Adnand Bitri

French Geological Survey | BRGM · Direction Risques et Prévention

The 4.9 Mw earthquake of 11 November 2019 at Le Teil (France) occurred at a very shallow depth (about 1 km), inducing the surface rupture of La Rouvière fault. The question was raised shortly after about the potential impact of a nearby surface quarry. Thanks to satellite differential interferometry, here, we revealed the existence of a secondary s...

The Mw 4.9 earthquake of 11 November 2019 at Le Teil (France) occurred at a very shallow depth (about 1 km) inducing the surface rupture of La Rouvière fault, nearby of a limestone quarry. Thanks to satellite differential interferometry, we detected the existence of the secondary surface rupture of the quasi-parallel Bayne Rocherenard fault. A newl...

The Pays d'Auge (Normandy, France) is impacted by large deep-seated landslides along its coastline. The largest of these landslides, the “Cirque des Graves”, has been studied since the 1980s because of significant stakes in the active zone. To characterize the hydromechanical functioning of the central part of the cirque, which is the most active p...

This contribution reviews the challenges of imaging collisional orogens, focusing on the example of the Pyrenean domain. Indeed, important progresses have been accomplished regarding our understanding of the architecture of this mountain range over the last decades, thanks to the development of innovative passive imaging techniques, relying on a mo...

On 11 November 2019, a 5 magnitude earthquake occurred in southeast France at Le Teil, close to the Rhone river. This seismic event is the strongest earthquake ever felt in France since the Arette (Pyrenees) earthquake in 1967. By using an updated 3D geological model, we focus this work on the comparison of the effect of hydraulic recharge linked t...

Hell Bourg landslide (Salazie, Reunion Island) is a large, inhabited, slow-moving landslide (>200 Mm3). This landslide covers and remobilizes debris from former volcanic flank collapses. The volume, lithology, structure and evolution through time of these ancient deposits make the Hell Bourg landslide particularly complex. To understand the dynamic...

La Guyane est une région qui présente une forte démographie. Depuis une dizaine d’années, sa population a augmenté de près de 30 % pour atteindre 283 540 habitants au 1er janvier 2019 (https://www.insee.fr/). Dans le secteur de la presqu’île de Cayenne, la géomorphologie se caractérise par la présence de nombreux monts dont l’altitude maximum frôle...

Comprehensive geophysical sub-surface investigations of coastal systems provide a better understanding of the organization of sediment deposits and the behavior of coastal areas. An innovative high yield multi-geophysical approach has been developed to investigate internal properties of coastal dunes and their associated environments, combining con...

This paper deals with the design, acquisition and processing of vertical seismic profiling (VSP) data collected in 2016 at the directional Thônex‐01 geothermal well, drilled in 1993 in the Geneva Canton (Switzerland). The aim of the study was to obtain additional information from existing‐abandoned well for downhole geophysical characterization of...

The investigation and monitoring of shallow hazards due to the presence of underground cavities remain a challenge for geophysical approaches. Thus, seismic surface waves have been tested in several recent research projects in order to detect and localize voids as well as to determine their geometries. Among these works, numerous numerical studies...

The Charnath Khola is a large river crossing the Himalayan thrust system in the region devastated by the great M 8.3 1934 Bihar-Nepal earthquake. Fluvial terraces are abandoned along the river and at the base of a ~20 m-high cumulative thrust escarpment. A trench across the fault scarp exposed Siwalik mudstone/siltstone overthrusting Quaternary uni...

Poster presentation of the study titled "The MAUPASACQ experiment: Preliminary results of a noise-based Rayleigh-wave analysis of the Mauleon Basin in western Pyrenees, France", communicated during the European Geosciences Union General Assembly 2019, Vienna, Austria.

In the framework of the MAUPASACQ project, a dense seismic network of 440 three-component stations was deployed throughout the Mauleon Basin, in the northern foothills of the Pyrenees, SW France. The network consisted of three different types of sensors, namely 190 SG-10 SERCEL geophone nodes, 197 5 Hz SEISMOTECH short-period sensors and 53 broadba...

At regional scale, various hydromechanical phenomena are affecting Normandy coast: deep-seated and surficial landslides, rockslides, cliffs collapse or mudflows. These phenomena are controlled by pore water pressure variations and are depending on the underlying lithostratigraphy. Coastal areas of the Bessin, of the Pays de Caux but also coastal an...

The MUST2(MUon Survey Tomography based on Micromegas detectors for Unreachable Sites Technology) camera is based on a thin Time Projection Chamber read by a resistive Micromegas. This innovative combination presents interesting distinctive features compared to existing muon detection technologies. Itallowsa wide angular acceptance of the detector w...

Transmission muography is an expanding technique based on the attenuation of the natural­occurring cosmic muons flux due to the opacity of the medium to obtain the distribution of density around the detector. The current work introduces the technology developed by the Temporal Tomography of the Densitometry by the Measurement of Muons (T2DM2) colla...

