BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:illuminating active fault zones through correlation of optical sat
 ellite imagery - James Hollingsworth - University of Grenoble
DTSTART:20191023T150000Z
DTEND:20191023T160000Z
UID:TALK131290@talks.cam.ac.uk
CONTACT:Jenny Jenkins
DESCRIPTION:Precise documentation of the spatial pattern and magnitude of 
 surface slip produced co-seismically in earthquakes\, and in the post- and
  inter-seismic phases of the seismic cycle\, is essential for understandin
 g the mechanics of how faults slip. Modern techniques in satellite geodesy
 \, such as GPS and InSAR\, provide powerful tools for retrieving surface d
 isplacements at high precision produced by earthquakes. However\, GPS meas
 urements are typically very sparse\, while InSAR often fails close to faul
 ts\, where strain gradients are large. Optical image correlation is a rela
 tively new technique for retrieving earthquake deformations close to fault
 s. Sub-pixel phase correlation of satellite (or aerial) images acquired be
 fore and after an earthquake can resolve displacements as low as 1/20th of
  the input imagery pixel resolution. Because optical image correlation ret
 rieves the displacement averaged over small areas (compared with spot meas
 urements collected in the field)\, they include any off-fault deformation 
 (OFD) occurring on secondary or distributed structures\, as well as deform
 ation localized on the main fault. Comparison with co-seismic field measur
 ements for large strike-slip earthquakes provides a unique opportunity det
 ermine the magnitude of OFD occurring in earthquakes globally. I discuss s
 everal case studies from earthquakes (including Landers\, Hector Mine\, Ba
 louchistan\, Kaikoura\, and Palu) where optical image correlation has been
  used to characterize near-field co-seismic displacements. OFD appears to 
 correlate with total geological offset on strike-slip faults\, suggesting 
 an increase in localisation and decrease in OFD as faults mature. Better c
 haracterization of the magnitude and width over which OFD occurs is essent
 ial for the correct assessment of fault slip rates using Quaternary dating
  techniques\, and earthquake slip histories determined from paleoseismolog
 y\, which are both key ingredients in seismic hazard assessment. I finish 
 with several examples of future research directions in which optical image
  correlation can be further developed to provide more detailed and precise
  3D measurements of ground deformation over time\; with huge potential for
  studying active fault zones\, as well as a wide range of other surface ph
 enomena occurring on Earth and throughout the solar system.\n---\n\nReadin
 g...\nFialko\,Y.\,Sandwell\,D.\,Simons\,M.\,Rosen\,P.\,2005.Three-dimensio
 nal deformation caused by the Bam\, Iran\, earthquake and the origin of sh
 allow slip deficit. Nature 435\, 295–299. http://dx.doi.org/10.1038/natu
 re03425\nDolan\, J. F.\, and Haravitch\, B. D.\, 2014\, How well do surfac
 e slip measurements track slip at depth in large strike-slip earthquakes? 
 The importance of structural maturity in controlling on-fault versus off-f
 ault deformation: Earth and Planetary Science Letters\, http://dx.doi.org/
 10.1016/j.epsl.2013.11.043.\nMilliner\, C.\, Dolan\, J.\, Hollingsworth\, 
 J.\, Leprince\, S.\, Ayoub\, A.\, and Sammis\, C.\, 2015\, Quantifying nea
 r-field and off-fault deformation patterns of the 1992 Mw 7.3 Landers eart
 hquake. Geochemistry Geophysics Geosystems\, 16\, doi:10.1002/2014GC005693
 .\nSocquet\, A.\, Hollingsworth\, J.\, Pathier\, E.\, and Bouchon\, M.\, 2
 018\, 2018 Mw7.5 Palu earthquake (Sulawesi\, Indonesia): evidence for supe
 rshear from space geodesy\, Nature Geoscience\, Nature Geoscience\, doi.or
 g/10.1038/s41561-018-0296-0.
LOCATION:Marine/Wolfson Building lecture hall\, Bullard Labs.
END:VEVENT
END:VCALENDAR