Control of the Lithospheric Mantle on intracontinental Deformation: Revival of Eastern U.S. Tectonism

NASA Astrophysics Data System (ADS)

Biryol, C. B.; Wagner, L. S.; Fischer, K. M.; Hawman, R. B.

2016-12-01

The present tectonic configuration of the southeastern United States is a product of earlier episodes of arc accretion, continental collision and breakup. This region is located in the interior of the North American Plate, some 1500 km away from closest active plate margin. However, there is ongoing tectonism across the area with multiple zones of seismicity, rejuvenation of the Appalachians of North Carolina, Virginia, and Pennsylvania, and Cenozoic intraplate volcanism. The mechanisms controlling this activity and the modern-day state of stress remain enigmatic. Two factors often regarded as major contributors are plate strength and preexisting inherited structures. Recent improvements in broadband seismic data coverage in the region associated with the South Eastern Suture of the Appalachian Margin Experiment (SESAME) and EarthScope Transportable Array make it possible to obtain detailed information on the structure of the lithosphere in the region. Here we present new tomographic images of the upper mantle beneath the Southeastern United States, revealing large-scale structural variations in the upper mantle. Our results indicate fast seismic velocity patterns that can be interpreted as ongoing lithospheric foundering. We observe an agreement between the locations of these upper mantle anomalies and the location of major zones of tectonism, volcanism and seismicity, providing a viable explanation for modern-day activity in this plate interior setting long after it became a passive margin. Based on distinct variations in the geometry and thickness of the lithospheric mantle and foundered lithosphere, we propose that piecemeal delamination has occurred beneath the region throughout the Cenozoic, removing a significant amount of reworked/deformed mantle lithosphere. Ongoing lithospheric foundering beneath the eastern margin of stable North America explains significant variations in thickness of lithospheric mantle across the former Grenville deformation front.

Seperating Long-term Hydrological Loading and Tectonic Deformation Observed with Multi-temporal SAR Interferometry and GPS in Qinghai-Tibetan Plateau

NASA Astrophysics Data System (ADS)

LI, G.; Lin, H.

2014-12-01

From 2000 till present, most endorheic lakes in Tibetan plateau experienced quick increasing. Several largest lakes, gathered several meters depth water during one decade. Such massive mass increasing will lead to elastic and visco-elastic deformation of the ground. Qinghai-Tibetan Plateau is one the most active tectonic places in the world; monitoring its ground deformation is essential, when loading effect is a nuisance item. Due to the sparse distribution of GPS sites and most are roving sites, it is hard to distinguish tectonic component from mass loading effect. In this research we took Selin Co Lake located at Nujiang-Bangoin suture zone and evaluated long time ground deformation at hundred kilometers scale by multi-temporal SAR interferometry and simulate the ground deformation by loading history evaluated by multi mission satellite altimetry and optical images observation. At Nujiang-Bangoin suture zone, where GPS presented the maximum ground subsidence in Qinghai-Tibetan Plateau of 3.6mm/a which was found at the shore of Selin Co Lake from 1999 to 2011, when it experienced water level increasing of 0.7m/a. A model of elastic plate lying over Newtonian viscous half-space matches well with the results of multi-temporal SAR interferometry and GPS observations. We concluded that near Selin Co Lake area, ground deformation is composed by both tectonic and hydrological loading part. As SAR image coverage is much smaller than tectonic scale, we contribute the deformation detected by InSAR to loading effect. After evaluating and removing the hydrological loading effect, we founds that Nujiang-Bangoin suture zone did not experience quick subsidence, but only limited to 0.5mm/a. Selin Co Lake's quick volume increasing caused 3mm/a subsidence rate to the nearest GPS site. The Second nearest site showed the 1.4mm/a subsidence totally, which were composed by 1.05mm/a hydrological loading effect and the rest was tectonic. We also found that Young's Modulus is the most

Effects of tectonic plate deformation on the geodetic reference frame of Mexico

NASA Astrophysics Data System (ADS)

Gonzalez Franco, G. A.; Avalos, D.; Esquivel, R.

2013-05-01

Positioning for geodetic applications is commonly determined at one observation epoch, but tectonic drift and tectonic deformation cause the coordinates to be different for any other epoch. Finding the right coordinates at a different epoch from that of the observation time is necessary in Mexico in order to comply the official reference frame, which requires all coordinates to be referred to the standard epoch 2010.0. Available models of horizontal movement in rigid tectonic plates are used to calculate the displacement of coordinates; however for a portion of Mexico these models fail because of miss-modeled regional deformation, decreasing the quality of users' data transformed to the standard epoch. In this work we present the progress achieved in measuring actual horizontal motion towards an improved modeling of horizontal displacements for some regions. Miss-modeled velocities found are as big as 23mm/a, affecting significantly applications like cadastral and geodetic control. Data from a large set of GNSS permanent stations in Mexico is being analyzed to produce the preliminary model of horizontal crustal movement that will be used to minimize distortions of the reference frame.

