The map below is a seismic hazard map of the continental United States produced by the USGS. The red bull's 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.
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.
By the end of Lesson 4 you should be able to:
Lesson 4 will take three weeks to complete. 9 -29 Oct 2019. 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 whole class paper discussion and the teaching and learning discussion will take place during the third week. The fact sheet paper is due at the end of the third week. See the table below for complete details.
Requirement | Submitted for Grading? | Due Date |
---|---|---|
Reading: "The Mississippi Valley Earthquakes of 1811 and 1812: Intensities, Ground Motion, and Magnitudes" | No | 15 Oct (end of 1st week) |
Reading: "Earthquake hazard in the heart of the homeland" | No | 15 Oct (end of 1st week) |
Reading: series of papers about glacial rebound, failed rift, and the Farallon slab. | No | 15 Oct (end of 1st week) |
Problem set: Earthquake catalog data analyses | Yes - Submitted to "Earthquake catalog problem set" assignment in Canvas | 22 Oct (end of 2nd week) |
Reading/Discussion: "Debating hazard at New Madrid" | Yes - Graded group discussion in Canvas | participation spanning 16 - 22 Oct (2nd week) |
Reading/Discussion: "Debating hazard at New Madrid" | Yes - Graded whole-class discussion in Canvas | participation spanning 23 - 29 Oct (3rd week) |
Paper: NMSZ Fact Sheet paper | Yes - Submitted to the "Fact Sheet Paper" assignment in Canvas | 29 Oct (end of 3rd week) |
Discussion: "Teaching and Learning About Earthquakes" | Yes - graded whole class to the "Teaching and Learning About Earthquakes" discussion forum in Canvas | participation spanning 23 - 29 Oct (3rd week) |
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.
Please read this article describing the 1811–1812 New Madrid earthquake sequence, then proceed with the rest of the lesson.
Nuttli, O. W. (1973). The Mississippi Valley Earthquakes of 1811 and 1812: Intensities, Ground Motion, and Magnitudes. Bulletin of the Seismological Society of America, 63(1), 227–248.
This paper was written by Otto Nuttli, a seismologist at Saint Louis University. He looked at many historical accounts of the 1811–1812 New Madrid earthquake sequence in order to describe the physics of these events with as much accuracy as possible. This is a technical paper, intended for an audience of other seismologists. I don't expect you to digest every detail of Nuttli's analysis.
Read these sections and their included figures: Abstract, Introduction, Intensity data, Discussion, Reflections.
Skim the following sections: Relations between intensity and ground motion, Magnitudes and ground motion of the 1811–1812 earthquakes, Appendix.
When you read this article try to answer or at least think about the following:What other questions do you have after reading this article? Post to the Questions discussion.
This is a slick USGS-produced poster with an overview of historical earthquakes in the New Madrid Seismic Zone. For best viewing, you will want to download the file from the USGS so you can zoom in and read the text.
Before you proceed, please complete the following reading assignment. Then, in the next part of the lesson, we will discuss the scientific background necessary to appreciate why there is a scientific controversy over the level of seismic hazard in the central USA.
Gomberg, J., & Schweig, E. (2002). Earthquake hazard in the heart of the homeland [4]. Fact Sheet - U. S. Geological Survey, 4.
This reading is a fact sheet published by the USGS [5]in 2002 that addresses the level of present-day earthquake hazard in the central USA. As you read, think about the following:
If you have questions or comments, especially pertaining to the questions I have posed above, please post to the Questions discussion. There is nothing to submit for this assignment, but you will want to read this fact sheet thoughtfully because your final assignment for this lesson will be to rewrite and update it with new data.
The theory of plate tectonics makes two mathematical assumptions:
In fact, the Earth is not a perfect sphere; it bulges at the equator a bit. The second assumption is also not quite true. If plates were perfectly rigid in their interiors, then earthquakes could only happen at plate boundaries. Nearly all earthquakes (98%+) do happen at the plate boundaries, but there are some anomalous events, called intraplate earthquakes, that happen far from the boundaries.
The map below shows earthquake locations around the world for a six-month period. Compare it to the plate boundary map below it and you will see that earthquakes roughly define the plate boundaries. Focus on the North American plate. It is bounded on the west at the edge of the continent and on the east by the Mid-Atlantic Ridge. The East Coast and the central United States are quite far away from any plate boundaries, yet you may notice a fair amount of seismicity locating there. Seismologists are interested in these earthquakes because plate tectonics doesn't explain their existence very well.
