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Role of Space Geodesy In GEOSS Timothy H. Dixon University of Miami/RSMAS and

Role of Space Geodesy In GEOSS Timothy H. Dixon University of Miami/RSMAS and Center for Southeastern Advanced Remote Sensing (CSTARS). Contributions from:. Jean Dickey (JPL) Jeff Freymueller (University of Alaska) Kristine Larsen (University of Colorado)

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Role of Space Geodesy In GEOSS Timothy H. Dixon University of Miami/RSMAS and

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  1. Role of Space Geodesy In GEOSS Timothy H. Dixon University of Miami/RSMAS and Center for Southeastern Advanced Remote Sensing (CSTARS)

  2. Contributions from: • Jean Dickey (JPL) • Jeff Freymueller (University of Alaska) • Kristine Larsen (University of Colorado) • Falk Amelung, Shimon Wdowinski, and Noel Gourmelen (University of Miami)

  3. Space Geodesy: GPS, VLBI, SLR DORIS, INSAR

  4. Geodesy and Subduction Zone Studies • Use steady state and time-dependent surface deformation from GPS to study locking and strain accumulation on plate interface (source of destructive earthquakes) • Combine with seismic data to define plate boundary geometry, measure and interpret physical processes of strain accumulation and release • Improve understanding of earthquake and tsunami hazard • Role for tsunami warning?

  5. Locked Slip (cm/yr)

  6. Plate Interface Locking vs Microearthquakes

  7. L Locked Slip (cm/yr) Present: Interseismic Strain Accumulation and Micro-earthquakes Past: Coseismic Rupture GPS and Seismic Data Highly Complimentary

  8. Role for GPS in Seismic/Tsunami Hazard? • Pre-seismic strain transients are rare or non-existent • Present strain accumulation rate can be related to size and timing of future strain release (earthquake) • Possible GPS role in tsunami warning, via accurate, rapid earthquake magnitude estimation

  9. Final Static Displacement F. Kimata, Nagoya University GPS Can Measure Magnitude… within minutes • Rapid, accurate magnitude estimation is difficult for largest earthquakes • High precision GPS receivers measure displacement, very sensitive to earthquake magnitude • Can estimate magnitude from only a few sites • But need to have data from sites near the earthquake in real-time, hypocenter (from short period data) and a system for real-time analysis. • Will require a real-time subduction zone network

  10. Other Applications of High-rate GPS • GPS is sensitive to displacement rather than acceleration. • GPS can measure dynamic response of Earth’s surface to earthquakes, landslides and volcanic eruptions • GPS does not saturate for large signals, can augment strong motion networks • Can be done in real-time

  11. 2002 November 3 Denali Earthquake Eberhart-Phillips et al., 2003

  12. * GPS “Seismograms” * 60 cm peak to peak in near field * Available seismometers clipped at several cm amplitude

  13. 2003 September 25 Tokachi-Oki (Hokkaido) Earthquake GPS network

  14. Acceleration vs. Displacement

  15. Seismic rupture model from GPS data (Miyazaki et al., 2004) Miyazaki et al., 2004

  16. Geodesy and Volcano Hazard Assessment • Most volcanoes undergo inflation days to months prior to eruption • Hazard Mitigation Strategy: monitor surface deformation for long term eruption precursors • Quantify Pressure build-up; is it dangerous yet? • Challenges: data quality, data density (time/space), data “latency” (how fast to the lab?) • Role for near-real time GPS and INSAR

  17. VolcanoGeodesy

  18. Vertical Component (N-S)

  19. InSAR Challenges • Most SAR data are C-band (6 cm wavelength) which decorrelates rapidly • L-band (24 cm wavelength) is better for most terrestrial applications involving change detection via interferometry • Most SAR systems are commercial, or otherwise have restricted data availability • Most SAR systems have no or limited DDL capability, hence no or limited real time capability

  20. Synergetic Applications Relevant to GEOSS • INSAR can be used to measure water levels in vegetated wetlands, soil moisture, and biomass • GPS can measure atmospheric water content • GPS and INSAR requires terrestrial reference frame definition and maintenance (SLR, VLBI, DORIS); this “behind the scenes” effort yields important global geophysical data

  21. Variation in Earth’s Oblateness (J2) • Earth’s dynamic oblateness (J2) is measured by SLR, and generally decreases due to post-glacial rebound • Beginning in ~1997, J2 began to increase, indicating profound global mass re-distribution • Most likely cause is melting of sub-polar alpine glaciers (Dickey et al., 2003)

  22. Conclusions • Space geodetic data are useful for monitoring dynamic solid earth effects associated with climate change, earthquake and volcano processes • Space geodetic data may augment warning systems for volcanic eruption (GPS+INSAR) and tsunami (GPS) if available in real-time • For GPS, lack of dense coverage in subduction zones is a problem • For INSAR, cost and rapid availability of data is a problem (needs to be like GSN/FDSN!)

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