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Exploring Plate Motion and Deformation in California Using GPS Time Series Plots

Exploring Plate Motion and Deformation in California Using GPS Time Series Plots Shelley Olds, UNAVCO Andy Newman, Georgia Institute of Technology. Parts of Activity. Part I: Analyze real time-series data of two GPS stations to determine plate tectonic motion

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Exploring Plate Motion and Deformation in California Using GPS Time Series Plots

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  1. Exploring Plate Motion and Deformation in California Using GPS Time Series Plots Shelley Olds, UNAVCO Andy Newman, Georgia Institute of Technology

  2. Parts of Activity • Part I: Analyze real time-series data of two GPS stations to determine plate tectonic motion • Part II. Investigate deformation at two GPS stations in California

  3. Processed Data SBCC GPS STATION • Located near Mission Viejo, CA • Position data collected every 30 seconds • One position estimatedeveloped for each day • North • East • Vertical

  4. Position time series plot • Time series plot shows the GPS station’s change in position over time • X-axis: • Date of the measurement • In 10ths of year or months • Y-axis: • North (N/S) • East (E/W) • Height (up/down) (sometimes called Vertical) • In millimeters

  5. Units of measurement • X Axis • Typically in 10ths of year • Y Axis • Usually millimeters (but always check)

  6. In Your Packet: Station Homepages • Station name/location • Latitude / longitude • Elevation • More information: • Area map – w/ nearby stations • Link to data (Excel readable format)

  7. In Your Packet: BEMT & SBCC Times Series Plots

  8. In Your Packet: Map of Southern California

  9. Part I Instructions • Work in pairs to complete the table (pg 2-3) • One person: BEMT GPS Station • One person: SBCC GPS Station • Required GPS station information is on pgs 4-5 • Get together with your partner • Plot the north-south and east-west velocity vectors on graph paper • Determine the magnitude and direction of the resulting velocity vector • Plot this vector on the map of southern California. • Answer the questions on pg 3 Vectors on next slide

  10. Velocity of plates • BEMT • 5.0 N • -5.4 E • -2.1 V • SBCC • 26.8 N • -26.8 E • -3.9 V BEMT SBCC

  11. Animation – through time

  12. What’s happening here?

  13. CAND: • Lat: 35.94 • Long: -120.43 • CARH • Lat: 35.89 • Long: -120.43 CAND CARH

  14. Anyone have a calculator • How much slip on the fault occurred during the event using the CAND time series plot? • ~ 75 mm south and ~ 60 mm east resulting in 96 mm combined slip to the southeast • Describe how the CAND GPS station’s position changed: • During the earthquake. • After the earthquake. • What was the magnitude* of the Parkfield earthquake based on the slip that you calculated? Sudden change in position to SE… Continued SE until ~Jan 2005, then resumed NW movement M = log10(D) + 6.32 0.9 where M = magnitude D= average slip in meters [1000 mm = 1 meter] M = log10(.096) + 6.32 0.9 M = 5.9 (according to the USGS, the Parkfield earthquake was a magnitude 6.0 Mw)

  15. Reoccurring Earthquakes • ~96 mm total slip • Plate moving ~22mm/yr at Parkfield • How long should it take to build enough strain energy to generate an earthquake with a similar magnitude? • 96mm / 22 mm per year = ~4.4 years Area map of Parkfield: USGS Red = epicenters of mainshock and aftershocks within one month of event. Yellow = Epicenters of earthquakes from 1973-2006.

  16. Reoccurring Earthquakes • Observed frequency of M6 earthquakes during the 20th century? • ~every 20 years • Predicted frequency: • 96mm / 22 mm per year = ~4.4 years • Why are these numbers different? • smaller earthquakes release some of the strain, • interaction with nearby faults, etc.

  17. Extension: Explore other GPS sites • Compare the slip at 4 – 6 more sites. • Choose sites increasingly further away from epicenter… • MNMC • CAND & CARH • MASW • LOWS, CRBT … • (check the installation dates)

  18. Getting a sense of motion

  19. Data for Educators Website http://www.unavco.org/edu_outreach/data.html

  20. Teaching Tips / Errors • What teaching tips to implement this lesson? • What sources of error would your students have?

  21. Questions? Contact info: Shelley Olds olds unavco.org 303-381-7496

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