EARTH 501
Controversies in the Earth Sciences

Lesson 4: Is the New Madrid Seismic Zone at risk for a large earthquake?

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The map below is a seismic hazard map of the continental United States produced by the USGS. The red bulls eye covering the bootheel of Missouri is the New Madrid Seismic Zone. In this lesson we will learn about the 1811-12 earthquake sequence in the New Madrid Seismic Zone and discuss the controversy regarding the extent of seismic risk in the central United States today. We will learn how to estimate earthquake recurrence interval using a variety of methods.

earthquake hazard map of the continental United States of America
USGS seismic shaking hazard map. Colors show the degree of horizontal shaking estimated to have a 1-in-50 chance of being exceeded in a 50-year period. Shaking is given as a percentage of g (9.8m/s^2).
From Gomberg, J., & Schweig, E. (2002). Earthquake hazard in the heart of the homeland. Fact Sheet - U. S. Geological Survey, 4pp.
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USGS seismic hazard maps explained! (and a close-captioned version).

 

 

About Lesson 4

Most people on the West Coast of the United States who live near faults or volcanoes (or both) are somewhat familiar with the risks involved with these phenomena. Far fewer East Coast dwellers have felt an earthquake. However, the central U.S. is actually fairly seismically active for a continental interior. This region has experienced large earthquakes in the past and these may happen again. How should residents of this area plan for a potential earthquake hazard? In this lesson we will explore intraplate seismicity and the New Madrid region in particular. We'll use seismic catalogs to estimate earthquake recurrence interval and we'll discuss the scientific controversy surrounding the potential for large earthquakes in this region.

What will we learn in Lesson 4?

By the end of Lesson 4 you should be able to:

  • Describe the cyclical process of strain accumulation, earthquake generation, and post-seismic relaxation along plate boundaries.
  • Define "recurrence interval."
  • Explain ways in which recurrence interval is estimated for a given fault, and compare the inherent uncertainties with each method.
  • Explain the basic mathematical and physical tenets of plate tectonics.
  • Summarize various hypotheses for the existence of seismicity away from plate boundaries.
  • Describe the 1811–1812 sequence of large events on the New Madrid Seismic Zone and explain how scientists have determined the properties of these events.
  • Describe potential hazards/consequences of a sequence similar to the 1811–1812 sequence occurring today.
  • Construct a frequency-magnitude plot using earthquake catalog data
  • Compare frequency-magnitude diagrams for intraplate regions, plate boundary regions, and global datasets
  • Extrapolate from a frequency-magnitude diagram to estimate an earthquake recurrence interval
  • Analyze a collection of various datasets to compare their predictions of seismic hazard at New Madrid.

What is due for Lesson 4?

Lesson 4 will take us three weeks to complete. 12 Oct - 1st Nov 2016 You will complete reading assignments by the end of the first week. You'll submit the data analyses at the end of the second week. The team reading and discussion assignments will take place over the second week. The teaching and learning discussion will take place during the third week and the fact sheet paper is due at the end of the third week. See the table below for complete details.

Lesson 4 Assignments
Requirement Submitted for Grading? Due Date
Reading: "The Mississippi Valley Earthquakes of 1811 and 1812: Intensities, Ground Motion and Magnitudes" No 18 Oct (end of 1st week)
Reading: "Earthquake hazard in the heart of the homeland" No 18 Oct (end of 1st week)
Reading: series of papers about glacial rebound, failed rift, and the Farallon slab. No 18 Oct (end of 1st week)
Problem set: Earthquake catalog data analyses Yes - Submitted to "Earthquake catalog problem set" assignment in Canvas 25 Oct (end of 2nd week)
Reading/Discussion: "Debating hazard at New Madrid" Yes - Graded group discussion in Canvas participation spanning 19 - 25 (2nd week)
Reading/Discussion: "Debating hazard at New Madrid" Yes - Graded whole class discussion in Canvas participation spanning 26 Oct - 1st Nov (3rd week)
Paper: NMSZ Fact Sheet paper Yes - Submitted to the "Fact Sheet Paper" assignment in Canvas 1st Nov (end of 3rd week)
Discussion: "Teaching and Learning About Earthquakes" Yes - posted to the "Teaching and Learning About Earthquakes" discussion forum in Canvas participation spanning 26 Oct - 1st Nov (3rd week)

Questions?

If you have any questions, please post them to our Questions? discussion forum (not e-mail). I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.