Tsunami records of the last 8000 years in the Andaman Island, India, from mega and large earthquakes: Insights on recurrence interval

Abstract

As many as seven tsunamis from the past 8000 years are evidenced by sand sheets that rest on buried wetland soils at Badabalu, southern Andaman Island, along northern part of the fault rupture of the giant 2004 Aceh-Andaman earthquake. The uppermost of these deposits represents the 2004 tsunami. Underlying deposits likely correspond to historical tsunamis of 1881, 1762, and 1679 CE, and provide evidence for prehistoric tsunamis in 1300–1400 CE, in 2000–3000 and 3020–1780 BCE, and before 5600–5300 BCE. The sequence includes an unexplained hiatus of two or three millennia ending around 1400 CE, which could be attributed to accelerated erosion due to Relative Sea-Level (RSL) fall at ~3500 BP. A tsunami in 1300–1400, comparable to the one in 2004, was previously identified geologically on other Indian Ocean shores. The tsunamis assigned to 1679, 1762, and 1881, by contrast, were more nearly confined to the northeast Indian Ocean. Sources have not been determined for the three earliest of the inferred tsunamis. We suggest a recurrence of 420–750 years for mega-earthquakes having different source, and a shorter interval of 80–120 years for large magnitude earthquakes.

A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa: REPLY

“…We agree with Somerville that the absence of sedimentary evidence for a tsunami near 900 CE in Aceh (Indonesia) and in the Andaman Islands (Rubin et al, 2017;Malik et al, 2019) does not preclude the likelihood of its occurrence, as more recent erosional events could have removed the deposit. For example, field studies in Sri Lanka (Moore et al, 2007) and Thailand (Szczuciński, 2012) described the limited preservation potential of the recent 2004 tsunami deposit due to the erosion generated by subsequent Monsoon rains.…”

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“…This would indicate perhaps that while these diseases are assumed to be relatively new to human experience as a whole, the evolutionary value of uniform behavioral response remains learned or passed down via myth, tales or other cultural means. A similar response to ancient, but recurrent catastrophic threat, was seen in the 2004 tsunami [169][170][171]. In fact, it seems that humans are devoid of any instinctual information concerning disease recognition.…”

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“…In a recent study from South Andaman (Fig. 1), Malik et al (2019) have reported six paleo-tsunamis prior to the 2004 tsunami. Among these, younger tsunami depositions are linked to the historically reported earthquakes of 1881 (Mw 7.9; Car Nicobar), 1762 (Mw ≤8.5; Arakan Coast, Myanmar) and 1679 (magnitude unknown;north Andaman;Iyengar et al, 1999).…”