From regional to local SPTHA: efficient computation of probabilistic tsunami inundation maps addressing near-field sources
<p>Site-specific seismic probabilistic tsunami hazard analysis (SPTHA) is a computationally demanding task, as it requires, in principle, a huge number of high-resolution numerical simulations for producing probabilistic inundation maps. We implemented an efficient and robust methodology using...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-03-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | https://www.nat-hazards-earth-syst-sci.net/19/455/2019/nhess-19-455-2019.pdf |
| Summary: | <p>Site-specific seismic probabilistic tsunami hazard analysis (SPTHA) is a
computationally demanding task, as it requires, in principle, a huge number of
high-resolution numerical simulations for producing probabilistic inundation
maps. We implemented an efficient and robust methodology using a filtering
procedure to reduce the number of numerical simulations needed while still
allowing for a full treatment of aleatory and epistemic uncertainty. Moreover, to
avoid biases in tsunami hazard assessment, we developed a strategy to
identify and separately treat tsunamis generated by near-field earthquakes.
Indeed, the coseismic deformation produced by local earthquakes necessarily
affects tsunami intensity, depending on the scenario size, mechanism and
position, as coastal uplift or subsidence tends to diminish or increase the
tsunami hazard, respectively. Therefore, we proposed two parallel filtering
schemes in the far- and the near-field, based on the similarity of offshore
tsunamis and hazard curves and on the similarity of the coseismic fields,
respectively. This becomes mandatory as offshore tsunami amplitudes can not
represent a proxy for the coastal inundation in the case of near-field sources.
We applied the method to an illustrative use case at the Milazzo oil refinery
(Sicily, Italy). We demonstrate that a blind filtering procedure can not
properly account for local sources and would lead to a nonrepresentative
selection of important scenarios. For the specific source–target
configuration, this results in an overestimation of the tsunami hazard,
which turns out to be correlated to dominant coastal uplift. Different
settings could produce either the opposite or a mixed behavior along the
coastline. However, we show that the effects of the coseismic deformation due
to local sources can not be neglected and a suitable correction has to be
employed when assessing local-scale SPTHA, irrespective of the specific
signs of coastal displacement.</p> |
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| ISSN: | 1561-8633 1684-9981 |