HR: 1340h
AN: T53C-1448    [Abstracts]
TI: Estimate of hydraulic diffusivity at 8 km depth from seismic activity migration
AU: * Cornet, F H
EM: cornet@ipgp.jussieu.fr
AF: Departement de Sismologie, Institut de physique du Globe de Paris, 4 place Jussieu, Paris, 75252 France
AU: Bourouis, S
EM: bourouis@ipgp.jussieu.fr
AF: Departement de Sismologie, Institut de physique du Globe de Paris, 4 place Jussieu, Paris, 75252 France
AU: Bourouis, S
EM: bourouis@ipgp.jussieu.fr
AF: Centre de Recherche en Astronomie, Astrophysique et Geophysique, B.P. 63 Bouzareah, Algiers, 16340 Algeria
AB: The Corinth Rift, in Western Greece, with an uplift of its southern shore that may reach up to 1.5 km, has been chosen for developing an in situ laboratory for investigating fluid-fault interactions. A tomographic investigation based on arrival times of signals generated by the natural seismicity suggests that this local activity occurs in zones with high fluid content around 7 to 9 km depths. Independently, analysis of fluids sampled in calcitic cements within different fault zones, indicates that faults were initially percolated by fluids of deep crustal origin that were replaced by saline fluids and finally by meteoric fluids. This is interpreted as a progressive upward fault growth, from the seismogenic zone up to the sea bottom of the Corinth Gulf, and then to ground surface. The significant role of fluids on the rifting process is corroborated by seismic swarms that occur recurrently. We show how automatic procedures for identifying multiplets, i.e. recurrent seismic events with sub-identical source mechanisms, help determine the rate of growth of these seismic clouds. These growths are assimilated with the migration of a fluid pressure front, in a manner somewhat similar to observations conducted during hydraulic stimulation of geothermal reservoirs. Hence the rate of growth is interpreted in terms of hydraulic conductivity for the corresponding seismic structures. Results for seven different seismic crises that occurred on the same structure over a period of 4.5 years are discussed.
UR: http://www.corinth-rift-lab.org
DE: 1209 Tectonic deformation (6924)
DE: 7205 Continental crust (1219)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8123 Dynamics: seismotectonics
SC: Tectonophysics [T]
MN: Fall Meeting 2005