Northridge: A Case Study of an Urban Earthquake
Michael Mayhew and Michelle Hall, Science Education Solutions
SummaryThe 1994 Northridge Earthquake Case Study explores the mystery of how such a major fault could have been missed within a tectonic basin that is one of the most studied in the world. It also helps students understand the relationship between subsurface geology and the damage patterns of an earthquake.
Type and level of course
The case study is designed for lower division undergraduate students in a geology, earth science, hazards or environmental science course. It could also be used by geoscience majors taking a structural geology, geophysics or hazards course. The case study can be completed in two full lab periods or a mix of homework time and one lab period, depending on how and when it is used in a course. The first activity (Earthquakes and you) could be used in class in a Think-Pair-Share activity at the beginning of a lecture on earthquakes. The complete case study could also be used as a semester project, with the students exploring pieces of the case study over the course of the semester or as a wrap up to the semester.
Geoscience background assumed in this assignment
The case study assumes the students have been introduced to plate tectonics, earthquakes and faulting, and basic sedimentary depositional processes. No prior experience with a GIS is required, as all instructions are provided.
GIS/remote sensing skills/background assumed in this assignment
The case study contains full instructions for the user, as we assume neither the instructor or student has prior experience with a GIS.
Software required for this assignment/activity:
We have designed the case study projects to work with either PASCO's MyWorld GIS or ESRI ArcGIS 9x. MyWorld is a full fledged GIS geared toward educational users and works on Windows, Macintosh, and Linux operating systems. Site licenses are very reasonably priced for institutions. ESRI ArcGIS is designed for professional users and is available from ESRI.com. Many universities have site licenses, making this a good choice.
Time required for students to complete the assignment:
The equivalent of two lab periods.
GIS/remote sensing techniques students learn in this assignment
Using the Teach with GIS method, we have created a series of in-depth case studies of natural hazards. The Teach with GIS approach allows students to learn GIS analysis techniques, while exploring an interesting scientific problem.
Other content/concepts goals for this activity
This case study of an "urban earthquake," considers scientific observations related to the earthquake, the consequences of the earthquake, and why variations in earthquake hazard exist within a seismically active region such as Los Angeles, using the tools of a geographic information system (GIS). Students explore not just what scientists know about earthquake hazards but how they know what they know.
Higher order thinking skills goals for this activity
A common misconception is that you need to teach your students everything about the GIS software before you can begin using these materials. Extensive field testing has shown that our investigations provide sufficient guidance for beginning users and that students learn best by using the software tools with a minimal introduction.
The purpose of these investigations is to explore and learn about natural processes and features and how they relate to human activities. As a bonus, students will learn the basics of GIS. For this reason, all of the data have been assembled into ready-to-use projects, and complex operations have been eliminated or simplified. Although it is helpful for students to have basic computer skills, they do not need experience with GIS software to complete the activities. Directions for each task are provided in the text, so they will learn to use the tool as they explore with it. The case studies barely scratch the surface of the data that have been provided, and students are encouraged to explore the data on their own and make their own discoveries.
Description of the activity/assignmentThe case study has four components and learning foci:
Earthquakes and you
Students reflect on the impact a major earthquake could have on them. What if there were no electricity, water, or heat available for one or more days? How might you plan for it and respond to it?
Before the earthquake
As a result of this investigation, students will be able to describe the tectonic setting and origin of seismicity in southern California. Students explore the tectonic setting within which the Northridge earthquake took place and begin to get a feel for why it occurred where it did. Why is southern California a seismically active region? What accounts for the pattern of seismicity? Where have large earthquakes like Northridge occurred historically? And what accounts for the complex network of active faulting that characterizes the region?
After considering these questions within a regional tectonic framework, they examine the concepts of earthquake hazard and associated risk. Then they develop a qualitative analysis of hazard and risk for the Los Angeles region before the Northridge earthquake, based on patterns of active faulting and historical seismicity up to that time. Later, after learning where the earthquake occurred, they examine the extent to which the earthquake's location was consistent with their analysis.
In this activity, students use triangulation to determine the location of the earthquake and explore the events that occurred in the hours and days following the earthquake. They examine the pattern of aftershocks and determine the strike and dip of the fault plane.
The damage from the Northridge earthquake was widespread and in some areas severe. Some areas suffered almost total destruction, yet others had minimal damage. In this investigation, students explore the factors that influence the distribution and degree of damage. Using geologic, liquefaction zone and sedimentary thickness maps, along with peak ground acceleration (PGA), Modified Mercalli Intensity and data on the damage levels for over 25000 buildings, they begin to understand the relationships among PGA, geology and damage. As a closing activity, students use the many datasets they have explored to generate a revised estimate of zones of elevated earthquake hazard and risk and compare it to their original interpretation.
Determining whether students have met the goals
More information about assessment tools and techniques.
URLs and References
All required materials for Northridge: A Case Study of an Urban Earthquake unit, including curriculum, instructor guide, and access to GIS tools and data sets, https://gsa.confex.com/gsa/2009AM/finalprogram/abstract_164541.htm
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