HR: 08:45h
AN: S51C-04    [Abstracts]
TI: Assessing tsunami hazard to the U.S. East Coast using relationships between submarine landslides and earthquakes
AU: * ten brink, U
EM: utenbrink@usgs.gov
AF: USGS, 384 Woods Hole Rd., Woods Hole, MA 02543, United States
AU: Lee, H
EM: hjlee@usgs.gov
AF: USGS, 345 Middlefield, Menlo Park, CA 94025, United States
AU: Geist, E
EM: egeist@usgs.gov
AF: USGS, 345 Middlefield, Menlo Park, CA 94025, United States
AU: Twichell, D
EM: dtwichell@usgs.gov
AF: USGS, 384 Woods Hole Rd., Woods Hole, MA 02543, United States
AB: Our knowledge of the size distribution and recurrence interval of earthquakes is better than that for submarine landslides. Because approximately 90% of landslide-generated tsunamis worldwide are associated with earthquakes, it is useful to try and predict the size and recurrence of submarine landslides from those of earthquakes. Several approaches for estimating the potential of earthquake-induced landslide tsunamis along the U.S. Atlantic continental margin are investigated and compared: calculating catastrophic slope failure conditions on this margin due to horizontal acceleration by earthquakes, using compilations of maximum observed distance to liquefaction [Ambraseys, 1988], and using compilations for the maximum area affected by earthquake-induced subaerial landslides [Keefer, 1984; Rodriguez et al., 1999]. The calculated slope stability predicts similar or slightly smaller triggering distances and failure areas than for subaerial observations. The results from all 3 approaches compare well with the slope failure observations of the M=7.2, 1929 Grand Banks earthquake. In terms of maximum triggering distance, these approaches suggest that an M=7.5 earthquake (the largest expected earthquake along the U.S. east coast) must be within 100 km of the continental slope to induce a catastrophic slope failure, a location which almost everywhere is offshore. The observed rate of seismicity offshore the U.S. Atlantic coast is very low with the exception of New England, where some micro-seismicity is observed. An extrapolation of annual strain rates from the Canadian Atlantic continental margin suggests that the New England margin may experience the equivalent of a magnitude 7 earthquake on average every 600-3000 years. In terms of minimum triggering magnitude, only earthquakes with magnitude larger than 5.5- 6 could probably cause a sufficiently large submarine failure to generate a devastating tsunami under specific conditions: if the epicenter is optimally located within the vulnerable area, if much of the area indeed fails, and if the slide moves rapidly.
DE: 4564 Tsunamis and storm surges
DE: 6309 Decision making under uncertainty
DE: 7215 Earthquake source observations (1240)
DE: 7220 Oceanic crust
SC: Seismology [S]
MN: 2007 Fall Meeting