First Order Seismic Microzonation of Delhi, India Using Geographic Information System (GIS)

Abstract

A first order seismic microzonation map of Delhi is prepared using five thematic layers viz., Peak Ground Acceleration (PGA) contour, different soil types at 6 m depth, geology, groundwater fluctuation and bedrock depth, integrated on GIS platform. The integration is performed following a pair-wise comparison of Analytical Hierarchy Process (AHP), wherein each thematic map is assigned weight in the 5-1 scale: depending on its contribution towards the seismic hazard. Following the AHP, the weightage assigned to each theme are: PGA (0.333), soil (0.266), geology (0.20), groundwater (0.133) and bedrock depth (0.066). The thematic vector layers are overlaid and integrated using GIS. On the microzonation theme, the Delhi region has been classified into four broad zones of vulnerability to the seismic hazard. They are very high (>52%), high (38-52%), moderate (23-38%) and less (<23%) zones of seismic hazard. The ''very high'' seismic hazard zone is observed where the maximum PGA varies from 140 to 210 gal for a finite source model of M w 8.5 in the central seismic gap. A site amplification study from local and regional earthquakes for Delhi region using Delhi Telemetry Network data shows a steeper site response gradient in the eastern side of the Yamuna fluvial deposits at 1.5 Hz. The 'high' seismic hazard zone occupies most of the study area where the PGA value ranges from 90 to 140 gal. The 'moderate' seismic hazard zone occurs on either side of the Delhi ridge with PGA value varying from 60 to 90 gal. The 'less' seismic hazard zone occurs in small patches distributed along the study area with the PGA value less than 60 gal. Site response studies, PGA distribution and destruction pattern of the Chamoli earthquake greatly corroborate the seismic hazard zones estimated through microzonation on GIS platform and also establishes the methodology incorporated in this study.

First level seismic microzonation map of Chennai city – a GIS approach

“…These weights also add up to 1 and can be used in deriving the weighted sums of rating for each region of polygons of the mapped layers. This approach has also been successfully used by Mohanty et al (2007) for the similar type of microzonation studies.…”

Multi-Pronged Search for Palaeo-Channels near Konark Temple, Odisha - Implications for the Mythical River Chandrabhaga

“…These were subsequently integrated using the respective weights obtained by Saaty's analytical hierarchy process (AHP) 7 , a methodology successfully applied for data integration in various geophysical studies [8][9][10] . AHP is a multi-criteria mathematical evaluation method in the decision-making process.…”

GIS Based Evaluation in Earthquake Hazard Micro-Zonation - A Case Study of Madang and Morobe Province, Papua New Guinea

“…According to Pal, et al (2006) the earthquake hazard zonation in Sikim Himalaya was prepared from analysing 8 thematic layers within the GIS platform. Pal et al (2006) have integrated several environmental and seismic data layers namely: Geology (GE), Soil Site Class (SO), Slope (SL), Landslide (LS), Rock Outcrop (RO), Frequency Wave number (F-K) simulated Peak Ground Acceleration (PGA), Predominant Frequency (PF), and Site Response (SR) at predominant frequencies using Geographic Information System (GIS). The study was carried through assigning ranking and weightage and then normalizing the weightage and rankings using Satty's analytical hierarchy process.…”

“…Pair-wise comparison matrix for 4 factors assessed for the delineation of earthquake hazard levels is shown in Table 2. After normalizing to restore consistency about the weight assigned for each factor and class, the spatial analysis 2456-1908(O) www.ijaers.com Page | 100 tool; raster calculator in ArcGIS 10 was employed to derive the final thematic map for Earthquake hazard levels for the study region through employing the formula adopted from Pal et al (2006). …”