Using IRIS and other seismic data resources in the classroom
John Taber, Incorporated Research Institutions for Seismology
Overview• IRIS Earthquake Browser
• Estimating seismic hazard• Exploring seismicity in Oklahoma
• Visualizations, animations, and waveforms– Recording and analyzing data from an
educational or research-grade seismometer– Viewing a set of seismograms from an
earthquake– Exploring regional tectonics using focal
mechanisms– USArray ground motion visualizations
As a story
Jointly produced with Univ. of Portland, collaborative content from USGS, UNAVCO and others
IRIS Earthquake Browser - www.iris.edu/iebMy_link_for_this_image
IRIS Earthquake Browser - www.iris.edu/ieb
• Can use for introduction to plate tectonics– Explore plate boundaries
– Turn plate boundary lines on and off
– Interactive 3D viewer
• General exploration of spatial distribution of local and regional seismicity
Estimating seismic hazard
You have been asked to compare the seismic hazard in two regions to determine which is safer for building a new manufacturing plant.
1.What type of data would you need to collect to make the comparison?
2. How could you express your findings in a quantitative way?
Earthquake hazard from a single fault
•Would like to know
•How often do the biggest earthquakes occur?
•When will the next big one occur?
•Extend earthquake history with geologic record
Earthquake recurrence along a single fault
Sieh et al., 1989
With a partner:
Determine when the next Pallett Creek earthquake is going to occur.
Can you estimate the uncertainty in your answer?
Earthquake recurrence along a single fault can be highly variable: probabilities hard to assess
M >7: mean = 132 yr
Standard deviation = 105 yr
Estimated probability of next earthquake in 30 yrs is 7-51%
-> Nearly Random!
Sieh et al., 1989
How can we deal with unpredictable nature of individual faults?
Try regional approach
•Use the rate of earthquake occurrencein one time period to forecast earthquake activity in another time period
•Combine results from multiple faults
•Consider more than just the biggest earthquakes
Estimating seismic hazard
Steps:• Select a region of the world that is of interest to you • Interrogate the earthquake catalog to determine the
number of events that occur in a 25 year period– Set the Time Range
– Set the Magnitude Range
• In an Excel spreadsheet, record the total number of events for each magnitude range
• Determine the number of earthquakes/year for each magnitude range
• Plot the magnitude range vs the number of earthquakes/year
Questions to discuss with a partner
• Given the range of the data, what sort of plot gives the clearest representation of the data?
• Do you see any patterns or trends in your data?
• How does your plot compare to your partner’s plot of a different region?
• What is the likelihood of earthquakes of magnitude 6.0 or greater and 7.0 or greater occurring in the next year in the 2 regions?
• What is the likelihood of these events occurring in the next 100 years in each region?
Gutenberg-Richter Plot
0.01
0.10
1.00
10.00
100.00
1000.00
3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5
Magnitude
Number/Year
California Eastern US Expon. (California) Expon. (Eastern US)
How often does a M6 earthquake occur?
Gutenberg-Richter Plot
0.01
0.10
1.00
10.00
100.00
1000.00
3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5
Magnitude
Number/Year
California Eastern US Expon. (California) Expon. (Eastern US)
How often does a M7 earthquake occur?
Interpretation questions
• How can you use the seismicity information to estimate which of your two regions would be a safer choice for the manufacturing plant mentioned at the beginning of the exercise?
• What are some assumptions, limitations, and potential sources of error in drawing conclusions about long-term seismic hazard using the above technique?
Customizable USGS Seismic Hazard Maps
Submitted draft exercise explores hazard map
http://geohazards.usgs.gov/eqprob/2009/index.php
Oklahoma seismicity - www.iris.edu/ieb
For Oklahoma: • Compare 5/1/95-5/1/05 and 5/1/05-5/1/15• Magnitude 2 and greater• Count the earthquakes
Rapid
Earthquake
Viewer
• Determine global travel times and infer Earth structure
• Rapid Earthquake Viewer
• Developed and maintained by Univ S. Carolina
• Real time data streaming and simple analysis– Simple filtering, arrival picking, locations, magnitudes
Recording and analyzing seismic data Jamaseis
• Visual sorting of normal, reverse, and strike-slip mechanisms
• Can explore distribution in a subduction zone• IRIS main menu: Data and Software > Products
– Select Moment Tensors, then Quick links– http://www.iris.edu/spud/momenttensor
• Focal mechanism animation available
Exploring regional tectonics using focal mechanisms
• Select a region and a submitted velocity model and generate a cross section
• Fate of slabs • Crustal and upper mantle thickness under
mountain ranges
Investigating Earth structure using tomographic models
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