Abstract
Indonesia is exposed to earthquakes, volcanic activities, and associated tsunamis. This is particularly the case for Lombok and Sumbawa Islands in West Nusa Tenggara, where evidence of tsunamis is frequently observed in its coastal sedimentary record. If the 1815 CE Tambora eruption on Sumbawa Island generated a tsunami with well-identified traces on the surrounding islands, little is known about the consequences of the 1257 CE tremendous eruption of Samalas on the neighboring islands, and especially about the possible tsunamis generated in reason of a paucity of research on coastal sedimentary records in this area. However, on Lombok Island, the eruption of the Samalas volcano produced significant volumes of pyroclastic flows that entered the sea in the North and East of the island. These phenomena must have produced a tsunami that left their traces, especially on Sumbawa Island, whose western coastline is only 14 km away from Lombok’s eastern shore. Therefore, the main goal of this study is to investigate, find evidence, and determine the age of marine-origin sediments along the shore of the Alas Strait, Indonesia. We collected and analyzed samples of coral and seashells from marine deposits identified along the west coast of Sumbawa, i.e., in Belang Island and abandoned fishponds in Kiantar Village, in order to identify the sources and the occurrence period of these deposits events. Based on the radiocarbon dating of coral and seashell samples, we concluded that none of the identified marine deposits along the western coast of Sumbawa could be related chronologically to the 1257 CE eruption of Samalas. However, possible tsunami deposits located in Belang Island and abandoned fishponds in Kiantar Village yielded 4th century CE, 9th century CE, and 17th century CE. We also conclude that past large earthquakes triggered these tsunamis since no known volcanic eruption occurred near the Alas Strait at that time that may have triggered a tsunami.
Highlights
The Indian Ocean earthquake and tsunami on 26 December 2004 is considered as a turning point of disaster awareness and mitigation, especially in Indonesia, since theyThe Indian Ocean earthquake and tsunami on 26 December 2004 is considered as a turning point of disaster awareness and mitigation, especially in Indonesia, since they changed their disaster paradigm from response to preparation and damage prevention changed their paradigm from response to and damage prevention following that disaster event
At selected locations, eight vertically contiguous sand samples were collected from previously cleaned outcrops for further analysis, i.e., grain size analysis and analysis with the anisotropy of magnetic susceptibility (AMS) technique, which in detail will be explained in the part
Deposits found on the western coast of Sumbawa have common characteristics with tsunami deposits, such as fining upwards within the deposits as well as poor sorting of sediments
Summary
The Indian Ocean earthquake and tsunami on 26 December 2004 is considered as a turning point of disaster awareness and mitigation, especially in Indonesia, since they changed their disaster paradigm from response to preparation and damage prevention changed their paradigm from response to and damage prevention following that disaster event. To its activities, tectonic configuration, Indonesia is continuously exposed to earthquakes andDue volcanic as well as their related is continuously exposed to earthquakes and volcanic activities, as well as their related hazards such as landslides and tsunamis [5,6,7,8,9,10,11,12] This makes it a useful natural laboratory. According to the global historical tsunami[5,6,7,8,9,10,11,12]
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