In this study, we present a complete and successful case study where gravity and seismic refraction surveys detect and map previously poorly known sand and clay-filled depressions within the top chalk layers in a costal context, near Dieppe, Normandy, France. This study was commissioned by local authorities after a coastal chalk cliff collapse expo...

A dense seismic network of about 450 three-component (3C) sensors recording continuously for 6 months, from March to October 2017, was deployed in the Mauleon basin which is located in the northern foothills of the western Pyrenees. Three different types of sensors were used: 191 SG-10 3C SERCEL nodes, 197 3C 5 Hz Seismotech short period stations,...

Muon tomography is a rising technique with promising applications. It was introduced in the late ‘70s by Alvarez and collaborators to unravel the secrets of the Egyptian pyramids. Nowadays it is a complementary method in several disciplines, such as: volcanology, nuclear management and geological surveys. The main issue resides in the way Muon Tomo...

Muon tomography is a rising technique with promising applications. It was introduced in the late '70s by Alvarez and collaborators to unravel the secrets of the Egyptian pyramids. Nowadays it is a complementary method in several disciplines, such as: volcanology, nuclear management and geological surveys. The main issue resides in the way Muon Tomo...

Seismic reflection imaging is a geophysical method that provides greater resolution at depth than other methods and is, therefore, the method of choice for hydrocarbon-reservoir exploration. However, seismic imaging has only sparingly been used to explore and monitor geothermal reservoirs. Yet, detailed images of reservoirs are an essential prerequ...

The detection of underground cavities is still a challenging problem despite the good potential of geophysical techniques. The seismic surface waves analysis method can be acceptable for the cavity localisation if observables in data are affected by the void. We propose here a combined approach based on numerical 3D simulations (Spectral Finite Ele...

Shallow cavities, such as karstic caves in carbonate bedrock, near-surface underground mine workings and tunnels, constitute serious hazards for people and existing constructions due to the risk of collapse and subsidence. This phenomena is growing fast with climate change involving damages to buildings and increasing urban development costs. Karst...

Cette présentation se focalise sur deux secteurs de la côte basque qui ont fait l’objet d’investigations par sismique (réfraction et ondes de surface) afin de mieux caractériser les formations d’altérites et d’alluvions qui participent activement à l’apparition et au déclenchement de glissements de terrain. Ce travail permet : 1. De faire le point...

Keywords: Géologie , Altération, Formations superficielles, Propriétés physiques, Hydrogéologie, Géophysique, Sismique, SASW, Résonance Magnétique protonique, Géotechnique, Pénétromètre dynamique, Limites d’Atterberg, Valeur au bleu

La géologie profonde du Nord du Bassin de Paris est peu connue, en partie du fait d’un manque de données sismiques terrestres et de forages profonds. Contrairement au domaine onshore, le domaine offshore possède un jeu de données de sismique pétrolière importante aujourd’hui disponible au format brut (source BEPH). Si ces dernières années, des levé...

Non-invasive geophysical methods are often used for detecting near-surface defects and monitoring seepage in river dykes or dams. Between 2008 and 2009, a series of geophysical experiments were conducted to detect karst features below the dykes of the Loire River, Orléans, France. Multi-channel analysis of seismic surface waves (MASW) was used to o...

We present a new cooperative inversion approach that allows for a combined inversion of independent physical parameters by exchanging structural information. The technique is based on an iterative cluster analysis step using a Fuzzy c-Mean technique (FCM). Cluster analysis aims at identifying groups of similar objects, and helps to discover distrib...

An integrated geophysical approach for detecting cavities was applied experimentally to an abandoned underground quarry network in cretaceous chalky limestone located in in Souzay-Champigny. Microgravity evidenced negative anomalies corresponding to known conduits and identified the probable extensions of this network in unmapped areas. Microgravit...

We present a new cooperative inversion approach that allows for a combined inversion of independent physical parameters by exchanging structural information. The technique is based on an iterative cluster analysis step using a Fuzzy c-Mean technique (FCM). Cluster analysis aims at identifying groups of similar objects, and helps to discover distrib...

Landslide analysis is increasingly based on the combination of multiple information sources at different spatial and temporal resolutions, spatial coverage, accuracy and acquired using various airborne and terrestrial platforms and geomorphological, geophysical, and geotechnical methods. Morphological mapping and morpho-structure characterization a...

The construction of a new industrial and commercial area in 2009 at the Givors’ former glass factory area in France involved heavy dynamic compaction work. For the purpose of founding the new buildings, it was necessary to improve the ground mechanical properties of 7–15 m of well-graded gravel backfill lying on geotechnical bedrock. In order to as...

Various studies operate seismic methods for imaging landslide structures. All those methods are more or less based on strong approximations and require complex data preprocessing. The issue of recovering the structural image of a landslide from the seismic velocity field estimated with an accurate, but not too unstable, method is thus posed. To sol...

The geometry of the bedrock, internal layers and shear surfaces/bands controls the deformation pattern and the mechanisms of landslides. A challenge to progress in the forecast of landslide acceleration in terms of early-warning is therefore to characterize the 3D geometry of the unstable mass at a high level of spatial res-olution, both in the hor...

