Structural Geology

Within the framework of the International Continental Drilling Program (ICDP) we propose a comprehensive initiative to drill the continental crust bordering modern and ancient convergent and collisional plate boundaries. These zones host the vast majority of modern megacities and industrial installations on Planet Earth, and at the same time are loci of major earthquakes , tsunamis, volcanic eruptions and other associated great natural threats to human life and to economies. In-depth understanding of dynamic Earthprocesses at convergent and collisional plate boundaries is not possible without scientific drilling embedded into integrated research programmes. The set of scientific questions identified here is rooted in the plate tec-tonic paradigm of a dynamic Earth. Proposed studies derived from these questions target on (1) the dynamics of active subduction and collision zones, with focus on the seismogenic zone at the plate interface, and the distribution of deformation and seismicity in general, (2) the role of mantle plumes in orogeny, (3) supra-subduction magmatism in arc systems, (4) the geological manifestation of deep subduction and exhumation of the lithosphere, and (5) aspects relating to continental birth and growth through Earth history. ICDP drilling in convergent and collisional plate margins faces unprecedented challenges regarding drilling technology, drilling depth and requirements for long-term monitoring of Earth processes in downhole observatories.

The left-lateral strike-slip Adıyaman fault is located in eastern Turkey within the plate boundary deformation zone between Arabia and Anatolia. The Adıyaman fault is a major splay from the East Anatolian Fault (EAF), one of the most important tectonic structures in the Eastern Mediterranean region. These faults are consequence of the collision between the Arabian and Anatolian plates and the resulting westward tectonic escape of Anatolia. Although the EAF has been intensively studied since its discovery in the late 1960s, little is known about the Adıyaman fault and its tectonic activity. In this study, we extract geomorphic indices including mountain-front sinuosity (Smf), valley floor width-to-height ratio (Vf), stream length-gradient (SL), catchment Asymmetry Factor (AF) and hypsometric integrals and curves (HI and HC) to evaluate the relative tectonic activity of the Adıyaman fault. These three geomorphic indices (AF, HI, and HC) are averaged to define an index for Relative Tec...

The rift phase of the Campos Basin is marked by NE-SW-trending normal faults, which are controlled by pre-existent Precambrian weak zones. The São Tomé Cape Transfer Zone was identified by gravimetric and hydrogeologic maps, and is an overlapping transfer zone situated between the São João Graben, located mostly offshore of the Campos Basin, and the Campos Graben, located onshore in this basin; both grabens are oriented in the NE-SW direction. The main fault of the Campos Graben, named São João da Barra Fault dips towards SE and presents maximum vertical displacement of 1.380 m. A WNW-ESE-trending release fault located in its hangingwall block presents an intermediate displacement of 460 m. A NW-SE-trending graben oriented transversally to the rift axis, cuts across the São Tomé Cape Transfer Zone and connects the São João and Campos grabens. One of its NW-SE-trending faults presents a flower structure and significant lateral lithologic difference, indicating components of strike-slip movements on some of these faults. This may be due to later crustal pull-apart movements and pole rotation, which reactivated NW-SE-trending normal faults as strike-slip faults. This NW-SE-trending graben compartmentalizes the onshore portion of Campos Basin in two distinct structural domains, which were interpreted as compressional towards SW, and extensional towards NE, of the São Tomé Cape Transfer Zone. NW-SE-trending faults are also common in the compartmentalization of other areas of the Campos basin. The compressional and extensional domains are related to the orientation of the strike-slip faults with respect to the plate-driven stresses, which allows characterizing regions with transpressional or transtensional styles. Another WNW-ESE-trending fault that shows a flower structure was interpreted as the result of the E-W-splitting between the South American and African continents. The studied data indicate that several events were superposed to the São Tomé Cape Transfer Zone. The tectonic evolutionary model of the Campos Basin can be correlated to the one named Bivergent Lithosferic Extension, which predicts mechanical subsidence, pull-apart basin, lithosferic extension, transitional phase and thermal subsidence. The integration of several data sources corroborates the correlation of the structures in the São Tomé Cape to a complex evolutionary system, of wide geochronological distribution in several extensional stages.

Chocolate-tablet boudins of quartzite are restricted to steep limbs of D1-folds along the SW coast of Portugal. The chocolate-tablet geometry results from older vertical and younger horizontal quartz veins. Both sets of veins developed during similar conditions by extension fracture in pre-existing necked domains: (1) both veins show stretched crystal fibers; (2) the boudin aspect ratio is the same in vertical (3.0 ± 1.4) and in horizontal sections (2.9 ± 1.2); (3) temperatures obtained from fluid inclusions are similar (200 ± 20° for vertical and 230 ± 22 °C for horizontal veins) and are compatible with temperatures obtained from illite crystallinity (ca. 200–ca. 250 °C). Given thermal equilibrium between the host rock and the precipitating fluid, the chocolate-tablet boudins formed close to the metamorphic peak. We interpret that the vertical veins developed after the limbs of the D1-folds had attained their steep attitude and the orientation of the greatest and intermediate principal strain axes had interchanged. Subsequently, the initial strain field was restored and opening of horizontal veins led to the chocolate-tablet geometry. The direction of the main shortening direction was constant from the initial buckling stage via isoclinal folding and during all boudinage stages.► The paper deals with chocolate-tablet boudins well exposed in 3D. ► The boudin aspect ratio (ca. 3) is the same in horizontal and vertical sections. ► Vertical and horizontal fractures of neck domains developed in sequence. ► Boudinage occurred during progressive shortening close to the metamorphic peak.

