Airborne Electromagnetics to Improve Landslide Knowledge in Tropical Volcanic Environments

Abstract

Caribbean areas are particular volcanic territories in tropical environments. These territories juxtapose several landslide-prone areas with different predisposing factors (poorly consolidated volcanic materials, superimposition of healthy materials on highly weathered materials, high heterogeneity of thicknesses, etc.). In these environments, where rapid development of slopes and land use changes are noticeable, it is necessary to better characterize these unstable phenomena that cause damage to infrastructure and people. This characterization has to be carried out on the materials as well as on the initiation conditions of the phenomena and requires complementary investigations. This study, focusing on La Martinique, proposes a landslide analysis methodology that combines new information about landslide-prone materials acquired by an airborne electromagnetics survey with a physical-based model. Once the data are interpreted and compared with field observations and previous data, a geological model is produced and introduced into the physical model to test different instability scenarios. The results show that geophysical investigations (i) improve the knowledge of the internal structure of landslides and surficial formations, (ii) specify the spatial limits of the materials that are sensitive to landslides, and (iii) give a better understanding of landslide initiation conditions, particularly hydrogeological triggering conditions.

Landslide Processes Involved in Volcano Dismantling From Past to Present: The Remarkable Open‐Air Laboratory of the Cirque de Salazie (Reunion Island)

“…From the methods used in this study, the innovations listed below can easily be replicated in other volcanic or non‐volcanic environments to identify relevant information on landslide processes and areas prone to landslides: AEM combined with geomorphological and geological observations allowed us to delineate three large landslides and define their internal structure. This method has also been successfully used on the volcanic island of Martinique (Thiery et al., 2017, 2021) and thus seems suitable for deep imaging of complex volcanic environments and identifying landslide‐prone material. This information can then be used, for example, to elaborate landslide scenarios with deterministic models (Thiery et al., 2017, 2021).…”

“…This method has also been successfully used on the volcanic island of Martinique (Thiery et al., 2017, 2021) and thus seems suitable for deep imaging of complex volcanic environments and identifying landslide‐prone material. This information can then be used, for example, to elaborate landslide scenarios with deterministic models (Thiery et al., 2017, 2021). SFM‐MVS applied on historical aerial photographs allowed the production of pre‐ and post‐cyclone event images and DEM of irregular and steep topography.…”

“…To image the internal structure of large landslides, we used AEM data acquired in 2014 (SkyTEM survey; Sørensen & Auken, 2004) conducted over Reunion Island (Dumont et al, 2019;Martelet et al, 2014). Resistivity contrasts, revealed by this technique, enabled the delineation of interfaces (e.g., weathered or clay layers, faults, and slip surfaces) within shallow and deep landslides (Godio & Bottino, 2001;Nakazato & Konishi, 2005;Thiery et al, 2017Thiery et al, , 2021. The resistivity gradient may also be attributed to water circulation (Vittecoq et al, 2019).…”

“…AEM combined with geomorphological and geological observations allowed us to delineate three large landslides and define their internal structure. This method has also been successfully used on the volcanic island of Martinique (Thiery et al, 2017(Thiery et al, , 2021 and thus seems suitable for deep imaging of complex volcanic environments and identifying landslide-prone material. This information can then be used, for example, to elaborate landslide scenarios with deterministic models (Thiery et al, 2017(Thiery et al, , 2021.…”

“Novel Approaches in Landslide Monitoring and Data Analysis” Special Issue: Trends and Challenges

“…Thiery et al [1] performed airborne electromagnetic measurements for rapid surveyance of the volcanic tropical environment of La Martinique, an island in the Caribbean. They combined their findings with a physical-based model to obtain improved and integrated information about the internal structure of landslides, founding a better understanding of landslides' initiation conditions.…”