Why do earthquakes happen in the center of the continent? Different scientists have different favorite explanations. Below are three scientific papers that each present a different hypothesis to explain why the New Madrid Seismic Zone is seismically active. I have also included three companion articles written for the popular press. For this activity, you will read the articles. You don't need to turn anything in, but you will want to internalize the main arguments of each hypothesis in order to include this information in your fact sheet paper (the culminating assignment for this lesson).
Read each of the following popular press articles and scientific papers. Keep track of any points made in the scientific papers that you don't understand so you can ask about them. There's no formal graded discussion of these papers, but feel free to post comments/questions in the Questions discussion forum. My suggestion is to read the companion popular press article in each set first so that you are already familiar with the main points of the hypothesis before tackling the scientific paper.
In the next part of this lesson, you will analyze seismic data and learn how to estimate earthquake recurrence times with seismicity catalogs. Then you'll read some scientific articles that detail the other ways recurrence intervals can be estimated. You will have to synthesize the uncertainties and limitations inherent with each method in order to get the complete picture of how earthquake risk is determined.
Here is an important observation about earthquake populations worldwide: earthquakes of a given magnitude happen about 10 times as frequently as those one magnitude unit larger.
Magnitude | Average Annually | How we know |
---|---|---|
8 and higher | 1 | observations since 1900 |
7.0-7.9 | 15 | observations since 1900 |
6.0-6.9 | 134 | observations since 1990 |
5.0-5.9 | 1319 | observations since 1990 |
4.0-4.9 | 13,000 | estimated |
3.0-3.9 | 130,000 | estimated |
2.0-2.9 | 1,300,000 | estimated |
Annual earthquake population statistics compiled by the USGS [9].
Earthquake populations approximately follow this relationship:
log N = a - bM.
This is a power-law equation in which N is the number of earthquakes whose magnitude exceeds M and a and b are constants. For the majority of earthquake catalogs, the constant b is approximately equal to 1. When b≈ 1, this equation describes a line whose slope is about -1.
Seismologists can test the validity of the equation above using catalogs of earthquakes to make "frequency-magnitude diagrams." These diagrams show how many earthquakes of a given magnitude there are in a population of earthquakes.
A frequency-magnitude plot with real data! [10]You can also read a transcript of my discussion of a frequency-magnitude diagram [11] of a year's worth of earthquakes from around the world.
Now observe the plot below. For two separate catalogs of earthquakes that occurred in the New Madrid region, magnitude is plotted vs. the mean annual occurrence of earthquakes greater than or equal to a given magnitude. This plot is only different from the example plot above in that the N values on the y-axis have been normalized to one year. This is so two catalogs that span different lengths of time can be compared directly.
Both of the curves in the plot above deviate from a straight line relationship log N = a - bM at small magnitudes. For the Nuttli Catalog, the line has a slope of about -1 at magnitudes greater than 3.5 and for the NMSZ catalog, the line has a slope of about -1 for approximately magnitude 1.5 and greater. Doesn't it look like in the Nuttli Catalog, there is the same number of magnitude 2 earthquakes every year as there are magnitude 3 earthquakes? But didn't we say that there should be ten times more magnitude 2's? What's going on?
Furthermore, how come there aren't any big earthquakes in this plot? The New Madrid Seismic Zone (NMSZ) catalog peters out at about magnitude 5 and the Nuttli Catalog doesn't have anything much over magnitude 6. But we know there have been big earthquakes in this region in the past, (or else why argue about seismic risk here), so where are they?
The answer to both of these problems is simply that any catalog of earthquakes is limited in two ways (pencast graphical explanation of observation limits [12]). The first way is that not every piece of the Earth has a seismometer sitting on it, therefore there will be some small earthquakes that don't get recorded, even though they happened. For most catalogs, some standard is applied with regard to how many seismometers have to record an earthquake in order to include it in the catalog. This is for quality control reasons. It is hard to locate an earthquake and calculate its origin time within acceptable error limits if not enough stations recorded it. Therefore, the farther apart the seismometers are, the fewer small earthquakes will end up being included in the catalog. For the Nuttli Catalog, we can say that the catalog is incomplete below the threshold of M ≈ 3.5 because that is where the slope of the line (or the "b-value") begins to deviate from -1. The threshold for the NMSZ catalog is lower. Why do you think this is?
