HR: 14:10h
AN: S33C-03    [Abstracts]
TI: Dynamic Rupture in the Presence of Fault Discontinuities: an Application to Faults in the Marmara Sea, Turkey
AU: * Oglesby, D D
EM: david.oglesby@ucr.edu
AF: Department of Earth Sciences, University of California, Riverside, CA 92521 United States
AU: Mai, P M
EM: mai@sed.ethz.ch
AF: ETH Hoenggerberg, ETH Hoenggerberg, Zurich, CH-8093 Switzerland
AU: Atakan, K
EM: kuvvet.atakan@geo.uib.no
AF: Department of Earth Science, University of Bergen, Allegt.41, Bergen, N-5007 Norway
AU: Pantosti, D
EM: pantosti@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Sismologia e Tettonofisica, Via di Vigna Murata, Rome, 605 00143 Italy
AU: Pucci, S
EM: pucci@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Sismologia e Tettonofisica, Via di Vigna Murata, Rome, 605 00143 Italy
AB: The faults in the Sea of Marmara, Turkey, contribute greatly to the seismic hazard in this region. Of particular interest for the mega-city Istanbul is the northern strand of the North Anatolian Fault Zone that crosses the Marmara Sea, consisting of several potentially linked faults, which have produced a number of devastating earthquakes (M > 7.2) in the past 500 yrs. (1509, 1719, 1766, a,b, 1894, 1912, 1999). Geological analysis has indicated that the strike-slip Central Marmara Fault, the oblique-normal North Boundary Fault, and the strike-slip Izmit Fault form a linked fault system, where the North Boundary Fault acts as a linking oblique-normal fault in a dilational step-over between the two strike-slip segments. At this point it is not known whether this fault system tends to rupture in multi-segment, very large events, or whether it tends to generate multiple events on the individual segments. The dynamics of each of these scenarios and the associated ground motions will strongly affect seismic hazard estimates for this region. In the present preliminary work we use the 3D dynamic finite element method to investigate whether this fault system could rupture in a single event, leading to a potentially large earthquake. We assume that all faults intersect at depth and that there is a simple regional stress field. We find that the ability of rupture to propagate over the entire fault system is strongly affected by the assumed hypocenter location: Through-going rupture is easier when nucleation is on one of the strike-slip segments, and more difficult if it is on the normal segment in the step-over region. The difference in behavior in these cases is directly linked to the large normal stress reduction induced on the linking fault by slip on the strike-slip segments. While such an effect is also present on the strike-slip segments due to slip on the linking normal fault, it is much smaller, and does not aid in rupture propagation to nearly the same degree. Thus, high directivity is necessary to propagate from the normal fault to the strike-slip faults. The results are consistent with more generic models of fault step-overs in the presence of linking faults, and could have important implications for the capacity of similar fault systems to produce large, multi-segment earthquakes.
DE: 0545 Modeling (4255)
DE: 7209 Earthquake dynamics (1242)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005