On November 1, 1755, the city of Lisbon was completely devastated by the combined effect of a tremendous earthquake, tsunami waves, and fire. The 1755 Lisbon earthquake was the most destructive cataclysm recorded in western Europe since the Roman Republic, with an estimated earthquake magnitude Mw∼ 8.5 [Martins and Mendes Victor, 1990] and estimated tsunami magnitude of Mt= Mw= 8.5. The earthquake was felt as far away as Great Britain and Finland. The tsunami hit many coastal cities along southwest Iberia and North ...

A family of asymmetric, northwest-verging back folds and crenulations occur on a regional scale in the Caledonian décollement zone in southwestern Norway. They are the result of reversal of the emplacement movement of the Jotun and other nappes in Early Devonian ...

SUMMARY Numerical simulations of long-term crustal deformation reveal the important role that damage healing (ie fault-zone strengthening) plays in the structural evolution of strike-slip fault systems. We explore the sensitivity of simulated fault zone structure and evolution patterns to reasonable variations in the healing-rate parameters in a continuum damage rheology model. Healing effectiveness, defined herein as a function of the healing rate parameters, describes the post-seismic healing process in terms of the characteristic inter- ...

Catastrophic flank collapses have occurred at many stratovolcanoes worldwide. We present a three-dimensional (3-D) slope stability analysis for assessing and quantifying both the locations of minimum edifice stability and the expected volumes of potential failure. Our approach can search the materials underlying a topographic surface, represented as a digital elevation model (DEM), and determine the relative stability of all parts of the edifice. Our 3-D extension of Bishop's [1955] simplified limit-equilibrium analysis incorporates spherical failure surfaces, variable material properties, pore fluid pressures, and earthquake shaking. Although a variety of processes can trigger collapse, we focus here on gravitationally induced instability. Even homogeneous rock properties strongly influence the depth and volume of the least stable potential failure. For large failures in complex topography, patterns of potential instability do not mimic local ground surface slope alone. The May 18, 1980, catastrophic failure of the north flank of Mount St. Helens provides the best documented case history to test our method. Using the undeformed edifice topography of Mount St. Helens in an analysis of dry, static slope stability with homogeneous materials, as might be conducted in a precollapse hazard analysis, our method identified the northwest flank as the least stable region, although the north flank stability was within 5% of the minimum. Using estimates of the conditions that existed 2 days prior to collapse, including deformed topography with a north flank bulge and combined pore pressure and earthquake shaking effects, we obtained good estimates of the actual failure location and volume. Our method can provide estimates of initial failure volume and location to aid in assessing downslope or downstream hazards.

Slope stability at open pit mining system for safety and economics element is critical issue with employees and equipment damage due to danger of slope failure at the mining environment. Commonly uncertainty on slope stability analysis consist of physical properties, mass movement, and structural geology. Slope stability monitoring with mass movement (displacement) considered to determine the stability of slope wall. Measurable real-time data monitoring provided to reduce risk of unstable slope wall involved with employees, equipment, and economics at the mining environmental. Slope Stability Radar as a monitoring instrument used in several of indonesian open pit mining. Accuration, realibilitation, intensity of SSR monitoring considered very realible to represent " real deformation " of slope wall. On Slope stability Radar data analysis, trend of graphics behaviour is " the key " of monitoring. Combined of trend deformation, velocity and inverse-velocity provide threshold with early warning system purpose. Geology structures fold and thrust fault deleterious stability of slope wall which a lot of case succeed as a " triggers " of failure occurs. By velocity and inverse-velocity rate represent the acceleration of the area with structural geology involved change rapidly. The case study conducted as an effort to help engineer boost " confident " to determine characteristic of failure by the data of slope stability radar and trend particularly with structural geology involved. Variety of graphics characteristic from 15 analysis data purpose to determine " threshold alarm " and proposed as reference on SSR monitoring system for the risk management program at coal mining environmental.

Uncertainty analysis is a critical component of field development plan which describes the risks and assists to achieve comprehensive understanding of reservoir characteristics. Accurately assessing and ranking key uncertainties provides necessary tools to the technical and management team to mitigate risks appropriately and generate robust development scenarios over the range of key uncertainties. Uncertainty in input parameters impacts the project in two ways—in-place volumes and recovery factor. In this study, an analysis methodology is adopted in such a way to assess the impact of uncertainty on both independently.

Iraq is located at the extreme northeastern part of the Arabian Plate, which is in collision with the
Eurasian Plate. This collision is still onward, and has caused alignment of the evolved structures in
NW-SE trend, mainly, especially in the northern, northeastern and eastern sides of Iraq. However,
many transversal linear features of NE-SW trend, represented by rivers, streams, valleys, playas,
anticlines and offsets are developed, in parallel trend to the main compressional forces created by
the aforementioned collision. Many examples from different parts of Iraq confirm the mechanism
of their formation through the geological, geomorphological, tectonics and structural aspects. Although
the existing linear features are tens of kilometers in length, but almost no surface displacements
were reported, except very few, in some parts of Iraq. The given examples are selected
to be the most obvious, when geophysical data are available, the surface and subsurface geology of
the involved area is correlated to deduce whether the surface expression coincides with the subsurface
or otherwise. A brief tectonic history is also given