In order to characterise the fissure field provoked by the Super-Sauze mudslide (South French Alps) in the surface material, we conducted a seismic survey and compared the resulting P-wave tomogram to surface observations and cone penetrometer tests. The first results show that the distribution of the P-wave velocities correlates well with the fiss...

From numerous studies, geophysical methods based on seismic surveying appear to be well-adapted to investigate the morpho-structure of landslides and to progress in understanding the related mechanisms. Indeed, these methods allow direct and non-intrusive measurements of acoustic (Vp) or shear (Vs) wave velocity, two important physical parameters f...

In this paper, we demonstrate that Common Receivers Location (CGX) cross-correlation gathers of multi-channel and multi-shot surface waves give accurate surface wave velocity perturbation estimation, and enable us to reconstruct two-dimensional (2D) velocity structures with high resolution, without the systematic calculation of surface wave dispers...

Many studies show that certain geophysical methods, such as seismic and electrical-resistivity imaging, appear to be well adapted for investigating the internal structures of landslides and understanding the related hydro-mechanical mechanisms. These are methods that allow the direct and non-intrusive measurement of acoustic (P) and shear (S) wave...

Non-invasive geophysical techniques offer an interesting alternative to traditional soil sampling methods, especially for estimating spatial variations of soil parameters in the landscape. The spectral analysis of seismic surface-waves (MASW) can be used to determine the vertical shear-wave velocity (Vs) model (i.e., vertical variations in Vs with...

Geophysical methods are adequate for imaging the CO2 plume in order to follow its migration within the reservoir and possible leakages through the caprock formation. In particular, changes in density, seismic velocity or electrical resistivity are associated with changes in the gas saturation and make methods such as gravity, 4D seismic and electri...

Objectifs - Elaborer une méthodologie permettant de déterminer une probabilité de présence de karsts sous les digues de la Loire - Caractériser l'hétérogénéité des digues de la Loire - Evaluer le niveau de susceptibilité de présence de karsts - Orienter les futurs actions complémentaires envisageables sur les digues de la Loire Phasage du projet -...

This study of the Ballandaz landslide (Savoie, French Alps) was carried out as part of the ANR/PGCU-SIGMA research project. Its aim was to characterize the slope by different methods of geophysical imagery, and then use this characterization to provide a combined interpretation of the morpho-structures in order to simulate the geomechanical behavio...

Frequency analysis of surface waves propagation is an efficient tool to retrieve the vertical shear-wave velocity profile. Surface waves result from the interaction of elastic body waves with a free surface. They are commonly generated by impulsive active sources but are also present in ambient noise. Here we compare the results of interferometric...

The purposes of the multidisciplinary DIGISOIL project are the integration and improvement of in situ and proximal technologies for the assessment of soil properties and soil degradation indicators. Foreseen developments concern sensor technologies, data processing and their integration to applications of (digital) soil mapping (DSM). Among availab...

As transport routes and population centers in mountainous areas expand, risks associated with rockfalls and rockslides grow at an alarming rate. As a consequence, there is an urgent need to delineate mountain slopes susceptible to catastrophic collapse in a safe and non invasive manner. For this purpose, we have first adapted a 3D tomographic seism...

Mayotte is a French Overseas Territory of the Comoros archipelago. Since the 1980, Mayotte has developed quickly: its population has multiplied by four in less than 30 years, infrastructure expanded rapidly in lowlands and slums developed in steep areas (through deforestation) or close to riverbeds. This development urgently required steps to ensur...

We present results and interpretation of a 72 km long deep seismic reflection profile acquired across the internal zone of the Hercynian belt of South Brittany. The profile is of excellent quality, most of the crust being highly reflective. The "ARMOR 2 South" profile, is correlated with the "ARMOR 2 North" profile that was published in 2003. Corre...

The detection of shallow objects such as tunnels, karsts, mines and other local heterogeneities is an important but difficult issue in subsurface studies. In general, their positions are not known, either because they are not recorded in a database or because location maps are not available. In such cases, geophysical methods can provide a cost-eff...

Natural underground caves such as karsts are quite common in the region “Centre”, France. These subsurface perturbations can be found underneath the protection dykes around “the Loire” River and the damage caused can create routes for floods. Geophysical methods such as Multi-channel Analysis of Surface Waves (MASW) can be used for locating voids o...

Seismic ambient noise analyses have been shown to be able to image structural features of the crust and to monitor underground changes of seismic wave ground velocity. We present results of cross-correlation techniques at Bouillante geothermal field, French Antilles, the largest French high-enthalpy geothermal system exploited for electrical power...

The need to understand the structural context of the Bouillante geothermal field (West Basse-Terre, Guadeloupe, French West Indies) has led to onshore and offshore studies in the “high-energy geothermal fields” project, carried out by ADEME and BRGM. To ascertain the structural context of the island and the offshore continuation of the structures i...