Now at: Geomatics College, National Cartographic Center (NCC), Meraj Av., Azadi square, P.O. Box 13185-1684, Tehran, Iran.
GPS and gravity constraints on continental deformation in the Alborz mountain range, Iran
Article first published online: 29 OCT 2010
© 2010 The Authors Geophysical Journal International © 2010 RAS
Geophysical Journal International
Volume 183, Issue 3, pages 1287–1301, December 2010
How to Cite
Djamour, Y., Vernant, P., Bayer, R., Nankali, H. R., Ritz, J.-F., Hinderer, J., Hatam, Y., Luck, B., Le Moigne, N., Sedighi, M. and Khorrami, F. (2010), GPS and gravity constraints on continental deformation in the Alborz mountain range, Iran. Geophysical Journal International, 183: 1287–1301. doi: 10.1111/j.1365-246X.2010.04811.x
- Issue published online: 15 NOV 2010
- Article first published online: 29 OCT 2010
- Accepted 2010 September 13. Received 2010 September 13; in original form 2010 April 28
- Satellite geodesy;
- Gravity anomalies and Earth structure;
- Plate motions;
- Intra-plate processes;
A network of 54 survey GPS sites, 28 continuous GPS stations and three absolute gravity (AG) observation sites have been set up in the Alborz mountain range to quantify the present-day kinematics of the range. Our results allow us to accurately estimate the motion of the South Caspian block (SCB) for the first time, and indicate rotation of the SCB relative to Eurasia, accounting for the left lateral motion in the Alborz range. In light of these new results, it clearly appears that deformation rates vary along the range, the eastern part accommodating mainly left lateral strike slip (2 mm yr−1 south of the range and 5 mm yr−1 north of the range) with a very low range normal shortening rate on the Khazar thrust fault (∼2 mm yr−1), and the western part accommodating range normal shortening (∼6 mm yr−1) on the Khazar thrust fault with a left lateral component of ∼2 mm yr−1 north of the range and 1 mm yr−1 south of the range. These present-day kinematics agree with geomorphologic estimated slip rates, but not the long-term deformation, corroborating the idea that the kinematics of the range have changed recently due to the change of SCB motion.
Modelling of the interseismic deformation suggests a deep locking depth on the central-western segment of the Khazar fault (∼30 km) in agreement with the Baladeh earthquake rupture and aftershock ranging between 10 and 30 km. Given this unusual deep locking depth and the 34° dip of the thrust, a large part of the Alborz range is located above the seismically coupled part of the fault. Based on our AG measurements this part of the range seems to uplift at a rate of 1–5 mm yr−1, in agreement with terrace uplift.