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SUMMARY:Optical geodesy in the near-field of earthquake ruptures - James H
 ollingsworth\, ISTerre\, Grenoble\, France
DTSTART:20250521T130000Z
DTEND:20250521T140000Z
UID:TALK230947@talks.cam.ac.uk
CONTACT:Adriano Gualandi
DESCRIPTION:The precise estimation of ground displacement caused by natura
 l hazards\, such as earthquakes\, volcanoes\, landslides\, as well as moni
 toring of glaciers\, can be performed by comparing (or spatially correlati
 ng) two optical satellite images of the same region acquired on different 
 dates. This technique can provide very rapid and robust constraints on gro
 und displacement\, and is especially valuable for large surface rupturing 
 earthquakes\, which typically involve very large strains in the near-fiel
 d region\, thus preventing the use of high precision InSAR techniques in r
 esolving ground deformation. However\, the challenge with optical correlat
 ion resides in the fact that the ground motion is generally smaller than t
 he satellite image resolution: sub-pixel precision is therefore critical. 
 One solution\, which forms the basis of many current optical correlation m
 ethods\, is to assume a uniform displacement over a small correlation wind
 ow (typically between 3 and 100 pixels wide/high). However\, this assumpti
 on can lead to wrong estimations\, notably close to sharp discontinuities 
 such as fault ruptures. I present here the first data-based method to perf
 orm ground displacement estimation\, relying on a machine learning model a
 nd a synthetically generated surface rupture database. This database is us
 ed to train a model to retrieve the local displacement for a given image p
 air. It includes images containing synthetic sharp displacement boundaries
  in order to learn a more realistic machine learning model. Our results sh
 ow that we improve the accuracy near fault ruptures compared to state-of-t
 he-art methods\, which is important for studying the mechanics of near-fau
 lt processes. I follow this with some recent examples of surface rupturing
  earthquakes where high resolution optical data has revealed new informati
 on on the surface rupture. Since surface ruptures are intimately linked wi
 th earthquake rupture dynamics\, we begin to look at how high resolution o
 ptical data can start to inform our understanding of the physics governing
  how faults slip.
LOCATION:Wolfson Lecture Theatre
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