RiskAssessment

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 . ~

4 4.2 State two possible solutions that might prevent the run-up height and distance that would be experienced during this tsunami and why this would help. Consider options that would allow the city to stay where it is currently located. (6 pts) a. Mitigation technique: (1 pt) Why is this helpful? (2 pts) b. Mitigation technique: (1 pt) Why is this helpful? (2 pts) Score: /50 References: Kline, M., 2017, Modeling Potential Impacts of tsunamis on Hilo, Hawai’i: Comparison of the Joint Research Centre’s Schema and FEMA’s HAZUS inundation scenarios; USC M.S. Thesis retrieved from https://spatial.usc.edu/wp-content/uploads/2016/07/Kline-Matthew.pdf Butler, R. Walsh, D., & Richards, K., 2016, Extreme tsunami inundation in Hawai’i from Aleutian-Alaska subduction zone earthquakes. Natural Hazards, v. 85, pp 1591-1619 PDC Global.com, 2022, Tsunami Evacuation Zones (Hawaii), http://static.pdc.org/tsunami/index.html , Accessed August 9, 2022 . Figure 3: Tsunami evacuation zone of Hilo, Hawaii. From http://static.pdc.org/tsunami/index.html . Keep in mind that this map is a close-up of Hilo in comparison to Figure 2. higher sea walls Lowering the height of the waves building larger artifical constructions This prevents structures and barries that protects the objects from the wave