HR: 16:30h
AN: G44A-03    [Abstracts]
TI: Postseismic Deformation Following the 1997 Manyi (Tibet) Earthquake: InSAR Observations and Modelling
AU: * Ryder, I
EM: isabelle@earth.ox.ac.uk
AF: Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX13PR United Kingdom
AU: Wright, T J
EM: tim.wright@earth.ox.ac.uk
AF: Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX13PR United Kingdom
AU: Parsons, B
EM: barry.parsons@earth.ox.ac.uk
AF: Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX13PR United Kingdom
AU: Funning, G
EM: gareth@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall, UC Berkeley , Berkeley, CA 94720-4760 United States
AB: Detailed spatial and temporal measurements of surface deformation following large earthquakes are crucial for determining stress adjustment mechanisms and the rheological structure of the lower crust and upper mantle. Realistic models must be able to explain the observed displacement field over the entire observation period, not just at a snapshot in time. In this study we use InSAR to investigate postseismic deformation following the magnitude (M_w) 7.5 Manyi earthquake, which occurred in northern Tibet in November 1997. We use ERS-2 data to create 26 two-frame interferograms along three tracks, covering the entire 175 km long fault. The time period covered is from 8 days to almost 4 years after the earthquake. Profiles through the central track show a fairly symmetrical line-of-sight deformation, with a peak at about 10 km from the fault trace. The maximum peak-to-peak range change is ~10 cm. The excellent coherence in these interferograms collectively enables us to construct a time series. Simple exponential decay functions calculated on a pointwise basis give a relaxation time of ~0.7 years. We test models that assume either Maxwell viscoelastic stress relaxation or localised afterslip on and below the coseismic rupture plane. We find that a single viscosity in the Maxwell model cannot fit the data at all dates in the time series: an increase in effective viscosity over time is required to explain the data. Kinematic afterslip modelling provides a better fit to the observed motion. We address whether or not coseismic stress loading can produce the observed postseismic surface deformation via localised afterslip.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
SC: Geodesy [G]
MN: Fall Meeting 2005