Research Interests

View on the Maca landslide (Peru)

– Dynamics of landslides during earthquakes
– Seismic monitoring of mass-movements
– Detection, characterization and monitoring of unstable slopes from remote sensing data
– Analysis of forcing factors on slow-moving landslides

Dynamics of landslides during earthquakes

The mechanics of landslides during earthquakes is highly unknown. In particular, the relative contribution of friction, damage in the bulk, grain crushing at the basal interface, fluid transport changes, and internal deformation, to the general landslide dynamics is a main question. Very few in situ data exists on active landslides during earthquakes that could be used to answer this problematics.
I focus my research on the monitoring of slow-moving landslides in seismic environments using both GNSS and satellite images (SPOT5, Pleiades, Sentinel-1) to measure the landslide surface deformation during earthquakes.

Two main projects structure this research: (1) The in-situ monitoring of two giant landslides in the Colca valley (South Peru) using both GNSS and seismic sensors. In particular, the Maca landslide is monitored permanently since 2012, (2) The satellite monitoring of landslides in the Himalayas (Nepal) and in the Zagros mountains (Iran).

Publications

  • 2014, Lacroix P., H. Perfettini, E. Taipe, B. Guillier, Co- and postseismic motion of a landslide ; observations, modeling and analogy with tectonic faults, Geoph Res. Lett., doi : 10.1002/2014GL061170
  • 2015, Lacroix P., E. Berthier, E. Taipe, Earthquake driven acceleration of slow-moving landslides in the Colca valley, Peru, detected from Pléiades images, Rem. Sens. Env, 165 (148-158).
  • 2016, Zerathe, S., Lacroix, P., Jongmans, D., Marino, J., Taipe, E., Wathelet, M., ... & Tatard, L. Morphology, structure and kinematics of a rainfall controlled slow‐moving Andean landslide, Peru. Earth Surface Processes and Landforms.
  • 2018, Bontemps, N., P. Lacroix, Doin, M. P.. Inversion of deformation fields time-series from optical images, and application to the long term kinematics of slow-moving landslides in Peru. Remote Sensing of Environment, 210, 144-158.
  • 2020, Bontemps N., P., Lacroix, E. Larose, E. Taipe & J. Jara. Rain and small earthquakes maintain a slow-moving landslide in a persistent critical state. Nature Communications. 11, 780
  • 2022, Cheaib, A., P. Lacroix, S. Zerathe, D. Jongmans , N. Ajorlou, M.-P. Doin, J. Hollingsworth, and C. Abdallah, Landslides induced by the 2017 Mw7.3 Sarpol-Zahab earthquake (Iran), Landslides,
  • 2022, Lacroix, P., T. Gavillon, C. Bouchant, J. Lavé , J.-L. Mugnier, S. Dhungel, and F. Vernier, SAR and optical images correlation illuminates post-seismic landslide motion after the Mw7.8 Gorkha earthquake (Nepal), Scientific Reports.

On the Maca landslide (Peru), the GPS monitoring during a Mw6.0 earthquake shows both a co and a postseismic motion.


– next page : "seismic monitoring of mass-movements"

Seismic monitoring of mass-movements

I use seismic monitoring of mass-movements for two reasons: (1) to detect instabilities with a very precise timing, allowing me to study their forcing factors, (2) to gain informations on the sub-surface processes. I developed a beam-forming method to locate the micro-seismicity produced by the landslide activity and the rockfalls. For instance on the Sechilienne rockslide, we show that the energy of the deformation is released by many micro-earthquakes of small magnitudes (Magnitude max=1, b exponent of 1.6), and that only 0.1% of the deformation is released seismically.

View of the Sechilienne rockslide above the Romanche valley (left) and micro-seismicity of the deformation (yellow stars) overlayed over the landslide field velocity (colour code).

Publications

  • 2011, Lacroix P., A. Helmstetter, Location of seismic signals associated with micro-earthquakes and rockfalls on the Séchilienne rockslide, French Alps, 101 (1), 341-353, Bull. Seism. Soc. Am.
  • 2012, Lacroix P., J.R. Grasso, J. Roulle, G. Giraud, D. Goetz, S. Morin, A. Helmstetter, Monitoring of snow avalanches using a seismic array: location, speed estimation and relationships to meteorological variables , J. Geophy. Res. - Earth Surface, 117, F01034, doi:10.1029/2011JF002106.
  • 2017, Bievre, G., Lacroix P., L. Oxarango, D. Goutaland, G. Monnot, Y. Fargier, Integration of geotechnical and geophysical techniques for the characterization of a small earth-filled canal dyke and the localization of water leakage, Journal of Applied Geophysics, 139, 1–15]
  • 2020, Bontemps N., P., Lacroix, E. Larose, E. Taipe & J. Jara. Rain and small earthquakes maintain a slow-moving landslide in a persistent critical state. Nature Communications. 11, 780
  • 2021, Shugar, D. H., Jacquemart, M., Shean, D., Bhushan, S., Upadhyay, K., Sattar, A., ... Lacroix P.... & Westoby, M. J.. A massive rock and ice avalanche caused the 2021 disaster at Chamoli, Indian Himalaya. Science.
  • 2022, Mourey, J., P. Lacroix, P.-A. Duvillard, G. Marsy, M. Marcer, L. Ravanel, and E. Malet, Rockfall and vulnerability of mountaineers on the west face of the Aiguille du Goûter (classic route up Mont Blanc, France), an interdisciplinary study, Natural Hazard and Earth Science System, 22, 445–460,


