HR: 11:20h
AN: G52A-05 INVITED    [Abstracts]
TI: Vertical Displacements During the Earthquake Cycle: Observations with InSAR.
AU: * Biggs, J
EM: jbiggs@rsmas.miami.edu
AF: COMET, University of Oxford, Parks Road, Oxford, OX1 3PR, United Kingdom
AU: Wright, T
EM: t.wright@see.leeds.ac.uk
AF: University of Leeds, School of Earth and Environment Environment Building The University of Leeds, Leeds, LS2 9JT, United Kingdom
AU: Freymueller, J
EM: jeff@giseis.alaska.edu
AF: University of Alaska, Fairbanks, Geophysical Institute, 903 Koyukuk Drive, Fairbanks, AK 99775-7320, United States
AU: Lu, Z
EM: lu@usgs.gov
AF: Cascades Volcano Observatory, 1300 SE Cardinal Court, Vancouver, WA 98683-9589, United States
AB: InSAR is a satellite based radar technique capable of measuring small ground displacements at high spatial resolution and, due to the look angle of the satellites used, is especially sensitive to vertical displacements. By combining images taken from different directions, and by using independent measurements of horizontal displacements (e.g. GPS, image matching), it is possible to measure the vertical component directly. We investigate the associated advantages and disadvantages in relation to studies of tectonic deformation through the earthquake cycle using examples from the Denali Fault, Alaska. InSAR has been used to measure the slip rate on several strike-slip faults using a single look direction under the assumption that displacements are horizontal only. However, many strike-slip faults are associated with mountain ranges and in reality, motion is likely to be transpressive. In addition, vertical motions not related to fault slip may also be present, caused by loading-related deformation or local effects such as differential subsidence. The tradeoff between horizontal and vertical motions on observations from a single look direction means the convergent motion or unrelated vertical movements can have a serious impact on rate estimates. For example, the observed displacement on the Denali Fault, Alaska could be explained by either a horizontal slip rate of 12 +/- 5 mm/yr or a vertical slip rate of 1.9 +/- 1.5 mm/yr. Using Radarsat data collected following the 2002 M7.9 Denali Fault Earthquake, the postseismic response occurred is found to occur at depths greater than 40 km. Vertical measurements from InSAR are seen to show a clearer spatial pattern than vertical GPS, but cover a more limited region. The spatial pattern can be modelled using either afterslip or viscoelastic relaxation, or a combination of mechanisms.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
SC: Geodesy [G]
MN: 2007 Fall Meeting