Recent seismic hazard assessments in Mayotte have highlighted the island's significant exposure to site effects during earthquakes. These are closely linked its complex geological setting, characterized by altered volcanic formations whose heterogeneous geometry leads strong spatial variations ground motion. In response governmental requests, a map is being developed raise public awareness and support risk-informed urban planning.A novel methodology for mapping has recently been at BRGM,...

Abstract. We conducted a multidisciplinary study at the watershed scale of an andesitic-type volcanic island in order to better characterize hydrogeological functioning aquifers and evaluate groundwater resources. A heliborne Time Domain ElectroMagnetic (TDEM) survey was over Martinique investigate underground structures lithology, characterized by high lateral vertical geological variability resulting very heterogeneity their characteristics. Correlations were made on three adjacent...

Abstract In volcanic islands, a crucial step in managing watershed water resources is the characterization of groundwater aquifers from local to regional scales. Airborne geophysical data provide high‐resolution images down hundreds meters below surface, over large areas. Yet, production an accurate interpretation imagery may be time consuming or limited by low density geological and hydrological field observations. Here, we propose approach combining airborne electromagnetic magnetic order...

Abstract The Cirque de Salazie is one of the large erosional depressions Reunion Island. Composed a thick accumulation loose volcaniclastic materials derived from successive volcanic flank collapses and exposed to high precipitation rates, this depression particularly prone landslides. Of 133 km 2 making up depression, at least 19% slopes are affected by various types diversity density landslides main issues for inhabited areas. We examine in area with goal providing key elements better...

Landslide hazard and risk assessment (LHA & LRA) in the French West Indies is a big challenge, particularly Martinique, where several factors contribute to high slope sensitivity landslides. This due volcanic ground, hurricane seasons, growing pressure from urban development. Thus, protect future goods inhabitants avoid increased landslide, it necessary analyze by different ways complementary approaches planned areas. research focuses on site City Council of ‘La Trinité’ wishes develop....

Abstract Present-day volcano imaging and monitoring relies primarily on ground surface satellite remote sensing observations. The overall understanding of the volcanic edifice its dynamics is thus limited by investigation, spatial resolution penetration depth methods, but also human material resources, harsh environments. Here, we show for first time that an airborne electromagnetic survey provides a 3D global resistivity model active volcano. high-resolution acquired at Piton de la...

Abstract Montagne Pelée, on the French island of Martinique, eastern Caribbean Sea, has been one deadliest volcanoes in world, with 30,000 victims following 1902 eruption. Thousands people still live nearby, and this volcano is a strategic “water tank” for Martinique Island, providing 40% island’s water supply. This research aimed to better understand its hydrogeological functioning relationship complex volcanological evolution, taking advantage high-resolution helicopter-borne geophysical...

Airborne Electromagnetic (AEM) data are increasingly used in many geoscientific applications. BRGM conducted regional AEM surveys on the French overseas volcanic islands, where issues, including groundwater management or risk assessment crucial. For such "infrastructural" surveys, intended to be for various purposes and over several years. In this type of environment, with a man-made imprint, complex geology rugged topography, processing can very challenging. We therefore developed...

Caribbean areas are particular volcanic territories in tropical environments. These juxtapose several landslide-prone with different predisposing factors (poorly consolidated materials, superimposition of healthy materials on highly weathered high heterogeneity thicknesses, etc.). In these environments, where rapid development slopes and land use changes noticeable, it is necessary to better characterize unstable phenomena that cause damage infrastructure people. This characterization has be...

Summary In a traditional HEM inversion scheme, the voltage data are usually normalized by effective area of system. This depends on tilt frame; pitch and roll frame monitored during survey with tilt-meters used to calculate correction term. However, using measured this term, it is assumed that terrain flat, which may lead inaccuracies results. Thus, though term generally small, can prove important accurately compute in rugged when high resolution needed. The has then be corrected apparent...

ABSTRACT We investigate a novel way to introduce resistivity models deriving from airborne electromagnetic surveys into regional geological modelling. Standard geometrical modelling can be strengthened using geophysical data. Here, we propose extract information contained in model the form of local slopes that constrain interfaces. The proposed method is illustrated on an survey conducted region Courtenay France. First, contrast corresponding clay/chalk interface was interpreted confronting...

In the last decade, EU became aware of its dependency on mining countries for mineral resources. that context in 2022, France launched new airborne geophysical surveys Limousin region (northwestern French Massif Central) which is historically renown gold, uranium, tungsten and tin production. Thanks to these data, it has become possible both explore Saint-Goussaud - Auriat zone, centered Puy-les-Vignes deposit investigate numerous W occurrences. To do so, direct modelling using gravimetric,...

To clarify the serpentinite correlation and kinematics in New Caledonia, we focus on northwestern boundary of Massif du Sud Mont Do Massif, Boulouparis area. On basis airborne electromagnetics data, structural analysis, field propose a significantly different model to one commonly proposed for Peridotite Nappe emplacement. The interpretation is that slivers basement actually correlate with instead older terrane serpentinites. Therefore basal fault not as planar simple previously thought....

Summary Exploring for underground resources using land-based electromagnetic methods can be very challenging due to the presence of strong human-generated and “geological” noise. In such context, some passive EM techniques like Magneto-Telluric method may not applicable at all a dedicated toolbox capable dealing with these issues is required. We focus here on challenges encountered while exploring geothermal in volcanic islands, namely highly heterogeneous near-surface creating...