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

Yesterday’s Earthquake

As recorded in the US

As a story

Jointly produced with Univ. of Portland, collaborative content from USGS, UNAVCO and others

Tectonics

http://www.iris.edu/hq/retm

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

IRIS Earthquake Browser - www.iris.edu/ieb

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?

Earthquakes, Magnitude >3.5, 1973-2007

Earthquakes, Magnitude >3.5, 1973-2007

Ear

thqu

akes

/yea

r

Magnitude

California (blue) and Eastern US Earthquakes (red)

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?

Real, imperfect data set

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

Recordings from the

Global

Seismic

Network

• 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

USArray

Ground

Motion

Visualizations

• Visualizations exist for all parts of lower 48

EPO

web

page from

www.iris.edu

• Feedback?• Comments?• Questions?

EXTRAS

Selection from focal

mechanism

ani

mation