Assessment of Physical Vulnerability of Buildings to an Earthquake Using Local TOPSIS and Global TOPSIS: A Case Study of the San Fernando Valley

Natural hazards occasionally cause significant structural and economic damage, along with the loss of human lives. Earthquakes are one type of natural hazards continue to threaten California due to the presence of many faults in the area. One way to reduce the threat to lives and property is to undertake a number of preventative measures aimed at reducing risk. Due to the fact that preventative measures are often expensive, it is important to target those structures at greatest risk of earthquake damage for earliest or most robust remediation, or even elimination. This study focuses on the San Fernando Valley in Los Angeles County, an area of active tectonism with more than 10,000 earthquakes per year, and aims to assess physical vulnerability of buildings within this area. This paper compares two risk analysis methods for buildings in Los Angeles’ San Fernando Valley. Global Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) and Local TOPSIS are evaluated as possible options for risk analysis. The data analyzed in this paper shows that there are significant differences between the results of the two methods. One of the limitations of Global MCDA method is that it assumes spatial homogeneity across the whole study area and does not take into account local factors. Although Local TOPSIS is better at assessing vulnerability of buildings to earthquakes based on local factors and ranges of values, the results of Global TOPSIS were found to more accurately predict buildings’ vulnerability to earthquakes.