GPS evidence for northward motion of the Sinai Block: Implications for E. Mediterranean tectonics
TL;DR: In this article, an elastic block model constrained by the GPS results that is consistent with the regional tectonics and allows us to estimate slip rates for Sinai bounding faults, including the Gulf of Aqaba-southern Dead Sea fault system, is presented.
About: This article is published in Earth and Planetary Science Letters.The article was published on 2005-09-30 and is currently open access. It has received 119 citations till now. The article focuses on the topics: Strike-slip tectonics.
Summary (1 min read)
1. Introduction
- The Sinai Peninsula (Fig. 1 ) lies at the northern end of the Red Sea.
- The tectonic history of the Sinai region is intimately tied to the separation of the Arabian plate from Africa along the Red Sea rift system.
- The Red Sea rift basin was well established by early Miocene at which time rifting was concentrated along the Red Sea and its northern extension along the Gulf of Suez [7] .
- Estimates of current fault slip rates in the Gulf of Aqaba and along the DSF vary considerably (e.g., see [12] for references).
- The authors use these velocities, and the velocities of IGS-GPS stations in Israel [12] to constrain an elastic block model to test the consistency of the GPS velocities with coherent block motion and to estimate slip rates on blockbounding faults.
2. GPS velocity field
- Fig. 2 shows GPS-derived velocities in the Sinai network along with velocities from continuously recording stations in surrounding areas relative to Nubia.
- Table 1 lists the velocity estimates and standard deviations.
- With the exception of sites CATH and KENS that were measured 4 times between 1997 and 2000 (sites destroyed), velocities for Sinai survey sites were determined from 5 to 7 surveys conducted between 1996 and 2003.
- In the second step the authors use the loosely constrained estimates of station coordinates, orbits, and EOP and their covariances from each day, aggregated by survey, as quasiobservations in a Kalman filter to estimate a consistent set of coordinates and velocities.
- Before estimating velocities in the second step of their analysis, the authors examine the time series of position esti- mates to determine the appropriate weights to be applied to each group's surveys.
4. Conclusions
- Survey-mode GPS observations in and around the Sinai Peninsula, in combination with continuous GPS observations in Israel, provide evidence for coherent, northerly motion of the Sinai Block.
- On average, the survey data indicate northward motion of 1.4 F 0.8 mm/yr.
- The authors use a simple elastic block model to characterize block motion and associated slip rates on block-bounding faults.
- These models suggest a 13 km locking depth for the DSF with left-lateral slip ranging from 4.4 F 0.3 to 4.7 F 0.4 mm/yr from the southern DSF to the DSF in western Syria.
- The authors are grateful to Muawia Barazangi, Francisco Gomez, Mustapha Meghraoui, and Shimon Wdowinski for helpful reviews that improved the paper.
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Figures (5)
Fig. 3. Elastic block model for the Sinai area showing GPS residual velocities (given in Table 1) for the model described in the text. Faults are vertical and assigned locking depths of 15 km except for the Gulf of Aqaba/Dead Sea fault system that has a locking depth of 13 km, and the western Cyprus Arc that has a 308 dip down to the NE. Residuals are well within the uncertainties for the velocity determinations. Numbers show fault strike slip and fault-normal slip rates and 1-sigma formal uncertainties (fault normal component in brackets; negative for left lateral and extension). Slip rates are averages along each segment. Light modeled faults indicate segments with fault-normal shortening, and dark extension. Inset shows a plot of the local Chi*2 computed from sites close to the fault (shaded error ellipses indicate sites used to estimate fault locking depth) and estimated fault strike slip rate as a function of the locking depth for the Dead Sea fault. The best fit is for a 13 km locking depth and a strike slip rate of 4.3 mm/yr. 
Fig. 1. Topographic (SRTM30) and tectonic map of the Sinai and surrounding region. Dots show seismicity (NEIC), focal mechanisms are from Harvard CMT. Inset shows location of study area within the context of the eastern Mediterranean. DSF=Dead Sea fault, Gulf of Iske.=Gulf of Iskenderum. 
Table 2 Euler vectors relative to Eurasia and 1-sigma uncertainties estimated from this study 
Fig. 2. Simplified tectonic map of the Sinai and surrounding regions show Lines with tick-marks are normal faults, ticks on downthrown block, doubl are given in Table 1. 
Table 1 GPS velocities in an Africa (Nubia)-fixed reference frame and 1-sigma uncertainties for sites shown in Fig. 2
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References
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TL;DR: In this article, the authors present and interpret GPS measurements of crustal motions for the period 1988-1997 at 189 sites extending east-west from the Caucasus mountains to the Adriatic Sea and north-south from the southern edge of the Eurasian plate to the northern edge of Africa.
Abstract: We present and interpret Global Positioning System (GPS) measurements of crustal motions for the period 1988–1997 at 189 sites extending east-west from the Caucasus mountains to the Adriatic Sea and north-south from the southern edge of the Eurasian plate to the northern edge of the African plate. Sites on the northern Arabian platform move 18±2 mm/yr at N25°±5°W relative to Eurasia, less than the NUVEL-1A circuit closure rate (25±1 mm/yr at N21°±7°W). Preliminary motion estimates (1994–1997) for stations located in Egypt on the northeastern part of Africa show northward motion at 5–6±2 mm/yr, also slower than NUVEL-IA estimates (10±1 mm/yr at N2°±4°E). Eastern Turkey is characterized by distributed deformation, while central Turkey is characterized by coherent plate motion (internal deformation of <2 mm/yr) involving westward displacement and counterclockwise rotation of the Anatolian plate. The Anatolian plate is de-coupled from Eurasia along the right-lateral, strike-slip North Anatolian fault (NAF). We derive a best fitting Euler vector for Anatolia-Eurasia motion of 30.7°± 0.8°N, 32.6°± 0.4°E, 1.2°±0.1°/Myr. The Euler vector gives an upper bound for NAF slip rate of 24±1 mm/yr. We determine a preliminary GPS Arabia-Anatolia Euler vector of 32.9°±1.2°N, 40.3°±1.1°E, 0.8°±0.2°/Myr and an upper bound on left-lateral slip on the East Anatolian fault (EAF) of 9±1 mm/yr. The central and southern Aegean is characterized by coherent motion (internal deformation of <2 mm/yr) toward the SW at 30±1 mm/yr relative to Eurasia. Stations in the SE Aegean deviate significantly from the overall motion of the southern Aegean, showing increasing velocities toward the trench and reaching 10±1 mm/yr relative to the southern Aegean as a whole.
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