distant sites in very different kinds of sediments. We suggest that these large events are representatives of the largest magnitude earthquakes in the Dead Sea region. We extrapolate the frequency-size statistics from the instrumental data using a power-law (Gutenberg-Richter) to estimate ranges of magnitude for these cataclysmic events.
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7221 Paleoseismology (8036)
DE: 7250 Transform faults
DE: 8036 Paleoseismology (7221)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting