HR: 17:00h
AN: S14B-05    [Abstracts]
TI: Segmentation and Maturity of Long-Term Faults Control Earthquake Slip-Length Scaling
AU: * MANIGHETTI, I
EM: imanighe@obs.ujf-grenoble.fr
AF: Laboratoire de Geophysique Interne et Tectonophysique, LGIT- CNRS, Universite J. Fourier, BP 53, Grenoble, 38041, France
AU: CAMPILLO, M
EM: michel.campillo@obs.ujf-grenoble.fr
AF: Laboratoire de Geophysique Interne et Tectonophysique, LGIT- CNRS, Universite J. Fourier, BP 53, Grenoble, 38041, France
AU: COTTON, F
EM: fabrice.cotton@obs.ujf-grenoble.fr
AF: Laboratoire de Geophysique Interne et Tectonophysique, LGIT- CNRS, Universite J. Fourier, BP 53, Grenoble, 38041, France
AU: BILLION, P
EM: pauline.billion@gmail.com
AF: Laboratoire de Geophysique Interne et Tectonophysique, LGIT- CNRS, Universite J. Fourier, BP 53, Grenoble, 38041, France
AB: Slip and length measurements on earthquakes suggest large stress drop variability. To seek for the possible origin(s) of this apparent variability, we analyze an extended set of surface slip-length measurements that we have compiled for more than 270 large continental earthquakes worldwide (M > 6; the data set has been extended from that provided by Manighetti et al., EPSL, 2007). Using satellite imagery, we simultaneously analyze the geometry and large-scale segmentation of the long-term faults on which the earthquakes have occurred, and identify (when possible) the major fault segments broken by the earthquakes. We find that most long-term faults are composed of a limited number of major segments, commonly 4 more or less 1, separated by discontinuities (inter-segment zones) that commonly appear in map view as significant steps, bends or zones of cross-cutting faulting. We also find that the earthquakes break a variable number of those major segments, with displacement- length ratios which depend on that number and actually decrease as that number increases. We suggest that the number of broken segments depends on the strength of the inter-segment zones, which itself depends on the structural maturity of the long-term faults. We propose new Dmax-L parameterizations based on that idea of multiple segment-ruptures. In such parameterizations, each broken segment roughly scales as a crack, while the total multi-segment rupture does not. Stress drop on individual segments is roughly constant, only varying between 3.5 to 9 MPa. The slight variation that is still observed depends on fault structural maturity; more mature faults have lower stress drops than immature ones. The new Dmax-L functions that we propose reduce uncertainties with respect to available relationships. They thus provide a more solid basis to estimate seismic hazard by integrating fault properties revealed by geological studies.
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8034 Rheology and friction of fault zones (8163)
SC: Seismology [S]
MN: 2007 Fall Meeting