International Symposium on Tsunami Disaster Mitigation in Future
Jan. 17-18, 2005, Kobe, Japan
extremely unlikely. Also, the Puerto Rico trench continues to be an active seismic region that could
pose a near-field hazard to Puerto Rico and the Leeward Islands. Within the last century, the Chilean
Earthquake of 1960 and the Alaska Earthquake of 1964 produced tsunamis that were the most
devastating to the U.S.
Historically, most civil defense planners have been worried about far-field tsunamis caused by
tectonic events or earthquakes on the ocean floor. The sudden movement and shaking of the earth's
plates as they react with one another produces tsunami waves on the oceans surface that travel great
distances across the ocean to distant coastlines. Although volcanic eruptions and asteroids can
trigger tsunamis, these are far less likely. Recent research indicates that many tsunamis can be
generated from co-seismic landslides, triggered by the violent shaking of the Earth's crust.
In the U.S., concern has recently focused not only on the landslide-generated tsunami, but also on
potential near-field or local tectonic sources. Both of these tsunami scenarios have the characteristic
of far less travel time (and reduced warning time for evacuation) from the generation area of the
tsunami to Pacific Ocean coastlines along the U.S. In particular, landslide and slump sources in the
Santa Barbara Channel and Palos Verdes area offshore southern California, and near-field faults in the
Cascadia Subduction Zone, 50 miles offshore the Pacific Northwest coast, and the San Clemente Fault,
southwest of Los Angeles, have received increasing attention.
Because the United States has not had any major tsunami disasters in recent years, the Army Corps
of Engineers does not currently have a formal policy for incorporating tsunami runup considerations in
the design wave height for coastal structures. Coastal structures (i.e., jetties, breakwaters, and vertical
walls) are designed for water levels and wave heights based on historical or numerically-hindcast
storms. Wave forces and loads, although defined in the Coastal Engineering Manual (CEM), are not
specifically calculated for tsunamis. Structural designs are pretty much the same as for storm surge,
e.g., place buildings on piles, allow wash through of ground floors, etc. The breakwaters, flood walls,
and gates, typical in Japan for tsunami protection, are not used in the U.S.
The main emphasis within the Corps is mitigation, or flood zone planning. Warning systems and
tsunami arrival time and height predictions are done by the Pacific Marine Environmental Laboratory
(PMEL) of the National Oceanographic and Atmospheric Administration (NOAA). The Corps
cooperates with other Federal, state, and local agencies such as the Federal Emergency Management
Agency (FEMA), Civil Defense, coastal zone management commissions, and Office of Emergency
Services (OES) organizations. The University of Southern California (USC) has begun preparing
tsunami wave inundation maps for the U.S. Pacific coastline.
The Coastal and Hydraulics Laboratory (CHL) of the U.S. Army Engineer Research and
Development Center (ERDC) does not currently have a mission in tsunami research. Previous CHL
research in the 1970's and 1980's included over 27 publications documenting physical, numerical, and
analytical modeling of far-field tsunami hazards in the Pacific Ocean. Oswalt and Boyd (1966)
conducted a physical model of Hilo Harbor, HI, to evaluate steady flow stability for a tsunami barrier.
Senter (1971) conducted a laboratory study of the effect of tsunami waves on the proposed Crescent
City, CA, Harbor design. Houston et al. (1977) calculated wave frequency of occurrence tables for
the Hawaiian Islands. Houston (1978) simulated the 1960 Chilean and 1964 Alaskan tsunami
interactions with the Hawaiian Islands and found remarkable agreement with all tide gages in the
islands. Camfield (1980) prepared a general manual on tsunami engineering. Houston (1980, 1985)
made tsunami flood level predictions for American Samoa. Farrar and Houston (1982) calculated the
response of Barbers Point Harbor, HI, to tsunami waves. Finally, Crawford (1987) prepared tsunami
predictions for Kodiak Island to Ketchikan in Alaska.
In the 1990's, the CHL was one of five PI's investigating the important physical parameters
involved in 3D tsunami runup that was funded by the National Science Foundation (NSF). In 2003, the
NSF funded the Network for Earthquake Engineering Simulation (NEES) for earthquake and tsunami
research in the academic community. Oregon State University (OSU) is the primary engineering
school in the U.S. selected for tsunami research. Details of the OSU facility will be presented by others
during this symposium.
In this paper, past laboratory experiments in tsunami runup at the CHL, current tsunami research
capabilities at CHL, and recent research on inundation maps for the U.S. are presented.
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