The second way a catalog is limited is that it is finite in time. Let's say for a given region, magnitude 8 earthquakes happen once every 1,000 years or so. If your catalog only spans 10 years, how likely are you to have a magnitude 8 in your catalog? For that matter, how likely are you to have a magnitude 7 in your catalog? How many magnitude 6's can you expect in 10 years? In the plot above, the time ranges for both catalogs are listed on the plot. Why does the NMSZ catalog have a lower maximum magnitude than the Nuttli Catalog?
In order to assess seismic risk, we want to know how often a large earthquake happens in this region. How do we do that if our seismometers haven't ever recorded a big earthquake? We have to extrapolate using the data that we do have. Extrapolation is a tricky business because small uncertainties turn into huge uncertainties the farther away you get from what you've actually measured. For a catalog of seismicity, we rely on the assumption that the relationship log N = a - bM holds true overall magnitudes and times. We then extend our catalog data into the realm of the unknown and predict how often large magnitude earthquakes are expected. In the plot above from Newman et al., 1999, they use dashed lines to show their extrapolations. How often do they predict a magnitude 7 will happen in the NMSZ? What about a magnitude 8? What uncertainties do they associate with these predictions?
How to extrapolate seismic catalog data in order to calculate a recurrence interval! [13]You can also read a transcript of my explanation of extrapolating catalog data [14] to calculate a recurrence interval.
For the following problem set, you will work with the seismicity catalog maintained by the University of Memphis for the New Madrid region in order to make your own frequency-magnitude diagrams and calculate a recurrence interval for a large earthquake at the NMSZ. You will also compare NMSZ data to seismicity catalogs for southern California and the world. The point of this comparison is that you will see that the overall shape of a frequency-magnitude diagram is scale-independent. It doesn't matter how big your regional area is, or how many years your catalog covers, the same basic -1 slope coupled to two sections on either end that deviate from -1 will always be there. What changes is the place on the diagram where the deviation occurs? Pay attention to this when you make your different plots.
Go to the New Madrid Earthquake Catalog Search. [15]
Once you get there, follow my directions to make a 1-year catalog of NMSZ seismicity:
Here is video above as plain text [16]
Create a word processing document (Microsoft Word, Macintosh Pages, Google Docs, or PDF) to record your work for this problem set.
On the worksheet, paste in your map of the 1-year catalog you made. Then answer the following questions:
1.1 How many earthquakes are in your catalog?
1.2 What is the largest magnitude earthquake in your catalog? How many earthquakes are there of this magnitude in your catalog?
1.3 What's the smallest magnitude earthquake in your catalog? How many earthquakes are there of this magnitude in your catalog?
1.4 Describe your map in a few sentences. (What part of the country is it? Are the earthquakes sprinkled randomly about or do they cluster in patterns? If the latter, describe what the patterns look like.)
Double-Check! Your worksheet should now have a map and answers to the Part 1 questions. If it does, you are ready to take on Part 2.
Make three different frequency-magnitude plots using the New Madrid Earthquake Catalog data: The first plot will use the one-year catalog you made in Part 1 of the problem set. In the second plot, you will add curves that correspond to a 10-year, 20-year, and 30-year catalog. The third plot will depict the same data as in the second plot, except that you will normalize all the catalogs to one year. Specific directions follow:
For this plot, all you need are the magnitudes, which are in column 7 of your plain text catalog file. Post to Questions if you need help isolating that column. My recommendation is to create a new file in whatever plotting/spreadsheet program you like and then you will type your counting statistics into this new file. In your new file, you want to create the values that will be on the x-axis of your plot. They will be magnitudes from your catalog's lowest to your catalog's highest in 0.1-unit bins. To create the values that will be on the y-axis of your plot, count how many earthquakes in your catalog are equal to or greater than each value of magnitude. These are your y-values: cumulative frequency. It's easier to count if you sort your magnitudes first, which is fine to do because we do not care what order they are in for this plot.
Then plot cumulative frequency vs. magnitude.
