ISTerre seminar

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Satellite-based and in-situ methodologies: application and signal extraction for the detection of landslide precursors.

Wednesday 22 June 2022 - 10h00

Benedetta Dini - ISTerre (séminaire post-doc)
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One of the major open questions in the domain of landslide hazard assessment and prediction is related to the timely and accurate detection of precursors, key indicators that precede failure or phases of large accelerations. In the last few decades, the increasing availability of satellite-based SAR imagery, characterised by large coverages and increasing temporal sampling, has allowed scientists to use InSAR techniques exploiting phase difference between successive images to identify previously unknown instabilities over inaccessible areas, to characterise gravitational phenomena and, in some cases, to accurately quantify displacements. However, the full potential of satellite based InSAR has not yet been realised for monitoring slope movements, owing to signal loss and a decrease in resolution caused by high noise levels due to vegetation, by high phase gradients due to large displacements over restricted areas, by unfavourable orientation and by the limitations of unwrapping procedures used to convert the direct measurement (radians) into displacements (mm). In addition, the incipient stages of deformation are rarely detected because they commonly develop over areas equivalent to a few pixels, challenging signal extraction with current available resolution. Key signals relying on the unwrapped phase as well as interferometric coherence are still relatively underused for landslide applications. Thus, there is the need to develop high resolution, ad hoc tools dedicated to the extraction of localised signal to complement the ever-growing large scale processing platforms. In addition to the InSAR-based methodology, I will also show the latest development achieved with bespoke, low-cost, in-situ sensors that combine accelerometer and gyroscope to measure small angular variations from rotational movements and subtle accelerations associated with ground movements. A first version of the sensors has been successfully deployed in Nepal, and an improved version is currently being tested at the Harmalière landslide. Crucial advantages over other in-situ methods are the relatively low cost, allowing long-term monitoring and dense networks; the high sensitivity to small surface rotations; the ability to activate on movement thresholds and real-time data transmission.

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Organizing team : Organisation labo

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères