SSBW - IRIS DMC Tutorial 4: dataselect Web Service and Filtering Seismograms

Mike Brudzinski, Miami University-Oxford

Initial Publication Date: August 18, 2021

Summary

In this interactive tutorial built for a learning management system, students 1) generate and interpret IRIS web service requests for metadata, earthquake information, and seismogram data (event, station, dataselect), 2) use SAC to visualize and interpret seismogram and spectrogram frequency content, and 3) design a bandpass filter to limit noise signatures.

Seismology | College Upper (15-16)

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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, IRIS web service requests, the SAC (Seismic Analysis Code) software, and an understanding of the relationships between time domain and frequency domain in converting from seismograms to spectrograms and in the process of filtering.

How the activity is situated in the course

This is assignment number 17 of 35 assignments in the Seismology Skill Building Workshop.

Goals

Description and Teaching Materials

Students will:
1. Learn about the Sept. 12, 2007 Magnitude 8.5 earthquake sequence in southern Sumatra
2. Generate and interpret IRIS event web service requests for earthquake catalog information
3. Generate and interpret IRIS station web service requests for recording metadata
4. Generate and interpret IRIS dataselect web service requests for seismograms
5. Use SAC to visualize and interpret seismogram frequency content
6. Use a Fast Fourier Transform to analyze spectral content
7. Design a bandpass filter to limit noise signatures.

Show Student Learning Outcomes

Student Learning Outcomes (with corresponding Question #s that address them):

Retrieve relevant information about web services and seismology from internet research or help pages (Q1, 7, 9, 16, 17, 22, 31).
Use the URL Builder to generate a web service request for specific metadata or earthquake information (event, station) (Q1, 4).
Interpret web service output tables for data or earthquake information (Q1, 2, 3, 4, 5, 6, 7).
Interpret what is a mainshock and aftershocks in a catalog of earthquakes (Q2, 3)
Describe general information about the 2007 Magnitude 8.5 Sumatra earthquake (Q1, 2, 3)
Use the URL Builder to generate a web service request to retrieve seismogram data (dataselect) (Q7, 9, 11).
Correctly identify or specify the network, station, channel, and location codes for a given recording. For channel, this involves frequency, gain, and orientation attributes (Q4, 5, 6).
Calculate a properly formatted date and time for arrivals and data requests using an earthquake origin and travel time (Q7, 8).
Create and navigate directories on a Linux system (Q10, 13).
Use wget and unzip on Linux to make web service requests and unpack data (Q11, 12).
Use the SAC READ command and wildcards to specify a selection of files (Q13, 23, 33)
Use the SAC LISTHDR command to review seismogram metadata (Q14)
Convert from period to frequency and calculate the Nyquist frequency (Q15, 16, 25)
Use correct units (Q14, 17, 24, 25, 28)
Use the SAC FFT and PSP command to convert a seismogram to the spectral domain and plot it (Q18, 26, 27)
Interpret the primary trends in a plot of spectral amplitude (Q18, 19, 20, 21, 28, 30)
Use exponential notation to express numbers (Q14, 15, 16, 19, 20, 21, 28, 30)
Use SAC PPK and WH commands to pick and save arrival time information (Q22).
Compare how frequency patterns differ for small and large earthquake, between time and spectral domain, and between noise and earthquakes (Q22, 29, 30, 32, 34)
Interpret the primary trends and frequencies in a seismogram (Q23, 24, 33, 35, 36, 37)
Use the SAC CUT, RTREND, and BANDPASS commands to adjust a seismogram (Q23, 24, 31, 32, 33, 34, 35, 36)
Discern which type of filter to use based on the seismic wave of interest (Q31, 32, 33, 34, 35, 36).

GIFT format file for SSBW IRIS DMC Tutorial 4 -- educator-only file

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

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Assessment

This assignment is automatically graded by the learning management system. The number of questions of each type used are:
17 multiple choice questions
3 multiple answer question
1 true/false question
8 numeric questions (number and magnitude of earthquakes, sampling interval, rate, frequency)
7 short answer (auto-graded) 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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SSBW - IRIS DMC Tutorial 4: dataselect Web Service and Filtering Seismograms

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