Use a logarithmic (base 10) scale for the y-axis or take the log of your cumulative frequency data and plot that on a linear axis. You can use a linear x-axis because magnitude is already a power of 10. [Is this confusing? Post to the Questions forum if you need help.]
If you are having trouble, see my example plot [17] for a one-year catalog of earthquakes in the New Madrid Seismic Zone (NMSZ). I used the year 1975, so this plot will not be precisely the same as yours, but it should look pretty close.
Start with the plot you just made.
Go back to the New Madrid Earthquake Catalog and make a catalog for a ten-year time period (you can choose any ten-year period). Overlay the frequency-magnitude curve for this ten-year catalog onto the curve you made in the first plot.
Repeat for a twenty-year period.
Repeat for a thirty-year period.
You should now have one plot with four curves on it.
Make sure each curve is distinguishable (by color or linestyle) and labeled.
Start with the original one-year catalog plot you made.
Overlay the curve for the ten-year catalog, but normalize the curve to one year. This is accomplished by dividing each of your y-values by 10.
Repeat for the twenty-year catalog (divide y-values by 20)
Repeat for the thirty-year catalog (divide y-values by 30)
You should now have one plot with four curves on it.
Use the same distinguishing color or linestyle for each curve as you did in your second plot.
Dust off your worksheet from Part 1. On the worksheet, first paste your three plots into the worksheet, then answer the following questions:
2.1 Look at the first frequency-magnitude plot you made of the one-year catalog. Approximately what is the lower magnitude threshold for this catalog? (Follow your data from right to left and tell me at about what magnitude the line flattens out to having zero slope?)
2.2 Now look at the other two plots you made. Do the other curves show a significantly different lower magnitude threshold? From this observation, what do you conclude about the relationship between catalog timespan and lower magnitude sensitivity?
2.3 Look at the second plot you made. Describe the differences and similarities among the four curves in a few sentences. For example, are the curves of the same shape? Where are the x- and y-intercepts relative to each other? What makes the y-intercepts different? What causes the x-intercepts to be different?
2.4 Look at the second plot you made. Imagine having a catalog that spans 100 years. Using the four curves you made as a guide, extrapolate where the x and y intercepts would each be for a 100-year catalog. What is the largest earthquake you would expect for a 100-year catalog?
2.5 Look at the third plot you made. Extrapolate your curves and predict how often a magnitude 7 earthquake will occur in this region and how often a magnitude 8 will occur in this region. I want you to make a reasonable eyeball-fit. I am not asking you to calculate a best fit line. **If the answer is a fraction less than one, then you can take the reciprocal and predict how many years go by in between magnitude 7's and in between magnitude 8's.
2.6 You have just used frequency-magnitude relationships to predict a recurrence interval for a large New Madrid earthquake. Cool! What are the sources of uncertainty in the prediction you made in problem 2.5? (One way to realize just how much uncertainty there is in an extrapolation like this one is to try making several slightly different fits to the data that all look "pretty good" to you and see how different your final answers end up being.)
Double-Check! Now your worksheet should have the map and answers from Part 1 as well as three plots and answers for Part 2. Hang on to the worksheet and use it for Part 3.
Use the Southern California Earthquake Center Web site to make a seismicity catalog, map, and frequency-magnitude plot.
Go to the Southern California Earthquake Data Center's Earthquake Catalog Search [18] page.
Or follow along as a plain text [19] to make a one-year catalog of seismicity.
Take a screenshot of the google map you made and paste it into your problem set.
Make a frequency-magnitude plot for the events in this catalog:
Use the United States Geologic Survey catalog to make a one-year global seismicity catalog, and add this data to your frequency-magnitude plot that has Southern Cal and the NMSZ on it.
Go to the USGS Earthquake Search [20] page.
Once you are there, follow my plain text directions for making a one-year global catalog [21].
Add to your plot!
3.1 How many earthquakes are in your one-year catalog for Southern California? What is the largest magnitude earthquake in the catalog? How many earthquakes are there of this magnitude?
3.2 How many earthquakes are in your one-year catalog for the world? Are you surprised by this number? What is the largest magnitude earthquake in the world catalog? How many earthquakes are there of this magnitude? Remember that we cut off our global catalog at a minimum magnitude of 4.5. Look at your frequency-magnitude curve for the global catalog and estimate how many earthquakes there would be in your catalog if we had gone all the way down to zero for the minimum magnitude. Translate that into an approximate number of earthquakes per day in the world. (wow, huh!)
