Procedure to construct three-dimensional models of geothermal areas using seismic noise cross-correlations : application to the Soultz-sous-Forets enhanced geothermal site

The aim of this work is to assess the feasibility of the noise-cross correlation tomography method for imaging and detecting potential geothermal reservoirs even in highly urbanised areas. We tested the noise correlation method to reconstruct the shape of the Soutlz-sous-Forets enhanced geothermal system (northern Alsace, France). We inverted Rayleigh waves (RWs) reconstructed from cross-correlations of 15 months of ambient seismic noise recorded by a seismic array installed around the Soutlz geothermal power plant. By correlating noise records between 22 receivers, we reconstructed RWs with sufficient signal-to-noise ratio for 231 interstation paths. The reconstructed waveforms were used to estimate group velocity dispersion curves at periods between 1.0 and 5.0 s. The results were inverted for 2-D group velocity maps, and finally for a 3-D S-wave velocity model from 0 to 5.2 km depth. Our results clearly show the presence of low velocity bodies in the crystalline basement below the Soultz power plant at depth of 4-5 km, and at shallower depth (2.5-3.5 km) beneath the Rittershoffen and Woerth villages. These observations, in agreement with some previous studies, confirm that our procedure is suitable for geothermal exploration. Furthermore, the model presented here provides some suggestions to improve the existing geothermal power plant and inferences for further explorations in the area

Modelling earthquake location errors at a reservoir scale: a case study in the Upper Rhine Graben

International audienc

Contribution of the Surface and Down-Hole Seismic Networks to the Location of Earthquakes at the Soultz-sous-Forêts Geothermal Site (France)

International audienc

Nonparametric identification of LPV models under general noise conditions : an LS-SVM based approach

Parametric identification approaches in the Linear Parameter-Varying (LPV) setting require optimal prior selection of a set of functional dependencies, used in the parametrization of the model coefficients, to provide accurate model estimates of the underlying system. Consequently, data-driven estimation of these functional dependencies has a paramount importance, especially when very limited a priori knowledge is available. Existing overparametrization and nonparametric methods dedicated to nonlinear estimation offer interesting starting points for this problem, but need reformulation to be applied in the LPV setting. Moreover, most of these approaches are developed under quite restrictive auto-regressive noise assumptions. In this paper, a nonparametric Least-Squares Support Vector Machine (LS-SVM) approach is extended for the identification of LPV polynomial models. The efficiency of the approach in the considered noise setting is shown, but the drawback of the auto-regressive noise assumption is also demonstrated by a challenging LPV identification example. To preserve the attractive properties of the approach, but to overcome the drawbacks in the estimation of polynomial LPV models in a general noise setting, a recently developed Instrumental Variable(IV)-based extension of the LS-SVM method is applied. The performance of the introduced IV and the original LS-SVM approaches are compared in an identification study of an LPV system with unknown noise dynamics

SODs are involved in the regulation of ICAM-1 expression in human melanoma and endothelial cells.

It is well known that ICAM-1 expression can be stimulated by TNF and by oxidative stress, via the activation of specific transcription factors. Two of these--NFkappaB and AP-1--can also be activated by reactive oxygen species, including the superoxide anion (also produced under TNF challenge). The latter is inactivated by superoxide dismutase of which two forms exist: Cu/Zn-SOD (cytoplasmic) and Mn-SOD (mitochondrial). We investigated whether superoxide anion direct generation or accumulation through specific SOD inhibition, may affect ICAM-1 expression in human melanoma and endothelial cells. Our results show a 20-50% increase in both SOD activities when cells were exposed to TNF or to an oxidative stress produced by Paraquat (a generator of superoxide anion radicals), both in terms of enzymes activity (zymogram) and protein levels (Western blotting and ELISA). Either with TNF or Paraquat, we could measure a significant increase of ICAM-1 expression with maxima ranging from 140 to 200%, depending on the cell line. Specific inhibition of Cu/Zn-SOD activity by DTIC (diethyldithiocarbamic acid), in presence of Paraquat or TNF, was followed by an upregulation of ICAM-1 expression (60 and 20%, respectively). In contrast, the addition of a SOD mimetic (MnTMPyP) completely inhibited Paraquat-stimulated ICAM-1 expression in melanoma cells and significantly decreased it in HUVEC (50%). In presence of TNF however, the same SOD mimetic inhibited TNF-stimulated ICAM-1 expression by 25% in melanoma and 17% in endothelial cells. In conclusion, these data provide evidence that melanoma and endothelial cells exposure to TNF or oxidative stress results in a significant increase of both Mn- and Cu/Zn-SOD activities. This increase seems to be associated with a reduction in the stimulation of ICAM-1 expression by TNF or oxidative stress.Comparative StudyJournal Articleinfo:eu-repo/semantics/publishe