Geoscience Reference
In-Depth Information
A third and inal strategy is to employ tsunami source research. The uncertainties noted
above, and in Appendix A, make clear that wide-ranging research is needed to advance the
understanding of tsunami sources. The challenge is how to keep abreast of, and selectively
encourage, research on the myriad sources of tsunamis that threaten U.S. shores. Nearly all
this research is supported outside NOAA's Tsunami Programs, through the National Science
Foundation (NSF), the U.S. Geological Survey (USGS), and other organizations. The research
engages physical scientists and engineers worldwide, illustrated by the research papers cited
in Appendix A. Two elements of the National Earthquake Hazards Reduction Program (NEHRP)
illustrate how the nation's tsunami programs might harness their efforts to help deine the
subset of tsunami sources that are located near U.S. shores. The irst of these elements is the
periodic assessment of the nation's seismic hazards. Every six years, the USGS produces, for
use in the seismic provisions of building codes, a set of probabilistic National Seismic Hazard
Maps (http://pubs.usgs.gov/fs/2008/3017/). These are supplemented by probabilistic seismic
hazard maps of regional scope—Alaska, the Paciic Northwest, California. Updates to the
earthquake maps involve a series of workshops (held in various parts of the country) that bring
together scientists from government, academia, and consulting companies. The workshops
provide a venue for new indings to be shared and vetted, earlier indings and assumptions
to be checked, and new collaborations and research directions to be inspired. Much of this
research bears directly on tsunami sources that adjoin U.S. shores. A second NEHRP element
that might be adapted by the nation's tsunami programs is an external grants program. NEHRP
external grants administered by the USGS support research that commonly complements the
earthquake research carried out internally by the USGS. A parallel external research program
through NOAA might be used, in part, to help reduce uncertainties about key tsunami sources.
Conclusion:
Because knowledge about the sizes and the recurrence intervals of tsunami
sources are only emerging, improving the understanding of the tsunami sources is critical
to producing comprehensive tsunami risk assessment. Currently, no formal procedures
for periodic re-evaluation of tsunami risks exist. The NEHRP serves as an example of a
successful and useful approach to periodic national assessments.
Recommendation:
NOAA and its NTHMP should institute a periodic assessment of the
sources of tsunamis that threaten the United States, focusing mainly on earthquakes, but
also on landslides and volcanoes.
These assessments could be modeled after, and made jointly with, the assessments for
National Seismic Hazard Maps. Like those maps, the appraisals could be updated every six
years, but with regional assessments as needed. Key unknowns emphasized through this
process could then become priority areas for an external research program that NOAA could
model on the external grants program of the NEHRP in the USGS.
