Earthquakes & Tsunamis in Oregon Adapted from Linn-Benton CC Lab Manual and from Megan Faust, Portland CC Tsunami Inundation Maps Go to DOGAMI’s “Tsunami Inundation Map” series. Scroll down and read through the explanation of “TIM Plate 1” and “TIM Plate 2”. Then continue down to the list of maps, and select “Newport South”. Choose the “onscreen-quality pdf”. Locate the legend, and make sure to zoom in to read the fine print! 1. Think back to the “hands of science” from lecture, and when your knuckles drop as the earthquake occurs. This happens in the real world too, and our fancy geology term for land dropping is “subsidence”. Why is it important to include expected subsidence when making a tsunami inundation map? 2. On your map, find the dashed line (legend: “Senate Bill 379 Line”). Using its physical location, can you think of what it might represent? In other words, why was it drawn at this location? 3. Under “Map Explanation”, look for text about “Senate Bill 379”. What is this line and what purpose does it serve? 4. How much time are people expected to have between the earthquake and the first tsunami waves? Part 1: Tsunami Evacuation Maps Go to DOGAMI’s Tsunami Evacuation Maps and select “Newport South”. 1) What is the difference between a tsunami inundation map and a tsunami evacuation map? 2) Why are the green shaded map areas safe? 3) What action should you take if you are at the beach when there is an earthquake? 4) Think about the difference between a distant tsunami (perhaps an earthquake in Alaska) and a local tsunami (CSZ EQ). Imagine you are at the beach. How would you know the difference? 5) Imagine you are at the South Beach Marina, and a full rip 9.0 goes off on the off-shore CSZ fault. You are staying with friends in Newport, across the Highway 101 bridge. Should you cross the bridge to find your friends? 6) Where should you go instead? DOGAMI Earthquake Hazard Maps (laptops) Adapted from Megan Faust, Portland CC Purpose: The main goal of this exercise is to consider our risk from an earthquake and utilize free, publicly available information. If you live in Oregon, you are at risk of experiencing a potentially harmful earthquake event at some time in your life. Understanding this risk can help you prepare for it and guide your viewpoints on how the state government should manage this risk. Learning Outcomes: When you have completed this lab you should be able to: 1..Describe the potential hazards relating to earthquake events 2. Rank types of Earth materials in terms of susceptibility to seismic damage. 3. Describe the risk that your home and our school face from a potential earthquake In this activity we will be looking at geologic hazard maps produced by the Department of Oregon Geology and Mineral Industries (DOGAMI). For this part of the lab, turn on and login to your computer, then search for “oregon geology hazvu”, which should bring up DOGAMI’s “Oregon HazVu: Statewide Geohazards Viewer”. Click on “Map” or just go to this link < https://gis.dogami.oregon.gov/maps/hazvu/ > to open the HazVu mapping app. If you get confused or frustrated, use the Help link at the top of the page! First, let us learn about “basemaps”, or the underlying map that you can see. Click on the 4 square icon (“basemap gallery”) and experiment with a few different options. I tend to use maps that both display elevation, land use, and place names, such as the National Geographic map, the Imagery with Labels map, and the Topographic map. However, there is no one size fits all; the point here is that you must choose which map to use in a given situation, and the only way to do that is to experiment! Now, we need to decide what layers we want to use. Click on the three stacked squares icon (“choose layers to display”). Select the general “Earthquake Hazard” layer. There are four sub-layers here: Active Faults, Earthquake Epicenters (1971-2008), Earthquake Liquefaction (Soft Soil) Hazard, and Expected Earthquake Shaking. Experiment with each of the 4 by turning them on / of, one at a time. Make sure to click on “Layers Currently Showing” to see the map legend for each layer. When you are ready to proceed, make sure that “Earthquake Hazard” is on, and all other layers are off. 1) Turn on “Active Faults” and explore by zooming in and zooming out. Is there a fault near your home? How many miles away is the nearest fault?_______ Sometimes, faults are very obvious, because the ground abruptly rises or drops as you cross over a fault. For example, look at the fault that crosses from the east side of Pilot Butte to the north across Butler Market Road. To see it, turn on the “Bare Earth Lidar Hillshade” layer. When viewing, try toggling “Active Faults” off and on to better Which side of the fault appears to be lower? __________________ The Cascadia Subduction Zone, an enormous fault that is not included on this map, is ~200 miles away. Which fault do you think will shake your home harder, and why? Note that there is no right answer here, I simply want you to think about the factors that influence shaking. 2) What is liquefaction and what sort of ground is most threatened by this hazard? Go to DOGAMI’s “Hazards & Assets” page for more information (https://www.oregongeology.org/hazvu/hazards-assets.htm). 3) Turn on “Earthquake Liquefaction” and compare the Willamette Valley (Eugene - Salem – Portland) with Central Oregon. Why do they have such different liquefaction hazards? 4) Turn on “Expected Earthquake Shaking”. Looking at Central Oregon, are there any specific regions that would not be safe during an earthquake? Find three places in Central Oregon that have elevated shaking, and hypothesize why they might shake more. Make sure to address each factor that affects shaking! A) B) C)
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