Archaeoseismology and Palaeoseismology in the Alpine ... - Tierra

Fig. 6: Comparison of the results of three different models for
runout prediction and possible landslide.
A comparison of the different model predictions for runout
distances is shown in Fig. 6. Results of all models (empirical
and numerical) agree with observed runout distances in
some areas. Here rock fall deposits might be characterised
1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology
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as younger events. In other areas, especially on the SW‐
flank, observed runout distances vary strongly from model
predictions. A secondary post‐depositional transport of
older rockfall deposits, by a landslide or by creep might
provide an explanation. A possible landslide that can be
derived from the topography is shown in figure 6. Another
explanation is a debris avalanche that was triggered by an
earthquake.
HAZARD MAPPING
As a preliminary step for risk analysis a hazard map, which
includes rockfall susceptable zones, is required. The
evaluation of the modelled data demands a choice of one
classification including adequate methods.
The classification after Aleotti and Chowdhury (1998) was
picked for hazard mapping, which distinguishes between
qualitative and quantitative approaches. Qualitative
methods contain e.g. geomorphologic analysis or index‐ or
parameter maps and the quantitative methods consist of
statistical or geotechnical operations. In this study, the
geomorphologic analsis and the deterministic simulation
with Rockfall 6.1 (Spang and Sonser, 1995) was combined
to generate the hazard map.
By using ArcGIS, the source zones, deposit areas, and
rockfall traces were created and combined. These
computation resulted in three rockfall susceptible zones,
which belong to different source areas, as shown in Fig. 7.
Fig. 7: Hazard map, as a result of combining data of field survey and simulations, with endangered zones and infrastructure on
the NE‐side of the San Bartolomé.