Seismic noise-based methods for soft-rock landslide characterization

Abstract

Abstract. -In order to better understand the mechanics and dynamic of landslides, it is of primary interest to image correctly their internal structure and their slip surface. Several active geophysical methods are able to provide the geometry of a given landslide, but were rarely applied in 3 dimensions in the past. The main disadvantages of methods like seismic reflection and electrical tomography are that there are heavy to set up and/or to process, and they consequently are expensive and time consuming. Moreover, in the particular case of soft-rock landslides, their respective sensitivity and resolution are not always adequate to locate the potential slip surfaces. Passive methods may represent an interesting alternative particularly for landslides difficult to access, as they require lighter instrumentation and easier processing tools. Among them, the seismic noise based methods have shown increasing applications and developments, in particular for seismic hazard mapping in urban environment. In this paper, we present seismic noise investigations carried out on two different sites, the "Super Sauze" mudslide and the "Saint Guillaume" translational clayey landslide (France), where independent measurements (geotechnical and geophysical tests) were performed earlier. Our investigations were composed of electrical tomography profiles, seismic profiles for surface-wave inversions, H/V measurements, which are fast and easy to perform in the field, in order to image shear wave contrasts (slip surfaces), and seismic noise array method, which is heavier to apply and interpret, but provides (S)-waves velocity profile versus depth. For both sites, landslide bodies are characterized by lower S wave velocity (Vs < 300 m.s -1 ) and lower resistivity ( < 60 Ohm.m) than in the stable part (Vs > 550 m.s -1 ; > 150 ohm.m). Their thickness vary from a few m to 50 m. Comparison between geophysical investigations and geotechnical data proved the applicability of such passive methods in 3D complex structures, with however some limitations. Caractérisation de glissements de terrain argileux par des méthodes de bruit de fond sismiqueMots clés. -Bruit de fond sismique, Glissement de terrain argileux, Caractérisation in-situ, Géométrie 3DRésumé. -Afin d'identifier les mécanismes de contrôle et de caractériser la dynamique de glissements de terrain, il est impératif d'imager correctement leur structure interne et leur surface de glissement. Plusieurs méthodes de prospection géophysique de proche surface sont utilisables pour identifier la géométrie d'un glissement de terrain, mais leurs potentialités ont été rarement testées en 3D. Les principaux inconvénients de méthodes géophysiques telles que la sismique réflexion ou la tomographie électrique sont la difficulté de mise en oeuvre et/ou la complexité des traitements de données, ce qui les rend chères et consommatrices en temps. De plus, pour le cas particulier de glissements argileux, leur sensibilité et résolution ne sont pas toujours adaptées à la détection des surfaces de glissem...

The effect of groundwater fluctuations on the velocity pattern of slow-moving landslides

“…The monitoring system has been complemented since 2003 by a geophysical investigation (seismic noise measurements, seismic soundings, electrical resistivity tomography; Guéguen et al, 2004;Méric et al, 2007), yielding more spatially detailed information on the geometry and depth of the slip surface and the bedrock (Tatard, 2006). These results have suggested that the slip surfaces develop first at the clay/bedrock interface where the bedrock is close to the surface and then within the clay layer.…”

“…The aim of this paper is to analyse quantitatively the relation between groundwater fluctuations and landslide velocity for two deep-seated landslides of the Trièves Plateau: the Monestier-du-Percy landslide (Giraud et al, 1980), and the Saint-Guillaume landslide (Azimi et al, 1994;Méric et al, 2007). First, the environmental settings of the landslides are described.…”

Pre-failure behaviour of an unstable limestone cliff from displacement and seismic data

“…Seismic noise correlation has been used at large scale (e.g., Shapiro et al, 2005) to infer lithospheric structures. Other methods, including the determination of spectral or horizontal-to-vertical (H/V) ratio modes, have been used at smaller scales for resonance studies of buildings, site effect estimation and engineering seismology (see e.g., Méric et al, 2007). Such analyses might be used to infer temporal variations in elastic properties of unstable rock massesas it has been already used to infer temporal variations on volcanoes (Brenguier et al, 2008) -or eventually in spectral modes, from a limited number of seismic sensors.…”

Resposta em Microtremor de um Movemento de Massa no Distrito Federal, Brasil

“…More recent applications of noise based techniques are microzonation studies based on seismic site response (Parolai et al, 2004), in the study of dynamical behaviour of buildings (Gallipoli et al, 2010;Nakata et al, 2013), crustal tomography through noise correlation techniques (Curtis et al, 2006), shallow crustal velocity profiling (Panzera & Lombardo 2013), monitoring of earth dams and levees by noise interferometry (Planès et al, 2015(Planès et al, , 2017, underground mining (Olivier et al, 2015 ) as well as active volcanoes (Ballmer et al, 2013;Cannata et al, 2017). Noise data can also potentially provide high resolution spatio-temporal information about the landscape dynamics and evolution (Méric et al, 2007). The sources of noise are usually dynamic in nature because of this dynamism the levels of noise in a region are not constant over time.…”