3.3 Look at your map of Southern Californian earthquakes. Describe it in a few sentences (i.e., Where are the earthquakes? Do they cluster in space? Beware of artificial clustering that we induced by where we set our search parameters.).
3.4 Look at the map of one year's worth of earthquakes made by the Advanced National Seismic System [22] and describe it in a few sentences. How do the earthquakes cluster?
3.5 Compare the frequency-magnitude curves for New Madrid and Southern California. Which one of the two catalogs is has its lower magnitude threshold at a smaller magnitude? Which region is more seismically active in terms of the number of earthquakes? Which region is more seismically active in terms of earthquake magnitude?
3.6 Compare all three frequency-magnitude curves. How often does a big earthquake (M > 7 or so) happen in the global catalog vs. in the two regional catalogs? Why is this?
Now your worksheet should contain the map and answers from Part 1, the three plots and answers from Part 2, and the map, plot, and answers from Part 3. And the green grass grows all around and the green grass grows all around. Haha, but seriously, save your file in the following format:
L4_catalog_AccessAccountID_LastName.doc (or .yourExtension)
For example, Cardinal pitcher Michael Wacha's file would be named "L4_catalog_mjw52_wacha.doc"
Create one document that contains:
Once you've finished this whole problem set, submit it to the "Earthquake catalog problem set" assignment in Canvas by the due date listed on the table on the first page of this lesson.
I will use my general rubric for grading problem sets [23] to grade this activity.
The New Madrid Seismic Zone presents a difficult problem. We know that large earthquakes have happened in the past. If earthquakes of that magnitude happened today, the damage and recovery would be difficult. Here is the problem: how big were those historical earthquakes actually? How likely are they to happen again? How should the cost of retrofitting be weighed against the predicted cost of a large earthquake? Scientists and policymakers have different training. Scientists are trained to assess the recurrence interval and estimate the ground motion of hypothetical events, while policymakers are trained to assess normative problems (i.e. given a seismic risk at some level, what should we do about it?)
In the data analyses you just completed, you became familiar with earthquake catalogs, including their strengths and limitations. You practiced looking at frequency-magnitude diagrams and you used this data to estimate the recurrence interval for earthquakes of various sizes. In fact, seismological data is just one of the tools scientists use to estimate earthquake recurrence interval. In the reading activity on the next page, you will break up into groups to investigate other methods of studying the NMSZ.
Over the past ten or fifteen years, global positioning system satellite data has become an invaluable tool for measuring plate motion and strain accumulation across faults. This data is gathered by installing geodetic markers in the ground. Scientists then use GPS receivers at the sites of the markers to find out their exact locations from satellites. Over time, the position of some markers may shift relative to each other; for example, markers on opposite sides of a fault may move closer together or further apart or be offset laterally as the years go by. This motion can be used to infer the strain rate in the crust. In the case of the New Madrid Seismic Zone, the faults are buried, so GPS data can help to find out exactly where the faults are and to determine the direction and extent of motion along them.
After several years of repeated measurements, the motion of the markers over the measurement time period is assessed. At active plate boundaries, such as along the San Andreas Fault on the West Coast of the United States, geodetic surveys have been used in concert with detailed records of seismicity to estimate stress buildup on faults and to predict seismic hazard. For example, a suite of geodetic markers may be placed around a fault of interest. After many measurements, the motion of the markers relative to each other can confirm the sense of motion on the fault, how fast the plates on either side of the fault are moving, and whether the fault itself is creeping or locked.
There have been several GPS campaigns over the last decade whose purpose has been to discover how much strain is building up at the New Madrid Seismic Zone. This work has been tricky because the faults involved are not well mapped, so the decision about where to place the markers hasn't been straightforward. The debate is still ongoing concerning whether the strain rates are high, thus posing a great seismic risk, or whether the strain rates are low, thus posing a lesser seismic risk to the area.
The map below shows current GPS stations operating in the USA.
