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Studying Volcanoes With InSAR: Where Have We Been and Where Are We Going? <br />Howard Zebker, Cody Wortham<br />Stanford ...
10 Years Ago: Where Were We?<br />Anticipated several new space radar systems for monitoring and forecasting of volcanic e...
Reality: What actually happened<br />Anticipated several new space radar systems for monitoring and forecasting of volcani...
Technology has advanced to where we know how to do this<br />Want long wavelength, high resolution, rapid repeat times<br ...
Longer wavelengths yield higher correlation<br />Wortham et al., 2010<br />ALOS Kilauea interferogram:  460 day separation...
Time series volcano observationsEyjafjallajokull<br />PS deformation<br />Time series 1993-2000<br />SBAS deformation<br /...
Precision of PS method<br />PS performance<br />PS image of San Andreas Fault - ERS satellite<br />RMS error ~1 mm/yr<br /...
Higher resolution promotes time series analyses<br />Brightest scatterer<br />Brightest scatterer<br />A fine resolution c...
 Pixel does not scintillate, is “persistent”
Bright scatterer perhaps less than rest of background
Pixel scintillates over time from background signal</li></li></ul><li>New spaceborne systems<br />Radar systems launched t...
ALOS/PALSAR<br />ALOS satellite, PALSAR radar instrument<br />L-band, wavelength 24 cm<br />Repeat period 46 days<br />Mul...
TerraSAR-X<br /><ul><li>X-band, wavelength 3 cm
Repeat period 11 days
Multipolarization
1-20 m resolution
Ideal for time-</li></ul>series observations<br />
Current research …<br />Most exciting area is time series analysis<br />Modeling continues to advance<br />Tandem satellit...
Time series mimics GPS imaging<br />From Lundgren et al.<br />
Modeling of Yellowstone caldera<br />Interpretation: Inflating sill<br />Interferograms: C-band<br />From Wicks et al., 20...
Modeling Uzon caldera, Kamchatka<br />(a) Distributed opening model, (b) distributed crack model,  (c) depth slice of mode...
Probabilistic modeling of Etna activity<br /><ul><li>Predict eruptive activity from observed deformation and thermal flux
Highest activity from coincident increases
PDF derived from spaceborne data only</li></ul>From Patrick et al., 2006<br />
Tandem observations for DEMs<br />Mt. Merapi Digital Elevation Model from Tandem TerraSAR-X observations<br />From DLR<br ...
 Could produce radar stereo, but this method is superior</li></li></ul><li>New local measurements<br />From C. Werner, Gam...
… but some things still lacking<br />Enabling technology is coverage, temporal and geographic<br />Optimizing designs for ...
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IGARSS2011_radarvolcanology.pptx

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IGARSS2011_radarvolcanology.pptx

