Assessment of uncertainties related to seismic hazard using fuzzy analysis

Abstract

Seismic hazard analysis in the last few decades has become a very important issue. Recently, new technologies and available data have been improved that have helped many scientists to understand where and why earthquakes happen, the physics of earthquakes, etc. Scientists have begun to understand the role of uncertainty in seismic hazard analysis. However, how to handle existing uncertainty is still a significant problem. The same lack of information causes difficulties in quantifying uncertainty accurately. Usually, attenuation curves are obtained in a statistical manner: regression analysis. Statistical and probabilistic analyses show overlapping results for the site coefficients. This overlapping takes place not only at the border between two neighboring classes but also among more than three classes. Although the analysis starts from classifying sites using geological terms, these site coefficients are not classified at all. In the present study, this problem is solved using fuzzy set theory. Using membership functions, the ambiguities at the border between neighboring classes can be avoided. Fuzzy set theory is performed for southern California in the conventional way. In this study, standard deviations that show variations between each site class obtained by fuzzy set theory and the classical manner are compared. Results of this analysis show that when we have insufficient data for hazard assessment, site classification based on fuzzy set theory shows values of standard deviations less than those obtained using the classical way, which is direct proof of less uncertainty.

Seismic Hazard Analysis Using Fuzzy-Probabilistic Approach for Chennai City, South India

“…The process of accounting for both the uncertainties in seismic hazard studies is known as Fuzzy -Probabilistic Seismic Hazard Analysis (FPSHA). Worldwide, the studies involving the FPSHA e.g., Frangopol et al (1988), Jorjiashvili et al (2012), Boostan et al (2015), Hiremath (2016) and Andric & Lu (2017) denote the importance and developments in the SHA using the fuzzy logic approach. It is noted that the seismic hazard studies considering the earthquake events after 2011 AD have not been accounted for in the study area, Chennai city, south India.…”