Although the geometry and kinematics of the fi rst-order structures accommodating Arabia-Eurasia convergence are relatively well known in Turkey and Iran, major shortening structures remain poorly understood within the central portion of the collision zone, in eastern Anatolia and the Caucasus. New remotely sensed neotectonic mapping, synthesis of regional geologic and stratigraphic data, and balanced cross sections suggest that the Kura fold-thrust belt has accommodated the majority of Arabia-Eurasia convergence since the early Pliocene between the longitudes of ~45°E and ~49°E. This belt lies southeast of the N80°W-striking Greater Caucasus Mountains and forms an eastwardnarrowing band of elevated topography that roughly parallels the range front for ~400 km along strike. The belt is separated from the Greater Caucasus to the north by the 10-to 25-km-wide Alazani Basin and comprises a series of predominantly south-verging folds deforming Eocene-Quaternary fl ysch and molasse. To document structural geometries within the Kura fold-thrust belt, we have used the Real-time Interactive Mapping System (RIMS) software to analyze Advanced Spaceborne Thermal Emission and Refl ection Radiometer (ASTER), visible to near-infrared (VNIR), and digital elevation model (DEM) data. This neotectonic mapping indicates an along-strike, eastward decrease in both structural complexity and the degree to which deformed geomorphic surfaces are dissected. Existing geologic maps indicate a corresponding eastward decrease in the depth of exposure. By integrating the structural geometries determined in our analysis of remote-sensing data with existing geologic data, we have constructed two balanced cross sections, which suggest these systematic along-strike variations result from a west-to-east decrease in total shortening within the Kura fold-thrust belt. We interpret this variable shortening to stem from eastward propagation of the Kura foldthrust belt. Comparison of our preliminary total shortening estimates with those predicted by current plate motions suggest that the Kura fold-thrust belt has accommodated ~30%-40% (~25 km) of total Arabia-Eurasia convergence since 5 Ma, and thus forms a fi rst-order structural system within the central portion of the collision zone.

To advance research and improve the scientific return on data collection and interpretation efforts in the geosciences, we have developed methods of interactive visualization, with a special focus on immersive virtual reality (VR) environments. Earth sciences employ a strongly visual approach to the measurement and analysis of geologic data due to the spatial and temporal scales over which such data ranges. As observations and simulations increase in size and complexity, the Earth sciences are challenged to manage and interpret increasing amounts of data. Reaping the full intellectual benefits of immersive VR requires us to tailor exploratory approaches to scientific problems. These applications build on the visualization method's strengths, using both 3D perception and interaction with data and models, to take advantage of the skills and training of the geological scientists exploring their data in the VR environment. This interactive approach has enabled us to develop a suite of tools that are adaptable to a range of problems in the geosciences and beyond.

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We present a software system that enables path-traced rendering of complex scenes. The system consists of two primary components: an application layer that implements the basic rendering algorithm, and an out-of-core scheduling and data-management layer designed to assist the application layer in exploiting hybrid computational resources (e.g., CPUs and GPUs) simultaneously. We describe the basic system architecture, discuss design decisions of the system's data-management layer, and outline an efficient implementation of a path tracer application, where GPUs perform functions such as ray tracing, shadow tracing, importance-driven light sampling, and surface shading. The use of GPUs speeds up the runtime of these components by factors ranging from two to twenty, resulting in a substantial overall increase in rendering speed. The path tracer scales well with respect to CPUs, GPUs and memory per node as well as scaling with the number of nodes. The result is a system that can render large complex scenes with strong performance and scalability.

The geological sciences are challenged to manage and interpret increasing volumes of data as observations and simulations increase in size and complexity. For example, simulations of earthquake-related processes typically generate complex, time-varying data sets in two or more dimensions. To facilitate interpretation and analysis of these data sets, evaluate the underlying models, and to drive future calculations, we have developed methods of interactive visualization with a special focus on using immersive virtual reality (VR) environments to interact with models of Earth's surface and interior. Virtual mapping tools allow virtual ''field studies'' in inaccessible regions. Interactive tools allow us to manipulate shapes in order to construct models of geological features for geodynamic models, while feature extraction tools support quantitative measurement of structures that emerge from numerical simulation or field observations, thereby enabling us to improve our interpretation of the dynamical processes that drive earthquakes. VR has traditionally been used primarily as a presentation tool, albeit with active navigation through data. Reaping the full intellectual benefits of immersive VR as a tool for scientific analysis requires building on the method's strengths, that is, using both 3D perception and interaction with observed or simulated data. This approach also takes advantage of the specialized skills of geological scientists who are trained to interpret, the often limited, geological and geophysical data available from field observations.