Analysis of a new geomorphological inventory of landslides in Valles Marineris, Mars

We completed a systematic mapping of landslides in a 10(5) km(2) area in Tithonium and lus Chasmata, Valles Marineris, Mars, where landslides are abundant. Using visual interpretation of medium to high-resolution optical images, we mapped and classified the geometry of 219 mass wasting features, including rock slides, complex/compound failures, rock avalanches, debris flows, and rock glacier-like features, for a total landslide area of A(LT) = 4.4 x 10(4) km(2), 44% of the study area, a proportion larger than previously recognised. Studying the landslide inventory, we showed that the probability density of landslide area p(A(L)) follows a power law, with a scaling exponent alpha = -1.35 +/- 0.01, significantly different from the exponents found for terrestrial landslides,alpha = -2.2 and alpha = -2.4. This indicates that the proportion of large landslides (A(L) > 10(7) m(2)) is larger on Mars than on Earth. We estimated the volume (V-L) of a subset of 49 deep-seated slides in our study area and found that the probability density of landslide volume p(V-L) obeys a power law trend typical of terrestrial rock falls and rock slides, with a slope beta = -1.03 +/- 0.01. From the combined analysis of landslide area and volume measurements, we obtained a power law dependency comparable to a similar relationship obtained for terrestrial bedrock landslides, V-L = (1.2 +/- 0.8) x A(L)((1.25 +/- 0.03)) . From the fall height H-L and run out length L-L of a subset of 83 slides unaffected by topographic confinement, we obtained the mobility index (Helm's ratio) HULL, a measure of the apparent friction angle of the failed materials, phi = 14.4 degrees +/- 0.4 degrees. Slope stability simulations and back analyses performed adopting a Limit Equilibrium Method, and using Monte Carlo approaches on failed and stable slopes, suggest that the large landslides in Valles Marineris were seismically induced. (C) 2014 Elsevier B.V. All rights reserved.