Seismically-induced changes in sea-level markers: Jolly Buoy Island, South Andaman

Sea-level markers like coastlines, landforms, tidal notches and coral reefs can unveil the seismic behaviour of subduction processes. Jolly Buoy Island, South Andaman, has undergone a remarkable change in shape and orientation due to rising sea levels and active tectonics. Involving integrated field, remote sensing and GIS techniques, we systematically estimated shoreline change rate, reef uplift and morphometry of tidal notches to track inter-, co- and postseismic periods. We quantified higher subsidence rates in the SW coast (-0.227m) than in the NE coast (-0.128m) during the coseismic period from geomorphology and biological resource mapping. The uplift was evident during the postseismic period in the NE and Eastern part of the Island compared to the SW and Western coast. The shoreline change analysis corroborates the results of the seaward migration of the northeast coastline. A gradual fading of uplift towards the southwest coast cause erosion in that part. The tidal notches identified during fieldwork also suggest similar subsidence and uplift patterns. Finally, here we proposed a model of geomorphological evolution of Jolly Buoy with possible local tectonic connections. More seismic data and geomorphic evidence from other islands can reveal regional significance.

Automated summary

Sea-level markers such as coastlines, landforms, tidal notches, and coral reefs can provide insights into the seismic behavior of subduction processes. In this study, the researchers investigated the changes in shape and orientation of Jolly Buoy Island in South Andaman, which were attributed to rising sea levels and active tectonics. By utilizing fieldwork, remote sensing, and GIS techniques, they systematically estimated shoreline change rate, reef uplift, and morphometry of tidal notches to track different seismic periods. The results showed higher subsidence rates in the southwest coast during the coseismic period and evident uplift in the northeast and eastern parts of the island during the postseismic period.