Authors / CoAuthors
Davies, G.
Abstract
Large tsunami occur infrequently but can be extremely destructive to human life and the built environment. Management of these risks requires an understanding of the possible sizes of future tsunami, and the probability that they will occur over some time interval of interest. Herein we present a globally extensive probabilistic assessment of tsunami runup hazards, considering only earthquake sources as these have been responsible for about 80% of destructive tsunami globally. The global scale of the analysis prevents us from exploiting detailed site specific data (e.g. high-resolution elevation data, tsunami observations), and because of this we do not suggest the analysis is appropriate for local decision making. However, consistent global analyses are useful to inform international disaster risk reduction initiatives, and can also serve as a reference and potential source of boundary conditions for regional and local tsunami hazard assessments. A global synthetic catalogue of 17000 tsunamigenic earthquake events is developed with magnitudes ranging from 7.5 to 9.6. The geometry of the earthquake sources accounts for the detailed three-dimensional shape of subduction interfaces, when the latter is well constrained. The rate of earthquake events is modelled such that on each earthquake source zone, the earthquakes follow a Gutenberg-Richter magnitude-frequency distribution, and the time-integrated earthquake slip balances the seismic moment release rate inferred from the convergence of neighbouring tectonic plates. Tsunami propagation from each earthquake is modelled globally, and runup height is estimated roughly by combining the global model with heuristic treatments of nearshore tsunami amplification. We evaluate the accuracy of this approach by comparing runup observations from four globally significant historical tsunami with model scenarios having the same earthquake magnitude and location (i.e. without event-specific calibration). Around 50% of runup observations are within a factor of two of the model predictions. The dominant source of uncertainty in the modelled runup seems related to limitations in the earthquake source representation, with limitations due to the global runup methodology being a significant but secondary issue. These uncertainties are modelled statistically, and integrated into the hazard computations. In most locations, the modelled tsunami runup exceedance rate is sensitive to assumptions about the maximum possible earthquake magnitude on nearby earthquake source zones, and the fraction of plate convergence accommodated by non-seismic processes. We model the uncertainties of these (typically) poorly constrained processes using a logic-tree. For any site and chosen exceedance rate, this allows the mean runup (integrated over all logic tree branches) to be estimated, and associated runup confidence intervals to be derived. As well as highlighting the uncertainties in tsunami hazard, the analysis suggests relatively high hazard around most of the Pacific Rim, especially on the east coast of Japan and the west coast of South America, and relatively low hazard around most of the Atlantic outside of the Caribbean. Runup hazards on the east and west coast of Australia are relatively poorly constrained, because there are large uncertainties in the maximum magnitude earthquake which could occur on key source zones in the eastern Indian Ocean and western Pacific.
Product Type
document
eCat Id
101660
Contact for the resource
Resource provider
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Keywords
- Australian and New Zealand Standard Research Classification: Fields of Research
-
- Earth Sciences
-
- Published_Internal
Publication Date
2017-02-17T12:00:00
Creation Date
2016-08-23T00:00:00
Security Constraints
Legal Constraints
Status
Purpose
Maintenance Information
notPlanned
Topic Category
geoscientificInformation
Series Information
Lineage
Drafted at GA and reviewed by co-authors
Parent Information
Extents
[-90, 90, -180, 180]
Reference System
Spatial Resolution
Globally extensive
Service Information
Associations
Downloads and Links
Source Information