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S U M M A R YIn this study we investigate the dynamics of the region that includes Greece, the Aegean Sea and Asia Minor. In a least-squares inversion we solve for a continuous strain rate field, and corresponding velocity field, that satisfies 872 GPS data. The estimate of the geodetic strain rate field provides constraints for our dynamic analysis. Next, we separately solve the depth integrated 3-D force balance equations for depth-integrated deviatoric stresses within the lithosphere, in which body force input comes from differences in vertically integrated vertical stress, or differences in gravitational potential energy per unit area (GPE). These GPE estimates calibrate the absolute magnitudes of deviatoric stresses that are acting within the lithosphere. Further, we investigate the sensitivity of our stress field solutions by using two different crustal structure models: one from compiled crustal structure estimates obtained primarily from relatively recent seismic observations and the other from the Crust 2.0 model. In an iterative least-squares inversion we then solve for stress field boundary conditions that, when added to the contribution of deviatoric stresses associated with GPE differences, provides a best fit to the directions of principal axes and relative magnitudes of the principal axes of the rates of strain obtained in the kinematic analysis. Robust features that arise from the boundary condition solution are NNE forcing along the southern boundary east of about 33 • E (0.5-1.2 × 10 12 N m −1 ), with a rapid anticlockwise rotation of forces to the west of this, along with an outward pulling force (∼0.4 × 10 12 N m −1 ) directed SSW along the entire Hellenic Arc segment. This force system along the Hellenic Arc can be interpreted as a result of slab rollback. The total depth integrated 3-D deviatoric stresses in the final dynamic solution provides an excellent match to the deformation indicators throughout the region, with vertically integrated stress magnitudes of order 0.5-2.5 × 10 12 N m −1 . We use constraints from derived stress magnitudes, together with GPS-defined scalar values of strain rate magnitude, to define bulk effective viscosities of the lithosphere. Depth-averaged effective viscosities for the entire lithosphere are high within the Black Sea, of order 0.7-3 ×10 23 Pa-s, relative to surrounding continental lithosphere. North Anatolian shear zone, northern Aegean Sea and Gulf of Corinth are characterized by low depth averaged viscosities of order 1-5 ×10 21 Pa-s. Deviatoric stresses from GPE differences and boundary condition effects combine in surprising ways in some regions, resulting in near total stress cancellation in areas such as the southern Aegean Sea and portions of the central Anatolian block. GPE differences combine with boundary condition effects along the eastern segment of the North Anatolian Fault (NAF) in a way that is compatible with the hypothesis that motion on the NAF was facilitated by slab detachment beneath East Anatolia and dynamic uplift of East Anatolian...

Fluids venting from the submarine portion of the Marmara Main Fault (part of the North Anatolian Fault system, Turkey) were sampled in Ti bottles deployed by submersible. The fluids consist of mixtures of fault derived gases, fault related cold seep fluids, and ambient seawater; these components can readily be distinguished using the isotopes of He and the He/Ne ratios. 3He/4He ratios range between 0.03±0.1 and 4.9±0.4 Ra, indicating that both crustal and mantle derived sources of helium are sampled by the fault. The dominant gas in all the samples analyzed is methane with the abundance of CO2 below detection (≤2%) in the mantle rich (high 3He/4He) fluids. This is in contrast to nearly all mantle derived fluids where the C species are dominated by CO2. While high CH4/CO2 ratios may reflect organic or inorganic reactions within the crust which reduce mantle derived CO2 to methane, this is not a priori necessary: we show that simple dilution of mantle fluids with methane produced within local sediments could result in the high 3He/4He, methane rich gases currently emanating from the fault. This observation is supported by an anticorrelation between 3He/4He and C/3He, which is consistent with addition of C and 4He simultaneously to the fluids. The highest 3He/4He ratios were found in the Tekirdag Basin, at the foot of the escarpment bordering the Western Sea of Marmara, where seismic data are consistent with the presence of a fault network at depth which could provide conduits permitting deep-seated fluids to rise to the surface. The lack of recent volcanism, or any evidence of underlying magmatism in the area, along with low temperature fluids, strongly suggests that the 3He-rich helium in these fluids was derived from the mantle itself with the Marmara Main Fault providing a high permeability conduit from the mantle to the surface. Assuming that the mantle source to the fluids originally had a 3He/4He ratio of 6 Ra, the minimum fluid velocities (considering only vertical transport and no mixing with parentless 4He) implied by the high 3He/4He ratios are of the order of 1-100 mm yr−1

The submarine Istanbul‐Silivri fault segment, within 15 km of Istanbul, is the only portion of the North Anatolian Fault that has not ruptured in the last 250 years. We report first results of a seafloor acoustic ranging experiment to quantify current horizontal deformation along this segment and assess whether the segment is creeping aseismically or accumulating stress to be released in a future event. Ten transponders were installed to monitor length variations along 15 baselines. A joint least squares inversion for across‐fault baseline changes, accounting for sound speed drift at each transponder, precludes fault displacement rates larger than a few millimeters per year during the 6 month observation period. Forward modeling shows that the data better fit a locked state or a very moderate surface creep—less than 6 mm/yr compared to a far‐field slip rate of over 20 mm/yr—suggesting that the fault segment is currently accumulating stress.

In this study, we aim to examine past dry and wet events for the western Anatolia, performing local and spatial reconstructions. 17 new black pine site chronologies were developed, May–June precipitation time series were reconstructed for four localities, and the first spatial May–June precipitation reconstruction was achieved for western Anatolia. The long-term local May–June precipitation reconstructions contain mostly one-year and less commonly, two-year drought events. The longest consecutive dry period (AD 1925–1928) in the reconstructed time series for Kütahya lasted four years. Spatial reconstructions revealed that between AD 1786 and 1930 the extreme dry years for all of western Anatolia were AD 1887, 1893, 1794 and 1740. The driest year during the 215-year-long period under consideration was 1887. The wettest years for the entire western Anatolia were determined to be AD 1835, 1876, 1881 and 1901. There is a big overlap between agricultural famine years and dry years as determined from reconstructions. In this context, our study provides a basis for understanding agricultural drought and better management of regional water resources.