Presented in the IAG International Symposium on Recent Crustal Movements (SRCM), Helsinki, Finland, August 2001
Radar Interferometric
Mapping and Numerical Simulation of Land Subsidence along the Dead Sea Shores,
Israel and Jordan
Gidon Baer (1) (972-2-5314231; baer@mail.gsi.gov.il); Uri Schattner (1, 3) (uris@gaia.tau.ac.il); Daniel Wachs (1) (dani.wachs@mail.gsi.gov.il); David Sandwell (2) (sandwell@radar.ucsd.edu); Shimon Wdowinski (3) (shimon@geo1.tau.ac.il); Sam Frydman (4) (cvrsfsf@techunix.technion.ac.il)
1. Geological Survey of Israel, 30 Malkhe Yisrael Street, Jerusalem
95501, Israel
2. Cecil H. and Ida M. Green Institute of Geo- physics and Planetary Physics,
Scripps Institution of Oceanography, , 9500 Gilman Drive, La Jolla, CA 92093-0225,
United States
3. Department of Geophysics and Planetary Sciences, Tel Aviv University,, Ramat
Aviv, Tel Aviv 69978, Israel
4. Faculty of Civil Engineering, Technion - Israel Institute of Technology,
Haifa 32000, Israel
During the last decade, sinkholes and wide shallow subsidence features have become major problems along the Dead Sea shores in Israel and Jordan. Sinkholes are readily observed in the field, but their locations and timing are unpredictable. Wide shallow subsidence features are often difficult to observe in the field. However, once identified, they delineate zones of instability and increasing hazard. In this study we apply interferometric synthetic aperture radar (InSAR) measurements to map and calculate rates of vertical displacement phenomena in the Dead Sea basin. We analyze 27 SAR scenes acquired during the years 1992 to 2001 by the ERS-1 and ERS-2 satellites. The interferograms span periods of 2 to 103 months. Wide shallow subsidence features include circular and elongate coastal depressions (a few hundred meters to a few kilometers in length), depressions in ancient alluvial fans, and depressions along salt diapir margins. Phase differences measured in our interferograms correspond to subsidence rates generally in the range of 0-20 mm/year, with exceptional high rates that exceed 60 mm/year in two specific regions. During the study period, the level of the Dead Sea and of the associated groundwater has dropped by about 8 meters. This water level drop within an aquifer composed of fine-grained material has caused aquifer system compaction resulting in gradual subsidence. Calculation of the expected compaction and comparison with the InSAR observations suggest that the observed subsidence along the Dead Sea shores occurred where the total thickness of the fine-grained marl layers is between 5 m and 20 m in the upper 30 m below the surface. Our observations also show that in certain locations subsidence appears to be structurally controlled by faults and salt domes. The temporal relationships between wide shallow subsidence features and sinkholes are still not fully resolved, excluding the use of gradual subsidence as a precursor to sinkholes.