Tectonic activity evolution of the Scotia-Antarctic Plate boundary from mass transport deposit analysis

NASA Astrophysics Data System (ADS)

Pérez, Lara F.; Bohoyo, Fernando; Hernández-Molina, F. Javier; Casas, David; Galindo-Zaldívar, Jesús; Ruano, Patricia; Maldonado, Andrés.

2016-04-01

The spatial distribution and temporal occurrence of mass transport deposits (MTDs) in the sedimentary infill of basins and submerged banks near the Scotia-Antarctic plate boundary allowed us to decode the evolution of the tectonic activity of the relevant structures in the region from the Oligocene to present day. The 1020 MTDs identified in the available data set of multichannel seismic reflection profiles in the region are subdivided according to the geographic and chronological distributions of these features. Their spatial distribution reveals a preferential location along the eastern margins of the eastern basins. This reflects local deformation due to the evolution of the Scotia-Antarctic transcurrent plate boundary and the impact of oceanic spreading along the East Scotia Ridge (ESR). The vertical distribution of the MTDs in the sedimentary record evidences intensified regional tectonic deformation from the middle Miocene to Quaternary. Intensified deformation started at about 15 Ma, when the ESR progressively replaces the West Scotia Ridge (WSR) as the main oceanic spreading center in the Scotia Sea. Coevally with the WSR demise at about 6.5 Ma, increased spreading rates of the ESR and numerous MTDs were formed. The high frequency of MTDs during the Pliocene, mainly along the western basins, is also related to greater tectonic activity due to uplift of the Shackleton Fracture Zone by tectonic inversion and extinction of the Antarctic-Phoenix Ridge and involved changes at late Pliocene. The presence of MTDs in the southern Scotia Sea basins is a relevant indicator of the interplay between sedimentary instability and regional tectonics.

Preliminary atlas of active shallow tectonic deformation in the Puget Lowland, Washington

USGS Publications Warehouse

Barnett, Elizabeth A.; Haugerud, Ralph A.; Sherrod, Brian L.; Weaver, Craig S.; Pratt, Thomas L.; Blakely, Richard J.

2010-01-01

This atlas presents an up-to-date map compilation of the geological and geophysical observations that underpin interpretations of active, surface-deforming faults in the Puget Lowland, Washington. Shallow lowland faults are mapped where observations of deformation from paleoseismic, seismic-reflection, and potential-field investigations converge. Together, results from these studies strengthen the identification and characterization of regional faults and show that as many as a dozen shallow faults have been active during the Holocene. The suite of maps presented in our atlas identifies sites that have evidence of deformation attributed to these shallow faults. For example, the paleoseismic-investigations map shows where coseismic surface rupture and deformation produced geomorphic scarps and deformed shorelines. Other maps compile results of seismic-reflection and potential-field studies that demonstrate evidence of deformation along suspected fault structures in the subsurface. Summary maps show the fault traces derived from, and draped over, the datasets presented in the preceding maps. Overall, the atlas provides map users with a visual overview of the observations and interpretations that support the existence of active, shallow faults beneath the densely populated Puget Lowland.

Soft-sediment deformation in a tectonically active area: The Plio-Pleistocene Zarzal Formation in the Cauca Valley (Western Colombia)

NASA Astrophysics Data System (ADS)

Neuwerth, Ralph; Suter, Fiore; Guzman, Carlos A.; Gorin, Georges E.

2006-04-01

seismites in the Zarzal Formation represents corroboration of tectonic activity in this area during the Pleistocene. Earthquakes with a magnitude higher than 5 can be postulated, based upon the proximity of active faults and the types of deformations.

Structural and diagenetic evolution of deformation bands in contractional and extensional tectonic regimes

NASA Astrophysics Data System (ADS)

Eichhubl, P.; O'Brien, C. M.; Elliott, S. J.

2016-12-01

Mechanisms of brittle deformation of sediments and sedimentary rock change with burial because of increasing confining stress, change in pore fluid chemical and temperature conditions, and diagenetic state. In the field, these changes are observed in a transition from early non-cataclastic to later cataclastic deformation bands and to joint-based structures. Jurassic eolian sandstones in the San Rafael monocline and adjacent San Rafael Desert region, Utah, allow comparison of deformation band structures and their diagenetic attributes in contractional and extensional tectonic settings in close proximity. In the Entrada and Navajo Sandstones, we observe up to six generations of deformation bands, with earliest non-cataclastic bands having diffuse boundaries to host rock, and short and irregular traces. Later bands are cataclastic, more sharply defined, with long and straight traces. Cataclastic bands in the San Rafael monocline are interpreted to form as reverse faults during progressive rotation of the steeply dipping fold limb, resulting in an array of bands of varying dip. Bands in the San Rafael Desert form as normal faults with a narrower dip range. Although structural characteristics of bands differ in extensional and contractional tectonic regimes, cataclastic bands in either regime have comparable amount of porosity loss and quartz cementation indicating that tectonic regime does not influence band diagenesis. Abundance of quartz cement in bands, determined by point counting of SEM images, increases from earlier to later generations of bands and, within a single generation, with increasing slip along the band, reaching up to 24% of band volume. This trend is attributed to an increase in cataclasis with increasing host rock cementation and confining stress during burial, and, within the same generation, with increasing slip. Porosity loss by cementation tends to dominate over porosity loss by mechanical compaction. These findings demonstrate that quartz

Late Neogene and Active Tectonics along the Northern Margin of the Central Anatolian Plateau,TURKEY

NASA Astrophysics Data System (ADS)

Yildirim, C.; Schildgen, T. F.; Melnick, D.; Echtler, H. P.; Strecker, M. R.