Some faults can be excavated and mapped geologically in order to find out about the recurrence interval for large earthquakes. This sort of work is often done by digging a big trench with a backhoe and then trying to date any large offsets that are found. This technique is useful because the largest possible earthquakes of even quite active faults usually happen several hundred years apart. (Recall the ballpark range of recurrence intervals you estimated in your data analysis exercise.) We simply don’t have seismicity records that go back that far in this country. Dates for prehistoric earthquakes can be estimated by using the dates of the sediments that have been interrupted by an earthquake or some bit of organic material, such as charcoal, in an adjacent layer that can be dated. In the New Madrid Seismic Zone, stream offsets and evidence of liquefaction (sand blows and dikes) caused by strong shaking are also clues to past earthquakes. Paleoseismologists use all these clues to try to put together a timeline of recurrence interval and the approximate earthquake magnitude for a particular fault. These data can be linked with seismicity catalogs and geodetic surveys to get a fuller picture of seismic hazard.
To see excavation and mapping in action, check out this short video from Teachers' Domain and NOVA Online about the work of Kerry Sieh [28], a paleoseismologist at The Earth Observatory of Singapore (He was a prof at Caltech when they made this video).
The Earth produces heat from the decay of radioactive elements in its interior. This heat drives mantle convection and therefore the movement of tectonic plates. Heat flow is routinely measured in boreholes around the planet. These measurements are compiled to produce a map of heat flow for the Earth's surface. Some degree of estimation and smoothing must be applied to the measurements because the boreholes are not evenly spaced and some are on continents while other measurements are taken in oceanic crust. The map below shows global heat flow.
This map shows color-coded contours of the global distribution of heat flow at the surface of the Earth's crust. Major plate boundaries and continent outlines are also shown. The fundamental data embodied in this map are the more than 24,000 field measurements in both continental and oceanic terrains, supplemented by estimates of the heat flow in the unsurveyed regions. The estimates are based on empirically determined characteristic values for the heat flux in various geological and tectonic settings. Observations of the oceanic heat flux have been corrected for heat loss by hydrothermal circulation through the oceanic crust. The global data set so assembled was then subjected to a spherical harmonic analysis. The map is a representation of the heat flow to spherical harmonic degree and order 12.
What does this have to do with the New Madrid Seismic Zone? By looking at the map above, you can see that the amount of heat flowing out of the Earth is not uniform over the surface of the planet. Some areas have much higher heat flow than others and these areas are usually associated with tectonic activity such as volcanism and plate boundaries. For example, the boundaries of the North American plate, the Mid-Atlantic Ridge and the San Andreas fault system, both show up as "warm" places on this map. Heat flow measurements have been made in the New Madrid Seismic Zone to see whether this is a high heat flow area compared to what would be expected for the interior of a continent. (Conventional geophysical wisdom holds that the interior of continents should be old, cold, and stable.) If heat flow is higher than expected, this would be evidence for why earthquakes happen in this area. This remains a point of scientific contention. Past surveys concluded that heat flow was high in the NMSZ, but the most recent studies disagree with those earlier findings.
The map below comes from the Global Heat Flow Database [31], at the University of North Dakota. They have heat flow maps and data files for all different parts of the world. This particular map shows borehole data for the United States. Warm colors denote higher heat flow than cool colors (see the legend, which shows milliwatts per meter squared values color-coded). Notice that this map looks different than the global map above. It looks different because it shows exact borehole measurements as opposed to smoothed values that have been interpolated over the whole map. Where is the heat flow highest? Where is it lowest? Compare this map with the map above to see whether they are consistent for the US.
In this assignment, you will break up into teams to read and discuss the papers designated for you. After this, the class will regroup as a whole and discuss all the papers.
I will divide the class into 3 teams.
Each team should begin by reading their assigned readings and consider the related discussion questions as described below. Papers are linked from your team's discussion board in Canvas.
Team 1: GPS measurements
Members of Team 1 should read thoroughly the seven letters, responses, and summaries listed below to get a sense of the debate about GPS measurements of the NMSZ. Then read/skim the two scientific papers to flesh out your understanding of the studies involved in this debate.
Team 2: Paleoseismology
From the list below, members of Team 2 should browse Martitia Tuttle's Web site and read the Geotimes and Economist articles to get a sense of the current state of the art in paleoseismology at New Madrid. The short article from The Economist discusses a pretty new and novel way of approaching paleoseismology. Then skim the two scientific papers by Roger Saucier to flesh out your understanding of the studies involved.
