SSBW - Network Tutorial 1: Local Seismogram Viewer and the Moho

Mike Brudzinski, Miami University-Oxford

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Summary

In this interactive tutorial built for a learning management system, students will 1) use the IRIS Local Seismogram Viewer to view a record section of local recordings from the 2011 M5 earthquake in Oklahoma, 2) pick the Pn and Pg arrivals at several stations with different distances, 3) use the trend1d GMT command to perform a linear fit to the traveltime data and estimate seismic wave speeds, 4) determine what portions of the crust and mantle that the different wave speeds represent.

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Context

Audience

The IRIS Seismology Skill Building Workshop (SSBW), which is a free, online, open-access, large-enrollment, 12-week summer workshop for upper level undergraduates.

Skills and concepts that students must have mastered

This assignment builds on prior experience using a Linux command line environment, GMT commands, picking arrival times on seismograms, estimating seismic wave travel paths based on distance traveled, and a general understanding of what a linear fit is.

How the activity is situated in the course

This is assignment number 20 of 35 in the Seismology Skill Building Workshop (SSBW).

Goals

Content/concepts goals for this activity

Proficiency with reading seismograms, picking arrival times, calculating seismic wave speeds, linear fits to data, estimating what depths seismic waves travel in the crust and mantle.

Higher order thinking skills goals for this activity

Retrieving relevant information from digital sources to accomplish tasks, using correct programming syntax, evaluating and describing computing output in the context of broader concepts.

Other skills goals for this activity

Description and Teaching Materials

Students will:
1. View a record section of local recordings from the 2011 M5 earthquake in Oklahoma using the IRIS Local Seismogram Viewer (LSV)
2. Pick the first arrival at the closest station and use it to calculate the P wave speed in the upper crust
3. Discern the Pn and Pg arrivals at several stations and store the times in separate input files
4. Determine the distance of each station and store it with the arrival time in the input files
5. Use the trend1d GMT command to perform a linear fit to the distance and time information
6. Convert the best-fitting slope from slowness to speed
7. Determine what portions of the crust and mantle that the Pn and Pg wave speeds represent
8. Calculate the depth of the Moho using the best-fitting Y-intercept and the wave speeds

 

Teaching Notes and Tips

This assignment was constructed in the Moodle learning management system, and has been exported in the GIFT format. More information about the syntax of this format can be found here: https://docs.moodle.org/en/GIFT_format

Assessment

This assignment is automatically graded by the learning management system. The number of questions of each type used are:
7 multiple choice questions
31 numeric questions (plot measurement, calculation, output values, quantifying output)
2 short answer (auto-graded) question
2 free response (all accepted) question

References and Resources

During the Seismology Skill Building Workshop, students are provided with a virtual Linux machine that was tailored to include the software specifically needed to complete the assignments. This software is all freely available on the internet, but interested parties are encouraged to contact the instructor for access to this tailored virtual machine.

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