SSBW - Network Tutorial 2: Global Seismogram Viewer and Forward Modeling
In this interactive tutorial built for a learning management system, students will 1) use the IRIS Global Seismogram Viewer to view a record section of global recordings from the 2010 M7 earthquake in Haiti, 2) pick the arrivals at several stations with different teleseismic distances, 3) construct a preliminary velocity model from traveltimes and distances, 4) predict arrival times from TauP using the velocity model, and 5) compare predicted times with observed times to revise the velocity model.
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, SAC, TauP, IRIS Fetch scripts for web services, picking arrival times on seismograms, estimating seismic wave travel paths based on distance traveled, and calculating velocities.
How the activity is situated in the course
This is assignment number 21 of 35 in the Seismology Skill Building Workshop (SSBW).
Content/concepts goals for this activity
Proficiency with reading seismograms, picking arrival times, calculating seismic wave speeds, SAC, TauP, estimating what depths seismic waves travel in the crust and mantle, what forward modeling is.
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, successfully performing forward modeling.
Other skills goals for this activity
Description and Teaching Materials
1. View a record section of global recordings from the 2010 M7 earthquake in Haiti using the IRIS Global Seismogram Viewer (GSV)
2. Describe the general pattern in the P wave arrivals and identify the cause of the shadow zone
3. Pick the first arrival at the closest station in the GSV and use it to calculate the P wave speed
4. Pick the arrival times and approximate distances for stations at teleseismic distances
5. Calculate seismic speeds for parts of the lower mantle using differences in time and distance
6. Retrieve the Haiti earthquake information with FetchEvent
7. Use a foreach loop in a script to retrieve a BHZ seismogram for each station using FetchData
8. Convert downloaded miniseed files to SAC files and then plot them sorted by distance in SAC
9. Construct a starting velocity model for the Earth using seismic speeds estimated with GSV
10. Use TauP to predict arrival times at different distances based on the velocity model and insert those predictions into the SAC files
11. Compare the predicted times with the observed times and then revise the velocity model
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
13 multiple choice questions
2 multiple answer questions
24 numeric questions (plot measurement, calculation, output values, quantifying output)
9 short answer (auto-graded) question
1 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.