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CSDMS 2018 annual meeting - Geoprocesses, geohazards

Simulating the tsunami hazard: quantitative predictions

Robert Weiss

Virginia Tech, United States

Earthquakes are the most frequent source of classic tsunami waves. Other processes that generate tsunami waves include, landslides, volcanic eruption and meteorite impacts. Furthermore, atmospheric disturbances can also generate tsunami waves or at least tsunami-like waves, but we are just at the beginning of understanding their physics and frequency. Classic tsunami waves long waves with wavelength that are much longer than the water depth. For earthquake-generated tsunami waves that is true. However, landslides and meteorite impacts generate tsunami waves that are shorter which has a profound effect on the tsunami evolution, but no less dangerous.
Fortunately, tsunamis do not occur frequently enough in any given region to make meaningful prediction of the future tsunami hazard based only on recorded history. The geologic record has to be interrogated. The inversion of meaningful and quantitative data from the geologic record is the main goal of my research. However, there are problems with the geologic record. The most important problem is that we often have trouble to identify tsunami deposits. Second, it is very often difficult to separate the tsunami record from the storm record in regions where storms and tsunamis are competing agents of coastal change. Other problems are concerned with he completeness of the deposits, but also the fact that sedimentary environment before the tsunami hit most likely was eroded is no longer part of the record makes inversion especially tricky. In my research, I assume that the tsunami deposit is identified, but perhaps not complete and what we know about the pre-event conditions is limited.
My talk will cover how the geologic record is used to invert quantitative information about the causative process. We are going to look at grain sizes from sand to boulders and what we can learn from the transport of these very different grain sizes about tsunamis and their impacts along respective coastal areas. The models that are employed to invert flow characteristics from deposits are based on Monte-Carlo simulations to overcome the issue of not knowing the pre-tsunami conditions with great confidence. If time permits, we also see how sea-level change affects tsunami impact at the coast.

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Of interest for:
  • Coastal Working Group