Team 3: Heat flow measurements
Members of Team 3 should read thoroughly the two summaries and news articles listed below to get a sense of the debate about heat flow measurements of the NMSZ. Then read the two scientific papers to flesh out your understanding of the studies involved in this debate.
Midcontinent heat may explain great quakes [38]. (1993).Science News, 143(22), 342.
Upon completion of the reading, you are to engage in a discussion of the readings, first within your team and then with the rest of the class. The team discussion component of this activity will take place over a few days and will require you to participate multiple times over that period. Likewise, the class discussion will then take place over the subsequent few days.
Team discussions:
Class discussion:
Once you have discussed these topics within your team, we will regroup to engage in a discussion with the entire class. This class discussion will take place in a separate discussion forum titled "Debating Hazard at New Madrid - Class Discussion."
You will be graded on the quality of your participation. Please see the rubric for teaching/learning discussions. [40]
For this activity, you will rewrite the USGS fact sheet you read earlier in the lesson, updating it with the research progress that has been made since it was published.
Rewrite USGS Fact Sheet FS-131-02, Earthquake Hazard in the Heart of the Homeland [1], highlighting the research progress that has been made since 2002, when this fact sheet was published. Specifically, your mission, should you choose to accept it, is to do a better job than the USGS did themselves when they updated FS-131-02 in late 2009 with this new fact sheet, FS09-3071, Earthquake Hazard in the New Madrid Seismic Zone Remains a Concern [41]. (Maybe they were worried that alums of this course would steal their jobs).
I expect your fact sheet to be well organized and coherent, with none or few grammatical and spelling errors. It needs to be completely rewritten in your own words. All references to the scientific work of others (this includes summaries of their results and/or any borrowed figures) must be properly cited and a bibliography must be included.
This fact sheet is meant to be explanatory and persuasive. It should be written for a hypothetical general audience (i.e., non-scientists). It should be clear to me that you understand the significance of the results of all the scientific studies you refer to in your paper (including your own). See grading rubric below for more details.
The successful paper should meet the following criteria (points out of 100 total in parentheses):
It is fine to use figures, graphics, and data from other sources as long as you cite them appropriately and include them in the bibliography. It is also fine (and encouraged!) to organize the fact sheet differently than the original or to emphasize different areas of research than the original. Be creative!
The following resources might be helpful to you in your task. (You are in no way limited to these, of course. You may use whatever appropriate sources you want to.) References that are not clickable are linked from the Canvas module for this lesson.
Save your paper as either a Microsoft Word or PDF file in the following format: L4_paper_AccessAccountID_LastName.doc (or .pdf) For example, Cardinal relief pitcher Trevor Rosenthal's file would be named "L4_paper_tjr26_rosenthal.doc"
Upload your paper to the Fact Sheet Paper assignment in Canvas by the due date indicated in the table on page 1 of this lesson.
Let's take some time to reflect on what we've covered in this lesson!
For this activity, I want you to reflect on what we've covered in this lesson and to consider how you might adapt these materials to your own classroom. Since this is a discussion activity, you will need to enter the discussion forum more than once in order to read and respond to others' postings.
You will be graded on the quality of your participation. Please see the rubric for teaching/learning discussions. [40]
Newman et al. (1999) Slow Deformation and Lower Seismic Hazard at the New Madrid Seismic Zone, Science, 284, 619–621.
Boyd, O.S., R. Smalley, Jr., and Y. Zheng (2015), Crustal deformation in the New Madrid seismic zone and the role of postseismic processes, J. Geophys. Res. Solid Earth, 120, 5782–5803, doi:10.1002/2015JB012049.
The New Madrid Seismic Zone is enigmatic because it has produced large earthquakes in the past, but its future is unclear. Deciding how to plan for the seismic hazard is not easy and this is compounded by the fact that large sums of money and large amounts of government intervention are involved. I want to stress that just because scientists do not agree, this does not mean that science doesn't work! The problem is that scientists and policy-makers have different training. What do you think forms the greatest barrier between science and public policy?
You have finished Lesson 4. Double-check the list of requirements on the Lesson 4 Overview page to make sure you have completed all of the activities listed there before beginning the next lesson.
