Understanding the Deep Earth

Online Workshop

(Using Glenn's idea for Group 1) Let's use this thread to get a start on ideas/activities we would like to work on.

Seems like there is a lot of interest for tomography activities at a variety of levels. One basic tomography activity might be to treat each student in a lecture as a grid cell, assign numbers to each student, and try to solve where anomalies are, Sudoku-style. I've done this in a small group and it worked, but I'm not sure yet how to execute it with more than a dozen or so students.

Hi Anna,

Could you explain the Sudoku bit some? I'm having a hard time visualizing it, but it sounds cool.

It's not actually like Sudoku in terms of rules but the logic style/idea seems to go over better with students than "solving systems of equations." In Sudoku, the idea is that in each row or column you must have the numbers 1-9, and you can reason out which numbers can or can't go somewhere based on what is going on in neighboring squares. With the tomography exercise, instead of using every number, you could set it up so that most squares are the average Earth properties from PREM at some depth, and some regions are made up of consistently higher than average numbers (seismically fast) and another area is made of consistently lower than average numbers (seismically slow).

When I tried this before, I gave students the numbers 1, 5 ("avg"), and 8 blindly, then told them to get together and tell me the sums of the "rows" and "columns" of desks in the room. I was able to figure out where the 1's and 8's were based on the sums, and could map out the anomalies similar to the way (really basic) tomography would work. Depending on the group, you may get close to the right answer but in slightly the wrong location, or you might come up with a couple of possibilities but no unique solution.

I'm not exactly sure how this would work on a larger scale, but thought putting the idea out there might spur other ideas/strategies. I like it because it's a hands-on approach that might give students some insight before setting them up with a USArray style tomography exercise. I'm happy to work with others to try to develop this a bit further if people are interested (or feel free to run with it on your own if you have ideas on how it could be set up!).

PS- We can follow up via phone if this wasn't terribly clear or if you want to bounce ideas back and forth...

Keith Sverdrup and I are working together on a better version of the "how thick is the crust under Milwaukee" piece that I included in my presentation Friday.

We are developing it in three pieces, which can be used together or separately. The first level is like the quick in-class activity I used Friday. The second level incorporates the fact that the UW-Milwaukee seismograph is 5.8 km north of the Hoan Bridge, so the record did not result from a simple down-and-back straight-line geometry. The third level may have the students work with the digital data.

My goal is to get the first level done for Wednesday morning, and to start on the second level. Keith has to track down the digital file for the event, so the third level will be something that we develop in the coming weeks.

This post was edited by Jacob Cohen on Jun, 2017
Two other items I plan to develop for this set in the coming weeks are as follows:

[1] A revision of my "compute the travel times assuming Earth is the same density throughout" homework sheet ( bearspace.baylor.edu/Vince_Cronin/www/EarthInterior/EarthIntHomework1.pdf )

[2] A "How do the predicted travel times compare with the observed travel times" project that would give students an experience using data from seismic data repositories like the IRIS DMC. This could complement a seismic tomography project by potentially having students find anomalies (i.e., differences between predicted and actual arrival times) in the data from a single earthquake.

Hi Seismo Group,

I can't do the call-in tomorrow - have class...but I'll keep on chugging along on my activity