Using Tsunami Deposits to Improve Assessment of Tsunami Risk

Abstract

In many places in the world the written record of tsunamis is too short to accurately assess the risk of tsunamis. Sedimentary deposits left by tsunamis can be used to extend the record of tsunamis to improve risk assessment. The two primary factors in tsunami risk, tsunami frequency and magnitude, can be addressed through field and modeling studies of tsunami deposits. Recent advances in identification of tsunami deposits and in tsunami sedimentation modeling increase the utility of using tsunami deposits to improve assessment of tsunami risk. WHY STUDY TSUNAMI DEPOSITS? Makers of public policy require a better understanding of where future destructive tsunamis might occur and what the possible magnitude, frequency, and history of occurrence of such events might be. Such information would help guide coastal development, location of emergency facilities, and tsunami evacuation planning (Geist et al. 2000). In many places in the world, the written record of tsunamis is too short to accurately assess the risk of tsunamis. Sedimentary deposits left by tsunamis can be used to extend the record of tsunamis to improve risk assessment. When sediment is deposited by a tsunami and preserved, a geologic record of that tsunami is created. By looking at the sedimentary record in an area, geologists may be able to identify such deposits and infer the occurrence of past tsunamis. The recognition of deposits from past tsunamis allows geologists to extend the relatively short or non-existent historical record of tsunamis in an area. Because scientists cannot yet predict when a tsunami will occur, obtaining a geologic record of past events may be one of the only means to assess future risk.