If you have anything you'd like to comment on or add to, the lesson materials, feel free to post your thoughts in the Teaching/Learning discussion! It's one of your final assignments in this lesson anyway. For example, what did you have the most trouble with in this lesson? Was there anything useful here that you'd like to try in your own classroom? Is seismic hazard a topic you and your students are interested in? Are there many well-known seismically active faults where you live? (Even if you don't think so, you could always try playing around with the seismic catalog search features we used in this lesson to find out.)
Links
[1] http://pubs.usgs.gov/fs/fs-131-02/fs-131-02.html
[2] https://www.youtube.com/user/duttoninstitute
[3] http://pubs.usgs.gov/imap/i-2812/i-2812.jpg
[4] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/file/NMSZ/fs-131-02.pdf
[5] http://www.usgs.gov/
[6] http://volcano.oregonstate.edu
[7] http://www.sciencedaily.com/releases/2001/03/010309080443.htm
[8] http://www.livescience.com/environment/070502_newmadrid_quake.html
[9] http://earthquake.usgs.gov
[10] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/flash/NewMadrid%20lesson/2008-02-27_1405.swf
[11] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/file/NMSZ/frequencyMagnitudeRealDataTranscript_0.txt
[12] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/flash/NewMadrid%20lesson/quakeFreqMagPencast.mp4
[13] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/flash/NewMadrid%20lesson/extrapolation.swf
[14] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/file/NMSZ/recurrenceIntervalExtrapolationTranscript.txt
[15] http://folkworm.ceri.memphis.edu/catalogs/html/cat_nm.html
[16] https://www.e-education.psu.edu/earth501/node/1816
[17] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/image/lesson2/nmsz1975.jpg
[18] http://scedc.caltech.edu/eq-catalogs/
[19] https://www.e-education.psu.edu/earth501/node/1817
[20] https://earthquake.usgs.gov/earthquakes/search/
[21] https://www.e-education.psu.edu/earth501/node/1818
[22] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/image/NMSZlesson/neic_2007janjun.jpg
[23] https://www.e-education.psu.edu/earth501/node/1807
[24] http://www.f64.nu/
[25] http://en.wikipedia.org/wiki/U.S._National_Geodetic_Survey
[26] http://www.ngs.noaa.gov/CORS/
[27] http://mptuttle.com/newmadrid5.html
[28] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/flash/NewMadrid%20lesson/ess05_vid_trench-PBS_LM_4x3_mezzanine-16x9-mp4-1200k.mp4
[29] https://wpsu.pbslearningmedia.org/
[30] https://lsa.umich.edu/earth
[31] https://engineering.und.edu/research/global-heat-flow-database/
[32] http://www.heatflow.und.edu/usa.jpg
[33] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/file/lesson3/stein_pressextra2009.pdf
[34] https://eos.org/research-spotlights/aftershocks-of-old-quakes-still-shake-new-madrid-seismic-zone
[35] http://mptuttle.com/newmadrid1.html
[36] http://www.geotimes.org/oct06/NN_RiverQuakes.html
[37] http://www.sciencedaily.com/releases/2006/12/061211221056.htm
[38] http://findarticles.com/p/articles/mi_m1200/is_n22_v143/ai_13825066%20
[39] https://pdfs.semanticscholar.org/700f/de6ac2e5ae4915812b896dcb4c1ad43e446f.pdf
[40] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/file/rubrics/Online_Discussion_Forum_grading_rubric.pdf
[41] https://www.e-education.psu.edu/earth501/sites/www.e-education.psu.edu.earth501/files/file/NMSZ/FS09-3071.pdf
[42] http://www.terradaily.com/reports/Should_Memphis_Build_For_California_Style_Earthquakes.html
[43] http://www.sciencedaily.com/releases/2000/09/000929072432.htm
[44] http://www.dnr.mo.gov/geology/geosrv/geores/techbulletin1.htm
[45] http://www.disastersrus.org/emtools/earthquakes/FEMA366.pdf
[46] http://www.huduser.org/Publications/PDF/newmadrid.pdf
[47] http://www.data.scec.org/education.html
[48] http://www.ceri.memphis.edu/perc/
[49] https://www.usgs.gov/science-support/osqi/yes/resources-teachers
[50] http://environment.nationalgeographic.com/environment/natural-disasters/forces-of-nature.html?section=e
[51] http://www.nature.com/nature/podcast/index-2011-11-10.html