HR: 14:55h
AN: G53A-06    [Abstracts]
TI: Subsidence in the Avcilar district of Istanbul, Turkey measured by satellite radar interferometry 1992 – 1999
AU: * Akarvardar, S
EM: samurayakarvardar@yahoo.com
AF: Labo. Dynamique Terrestre & Planetaire, Universite Paul Sabatier, Toulouse, 31400, France
AU: Feigl, K L
EM: feigl@wisc.edu
AF: Dept. of Geology & Geophysics, University of Wisconsin-Madison 1215 West Dayton Street, Madison, 53706, United States
AU: Ergintav, S
EM: Semih.Ergintav@mam.gov.tr
AF: TUBITAK Marmara Research Center, Earth and Marine Sciences Institute, Gebze, 41470, Turkey
AB: Analysis of 14 synthetic aperture radar images acquired by the ERS-1 and ERS-2 satellites between 1992 and 1999 by interferometry (INSAR) reveals subsidence around the Avcilar area of Istanbul. Using the General Inversion for Phase Technique, (GIPhT), we analyze a set of 24 interferometric pairs. The interferometric fringe patterns show a crescent shape. We interpret them as purely vertical subsidence at a secular rate. The maximum subsidence rate of at least 5 mm/yr occurs at a point located at latitude 40.98 deg N and longitude 28.71 deg E. A simple 4-parameter elastic Mogi model consisting of three infinitesimal spherical sinks at a depth of the order of 2 km deflating at 50 to 100 thousand cubic meters per year describes subsidence signal to first order. The model also accounts for tropospheric effects by estimating one vertical phase gradient for each image acquisition epoch. The model fits the data significantly better than a null model with 95 percent confidence. The spatial distribution of the subsidence suggests that most of the subsidence occurs as compaction in a shallow layer of unconsolidated, partially saturated soil with a relatively weak lithology. This layer appears to deform easily in several processes, including compaction, landslide failure, and seismic wave amplification. It may also be susceptible to liquefaction during a large earthquake.
DE: 1211 Non-tectonic deformation
DE: 1294 Instruments and techniques
DE: 1855 Remote sensing (1640)
SC: Geodesy [G]
MN: 2007 Fall Meeting