Abstract
We use continuously recording GPS (CGPS) and survey-mode GPS (SGPS)
observations to determine Euler vectors for relative motion of the
African (Nubian), Arabian and Eurasian plates. We present a well-constrained
Eurasia-Nubia Euler vector derived from 23 IGS sites in Europe and
four CGPS and three SGPS sites on the Nubian Plate (-0.95 +- 4.8N,
-21.8 +- 4.3E, 0.06 +- 0.005 degMyr) . We see no significant (>1
mm yr-1) internal deformation of the Nubian Plate. The GPS Nubian-Eurasian
Euler vector differs significantly from NUVEL-1A (21.0 +- 4.2N, -20.6
+- 0.6E, 0.12 +- 0.015 deg/Myr) , implying more westward motion of
Africa relative to Eurasia and slower convergence in the eastern
Mediterranean. The Arabia-Eurasia and Arabia-Nubia GPS Euler vectors
are less well determined, based on only one CGPS and three SGPS sites
on the Arabian Plate. The preliminary Arabia-Eurasia and Arabia-Nubia
Euler vectors are 27.4 +- 1.0N, 18.4 +- 2.5E, 0.40 +- 0.04 deg/Myr,
and 30.5 +- 1.0N, 25.7 +- 2.3E, 0.37 +- 0.04 deg/Myr , respectively.
The GPS Arabia-Nubia Euler vector differs significantly from NUVEL-1A
(24.1 +- 1.7N, 24.0 +- 3.5E, 0.40 +- 0.05 deg/Myr), but is statistically
consistent at the 95 per cent confidence level with the revised Euler
vector reported by Chu & Gordon based on a re-evaluation of magnetic
anomalies in the Red Sea (31.5 +- 1.2N, 23.0 +- 2.7E, 0.40 +- 0.05
deg/Myr) . The motion implied in the Gulf of Aqaba and on the Dead
Sea fault (DSF) by the new GPS Nubia-Arabia Euler vector (i.e. ignoring
possible Sinai block motion and possible internal plate deformation)
grades from pure left lateral strike-slip in the Gulf and on the
southern DSF with increasing compression on the central and northern
DSF with relative motion increasing from 5.6 to 7.5 mm/yr (+-1 mm/yr)
from south to north. Along the northern DSF (i.e. north of the Lebanon
restraining bend) motion is partitioned between 6 +- 1 mm/yr left-lateral
motion parallel to the fault trace and 4 +- 1 mm/yr fault-normal
compression. Relative motions on other plate boundaries (including
the Anatolian and Aegean microplates) derived from the GPS Euler
vectors agree qualitatively with the sense of motion indicated by
focal mechanisms for large crustal earthquakes (M > 6) . Where data
are available on fault-slip rates on plate bounding faults (North
Anatolian fault, East Anatolian fault, Dead Sea fault, Red Sea rift),
they are generally lower than, but not significantly different from,
the full plate motion estimates suggesting that the majority of relative
plate motion is accommodated on these structures.
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