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SUMMARY: InSAR Monitoring of Tectonic Deformation and Climatic Forcing in 
 North-Eastern Tibet [Rescheduled to online] - Dr. Simon Daout\, University
  of Oxford
DTSTART:20200513T110000Z
DTEND:20200513T120000Z
UID:TALK142021@talks.cam.ac.uk
CONTACT:Camilla Penney
DESCRIPTION:*This seminar will be held online. Details will be sent to the
  Earth Sciences and Bullard mailing lists. If you are not in Earth Science
 s but would like to attend\, please contact the talk organisers.*\n\nUntil
  today\, measuring slow deformations in mountainous areas with Synthetic A
 perture Radar Interferometry (InSAR) has been challenging\, in large part 
 due to the sporadic nature of the available acquisitions. The recent launc
 h of the Sentinel-1 satellites from the European Space Agency (ESA) in 201
 4 brings a new paradigm in Earth Science using space-based geodesy to meas
 ure at a greater scale (250 km swath)\, and with a better temporal resolut
 ion (6/12 days revisit time)\, subtle ground movements in remote\, vast an
 d largely inaccessible regions. In this presentation\, we illustrate the b
 enefits of such data sets by performing a multi-temporal InSAR analysis in
  the North-Eastern part of the Tibetan plateau to (1) study the tectonic d
 eformation and (2) characterise the spatial and temporal dynamics of perma
 frost's active layer. We process three Sentinel-1 tracks acquired from 201
 4 to 2019\, as well as\, the complete Envisat data archive along four trac
 ks between 2003 and 2011\, extending from the Qilian Shan\, in the north\,
  to the Qaidam Basin\, in the south.\n(1) Regional deformation maps show t
 hat seasonal thaw and frost effects are controlled by the sediment type an
 d local topography\, with concentrations of the deformation on shallow slo
 pes and poor-drainage areas in unconsolidated\, frost-susceptible and fine
 -grained sediments. Fast subsidence due to thaw settlement takes place dur
 ing June/July while frost heave is intense during December/January when tw
 o-sided freezing of pore water under pressure causes prolonged ice segrega
 tion near the permafrost table. The analysis also reveals pervasive subsid
 ence of the ground\, affected by freeze and thaw cycles\, of up to 2 cm/yr
 \, and increasing by a factor of 2 to 5 from 2003 to today in some areas\,
  as well as high-rates of widespread gravitational mass movements of non-c
 onsolidated sediments. (2) The tectonic analysis illuminates the steady-st
 ate inter-seismic creep along thrusts within the Qaidam foreland basins\, 
 as well as spatio-temporal changes of the long-term post-seismic surface d
 isplacement rates and patterns that follow the three 2003\, 2008 and 2009 
 Mw 6.3 Qaidam earthquakes. Long-term transient uplift coincides spatially 
 with basin deformed sequences and bedding planes and continues more than t
 en years after the seismic events\, providing evidence of co-seismic slip 
 translated into permanent deformation during the post-seismic phases. \nTh
 e findings show that is critical to delineate the areas affected by surfac
 e processes to avoid erroneous interpretations of the tectonic loading alo
 ng faults and demonstrate that periglacial processes currently participate
  in relief smoothing by moving large quantities of loose sediments from th
 e high ranges to the lowland regions in this internal part of the Tibetan 
 plateau. 
LOCATION:ONLINE - Details to be sent by email
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