Terrestrial Laser Scanner has been used to detect rock falls which
have occurred in a limestone cliff during some years, in the difficult
configuration of the Subalpine Chains. In a rock wall of width 750
m and height 200 m, 130 rock falls larger than 0.1 m3 have been detected
for a period of 1180 days.
The distribution of the rock fall volumes is well fitted by a power
law, with an exponent which is compatible with the exponent found
for the 120 km long cliffs of the Grenoble area. But the spatialtemporal
frequencies given by the two analyses are very different. The number
of rock falls larger than 1 m3, which occur per century and per hm2,
is about 150 times larger for the bedded limestone of Sequanian stage
than for the massive limestones of Tithonian and Barremian stages.