HR: 0800h
AN: T51C-0689    [Abstracts]
TI: Monitoring Seismic Velocity Variations Across the Fault System of the Gulf of Corinth Using Coda Wave Interferometry
AU: * Cociani, L
EM: lorenzo.cociani@ucd.ie
AF: Seismology and Computational Rock Physics Laboratory, UCD School of Geological Sciences, University College Dublin, Belfield., Dublin, 4, Ireland
AU: Bean, C J
EM: Chris.Bean@ucd.ie
AF: Seismology and Computational Rock Physics Laboratory, UCD School of Geological Sciences, University College Dublin, Belfield., Dublin, 4, Ireland
AU: Lyon-Caen, H
EM: Helene.Lyon-Caen@ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure 24 rue Lhomond 75231 Paris Cedex 05, Paris, 75231, France
AU: Mollhoff, M
EM: Martin.Mollhoff@ucd.ie
AF: Seismology and Computational Rock Physics Laboratory, UCD School of Geological Sciences, University College Dublin, Belfield., Dublin, 4, Ireland
AB: Studying fault and fracture in-situ properties is important for gaining a better understanding of many geological and geophysical phenomena. In this work we focus on the temporal variations of fracture stiffness across an active fault system. The analysis of the temporal variations in the seismic velocity across faults can be used to estimate the in-situ stress variations. Seismic velocity of propagation depends on the fault stiffness, which is a function of stress. Traditional methods for inferring velocity variations are not sufficiently accurate because these changes are likely to be too small to be observed, a fraction of one percent. We use the Coda Wave Interferometry (CWI), technique to measure fractional velocity changes using repeating Earthquake sources or multiplets. This technique allows us to estimate with high precision, velocity changes between repeating earthquakes. CWI was applied to the CRLNET data close to the town of Aigion on the southern shore of the Gulf of Corinth. This area is the most seismically active place in Europe and is possibly the fastest extensional continental rift in the world hence is a suitable natural laboratory for studying active fault systems. Initial results show a 0.2% decrease in the seismic velocity of wave propagation across the fault system coincident or immediately after a local 4.2 magnitude event. This velocity variation indicates a probable decrease in the fracture stiffness, possibly associated with a local unclamping of the dominant fault system. In this study we also try to limit the geographical location of the change, by precise relocation of the repeating events used for the estimation of the velocity variations detected with CWI.
DE: 8010 Fractures and faults
DE: 8100 TECTONOPHYSICS
DE: 8168 Stresses: general
SC: Tectonophysics [T]
MN: 2007 Fall Meeting