The Cascadia Earthquakes and Tsunami Suite contains five case studies organized around understanding the potential for large earthquakes and tsunami and their impact in the Cascadia region of North America. They not only explore the potential for a great earthquake in Cascadia and its impact, but they also include an investigation of the 2004 Great Sumatra earthquake and tsunami and an investigation of the potential for and impact of a magnitude 7 earthquake on the Seattle fault, which runs through downtown Seattle Washington.
The case studies make use of tools for organizing, manipulating, and analyzing data, so as to simulate real scientific investigations. Liberal use is made of model animations, videos, and Google Earth tools, both to illustrate key concepts and to engage the interest of student learners. All Case Study documents, GIS project files and data sets can be downloaded with the link at the bottom of this page.
Target Learning Audience
The case studies are designed for lower division undergraduates taking geology, geophysics, earth systems, environmental science, or hazards courses; they require a basic knowledge of plate tectonics, earthquakes and tsunami, and sedimentary depositional processes.
Options for Teaching with the Cascadia Suites
The five case studies are designed for flexibility of use. All five modules can be used in a logical sequence as a complete package. However, each case study is self-contained, and can be used by itself or in combination with one or more of the others. We have identified possible mix-and-match combinations that instructors might wish to consider using for specific purposes. View suggested teaching options.
Case Study Descriptions
Unit I. The Great Sumatran Earthquake and Tsunami of December 2004
The 2004 M9.3 Sumatran earthquake and the mega-tsunami it generated devastated coastal areas throughout the Indian Ocean; stretches of human habitation along the shores of Indonesia, notably Banda Aceh, were obliterated. This unit contains investigations of the seismicity and plate deformations over the shallow subduction zone preceding and accompanying the earthquake. Students then study analogous great events: the 1960 M9.6 earthquake on the shallow subduction zone off Chile and the 1964 M9.2 earthquake on the shallow subduction zone south of Alaska. They discover the characteristic deformations associated with the accumulation of strain at a locked portion of a shallow subduction zone and its sudden release, generating a great earthquake. The case study is self-contained, but also sets up an investigation of present-day strain along the Cascadia subduction zone.
Unit II. Is the stage being set for a Great Cascadian Earthquake and Tsunami?
The Cascadian subduction zone is one of the seismically quietest on Earth. At one time, it was assumed that subduction is going on aseismically, but present-day geodetic investigations tell a very different story. Students use GPS data to determine plate deformation patterns using basic algebra, geometry and trigonometry. They discover that strain accumulation over a locked portion of the shallow Cascadian subduction zone is like the strain that has preceded great earthquakes at other subduction zones in the past.
Unit III. The Search for Great Cascadian Earthquakes and Tsunamis in the Past
While there is no written record of great earthquakes along the Cascadian subduction zone since the beginnings of European colonization in the late 18th century, Native oral histories tell a different story. So does the geology. Students explore the stratigraphic evidence from Cascadian estuaries that points to repeated collapse of the coastal region, followed by catastrophic tsunami inundation. They determine recurrence intervals from this data and from deep sea cores from the Cascadia Basin. They figure out the exact year, month, day, and hour of the last great Cascadian earthquake. It might be a useful adjunct to a class unit on stratigraphy.
Unit IV. Impact of a Great Cascadian Earthquake and Tsunami on a Coastal Community
Seaside is a small town at the north end of coastal Oregon, a popular tourist destination. Most visitors are likely unaware of the extreme tsunami hazard there, should an M9+ earthquake occur on the Cascadia subduction zone. Students gain an appreciation of the hazard by studying the effects of the 2004 Sumatra earthquake in Banda Aceh. Using GIS, they analyze stratigraphic evidence for the extent of previous tsunami inundations in Seaside. Using simple algebra, they calculate evacuation times to safety under two scenarios, from a school and from the Convention Center. They also develop elements of an evacuation plan.
Unit V. Impact of a Rupture on the Seattle Fault: A Case Study
Students investigate earthquake hazard in a large Cascadian urban center, the City of Seattle. They focus on the hazard represented by a scenario M7+ earthquake on the Seattle Fault Zone, an active east-west-trending thrust system that passes right through the city. The hazard is dramatically revealed in Google Earth views. Students evaluate hazard to specific elements of the city’s infrastructure and “lifelines”— roads, bridges, port facilities, and schools — with GIS. Comparison with the Northridge and Kobe earthquakes as possible analogs supports student evaluation of the Seattle hazard. Since this case study does not focus on hazard related to a potential M9+ earthquake on the subduction zone per se (although it does include a tsunami hazard component), it stands somewhat apart from the others in the suite. It can be used alone, with the entire Cascadia suite or paired with our Northridge: Case study of an Urban Earthquake module.
Using GIS
The case study contains full instructions for the user, as we assume neither the instructor or student has prior experience with a GIS. We developed these materials for use with PASCO’s MyWorld GIS and ESRI ArcGIS. MyWorld is no longer supported. ESRI ArcGIS is designed for professional users and is available from ESRI.com. Many universities have site licenses, making this an good choice.
Alternative Link: https://www.dropbox.com/sh/3j37tviw24uwn09/AACetS5ijDO6XOxMgiP-j0_1a?dl=0
This material is based upon work supported by the National Science Foundation under Grant Number DUE-0521936. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.