Integrating GIS and multi-criteria decision making techniques (AHP and TOPSIS) for earthquake hazard map generation and analysis: Case of Kucukcekmece region

Earthquake disasters and related hazards have continued to cause severe impacts on human lives and livelihood resulting in widespread socio-economic and environmental damages worldwide. These significant risks associated with earthquakes are not likely to recede in the future posing serious threats to many communities and populations unless intervention measures are undertaken. To this effect, there has been rising need and recognition of comprehensive and effective disaster and emergency management (DEM) efforts required for relevant planning, response and development of strategy for risk reduction and mitigation. Recent developments in geospatial technologies have emerged that have opened new opportunities in issues of DEM with increasing demand for spatial data now becoming more and more required to meet the demands in aiding the increasingly complex decision making process by emergency managers involving large number of stakeholders across multi-disciplinary teams and conflicting evaluation alternatives. This has led to the development of scientific methods known as Multi-Criteria Decision Analysis (MCDA) that greatly improve the quality of the decision-making process to make it more explicit, rational and efficient. These combined attributes of the method enable a real participatory process involving stakeholders, conflicting criteria and multiple teams involved in emergency management, which are critical for successfully implementing sustainable disaster management mitigation strategies. In this study, MCDA techniques of Analytical Hierarchical Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) integrated with GIS, were used to produce earthquake hazard and risk maps for earthquake disaster monitoring and analysis for a case study region of Küçükçekmece in Istanbul, Turkey. Five (5) main criteria and parameters that have the strongest influence on the impact of the earthquake on the study region were determined as topography, distance to epicentre, soil classification, liquefaction, and fault/focal mechanism. Using the AHP approach (pairwise comparison technique), the weights of the parameters that affect the earthquake ground motion at the study area were determined and an earthquake hazard map was produced using GIS software (ESRI ArcGIS). These weights were also used as input into the TOPSIS method for generation of earthquake hazard map. This TOPSIS map result was subsequently used, for comparison and analysis with the output from the AHP technique. The model outputs generated were comparable with each other showing how closely they matched and from statistical analysis performed, had a high correlation. The map outputs also reflected the cooperate opinions of experts involved in earthquake disaster and risk assessment, thus more comprehensive. To analyze the earthquake risk for the study region, population and building data were used with the AHP and TOPSIS hazard map outputs to map the elements at risk for potential loss assessment. Thus, demonstrating the potential of integrating GIS and MCDA by use of AHP and TOPSIS in generating hazard maps for more effective disaster and risk management of earthquakes. This study further reviewed and analysed selected spatial decision support systems (SDSSs) related to GIS-based applications in earthquake DEM ranging from simulation based, early warning and rapid response and loss estimation systems. These are broadened into global systems to include HAZTURK, QLARM, SELENA, DBELA, CATS, PAGER and regional and local systems comprising of ELER, HAZUS-MH, KOERILoss, MAEviz, EQRM and LNECLOSS. From the analysis of SDSS usage worldwide and in Turkey, HAZTURK software was recommended for implementation of earthquake risk and loss estimation studies in Turkey based on its significant comparative advantages over other SDSS and suitability and applicability to the local conditions of Turkey, which have been discussed in this study. Key challenges to be addressed range from issues in spatial data acquisition, quality, interoperability, data exchange and lack of coordination among associated institutions involved in earthquake DEM and recommendations as well as future functional improvements and developments of HAZTURK software, to this effect, have been characterised for successful implementation in Turkey.