Numerical Simulation of Tsunami Generated by the Dense Pyroclastic Deposit Landslide from the 1815 Tambora Caldera Eruption

Abstract

The 1815 eruption of the Tambora caldera was one of the most powerful volcanic events ever recorded and generated tsunamis that affected coastal areas around Sumbawa and parts of East Java. One mechanism thought to have contributed to tsunami generation is the entry of dense pyroclastic flow deposits into the sea. This study conducts numerical simulations using COMCOT version 1.7 Beta and TUNAMI N1 to model tsunami waves produced by two potential triggering mechanisms: dense pyroclastic deposit landslides and artificial waves representing non-landslide processes. The simulations were applied to several potential source zones identified from geological evidence around the caldera. The primary objective of this research is to evaluate and compare the accuracy of these two mechanisms by examining how well each reproduces the historical characteristics of the 1815 tsunami, particularly wave heights and arrival times in both near-source and far-field regions. The results show that the artificial-wave scenario produces wave heights that greatly exceed historical accounts in proximal areas, with values of 16.17 meters at Tambora and 14.67 meters at Sanggar. In contrast, the dense-landslide scenario yields 6 meters and 3.67 meters at these locations, values that closely match historical reports of 5 to 6 meters and 4 meters. In distal regions such as Sumenep and Besuki, both scenarios underestimate the recorded tsunami heights, producing less than 1 meter compared with documented values of 1 to 2 meters. These discrepancies suggest the presence of additional tsunami-generating processes not captured by the models. Overall, the dense-landslide scenario offers a more realistic representation of the near-field tsunami impacts, while further refinement is required to fully account for the observed effects in more distant areas.