Tectonic deformation along subduction zone usually causes prominent land-level changes, and signatures of such land-level changes are well preserved in the sediment succession as well as in coastal landforms. It has been observed around the globe that most of the subduction zone earthquakes have usually resulted into uplift or subsidence along the coastline adjacent to the ruptured segment (McCalpin, 1996; Satake and Atwater, 2007). Numerous studies of near sub-surface stratigraphic records and coastal landforms have helped in identifying evidences of great earthquakes and associated tsunamis which occurred during recent pre-historic and historic past, and also in reconstructing the history of such events (e.g., Atwater and Moore, 1992; Nelson et al. 1996; Goff et al. 2006, 2012; Bourgeois and Johnson, 2001; Nanayama et al. 2003; Cisternas et al. 2005; Satake and Atwater, 2007; Malik et al. 2011, 2015, 2019).
The past seismicity data from Andaman and Nicobar Islands is available for a very short period of about 400 years (Iyengar et al. 1999; Oritz and Bilham, 2003; Bilham et al. 2005). These large magnitude earthquakes are 28 January 1679 (Mw 7.5?), 2 April 1762 (Mw 8.5–8.7), 31 October 1847 (Mw 7.5–7.9), 31 December 1881 (Mw 7.9), 26 June 1941 (Mw 7.7) and the 26 December 2004 Sumatra-Andaman earthquake (Mw 9.3) (Fig. 1a). The damage pattern and total life loss by Indian Ocean Tsunami (IOT) caused by the 2004 earthquake clearly revealed a poor understanding of such threats along the shorelines of Andaman and Nicobar (A&N), Indian Mainland and regions surrounding Indian Ocean. The 2004 earthquake caused dramatic land-level changes along the Sumatra-Andaman arc (Malik and Murty, 2005; Meltzner et al. 2006; Kayanne et al. 2007). An uplift of > 1 m occurred along the west coasts of the Andaman Islands, whereas a wide zone of subsidence was experienced on the back-arc side with its axis near Port Blair, where 0.95 m of coseismic subsidence was measured by tidal observations (Malik and Murty, 2005; Malik et al. 2006). The zone of subsidence, which occurs above the down-dip edge of the source rupture, is traceable farther south to Great Nicobar Island where the maximum subsidence of about 3 m was observed (Malik and Murty, 2005). Studies during the last two decades (e.g., Malik and Murty, 2005; Malik et al., 2006, 2011, 2015, 2019; Kayanne et al. 2007; Cummins, 2007; Monecke et al. 2008; Jankaew et al. 2008; Rajendran et al. 2008, 2011, 2013; Fujino et al. 2008, 2009; Rubin et al. 2017) have provided significant understanding towards the occurrence of paleo-earthquakes and paleo-tsunami events along the Sumatra-Andaman Subduction Zone and the Arakan Subduction Zone. Several tsunami events in addition to the 2004 event and the associated giant tsunami have been reported that occurred during the medieval period CE 660–880, CE 850–900, CE 1100–1300, CE 1679, and CE 1762 (Malik et al. 2011; 2015). Among them, the CE 660–880 and CE 1100–1300 were transoceanic tsunami events triggered along the Andaman-Arakan and Andaman segments respectively (Malik et al., 2015). The earliest tsunamis occurred between the second and sixth centuries CE, evidenced by coral debris of the southern Car Nicobar Island. A subsequent tsunami, probably in the range CE 770–1040, is inferred from deposits both in A&N and on the Indian subcontinent. Recent paleo-seismic and paleo-tsunami studies from South Andaman revealed signatures of seven tsunamis from shallow stratigraphic record of the past 8000 years (Malik et al., 2019). These tsunamis correspond to historical tsunamis those occurred in CE 1881, 1762, and 1679, and provide evidence for prehistoric tsunamis in CE 1300–1400, in BCE 2000–3000 and 3020–1780, and before BCE 5600– 5300 (Malik et al., 2019).
Amongst the historical events the 1881 event (Mw7.9) caused land-level changes near the sources area around Car Nicobar. It has been suggested that the location of the 1881 rupture was close to Car Nicobar, which resulted in tilting the island by uplifting the west coast by 50 cm relative to east coast (Bilham et al. 2005). Also the event of 1941(Mw7.7) resulted into land-level change, causing submergence of Little Andaman and South Andaman by > 50 cm (Ortiz and Bilham, 2003). However, the amount of subsidence compared to the 2004 Sumatra-Andaman event is smaller because of the smaller magnitude (Ortiz and Bilham, 2003; Bilham et al. 2005).
Here, in this article we report the geomorphological changes that occurred inland away from the coastal zone, and to compare them with the GPS measurements obtained in the following years after the earthquake. Shallow stratigraphic record obtained from the study area revealed geological signature of land-level changes (uplift and subsidence) caused by the past earthquakes and paleo-tsunami deposits. The present study also helped us comparing the effect of 2004 earthquake and tsunami with the past events.