Research opportunities using IRIS and other seismic data

resources

John Taber, Incorporated Research Institutions for Seismology

Michael Wysession, Washington University

Overview• Hands on

– Estimating seismic hazard using IRIS Earthquake Browser

• Discovering a predictive mathematical model

• Demo– Exploring regional tectonics using focal mechanisms– Recording and analyzing data from an educational

or research-grade seismometer– Viewing a set of seismograms from an earthquake– USArray ground motion visualizations– Understanding earthquakes via a simple physical

model

Estimating seismic hazard

Research problem

You and your partner 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

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

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

IRIS Earthquake Browser - www.iris.edu/ieb

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?

http://pasadena.wr.usgs.gov/office/hough/east-vs-west.jpg

Ground shaking from a magnitude 5 earthquake in the east is approximately equivalent to that of a magnitude 6 earthquake in the west.

Virginia M 5.8

California 6.5

Going from seismicity rate to ground shaking

USGS National Seismic Hazard Map

Submitted draft exercise explores hazard map

Exploring regional tectonics

using focal

mechanisms

• 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

Recording

and

analyzing seismic

data

using jAmaseis

• Real time data streaming and simple analysis– Simple filtering, arrival picking, locations, magnitudes

Recording

and

analyzing seismic

data

using jAmaseis

• Real time data streaming and simple analysis– Simple filtering, arrival picking, locations, magnitudes

• Up to 3 data streams can be viewed and stored locally– Local or remote educational seismographs– Any global research station received and stored

in the IRIS Data Management Center

Recordings from the

Global

Seismic

Network

• Real time data streaming and simple analysis

Potential seismograph-related research topics

• Local seismograph calibration and sensitivity– Distance/magnitude relationship

• Alan Kafka

– Analyzing seismic data to find what earthquakes were recorded and then learning about the tectonics of each region

• Dave Voorhees’ student

– Finding the best recording location

Rapid

Earthquake

Viewer

• Developed and maintained by Univ S. Carolina

Understanding

earthquakes via

a si

mple

physical

model

• Earthquake machine

• Simple data collection and analysis leads to very similar result to real earthquake catalog

USArray

Ground

Motion

Visualizations

• Visualizations exist for all parts of lower 48

• 1D and 3D versions

EPO

web

page from

www.iris.edu

• Feedback?• Comments?• Questions?

EXTRAS

USArray

Ground

Motion

Visualizations

• Visualizations exist for all parts of lower 48

Investigating

Earth structure

using tomographic

models

• Select a region and a submitted velocity model and generate a cross section

• Fate of slabs • Crustal and upper mantle thickness under

mountain ranges

Selection from focal

mechanism

ani

mation