RiskAssessment
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Northern Arizona University *
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Course
112
Subject
Geography
Date
Apr 3, 2024
Type
Pages
4
Uploaded by ChancellorGuanaco4197
Name: Section: Due Date: GLG 112: Geologic Disasters
Risk Assessment #3: Tsunami at Hilo, Hawai’i
In this activity, you will assess the risk of tsunami for the Hawaiian city of Hilo. Part 1: The 1964 Alaskan Tsunami
Figure 1 shows data collected on the tsunami wave from the 1964 M
w
9.2 earthquake. We will use this
historical event to see what could happen to the city of Hilo on the Big Island of Hawaii in the event of
another large earthquake along the Aleutian trench.
1.1
From the epicenter, what direction is Hawaii? (1 pt)
1.2
The lines on the map show tsunami travel times in hours. About how long did it take the tsunami to reach Hawaii? (
1 pt)
1.3
Approximately how far away from Alaska is Hawaii (there are 1.609 km in every mile)? Measure from the star to the Big Island of Hawaii. (2 pt) _____ km _____ mi 1.4
How fast was the tsunami traveling? (
2 pt)
_____ km/hr _____ mi/hr Figure 1: 1964 Alaskan Earthquake epicenter is marked with a star on the map. Each black line and color indicate the travel time of the tsunami that was generated by this earthquake. It took about 15 hours to reach the north coast of Australia. A 1000 km scale is provided in the bottom left corner. 1.5
What general type of plate boundary is found at the Aleutian Trench? (1 pt) 1.6 Describe how elastic rebound and slip on a fault can cause a tsunami. This is how a tsunami is formed at the type of boundary in 1.5. (2 pt)
Alfonso
Aguirre
005
11
/
19/23
5000
3107
714
28
443
8
Convergent
plate
Boundary
There
is
pressure
in
the
tectonic
plate
and
the
more
the
area
is
presurized
,
the
more
elastic
energy
it
will
have
.
With
this
is
will
cause
a
Tsunami
2 Part 2: The 2035 Alaskan Tsunami Scenario
Background: The following scenario is based on data from numerical modeling of a megaquake in the Aleutian Trench. On November 2, 2035, a M
w
9.3 earthquake occurs just south of the Aleutian Islands (Alaska). Similar earthquakes in the past (such as the 1964 Alaskan earthquake & the 1946 Alaskan Earthquake) have generated large tsunamis that spread around the Pacific Ocean, from Alaska all the way to Japan, the South Pacific, and North and South America. In the open ocean, the wave height of the 2035 mega-tsunami approaching the north shore of Hawai’i would be ~32 feet (Butler et al, 2017). Given that the offshore wave height is typically amplified 2-3x on land, the estimated maximum wave run-up height for this tsunami is 98 feet
. Wave run-up height and distance will vary depending on the shape and topography of the shoreline, if there are any offshore barriers present, and the direction from which the tsunami is coming. 2.1
On average, tsunamis travel at about 700 km/hr in the open ocean. Using this average, how long will it take for the fictional tsunami generated at the Aleutian trench to reach the following areas? Make sure your answer includes units! (6 pts, 1 pt each for set up, 1 pt for units, 1 pt for correct answer)
a.
Seattle, WA, USA (~3,600 km away) b. Northeast shore of Honshu, Japan (~5,690 km away) Use the Figure 2 to answer the following questions: 2.2
Knowing the maximum wave run-up height
, shade in all the areas that could possibly be inundated by the tsunami in Figure 2. (2 pt)
2.3
If the tsunami originated due north, compare the differences in run-up height
at the location below. Be concise and make sure to consider the topography and any features that may reduce or increase run-up heights at these locations. The seawall is only 10 ft. high. East of Wainaku: Topography Description: (2 pt)
Wave reduction features? (1 pt)
Coast around Kaula’ inaiwi island: Topography Description: (2 pt)
Wave reduction features? (1 pt) Which would have a higher run-up height? (1 pt)
Why? (2 pts) N Figure 2. Topographic map of Hilo Bay area, Hawaii. Contours are elevations in feet
. Port &
cruise
terminal
Oil & gas
terminal
0
=
5
.
14
hours
-
8
.
12
8
12
hours
Lower
elevation
length
on
the
topography
Most
land
&
in
between
200
-
800
steep
elevation
change
low
elevation
200
-
600
Sea
Wall
Count
around
Kaula'inaiwi
became
of
the
lower
land
elevation
and
a
small
sea
wall
reduction
.
~
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