  1. 1. Studying Volcanoes With InSAR: Where Have We Been and Where Are We Going? <br />Howard Zebker, Cody Wortham<br />Stanford University<br />
  2. 2. 10 Years Ago: Where Were We?<br />Anticipated several new space radar systems for monitoring and forecasting of volcanic events<br />Developing inverse methods to reveal the details of faulting or pressure changes at depth, and better describe precise magma chamber geometries<br />Beginning reliable interferometric imaging,m-scale resolution of mm-scale deformation over wide areas<br />Proposed high-res stereo radar for 3-D topographic maps fast events, e.g. rapid dome growth <br />Foresaw data collection over all of Earth’s 600 potentially active volcanoes weekly or even daily<br />Designing satellite constellations in along-track interferometric formation to map flow velocities<br />
  3. 3. Reality: What actually happened<br />Anticipated several new space radar systems for monitoring and forecasting of volcanic events<br />Developing inverse methods to reveal the details of faulting or pressure changes at depth, and better describe precise magma chamber geometries<br />Beginning reliable interferometric imaging,m-scale resolution of mm-scale deformation over wide areas<br />Proposed high-res stereo radar for 3-D topographic maps fast events, e.g. rapid dome growth <br />Foresaw data collection over all of Earth’s 600 potentially active volcanoes weekly or even daily<br />Designing satellite constellations in along-track interferometric formation to map flow velocities<br />
  4. 4. Technology has advanced to where we know how to do this<br />Want long wavelength, high resolution, rapid repeat times<br />Systems beginning to reflect community knowledge<br />Still waiting for the “perfect” system<br />Reliable imaging<br />
  5. 5. Longer wavelengths yield higher correlation<br />Wortham et al., 2010<br />ALOS Kilauea interferogram: 460 day separation, 1490 m baseline<br />
  6. 6. Time series volcano observationsEyjafjallajokull<br />PS deformation<br />Time series 1993-2000<br />SBAS deformation<br />From Hooper, 2008<br />
  7. 7. Precision of PS method<br />PS performance<br />PS image of San Andreas Fault - ERS satellite<br />RMS error ~1 mm/yr<br />PS spacing is ~1km<br />
  8. 8. Higher resolution promotes time series analyses<br />Brightest scatterer<br />Brightest scatterer<br />A fine resolution cell<br />A coarse resolution cell<br /><ul><li> Same brightest scatterer, much less background
  9. 9. Pixel does not scintillate, is “persistent”
  10. 10. Bright scatterer perhaps less than rest of background
  11. 11. Pixel scintillates over time from background signal</li></li></ul><li>New spaceborne systems<br />Radar systems launched this decade have expanded the data modalities for InSAR<br />New frequency bands and orbit repeat geometries<br />ALOS PALSAR (Japan) launched 2006<br />TerraSAR-X (Germany) launched 2007, Tandem-X satellite launched 2010<br />Some commercial systems as well<br />
  12. 12. ALOS/PALSAR<br />ALOS satellite, PALSAR radar instrument<br />L-band, wavelength 24 cm<br />Repeat period 46 days<br />Multipolarization<br />10-20 m resolution<br />Very high correlation<br />Just ended successful <br /> mission<br />
  13. 13. TerraSAR-X<br /><ul><li>X-band, wavelength 3 cm
  14. 14. Repeat period 11 days
  15. 15. Multipolarization
  16. 16. 1-20 m resolution
  17. 17. Ideal for time-</li></ul>series observations<br />
  18. 18. Current research …<br />Most exciting area is time series analysis<br />Modeling continues to advance<br />Tandem satellites supersede previous desire for radar stereo<br />New measurements and methods will yield new descriptors<br />
  19. 19. Time series mimics GPS imaging<br />From Lundgren et al.<br />
  20. 20. Modeling of Yellowstone caldera<br />Interpretation: Inflating sill<br />Interferograms: C-band<br />From Wicks et al., 2006<br />
  21. 21. Modeling Uzon caldera, Kamchatka<br />(a) Distributed opening model, (b) distributed crack model, (c) depth slice of model b<br />Radarsat measurements<br />2000-2005<br />Lundgren and Lu, 2006<br />
  22. 22. Probabilistic modeling of Etna activity<br /><ul><li>Predict eruptive activity from observed deformation and thermal flux
  23. 23. Highest activity from coincident increases
  24. 24. PDF derived from spaceborne data only</li></ul>From Patrick et al., 2006<br />
  25. 25. Tandem observations for DEMs<br />Mt. Merapi Digital Elevation Model from Tandem TerraSAR-X observations<br />From DLR<br /><ul><li> Higher resolution and accuracy than traditional stereo
  26. 26. Could produce radar stereo, but this method is superior</li></li></ul><li>New local measurements<br />From C. Werner, Gamma Res.<br />
  27. 27. … but some things still lacking<br />Enabling technology is coverage, temporal and geographic<br />Optimizing designs for InSAR<br />Orbits: poor north retrieval<br />System parameters<br />High resolution, long wavelength helps<br />Future mission prospect good/bad/?<br />
  28. 28. Vector deformation<br />SBAS vector solution for average deformation rate at Kilauea, HI<br />Wortham et al., 2010<br /><ul><li>ALOS yields fairly high correlation over 2 year time span
  29. 29. Near polar orbit results in poor northing component retrieval</li></li></ul><li>Poor retrieval – northing componentKilauea: GPS – black line, InSAR – Red symbols<br />Up North East<br />Wortham et al., 2010<br />
  30. 30. Multiple Aperture InSAR (MAI) Method<br /><ul><li>SLCs formed from forward and </li></ul> backward squinted beams <br /><ul><li> Beam filtered in Doppler
  31. 31. Interferograms formed from each beam
  32. 32. MAI phase gives along-track displacement from differencing forward/backward interferograms</li></ul>N. Bechor, PhD Thesis (2006)<br />
  33. 33. Average north displacement using MAI<br />North component of displacement averaged over all InSAR acquisitions<br />
  34. 34. Coverage<br /><ul><li>ALOS L-band yields high correlation over challenging volcanoes
  35. 35. South America data show comprehensive coverage possible
  36. 36. 46 day repeat is too long- misses many signals
  37. 37. PALSAR data rate/volume too low to monitor 600 volcanoes</li></ul>From: Fournier et al., 2010<br />
  38. 38. NASA DESDynI-R Mission<br />Launch in 20XX<br />L-band, potential 2 m resolution<br />Free and open data policy<br />Specifically designed for InSAR<br />Volcano hazards one of the major science objectives<br />Artist’s concept from JPL<br />
  39. 39. Additional exciting missions<br />ALOS-2 (Japan): L-band follow-on to ALOS, launch 2013?, 1-10 m resolution, 14 day repeat<br />But likely will be commercially oriented with data hard to get<br />Tandem-L (Germany): Similar in philosophy to Tandem-X, but companion to DESDynI, no money yet<br />Sentinel-1 (ESA): C-band heir to Envisat, 12 day repeat, 5 m resolution, 201w? Launch<br />There are others…<br />
  40. 40. Summary and looking ahead<br />InSAR continues to evolve better accuracy and temporal/spatial coverage<br />Volcano hazard applications benefit<br />Future satellites converging on ~12 day repeats and m-scale resolution<br />Limiting factor is probably data policy- agencies still don’t get the science message and pursue commercialization<br />If data are acquired, volcanologists will come<br />

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