The Urgonian project......multidisciplinarity in practice
Coupling hydrogeological and speleological data : interest of the approach through a comparison between the studies in LSBB and statements made in the sinkhole of Autrans.
Seismicity triggered by stress transfer from a fluid injection-induced fracture activation
Benoit Derode, Frédéric Cappa, Yves Guglielmi, Jonny Rutqvist
Precise mechanisms relating fluid pressures and seismicity into fault zones, landslides or fractured reservoir remain nowadays unclear. Here, we studied by a numerical analysis of experimental data the effects of stress transfer on seismicity triggered in the near field of an active fluid pressure source controlled by a step-rate hydraulic injection (a few MPa) within a fractured medium. Results show that complex fracture’s permeability variations are associated to micro-seismic shearing ruptures in mechanical weak zones, and that the weakening of the medium strength
Seismic anisotropy analysis at the Low-noise underground Laboratory (LSBB) of Rustrel (France)
Ján Bereš, Hermann Zeyen, Guy Sénéchal, Dominique Rousset, Stéphane Gaffet, pdf file
Seismic data acquired at the LSBB site have been analysed in terms of angular anisotropy. Preliminary results are presented. We found a strong anisotropy of nearly ±10%. The high velocity is oriented at N30°E, low velocity at N120°E (40° inclined with respect to the main gallery). The direction of the high velocity is approximately parallel to the local direction of the main fractures.
Electrical Resistivity Tomography and Ground Penetrating Radar to study karst unsaturated zone ; first results, LSBB Rustrel, France
The Low-Noise Underground Laboratory of Rustrel (LSBB) is a unique place to apply surface-based geophysical surveys due to numerous and various geological and hydrogeological knowledge under the investigated zone.
Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) provide complementary information about structure of karst unsaturated zones. This information will enhance understanding of karst hydrosystems.
MRS APPLICABILITY FOR THE CHARACTERISATION OF THE UNSATURATED ZONE OF KARST HYDROSYSTEMS : FIRST RESULTS FROM THE LSBB SITE (RUSTREL, FRANCE)
The Low-Noise Underground Laboratory (LSBB) of Rustrel is an ideal laboratory for the study of flow processes in the unsaturated zone of karst aquifers.
In this paper we discuss the applicability of the Magnetic Resonance Soundings (MRS) method for the characterisation of the unsaturated zone of karst systems, based on the results of fields campaigns conducted on the surface of the LSBB. The MRS method is the only geophysical method which is specifically sensitive to groundwater.
EARTH SOUNDING AT LSBB
1GPR IMAGE ENHANCEMENT USING ADVANCED TECHNOLOGY FROM REFLECTION SEISMICS : NON-STATIONARY DECONVOLUTION AND PRESTACK DEPTH-MIGRATION.
M. J. Yedlin
GRAVIMETRY AND GEOPHYSICAL OBSERVATIONS APPLIED TO KARST HYDROLOGY : CASE STUDIES WITH THE LSBB AND THE LARZAC RESEARCH STATION
S. Deville, C. Champollion, N. Lemoigne
The objectives of the present studies are to enhance the synergy between hydrology, gravity and geophysics for karst research trough two main sites. The first LSSB site is located in the limestone Vaucluse karst and allow both surface and in-situ measurements of absolute and relative gravity. Since two years, gravity measurements have done in a 6 months basis to monitor the seasonal cycle of ground water storage. First results show that 1/3 of the infiltration is stored between the surface and the LSBB laboratory, 1/3 flow away from the gravity station and 1/3 is stored below the gravity station.
The Jasse site (GEK Observatoty OSU OREME / OER H+) is located in the south of the dolomite Larzac karst area. The dataset includes continuous high accuracy gravity, various geophysics and water vapor flux measurements. First results show that about 100% of the rainfall during the winter is stored in the ground with few water fast transfer. From another point of view, in-situ (boreholes) epikarst petrophysical characterization in synergy with surface geophysics allow to study local water storage and transfer