– next page : "Earthquake-triggered rapid landslides"

Detection, characterization and monitoring of unstable slopes from remote sensing data

The detection, and characterization (volumes, speed) are the first inputs required to derive a hazard analysis. Satellite images are of main interest to retrieve these properties in remote areas. My research focus on the validation of various satellite data (SPOT6, Pléiades, Sentinel-2, Landsat-8) to estimate volumes of rapid landslides or ground displacement of slow-moving landslides. In particular, I developed a technique to derive time-series of ground displacement from a time-series of optical images. These time-series are the base for the the slow-moving landslide detection and monitoring, with two main perspectives: (1) operational monitoring of landslides to provide an early-warning system from space, (2) studying the mechanics of landslides.

Publications

  • 2015, Lacroix P., E. Berthier, E. Taipe, Earthquake driven acceleration of slow-moving landslides in the Colca valley, Peru, detected from Pléiades images, Rem. Sens. Env, 165 (148-158).
  • 2016, Lacroix P., Landslides triggered by the Gorkha earthquake in the Langtang valley, volumes and initiation processes. Earth, Planets and Space, 68(1), 1-10.
  • 2018, M. Q. Pham, P. Lacroix, M.P. Doin, Sparsity optimization method for slow-moving landslides detection in satellite image time-series, IEEE Transactions on Geoscience and Remote Sensing.
  • 2018, P. Lacroix, G. Bievre, E. Pathier, U. Kniess, D. Jongmans, Use of Sentinel-2 images for the detection of precursory motions before landslide failures, Remote Sensing of Environment, 215, 507-516.
  • 2018, Bontemps, N., P. Lacroix, Doin, M. P. (2018). Inversion of deformation fields time-series from optical images, and application to the long term kinematics of slow-moving landslides in Peru. Remote Sensing of Environment, 210, 144-158.
  • 2019, Desrues, M., P. Lacroix, & O. Brenguier. Satellite Pre-Failure Detection and In Situ Monitoring of the Landslide of the Tunnel du Chambon, French Alps. Geosciences 9.7, 313.
  • 2019, Lacroix, P., Araujo, G., Hollingsworth, J., & Taipe, E.. Self entrainment motion of a slow‐moving landslide inferred from Landsat‐8 time‐series. Journal of Geophysical Research: Earth Surface.
  • 2021, Fiolleau, S., Jongmans, D., Bièvre, G., Chambon, G., Lacroix, P., Helmstetter, A., ... & Demierre, M. Multi-method investigation of mass transfer mechanisms in a retrogressive clayey landslide (Harmalière, French Alps). Landslides, 1-20.
  • 2022, Provost, F., D. Michea, J.-P. Malet, E. Boissier, E. Pointal, A. Stumpf, F. Pacini, M.-P. Doin, P. Lacroix, P. Bally, Terrain deformation measurements from optical satellite imagery: the MPIC-OPT processing services for geohazards monitoring, Remote Sensing of Environment,


– next page : "Analysis of forcing factors on slow-moving landslides"

Analysis of forcing factors on slow-moving landslides

A landslide evolution results from a complex combination of geological and topographical factors, with possible interaction with external factors such as water infiltration, seismic shaking, fluvial erosion, or postglacial debutressing of the valley flank. All these processes act at different time and spatial scales, and their coupling is difficult to quantify.
My research focus on the analysis of geodetic time-series and mechanical modelling on a long term to study the mechanics of landslides and impacts of different forcings.

In addition to opportunities provided by collaborations with different colleagues in Norway, Iceland, Iran, Nepal, Lebanon, France, my research on this thematic is structured by two main projects on landslide analysis in Peru: (1) landslides in the Colca valley forced by earthquakes (see before), (2) landslides in the desertic valleys of Siguas and Vitor triggered by massive irrigation.

Publications

  • 2011, A. Helmstetter, G. Ménard, D. Hantz, P. Lacroix, F. Thouvenot & J.-R. Grasso, Etude multidisciplinaire d’un effondrement dans la carrière de ciment de Saint-Martin-le-Vinoux, Journées Aléa Gravitaire, Sept 2011, Strasbourg.
  • 2013, Lacroix P., D. Amitrano, Long term dynamic of rock slides and damage propagation inferred from mechanical modelling, J. Geophy. Res. - Earth Surface. doi : 10.1002/2013JF002766
  • 2016, Zerathe, S., Lacroix, P., Jongmans, D., Marino, J., Taipe, E., Wathelet, M., ... & Tatard, L. Morphology, structure and kinematics of a rainfall controlled slow‐moving Andean landslide, Peru. Earth Surface Processes and Landforms.
  • 2019, Lacroix, P., Araujo, G., Hollingsworth, J., & Taipe, E.. Self entrainment motion of a slow‐moving landslide inferred from Landsat‐8 time‐series. Journal of Geophysical Research: Earth Surface
  • 2020, Lacroix, P., Dehecq, A. & Taipe, E. Irrigation-triggered landslides in a Peruvian desert caused by modern intensive farming. Nature Geosciences. 13, 56–60 (2020) doi:10.1038/s41561-019-0500-x
  • 2020, Lacroix P., A. Handwerger, G. Bièvre. Life and death of slow-moving landslides, Nature Reviews Earth & Environment.

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