Quote from M. Nafi Toksoz (3 September 2013)

I have known Omer Alptekin since his graduate schooldays some decades ago. I really got to know him better during his sabbatical visits to MIT. He is an eminent Turkish seismologist with great skill for extracting information from seismic data. Among other things, his analysis of source mechanisms of earthquakes on the northeast and southwest shores of the Black Sea produced the first evidence of the Black Sea lithosphere being over-thrust by the Anatolian and Asian plates.

I wish Omer Alptekin many more productive and healthy years, as the "DEAN" of the Turkish seismologists.

Nafi

Arabia-Eurasia continental collision, active tectonics of the E Turkey Plateau/Caucasus, and crustal strain along the Greater Caucasus Thrust

Robert Reilinger, Robert King, Michael Floyd, MIT, USA

Semih Ergintav, Haluk Ozener, Bogazici Univ., Turkey

Rahsan Cakmak, Ali Ozkan, TUBITAK MAM, Turkey

Philippe Vernant, Univ. of Montpellier, France Simon McClusky, Australian National Univ., Australia Giorgi Sokhadze, Ilia Univ., Republic of Georgia Galaktion Hahubia, NAPR, Republic of Georgia Fakhraddin Kadirov, Geology Institute, NAS, Azerbaijan Arkadi Karakhanian, IGS, NAS, Armenia Tamara Guseva, Natalie Rosenberg, UIPE, Russia Vadim Milyukov, Moscow State Univ., Russia

Special Acknowledgement to: The late Aykut Barka, the Father of GPS-Geodynamics in Turkey

cGPS Sheki, AZ sGPS Nardimli, Georgia

Africa-Arabia-Eurasia plate motions

35 Partner Institutions

in

16 Host Countries

Geodetic vs. Geologic and Plate Tectonic Rates

Lat (°) Long. (°E) Rate (°/Ma ccw) Ref 31.7 ± 0.2 24.6 ± 0.3 0.37 ± 0.01 JGR 06 32.8 ± 1.2 23.8 ± 2.7 0.39 ± 0.05 DeMets et al. (2010)

Implications for Plate dynamics

Caucasus seismicity and tectonics

E Turkey Plateau/Caucasus ccw rotation/MCTF shortening

GPS Velocities circa 2012

Baku, Az. Profile (A) ((note different scales)

1. ~ 11-12 mm/yr shortening over ~ 100 km 2. ~ 8 mm/yr perp., step-wise change (r-l, s-s?) 3. Low deformation (< 1 mm/yr) in Lesser Caucasus

Shamakhi, Az., 1667, M6.9 Eq. Profile (B)

1. ~ 10 mm/yr shortening normal to MCTF, ~ 100 km 2. ~ 2 mm/yr right-lateral s-s on MCTF? 3. Lesser Caucasus deformation <95% confidence 4. Similar strain rate to Baku profile

Armenia/E Georgia Profile (C)

1. ±2 mm/yr scatter. Stability? 2. ~3-4 mm/yr shortening on KFTB (MCTF?) 3. ~2-3 mm/yr on MCTF 4. ~1-3 mm/yr shortening on N Caucasus thrust

Tbilisi Profile (D)

1. ~3-5 mm/yr shortening on KFTB/MCTF 2. ~1 mm/yr, r-l, s-s in Lesser Caucasus?

W Georgia Profile (E)

1. ~3-4 mm/yr shortening 2. Too sparse coverage

An Illustrative Model

Projection to surface

MCTF

? ?

N S 15 km

293°/30°/90°/15 km/15 mm/yr 160°/45°/135°/15 km/15 mm/yr

Ilia/NAPR densification in Georgia

GPS/Seismic network expansion in Azerbaijan (RSSC and GI, NAS)

Summary • International cooperation in GPS is providing a quantitative

framework to understand the kinematics, earthquake hazards, and plate dynamics for the AR-EU continental collision zone

• To first order, the Lesser Caucasus rotate as a coherent block with low, but significant internal strain (e.g., 1988 Spitak Earthquake)

• Main strain is focused on the Greater Caucasus Thrust fault system increasing from ~3 mm/yr in W Georgia to ~ 12 mm/yr in E Az.

• Complex intersecting fault systems at boundary of the Caspian Sea and the MCTF produce potential seismic and environmental hazards for an area of expanding population and petroleum infrastructure

• Enhanced GPS observations can provide direct constraints on fault character (strain accumulation rates, fault locking depths, fault behavior [creep vs. stick slip], earthquake cycle) for earthquake hazard estimation and developing effective risk reduction strategies

• There is substantial hazard to cities and infrastructure in the AR-EU collision zone, including, the most populated from western Turkey to Turkmenistan (e.g., Istanbul, Tbilisi, Yerevan, Baku, Terhan, Ashgabat), and many others with populations exceeding 100,000.

We are not “prophets of doom”! Our message is clear and simple:

Know the hazard so you can reduce the risk! (Denali, Alaska pipeline following 2002, M7.9 Earthquake – a disaster avoided)