11 research outputs found
Slope vulnerability to earthquakes at subregional scale, using probabilistic techniques and geographic information system
The susceptibility of slopes to failure during earthquakes is calculated, in terms of critical horizontal acceleration,
on a subregional scale for the upper part of the Serchio River basin (Tuscany, Italy). According to the working scale
(1:10 000) and to the availability and accuracy of the input data, the infinite slope analysis was judged to be the most
appropriate method, but particular attention was devoted to the error evaluation due to spatial variability of the
geotechnic, geometric, and hydrologic parameters. A geologic, geomorphologic and hydrologic survey of the area was
therefore performed, and the geotechnic parameters were collected at local administrations. All the data were stored
in a GIS, used as a tool to build the spatial and attribute data base and to prepare the input data layers for the
stability analysis. In order to assess the variability of geotechnic parameters, a statistical analysis was performed to
assign the best-fitting probability distribution to cohesion, angle of internal friction and unit weight of the soil. As
hydrogeologic data were not available for the area, only surface hydrology information could be used; a map of
probability of spring occurrences was derived by a bayesian method, the Weight of Evidence Modelling, and was
used as groundwater indicator. A Monte Carlo procedure and a first-order second-moment method were applied and
compared as error estimators in assessing the slope susceptibility to failure. The differences between the two methods
are discussed, and two maps showing, respectively, the critical horizontal acceleration and the probability of failure
associated with each slope are presented, together with the curve plotting the reliability index against the probability
of failure