Moment-Frequency distribution as a constraint for hydro-mechanical modelling in fracture networks

International audienceShear re-activation of deep fractured rocks for EGS purposes is accompanied by microseismicity. From our numerical hydro-mechanical coupling in discrete fracture network models which incorporates stress drops with known amplitudes and neglects the influence of static stress changes, it happens that the moments of induced seismic events are scaling with the power 3 of the fracture size. It follows that the value of the slope of the moment-frequency diagram better known as the b'value obtained from numerical experiments correlates with the exponent of the power law distribution used for the fracture size generation. Our suggestion is therefore to use these diagrams for constraining the fracture network generation proces

A new conceptual methodology for interpretation of mass transport processes from seismic data

International audienceIdentification and seismic mapping of mass-transport deposits (MTDs) are vital targets for marine geological studies both for a better understanding of mass wasting processes and geohazards and for economic prospects in sedimentary basins. In recent decades, refinements in the interpretation of these geobodies have benefited from increasingly good quality 3D seismic data. However, approaches to define the characteristics, rheology and mechanics of such slope failure deposits still rely mainly on inferences from case-dependent interpretations of these stratigraphic elements; what is more, features and seismic characteristics of MTDs may vary significantly from one case to another, implying the existence of many different environments and related physics. This makes the study of submarine mass movement a challenging task for a seismic interpreter. In this paper, we present a new conceptual analytical method based on an objective approach for interpreting the wide range of diverse objects related to mass wasting, in order to minimize seismic interpretation subjectivity. We propose an ontology-like methodology, based on a conceptual organization of a diversity of interpretation elements arranged in a knowledge base. MTDs are considered as objects with representative properties, each one characterized by several descriptors, which are themselves impacted by multiple physical processes in a graph-based conception. We thus propose a method to infer the most probable interpretations for one mass movement from its deposit characteristics. We applied our graph-based methodology to two MTDs delineated in 3D seismic data in the Offshore Amazon Basin, Brazil. Based on the analysis of all MTD properties and their possible causes, several candidate interpretations were provided. The interpretations yielded by the graph are in line with the known geology and instability processes of the region, thereby validating the feasibility of the approach. The next development stage is a numerical definition of the knowledge base for further sharing and operability

Smoke extracts and nicotine, but not tobacco extracts, potentiate firing and burst activity of Ventral Tegmental Area dopaminergic neurons in mice

International audienceNicotine prominently mediates the behavioral effects of tobacco consumption, either through smoking or when taking tobacco by snuff or chew. However, many studies question the exclusive role of nicotine in these effects. The use of preparations containing all the components of tobacco, such as tobacco and smoke extracts, may be more suitable than nicotine alone to investigate the behavioral effects of smoking and tobacco intake. In the present study, the electrophysiological effects of tobacco and smoke on ventral tegmental area dopamine (DA) neurons were examined in vivo in anesthetized wild-type (WT), ß2 nicotinic acetylcholine receptor (nAChR) knock-out (ß2-/-), α4-/- and α6-/- mice and compared to those of nicotine alone. In WT mice, smoke and nicotine had similar potentiating effects on DA cells activity, but the action of tobacco on neuronal firing was weak, and often inhibitory. In particular, nicotine triggered strong bursting activity, while no bursting activity was observed after tobacco extract administration. In ß2-/- mice, nicotine or extract elicited no modification of the firing patterns of DA cells, indicating that extract act predominantly through nAChRs. The differences between DA cells activation profiles induced by tobacco and nicotine alone observed in WT persited in α6-/- mice but not in α4-/- mice. These results would suggest that tobacco has lower addiction generating properties compared to either nicotine alone or smoke. The weak activation and prominent inhibition obtained with tobacco extracts suggest that tobacco contains compounds which counteract some of the activating effects of nicotine and promote inhibition on DA cell acting through α4ß2*-nAChRs. The nature of these compounds remains to be elucidated. It nevertheless confirms that nicotine is the main substance involved in the tobacco addiction-related activation of mesolimbic DA neurons