Environmental Engineering Reference
In-Depth Information
maximum energy radiation to not directly face the area of interest. Thus, increases
in the earthquake magnitude and maximum co-seismic slip may not cause linear
increases in the resulting tsunami height and fl ow depth.
10.3.2
Model Application in the Post-disaster Area
On the Sendai plain, all M 7 class earthquakes generated insignifi cant inundations.
This result is consistent with the offi cial hazard maps prior to the 2011 East Japan
earthquake, which predicted the tsunami hazard zone to be less than 1 km from the
shore. The impacts of the minor tsunamis generated by the M 7 class earthquakes
coming from the offshore Miyagi and Fukushima prefectures should be diminished
by 3-m-high coastal dikes and a 250-m-wide pine forest along coastal areas.
However, the M 8 and the M 9 class earthquakes, excluding the 2011 event, gener-
ated large tsunamis that fl ooded areas comparable to the one caused by the 2011
East Japan tsunami (Fig.
10.8
).
The simulation results indicated that the existing topographic condition allowed
the penetration of tsunami inundations up to 6 km inland because the average
ground height up to the inundation limit of the 2011 tsunami was less than 2 m.
Thus, the tsunamis generated by M 8 to M 9 class earthquakes can reach far inland
once they overtop the coastal dike and pass through the coastal forest.
Because of the huge exposed area, the Sendai City offi ce for reconstruction has
decided to localize the impact of future tsunamis to only the area near the coast. In
a post-disaster situation, fortunately, the modifi cation of land use is possible because
Affected
Ratio
Tsunami flow depth
(meter)
0.0-0.2
0.2-0.4
0.4-0.6
0.6-0.8
0.8-1.0
0.0-1.0
5.1-6.0
6.1-7.0
7.1-8.0
8.1-9.0
9.1->10.0
1.1-2.0
2.1-3.0
3.1-4.0
4.1-5.0
0
2.5
5
10 Kilometers
0
2.5
5
10
Kilometers
Fig. 10.8
The affected ratio (
left
) and the maximum tsunami fl ow depth (
right
) of the area up to
6 km from the coastline of the Sendai plain, based on the simulated tsunami inundations. The
solid
black line
is the observed maximum inundation from the 2011 East Japan tsunami
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