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Analyzing the 2011 Honshu Tsunami Propagation across the Pacific Ocean

Background: NOAA's Center for Tsunami Research (NCTR) has produced models of the 2011 Honshu Tsunami as it propagated across the Pacific. One of NCTR's research goals focuses on developing accurate wave propagation models for tsunami events so that when actual catastrophes are detected, the center's scientists can issue forecasts and warnings to help protect lives around the world. One of the constant activities undertaken by these scientists is to reconcile predictive models with actual measurements of such events. The goal is to improve the algorithms used to produce the predictive models so they are more and more accurate.

Note: You will need to download the Worksheet below to submit your work and answers to the questions below.

Files

Download the Worksheet (Microsoft Word 2007 (.docx) 76kB Sep7 16)

Instructions:In this assignment, you will compare wave propagation models to actual observations of the tsunami event. The primary questions at hand are: Do the models used to predict the tsunami arrival align with the data captured directly from instruments deployed around the Pacific Ocean? Can these data be used to better effect policies to help inform citizens living in risk zones for tsunamis so they can evacuate effectively? In addition, you should think about the relative differences between wave heights in different regions owing to water depth, proximity to land, distance from the epicenter of the earthquake that produced the tsunami, etc. To do this, you will use NOAA's Center for Tsunami Research (NCTR) website and database of records from the tsunami on March 11, 2011.

• To begin, download the worksheet linked above. Navigate to the NCTR Tohoku Tsunami Event Page and locate the stations given in the first column of the table you downloaded.
• The data you will be working with are actual water height measurements taken from instruments either on land (tide gauge stations) or at sea (floating DART buoys).
• For all sites:
  • click on the balloon marker for the site you are interested in investigating on the map. A pop-up window will come up.
  • Click the name of the DART buoy or tide gauge site at the top of the pop-up window.
  • This will pull up a graph comparing the NCTR Model (prediction) of the tsunami wave arrival with the actual measured water level change. Make note of how well or poorly the model predicted the actual event at each site.
• For the DART buoy data sites (yellow balloon markers):
  • First, click a buoy site on the map and select "Sea Level Data" from the bottom of the pop-up window.
  • This will take you to a new page at the National Data Buoy Center. Verify the site loaction and record the water depth at the buoy site in your table.
  • Scroll down to the "Data Access" section to select a start date "2011, March, 11". If the site is close to the earthquake epicenter (green star), you can also use March 11 as your end date. If the site is far from Tohoku, select an end date "2011, March 12." Click "Submit".
  • Using the 1-minute data (green line), identify the approximate tsunami arrival time. This will appear as a tall peak that stands apart from the "normal" fluctuations in the data.
  • Scroll through the data block (located just below the place where you selected your start and end dates) to find the time interval around your estimated tsunami arrival time. Identify the maximum water level recorded (make sure it agrees with what you observed in the plot) and record the date, time, and water height in your table.
  • Calculate the tsunami wave height by subtracting the water depth at the site from the peak recorded water level. Enter this value in your table.
• For tide gauge data sites (red balloon markers):
  • Click a tide gauge site on the map and select "Sea Level Data" from the bottom of the pop-up window.
  • You will be re-directed to the NOAA Tides & Currents website. Click the Tides/Water Levels tab for the site. You will then need to scroll down and set the date From March 11 or 12th 2011.
  • Make sure the units you use are Meters, the Time zone should be GMT, and make sure you select 6 minute as your interval (you want to make sure to capture the tsunami wave as it passes the recording station) and then click Plot. Your chart will be generated at the top of the page.
  • Identify the segment of the hydrograph that is abnormal from the background trends and therefore the segment that likely represents the tsunami wave. As you hover the cursor over the hydrograph plot, each individual reading will be highlighted and you can read the exact values accordingly.
  • Identify the maximum verified water height (green line) and record the date, time, predicted water height, and verified water height in your table.
  • Calculate the tsunami wave height by subtracting the predicted water height from the verified water level. Enter this value in your table.
• Fill in the chart with your observations and make the appropriate calculations to complete the worksheet. We have provided an example data entry for a buoy and for a land-based tide gauge station so you can easily replicate them for your selected sites. Your entries should follow the same format.
• Finish the assessment by answering the questions on the next page. You will submit your answer, along with the word document containing your completed data table.

• Questions
• Summarize Your Findings