Kinematics and Dynamics of Active Rifting of the Northern andCentral Red Sea

Robert Reilinger, MIT

RCL

7/1/2003 – 5/31/2006 EAR 03-05480

Preface:

• This project involves using the Global Positioning System (GPS) to measuredirectly active rifting of the Red Sea. This will require making repeat GPS-surveyobservations and operating continuously recording CGPS stations for at least 3years. These GPS results are providing quantitative constraints on kinematic anddynamic models for the complex deformation associated with plate interactions,including rifting and the development of ocean spreading in the Red Sea and Gulfof Aden.

Scientific Accomplishments:

• Compiled, processed, and analyzed GPS data to constrain overall Africa (Nubia)and Arabia plate motion (McClusky et al., 2003). These results provide broad-scale constraints on plate motions and provide the “framework” for monitoringspreading in the Red Sea.

• Compiled, processed, and analyzed GPS survey data from the Sinai Peninsulaand the Levant region in collaboration with our partners at the National ResearchInstitute for Astronomy and Geophysics (NRIAG), Helwan, Cairo, Egypt. The mainresult (Mahmoud et al., 2005) is that the Sinai and Levant south of the Lebanonrestraining bend is a separate block from both Nubia and Arabia moving ~N andproducing rifting and left lateral motion in the Gulf of Suez (1-2 mm/yr) and leftlateral strike slip along the Gulf of Aqaba and Dead Sea fault (4 mm/yr).

• Determined a new E. Mediterranean GPS-velocity field including first results fromSaudi Arabia, Yemen, Oman, and Sinai, providing improved constraints on Nubia-Arabia motion and other regional deformation. An important result is thatsubduction along the Hellenic-Cyprus trench system and along the Makran in SIran drives intra- and inter-plate deformation throughout the greater Mediterraneanregion, including rifting along the Red Sea and Gulf of Aden. In finding no evidencethat mantle upwelling associated with the Afar Hot Spot is driving motion of Arabia,it is hypothesized that separation of Arabia from Africa is primarily a response todynamic processes associated with subduction. However, the focusing ofdeformation along the Red Sea and Gulf of Aden is likely due to the presence ofanomalously hot mantle below the Afar Triple Junction.

• Submitted a paper including the new velocity field, a kinematic block model, anddiscussion of regional dynamics. The new data require new dynamic models sincethey are incompatible with Arabia indentor and associated crustal extrusion.

• Based on the broad spatial scale of the observed deformation, the increasing rateof motion towards the Hellenic-Cyprus trench system, and the approximatebalance between surface area consumed at trenches and created at ridges, it ishypothesized that deformation in the Africa-Arabia-Eurasia collision zone is drivenin large part, if not entirely, by rollback of the subducting African lithospherebeneath the Hellenic and Cyprus trenches aided by slab pull on the northeasternside of the subducting Arabian plate along the Makran subduction zone (Reilingeret al., 2005).

et al., 2005).

Logistical Accomplishments:

• Completed a draft agreement with the NRIAG for GPS work along the Red Sea.

• Hosted a visit to MIT for Dr. Salah Mahmoud, Head of GPS-Tectonics Group atNRIAG.

• Purchased GPS equipment for installation in Egypt, Eritrea, and Saudi Arabia, andare working on acquiring necessary US export licenses.

• Established new continuous GPS (CGPS) sites adjacent to the Red Sea in SaudiArabia (Al Waj) and Eritrea (Sheib) (see map).

• Established and surveyed GPS sites along 3 Red Sea-normal profiles in SaudiArabia and also across the Danakil block in Eritrea (see Figure). In the process,provided training to King Abdulaziz City for Science and Technology (KACST),Saudi Arabia, and U. of Asmara, Eritrea students and staff on GPS dataacquisition procedures.

• Presented seminars at KACST and U. of Asmara and wrote an article for the U. ofAsmara News Letter about our joint project.

• Did reconnaissance for CGPS and survey sites in Egypt from the Sinai to theEgypt-Sudan border. We identified a number of possible sites that we hope toestablish this year or early next year (2005- 2006) in cooperation with NRIAG.

• Hosted a 2-month visit to MIT by Prof. Woldai Ghebreab, U. of Asmara, Eritrea fortraining in GPS data analysis and modeling crustal deformation. Assisted Prof.Ghebreab in preparing a Fulbright Visiting Faculty proposal for an extended visit towork with our group.

Figures and Captions

Figure 1: GPS-derived station velocities for the zone of interaction of the African,Arabian, and Eurasian plates from data spanning the period 1988-2005. GPS stationsinstalled with support from the NSF MARGINS RCL Red Sea Project are indicated byred diamonds. The blue diamonds show sites that we plan to establish in cooperationwith our host-country partners. Analysis of data from the Sinai was also supported byMARGINS (Mahmoud et al., 2005).

Publications and Presentations

Mahmoud, S., R. Reilinger, S. McClusky, P. Vernant, and A. Tealeb, GPS evidence fornorthward motion of the Sinai block: Implications for E. Mediterranean tectonics, Earthand Planetary Sci. Lett., 238, 217-227, 2005.

McClusky, S., R. Reilinger, S. Mahmoud, D. Ben Sari, and A. Tealeb, GPS constraintson Africa (Nubia) and Arabia plate motion, Geophys. J. Int., 155, 126-138, 2003.

Taymaz, T., R. Westaway, and R. Reilinger, Active faulting and crustal deformation inthe eastern Mediterranean region (Introduction to Special Issue), Tectonophysics, 391,1-9, 2004.

Reilinger, R., S. McClusky, P.Vernant, and 18 others, GPS constraints on continentaldeformation in the Africa-Arabia-Eurasia continental collision zone and implications forthe dynamics of plate interactions, J. Geophys. Res., submitted, 2005.

Saudi Arabia Permanent GPS Network

Robert Reilinger, MIT; Abdullah ArRajehi, KACST; Jacob Sklar, UNAVCORCL

2/9/2004 – 2/27/2004 Linked to EAR 03-05480

Introduction: During Reilinger's visit to KACST the group and others from KACSTworked on updating and installing new GPS stations for the Red Sea Expansion Project.The project looks at continental drift. Specifically; Asia and Africa. Arabia, as thesouthwest corner of Asia, is moving away from Africa in two motions: translation androtation counter-clockwise. These motions are believed to cause earthquakes withinArabia and regions around it.

Purpose: 1) Upgrade communications systems on GPS stations installed 03/2002 in AnNamas and Halit Ammar, Saudi Arabia. 2) Install GPS continuous tracking systems atthe Solar Village SLR station (~45 km NW of Riyadh) and at a site ~60 km E of Jeddah,Saudi Arabia. All systems are located in secure KACST observatory facilities.