The topography of the escarpments allows us to estimate the mode of slip of the faults
Fault slip, particularly during earthquakes, can generate topographic jumps on the surface, commonly known as fault escarpments. Since the 1970s, numerous studies have demonstrated that the topography of a fault escarpment can be used to date its formation and constrain the rate of fault slip.
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Publication date: 22/03/2023
Press, Research
Related teams :
Tectonics and Mechanics of the Lithosphere
Related themes : Earth System Science
Once an escarpment has formed, it is progressively eroded according to a law of diffusion, resulting in a decrease in its slope and curvature. This decrease provides information about the length of time the escarpment has been eroded, and therefore about its age. The height of the escarpment divided by this age indicates the rate of sliding.
A study carried out by a team of scientists from the CNRS-INSU (see box) goes further and shows that the topography of escarpments also records the history of seismic or asismic landslides that formed the escarpment. A new analytical model of the topographic evolution of an escarpment has been developed, taking into account erosion by diffusion, the slip speed of the fault and, above all, the mode of slip of the fault, whether it be a single seismic rupture, several seismic ruptures or an asismic slip (i.e. a continuous slip). Using this model, the study shows that the final topographic shape of the escarpment generated by a single seismic rupture or by asismic slip, of the same amplitude, can deviate by 10 to 20%.
This result opens up the theoretical possibility of estimating not only cumulative slip or slip velocity, but also the number and size of earthquakes based on escarpment morphologies. In addition, this study is the first to show that the topography of landforms provides information not only on the speed of faults, but also on their mode of slip.
Article originally published on the CNRS-INSU website: https://www.iledefrance-villejuif.cnrs.fr/fr/cnrsinfo/la-topographie-des-escarpements-permet-destimer-le-mode-de-glissement-des-failles
