Sensitivity Analysis of Soil Site Response Modelling in Seismic ... - ITC

As the population grows the risk gets higher in many earthquake prone areas, especially in developing
countries. Over 90 % of disaster related deaths occur among the two-thirds of the world’s population
who live in the less developed countries and about three quarters of all the economic damage is confined
to the more developed countries (Smith 2001). Thus Asia, suffers greatly from natural disasters
because of its large population, many of whom live in poverty and are concentrated in dense clusters
in tectonically active zones or near low-lying coasts subject to cyclones and floods. Additionally, most
earthquakes killing more than 100,000 people have occurred along the Himalayas, the Middle East and
the Alps to the western Mediterranean and North Africa (Smith 2001). Casualty and the occurrence
rate make Nepal one of the most vulnerable areas in the world. Above all, being a developing country,
it is one of the places that need special attention regarding the disaster issues.
Many developing countries lack in funding for the studies that are needed for risk analysis and further
studies. Many big organizations such as European Commission (EC) and United Nations (UN) have
projects ongoing in the area. Although the special attention needed is given, there is still need for new
researches and implementations.
One of the current research projects at ITC also focuses on risk management, and is entitled “Strengthening
Local Authorities in Risk Management”. In this project Kathmandu and its surrounding regions
are chosen as case study areas. This research falls into the seismic hazard assessment section and also
will be an input for further analysis such as, building and population vulnerability estimation.
As mentioned before risk management starts with the characterization of the hazard, which is seismic
hazard analysis. For seismic hazard analysis and mapping a popular approach is to create zones. Seismic
zoning can be distinguished into two: macro and microzoning. Seismic macrozoning consists of
dividing the national territory into several areas indicating progressive levels of expected seismic intensity
for different return periods. These zones can be described in terms of peak acceleration values
or any other strong ground motion parameter (Giardini 1999). Macrozoning, different then microzoning
focuses on small scales and includes probability. As seen below (Figure 1-2), the scale of the maps
helps just to give an overall idea of the earthquake prone regions. For defining earthquake source
zones regional tectonics are used but they do not take into account the regional geology. Earthquake
catalogues are important in this assessment since they point out the tectonically active regions.
2
Sensitivity Analysis Of Soil Site Response Modelling In Seismic Microzonation For Lalitpur, Nepal