COMMON EARTHQUAKE EFFECTS - Geotechnical Earthquake Engineering - page 80

FIGURE 3.57 Tsunami damage caused by the Niigata earthquake in Japan on June 16, 1964. ( Photograph
from the Steinbrugge Collection, EERC, University of California, Berkeley. )
As discussed in Sec. 2.4.5, the Chile earthquake in 1960 was the largest earthquake in
the 20th century (moment magnitude 9.5). According to Iida et al. (1967), the tsunami
generated by this earthquake killed about 300 people in Chile and 61 people in Hawaii.
About 22 h after the earthquake, the tsunami reached Japan and killed an additional 199
people. Figure 3.58 shows an example of tsunami damage in Chile.
Seiche. An earthquake-induced seiche is very similar to a tsunami, except that it devel-
ops in inland waters, such as large lakes. An example of damage caused by a seiche is
shown in Fig. 3.59. The building in the water was formerly on the shore about one-quarter
mile up the lake. The house was apparently jarred from its foundation by the earthquake
and then washed into the lake by a seiche generated by the Hebgen Lake earthquake (mag-
nitude of 7.5) in Montana on August 17, 1959. The house shown in Fig. 3.59 later drifted
into the earthquake-created harbor.
Mitigation Measures. It is usually the responsibility of the engineering geologist to eval-
uate the possibility of a tsunami or seiche impacting the site. Because of the tremendous
destructive forces, options to mitigate damage are often limited. Some possibilities include
the construction of walls to deflect the surging water or the use of buildings having weak
lower-floor partitions which will allow the water to flow through the building, rather than
knocking it down, such as shown in Fig. 3.58.
The March 13, 2011 earthquake (magnitude 9.0) off the coast of Japan generated a spec-
tacular and destructive tsunami. Videos of this tsunami are available on the Internet. This
tsunami devastated the coastal areas of Japan and resulted in nuclear reactor meltdowns
when the water overtopped the protective sea walls and cut off power to the facility. Clearly
this mitigation measure of using sea walls to protect the nuclear facility did not work.