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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) 136kB Sep7 16)

Download the Rubric

Instructions:In this assignment, you will compare the wave propagation models to empirical observations of the event. The primary question at hand is: Do the models used align with the data capture directly from instruments deployed around the Pacific Ocean and 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, select at least 3 locations that recorded data from March 11, 2011 to March 12, 2011. Select sites that form more-or-less a straight transect from Japan toward the U.S.
• The data you are working with are actual measurements taken from instruments either on land (tide gauging stations) or at sea (floating buoys). You can select any site, but make sure they are spaced out relative to each other.
• For the buoy data sites, once you click a location on the website, use the Data Access section to select a start date "2011, March, 11" and an end date "2011, March 12."
• For tide gauge data sites, you will be re-directed to NOAA Tides & Currents website that you are familiar with from Module 4. 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.
• Once the website plots the data, study the plots and 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.
• Fill in the chart below 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 below the table, type up your data and submit a Microsoft Word document, together with a neat, orderly, typed data table showing your readings and calculations.

Questions:

1. Based on the details above, what have you learned about the evolution of the tsunami wave as it propagated by refraction and reflection across the Pacific Ocean?

1. How long did it take for the wave to make the trip between your sites?

1. Based on your data, calculate the tsunami wave velocity (kilometers per hour) for the direct wave. To calculate velocity, you need distance and time.
   1. You have time from the measurements above.
   2. To find distance:Use Google Earth's measuring tool to measure the distance between your observation sites (use the Latitude & Longitude if needed). Once you have the separation distance between two of your sites, you can divide the distance in kilometers (numerator) by time between observations in hours.
   3. In our example in the table – the wave passed station 21413 at 11:22 a.m. on 3/11/11 and arrived at San Diego at 7:30 a.m. on 3/12/12. Thus the time between arrivals is just about 20 hours. Reasoning: 11:22 a.m. to 11:22 p.m. is 12 hours plus 11:22 p.m. to 7:22 a.m. is 8 hours for a total of about 20 hours – don't worry about the 8 minutes, as it is negligible for our purposes.

1. Based on these observations and calculations, if you were a NCTR scientist responsible for issuing a warning after an earthquake occurs, how much time would it take to issue warnings and help get people to safety? What distance from the epicenter do you feel would essentially be a loss because of the inability to warn people appropriately within the bull's eye region? This question is open-ended, as long as you provide details and logic to support your point of view.