HR: 17:30h
AN: G44A-07    [Abstracts]
TI: Using high-resolution aeromagnetic survey to map tectonic elements of plate boundaries: An example from the Dead Sea Fault
AU: Al-Zoubi, A S
EM: aalzoubi@go.com.jo
AF: Al-Balqa Applied University, Faculty of Science, Salt, 19117 Jordan
AU: * ten Brink, U S
EM: utenbrink@usgs.gov
AF: U.S. Geological Survey, 384 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Rybakov, M
EM: rybakov@gii.co.il
AF: Geophysical Institute of Israel, p.o.box 182, Lod, 71100 Israel
AU: Rotstein, Y
EM: yair.rotstein@gii.co.il
AF: Geophysical Institute of Israel, p.o.box 182, Lod, 71100 Israel
AB: The Dead Sea Fault (DSF) is a transform plate boundary between the African and the Arabian plates. The 200-km-long DSF segment between the Gulf of Aqaba/Elat and the Dead Sea, which has the morphology of a rift valley, shows little seismic activity, and its surface trace is only intermittently visible. High-resolution magnetic data were collected in October 2003 aboard a Jordanian military helicopter flying at an altitude of 100 m over the southern 120-km-long section of this fault segment. The survey was part of a US-AID Middle Eastern Regional Cooperation project between Jordanian, Israeli, Palestinian, and American scientists. Data were collected along rift-perpendicular lines spaced 300 m apart, requiring frequent crossings between Israeli and Jordanian air spaces. The data were gridded at 75 m interval following resolution tests, reduced to pole, and incorporated into a GIS together with elevation, geology, and gravity maps to facilitate interpretation. The main findings of the magnetic survey are the absence of magnetic anomalies crossing the rift valley, and the presence of a rift-parallel regional lineament corresponding to the active trace of the DSF. The lineament extends NNE as an almost continuous trace from Elat, Israel, to the eastern side of the valley 5 km north of Rahmeh. Jordan. Another fault trace located 2-3 km to the west may overlap and continue NNE through Gebel A-Risha, and into the central Arava/Araba valley, where it is visible on the surface. Alternatively, the two traces may be connected. If an offset between the two traces exists, it may be small enough to allow an earthquake rupture to propagate across the offset, and generate an earthquake with a moment magnitude of up to 7.5. Traces of buried faults in the central Arava/Araba valley that were previously active in the DSF system, are visible as abrupt terminations of an area of short wavelength magnetic anomalies. These anomalies probably represent shallow subsurface magmatic intrusions. The closest exposed intrusion is dated at 20.7 Ma, shortly before the development of the DSF. Other anomalies can be traced at the edges of our survey area and are likely related to Precambrian outcrops along the rift shoulders. Comparison of the magnetic and the sparser land-gravity data shows the same general azimuth of the magnetic lineament and of the segmented fault system as derived from the gravity and a surprisingly good coincidence between local gravity and magnetic anomalies over the Timna pull-apart basin, owing perhaps to the sensitivity of the high-resolution magnetic data to the thickness of the sedimentary cover.
DE: 8107 Continental neotectonics
DE: 8110 Continental tectonics--general (0905)
DE: 8150 Plate boundary--general (3040)
DE: 1219 Local gravity anomalies and crustal structure
DE: 1517 Magnetic anomaly modeling
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting