SUMMARY
We describe best-fitting angular velocities and MORVEL, a new closure-enforced set of angular velocities for the geologically current motions of 25 tectonic plates that collectively occupy 97 per cent of Earth's surface. Seafloor spreading rates and fault azimuths are used to determine the motions of 19 plates bordered by mid-ocean ridges, including all the major plates. Six smaller plates with little or no connection to the mid-ocean ridges are linked to MORVEL with GPS station velocities and azimuthal data. By design, almost no kinematic information is exchanged between the geologically determined and geodetically constrained subsets of the global circuit—MORVEL thus averages motion over geological intervals for all the major plates. Plate geometry changes relative to NUVEL-1A include the incorporation of Nubia, Lwandle and Somalia plates for the former Africa plate, Capricorn, Australia and Macquarie plates for the former Australia plate, and Sur and South America plates for the former South America plate. MORVEL also includes Amur, Philippine Sea, Sundaland and Yangtze plates, making it more useful than NUVEL-1A for studies of deformation in Asia and the western Pacific. Seafloor spreading rates are estimated over the past 0.78 Myr for intermediate and fast spreading centres and since 3.16 Ma for slow and ultraslow spreading centres. Rates are adjusted downward by 0.6–2.6 mm yr−1 to compensate for the several kilometre width of magnetic reversal zones. Nearly all the NUVEL-1A angular velocities differ significantly from the MORVEL angular velocities. The many new data, revised plate geometries, and correction for outward displacement thus significantly modify our knowledge of geologically current plate motions. MORVEL indicates significantly slower 0.78-Myr-average motion across the Nazca–Antarctic and Nazca–Pacific boundaries than does NUVEL-1A, consistent with a progressive slowdown in the eastward component of Nazca plate motion since 3.16 Ma. It also indicates that motions across the Caribbean–North America and Caribbean–South America plate boundaries are twice as fast as given by NUVEL-1A. Summed, least-squares differences between angular velocities estimated from GPS and those for MORVEL, NUVEL-1 and NUVEL-1A are, respectively, 260 per cent larger for NUVEL-1 and 50 per cent larger for NUVEL-1A than for MORVEL, suggesting that MORVEL more accurately describes historically current plate motions. Significant differences between geological and GPS estimates of Nazca plate motion and Arabia–Eurasia and India–Eurasia motion are reduced but not eliminated when using MORVEL instead of NUVEL-1A, possibly indicating that changes have occurred in those plate motions since 3.16 Ma. The MORVEL and GPS estimates of Pacific–North America plate motion in western North America differ by only 2.6 ± 1.7 mm yr−1, ≈25 per cent smaller than for NUVEL-1A. The remaining difference for this plate pair, assuming there are no unrecognized systematic errors and no measurable change in Pacific–North America motion over the past 1–3 Myr, indicates deformation of one or more plates in the global circuit. Tests for closure of six three-plate circuits indicate that two, Pacific–Cocos–Nazca and Sur–Nubia–Antarctic, fail closure, with respective linear velocities of non-closure of 14 ± 5 and 3 ± 1 mm yr−1 (95 per cent confidence limits) at their triple junctions. We conclude that the rigid plate approximation continues to be tremendously useful, but—absent any unrecognized systematic errors—the plates deform measurably, possibly by thermal contraction and wide plate boundaries with deformation rates near or beneath the level of noise in plate kinematic data.

Geologically current plate motions

http://www2.ess.ucla.edu/~yin/05-Publications/papers/124-Yin-2010-Tectonophysics.pdf

Cenozoic tectonic evolution of Asia: A preliminary synthesis

We present a new global model of plate motions and strain rates in plate boundary zones constrained by horizontal geodetic velocities. This Global Strain Rate Model (GSRM v.2.1) is a vast improvement over its predecessor both in terms of amount of data input as in an increase in spatial model resolution by factor of ∼2.5 in areas with dense data coverage. We determined 6739 velocities from time series of (mostly) continuous GPS measurements; i.e., by far the largest global velocity solution to date. We transformed 15,772 velocities from 233 (mostly) published studies onto our core solution to obtain 22,511 velocities in the same reference frame. Care is taken to not use velocities from stations (or time periods) that are affected by transient phenomena; i.e., this data set consists of velocities best representing the interseismic plate velocity. About 14% of the Earth is allowed to deform in 145,086 deforming grid cells (0.25° longitude by 0.2° latitude in dimension). The remainder of the Earth's surface is modeled as rigid spherical caps representing 50 tectonic plates. For 36 plates we present new GPS-derived angular velocities. For all the plates that can be compared with the most recent geologic plate motion model, we find that the difference in angular velocity is significant. The rigid-body rotations are used as boundary conditions in the strain rate calculations. The strain rate field is modeled using the Haines and Holt method, which uses splines to obtain an self-consistent interpolated velocity gradient tensor field, from which strain rates, vorticity rates, and expected velocities are derived. We also present expected faulting orientations in areas with significant vorticity, and update the no-net rotation reference frame associated with our global velocity gradient field. Finally, we present a global map of recurrence times for Mw=7.5 characteristic earthquakes.

A geodetic plate motion and Global Strain Rate Model

[1] The amount of H2O subducted to postarc depths dictates such disparate factors as the generation of arc and back-arc magmas, the rheology of the mantle wedge and slab, and the global circulation of H2O. Perple_X was used to calculate phase diagrams and rock physical properties for pressures of 0.5–4.0 GPa and temperatures of 300–900°C for a range of bulk compositions appropriate to subduction zones. These data were merged with global subduction zone rock fluxes to generate a model for global H2O flux to postarc depths. For metasomatized igneous rocks, subducted H2O scales with bulk rock K2O in hot slabs. Metasomatized ultramafic rocks behave similarly in cold slabs, but in hot slabs carry no H2O to magma generation depths because they lack K2O. Chert and carbonate are responsible for minimal H2O subduction, whereas clay-rich and terrigenous sediments stabilize several hydrous phases at low temperature, resulting in significant postarc slab H2O flux in cold and hot slabs. Continental crust also subducts much H2O in cold slabs because of the stability of lawsonite and phengite; in hot slabs it is phengite that carries the bulk of this H2O to postarc depth. All told, the postarc flux of H2O in cold slabs is dominated by terrigenous sediment and the igneous lower crust and mantle and is proportional to bulk rock H2O. In contrast, in hot slabs the major contributors of postarc slab H2O are metasomatized volcanic rocks and subducted continental crust, with the amount of postarc slab H2O scaling with K2O. The Andes and Java-Sumatra-Andaman slabs are the principal suppliers of pelagic and terrigenous sediment hosted H2O to postarc depths, respectively. The Chile and Solomon arcs contribute the greatest H2O flux from subducted continental and oceanic forearc, respectively. The Andean arc has the greatest H2O flux provided through subduction of hydrated ocean crust and mantle. No correlation was observed between postarc slab H2O flux and slab seismicity.

/pdf/h2o-subduction-beyond-arcs-3zphrxlmhk.pdf

H2O subduction beyond arcs

The Mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt. Lithospheric dynamics are affected by slab rollback and collision of two large, slowly moving plates, forcing fragments of continental and oceanic lithosphere to interact. This paper reviews the rich and growing set of constraints from geological reconstructions, geodetic data, and crustal and upper mantle heterogeneity imaged by structural seismology. We proceed to discuss a conceptual and quantitative framework for the causes of surface deformation. Exploring existing and newly developed tectonic and numerical geodynamic models, we illustrate the role of mantle convection on surface geology. A coherent picture emerges which can be outlined by two, almost symmetric, upper mantle convection cells. The downwellings are found in the center of the Mediterranean and are associated with the descent of the Tyrrhenian and the Hellenic slabs. During plate convergence, these slabs migrated backward with respect to the Eurasian upper plate, inducing a return flow of the asthenosphere from the backarc regions towards the subduction zones. This flow can be found at large distance from the subduction zones, and is at present expressed in two upwellings beneath Anatolia and eastern Iberia. This convection system provides an explanation for the general pattern of seismic anisotropy in the Mediterranean, first-order Anatolia and Adria microplate kinematics, and may contribute to the high elevation of scarcely deformed areas such as Anatolia and Eastern Iberia. More generally, the Mediterranean is an illustration of how upper mantle, small-scale convection leads to intraplate deformation and complex plate boundary reconfiguration at the westernmost terminus of the Tethyan collision.

Mantle dynamics in the Mediterranean

The territory of Azerbaijan covers a part of the Mediterranean Alpine belt of Eurasia, being characterized by complex geological and tectonic structures and numerous formational types of hard minerals and hydrocarbons within folded systems of the Greater and Lesser Caucasus, Talysh Mts., Kur Depression and South Caspian Basin.

Economic Minerals of Azerbaijan

Geological and structural conditions within Azerbaijan permit to isolate the Greater and the Lesser Caucasus mountain zones and the Kur-Araz Lowland that separates them, though the Talysh Mountains is separated from the Lesser Caucasus by the Araz River in the southeast. Three regions are isolated as geostructural regions (first-order tectonic structures): A—the Greater Caucasus fold-mountain zone, B—the Lesser Caucasus fold-mountain zone, and C—the Kur-Araz Lowland (Alekperov et al. 2008).

Groundwater Generation and Distribution Regularities

Geophysical monitoring of oil and gas pipelines (primarily in Baku–Tbilisi–Ceyhan (BTC) and South Caucasus pipelines (SCP).

Engineering, Environmental, and Archaeological Geophysics

It should be underlined that Azerbaijan is the most ancient hydrocarbon province of the world. For example, the world’s first oil well was drilled in 1848 in the Absheron Peninsula. This event took place eleven years prior to the drilling of the first oil well in Pennsylvania. Geophysical methods for oil and gas searching (localization) began to apply in Azerbaijan since 20s of the twentieth century.

Oil and Gas Geophysics

Orogenic wedges are common at convergent plate margins and deform internally to maintain a self‐similar geometry during growth. New structural mapping and thermochronometry data illustrate that the eastern Greater Caucasus mountain range of western Asia undergoes deformation via distinct mechanisms that correspond with contrasting lithologies of two sedimentary rock packages within the orogen. The orogen interior comprises a package of Mesozoic thin‐bedded (<10 cm) sandstones and shales. These strata are deformed throughout by short‐wavelength (<1 km) folds that are not fault‐bend or fault‐propagation folds. In contrast, a coeval package of thick‐bedded (up to 5 m) volcaniclastic sandstone and carbonate, known as the Vandam Zone, has been accreted and is deformed via imbrication of coherent thrust sheets forming fault‐related folds of 5–10 km wavelength. Structural reconstructions and thermochronometric data indicate that the Vandam Zone package was accreted between ca. 13 and 3 Ma. Following Vandam Zone accretion, thermal modeling of thermochronometric data indicates rapid exhumation (∼0.3–1 mm/yr) in the wedge interior beginning between ca. 6 and 3 Ma, and a novel thermochronometric paleo‐rotation analysis suggests out‐of‐sequence folding of wedge‐interior strata after ca. 3 Ma. Field relationships suggest that the Vandam Zone underwent syn‐convergent extension following accretion. Together, the data record spatially and temporally variable deformation, dependent on both the mechanical properties of deforming lithologies and perturbations such as accretion of material from the down‐going to the overriding plate. The diverse modes of deformation are consistent with the maintenance of critical taper.

Diverse Deformation Mechanisms and Lithologic Controls in an Active Orogenic Wedge: Structural Geology and Thermochronometry of the Eastern Greater Caucasus

Fakhraddin Kadirov

Papers

Economic Minerals of Azerbaijan

Groundwater Generation and Distribution Regularities

Engineering, Environmental, and Archaeological Geophysics

Oil and Gas Geophysics

Diverse Deformation Mechanisms and Lithologic Controls in an Active Orogenic Wedge: Structural Geology and Thermochronometry of the Eastern Greater Caucasus