Revealing effect of bathymetry over tsunami run-up through factor analysis

Abstract

The east coast of Tamil Nadu, particularly Chennai–Nagapattinam was worstly affected by the 2004 tsunami. Run-up shows remarkable variation of 2–8 m with maximum at Cuddalore port and minimum at Marina beach. Factors like width of dislocation, source distance, orientation of the coastline, and bathymetry guide tsunami surge. While most of the parameters are similar in characteristics for the entire coast, it is presumed that variation in bathymetry have played an imperative role in guiding run-up. Based on gradient bathymetry, up to 50 km off the coast was classified into five classes, viz shallow, moderate, and steep continental slope and continental shelf. Statistical analysis was performed between offshore bathymetry and run-up. The results clearly indicate that moderate slopes have guided tsunami to attain maximum height. While steeper slope have acted as barriers and gentle slopes have shoaled tsunami surge resulting in reduced run-up height. The study offers early but potentially meaningful guidance on the role of bathymetry on run-up.