GIS TOOL FOR SEMI-AUTOMATIC HAZARD ASSESSMENT OF EARTHQUAKE-TRIGGERED LANDSLIDES

A new GIS code was developed for analyzing the risk of seismically induced slope instabilities in order to obtain maps showing areas with the greatest level of risk. Semi-automatic program was written in Phyton, using ArcGIS software and feeding by geologic-geotechnical data.

The code consists on the implementation of the Newmark’s method in local and regional scale, with the objective of obtaing the Newmark displacement maps and critical acceleration. For that purpose, we need to use an infinite-slope limit equilibrium model by means of a geographic information system.

It is important to emphasize that the code obtains the safety factors and critical acceleration values for circular and non-circular failure surfaces based on different methods of limit equilibrium, such as Bishop or Janbu and Morgenstern-Price.

In order to feed the program, we need a huge quantity of empirical data could be difficult to obtain, for instance, geologic-geotechnical from lithological classification.

Such data can be obtained from the standard penetration test (SPT), from the field campaign, if and when the terrain is a soil. Nevertheless, it can exist a rock substratum; in that case we need to know the strength parameters presents in the rock discontinuities, for example the cohesion or the angle of frictional.

On the other hand, we need to take into account the slope maps. These are essential for instabilities. Depending, fundamentally, on lithology, hydrologic conditions (dry or saturated) and other external factors, for example the intensity level of the ground shaking during the occurrence of an earthquake.