International Symposium on Tsunami Disaster Mitigation in Future
Jan. 17-18, 2005, Kobe, Japan
uneven spacing were located on the backside of the island (i.e. 90 deg) to improve the resolution in
this critical area. Changes in runup shape and magnitude were investigated by varying the water depth,
wave height, source length (number of modules), and eccentricity of the source. Figure 4 is a polar
plot (4a) and overhead photograph (4b) of maximum vertical runup around the island for Case C.
Waves approach the island from the bottom or 270 deg. The island crest, waterline, and toe are
shown for reference. Two runs are overlain, demonstrating excellent repeatability.
The runup on the backside is almost as large as that on the front side of the island. Refraction
and diffraction cause the wave to bend around the island as edge waves. Because the island and
source were symmetric, the wave wraps evenly around the island and produces relatively large runup
on the backside. This is a very interesting phenomenon since most people would feel "safe" on the
backside of an island.
Corps Tsunami Disaster Mitigation and Research Facilities
The ERDC's TeleEngineering Operations Center (TEOC) has been asked to locate the extent of
damage to the existing infrastructure from the 2004 Asia Tsunami in the affected countries. The
initial areas of concern are the roads and bridges in Indonesia, Sri Lanka, and Thailand. This
information will be used in support of the humanitarian relief efforts to deliver food and supplies to the
devastated areas. Thus, predictions, satellite imagery, and measurements of tsunami wave heights are
being used to estimate inundation on topographic maps so that routes can be most efficiently planned
for disaster relief.
The CHL has many physical modeling facilities that can be used for tsunami disaster mitigation
research including 7 flumes, 2 stability basins, 5 harbor basin models, and the multidirectional DSWG.
Wavemakers in the flumes and basins are either piston- or plunger-type, with a wave height capability
of 7 cm to 60 cm. One of CHL's most unique models is the three-dimensional model (Figure 5) of
the ports of Los Angeles and Long Beach (LALB). It is probably the largest operating physical
model in the world, covering an area of 655 sq km in the prototype, from San Pedro Bay out to the 92-
m contour and shoreline from 3.2 km northwest of Point Fermin to Huntington Beach, CA. It is a
distorted scale model, with a prototype scale of 1:100 in the vertical and 1:400 in the horizontal.
In FY00, the CHL replaced its existing DSWG with a new state-of-the-art multidirectional
wavemaker (Briggs 2001). The new DSWG was designed and built by MTS Systems Corporation,
Minneapolis, MN. It is 27.4-m long and consists of 60 paddles, each 46-cm wide and 1 m high
(Figure 6). Each paddle is driven at the joints by an electrical motor in piston mode, producing very
smooth and clean model waves. The stroke of 36 cm generates wave heights up to 30 cm in 60 cm
water depths. Angles between paddles can be continuously varied using the "snake principle" to
produce waves at angles approaching 85 deg. The DSWG is composed of 4 modules that enhance
portability, and has PC-based control, calibration, data acquisition, and analysis systems.
Passive
wave absorber frames around the basin perimeter and active wave absorption on the DSWG reduce
reflections from model structures and basin walls. Two hydraulic gates facilitate model construction
and access.
Tsunami Inundation Maps for California
Inundation maps are depictions of coastal areas that identify regions, populations, and facilities that are
at risk from tsunami attack. They are used by emergency planners for disaster response and mitigation.
Inundation maps require an assessment of local and far-field geologic hazards, and the calculation of
coastal flooding. The first set of maps for California posed a unique challenge since (a) it has a short
historical record of tsunamis, (b) very little information on offshore faults or landslide and slump scars,
(c) historical records based mostly on far-field and pre-1980's technology, (d) near-field tsunamis have
short arrival times, and (e) its high population density.
Houston and Garcia (1974, 1978) and Houston (1974,1980) used a combination of finite difference
and finite element models to predict tsunami inundation on the west coast of U.S. and Hawaii. The
1960 Chilean and 1964 Alaska earthquakes were used to define the source characteristics. They
calculated 100-year and 500-year tsunami runup heights. Borrero (2002) and Synolakis et al. (2002)
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