2009-12-01

Margins of orogenic plateaus are conspicuous geomorphic provinces that archive tectonic and climatic variations related to surface uplift. Their growth is associated with spatial and temporal variations of mode and rate of tectonics and surface processes. Those processes can be strongly linked to the evolution of margins and plateaus thorough time. As one of the major morpho-tectonic provinces of Turkey, the Central Pontides (coinciding with the northern margin of the Central Anatolian Plateau (CAP)) display a remarkable topography and present valuable geologic and geomorphic indicators to identify active tectonics. Morpho-tectonic analysis, geological cross-sections, seismic profiles, and geodetic analysis reveal continuous deformation characterized by brittle faults from Late Miocene to recent across the northern margin of the CAP. In the Sinop Peninsula and offshore in the southern Black Sea, pervasive faulting and folding and uplift of Late Miocene to Quaternary marine deposits is related to active margin tectonics of the offshore southern Black Sea thrust and the onshore Balifaki and Erikli faults. In the Kastamonu-Boyabat sedimentary basin, the Late Miocene to Quaternary continental equivalents are strongly deformed by the Ekinveren Fault. This vergent inverse and thrust fault with overstepping en echelon segments deforms not only Quaternary travertines and conglomerates, but also patterns of the Pleistocene to Holocene drainage systems. In the southern Kastamonu-Boyabat basin, an antithetic thrust fault of the Ekinveren Fault system deformed also Quaternary fluviatile terrace deposits. Farther south, a dextral transpressive splay of the North Anatolian Fault (NAF) deforms pediment surfaces and forms the northern flank of the Ilgaz active mountain range. The Ilgaz Range rises up to 2587 m.a.s.l and is delimited by active segments of the NAF.The Central Pontides are located at the apex of northward convex arc of the NAF. Geodetic analysis indicate a deviation

The Role of Deformation Energetics in Long-Term Tectonic Modeling

NASA Astrophysics Data System (ADS)

Ahamed, S.; Choi, E.

2017-12-01

The deformation-related energy budget is usually considered in the simplest form or even entirely omitted from the energy balance equation. We derive a full energy balance equation that accounts not only for heat energy but also for mechanical (elastic, plastic and viscous) work. The derived equation is implemented in DES3D, an unstructured finite element solver for long-term tectonic deformation. We verify the implementation by comparing numerical solutions to the corresponding semi-analytic solutions in three benchmarks extended from the classical oedometer test. We also investigate the long-term effects of deformation energetics on the evolution of large offset normal faults. We find that the models considering the full energy balance equation tend to produce more secondary faults and an elongated core complex. Our results for the normal fault system confirm that persistent inelastic deformation has a significant impact on the long-term evolution of faults, motivating further exploration of the role of the full energy balance equation in other geodynamic systems.

Editorial: Introduction to the Special Issue ;Slope Tectonics: Inherited Structures, Morphology of Deformation and Catastrophic Failure;

NASA Astrophysics Data System (ADS)

Hermanns, R. L.; Oppikofer, T.; Jaboyedoff, M.; Clague, J. J.; Scarascia-Mugnozza, G.

2017-07-01

The "Conference on Slope Tectonics" has become an international scientific meeting point to present and discuss a variety of topics related to slope deformation and the deposits of related failures. The first conference took place on February 15-16, 2008 at University of Lausanne (Switzerland). It was followed by a second conference on September 6-10, 2011, in Austria (organized by the Geological Survey of Austria) and a third on September 8-12, 2014, in Norway (organized by the Geological Survey of Norway). The two later events included field trips. It has become a tradition that selected papers from these conference are published - papers from the first conference were published by the Geological Society as Special Publication 351 (Jaboyedoff, 2011), and those from the second conference were published in a special issue of Tectonophysics (Baron and Jaboyedoff, 2013). This special issue of Geomorphology is a collection of papers presented at the Norwegian Conference on Slope Tectonics. This collection of papers focuses on the role of tectonics in gravitationally induced rock-slope instabilities. The slopes either deform over long periods as deep-seated gravitational slope deformation (DSGSD) or more rapidly as rockslides or rock avalanches. The reconstruction of slope deformation is an integral part of the studies captured in this special issue.

Deformation associated with the Ste. Genevieve fault zone and mid-continent tectonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schultz, A.; Baker, G.S.; Harrison, R.W.

1992-01-01

The Ste. Genevieve fault is a northwest-trending deformation zone on the northeast edge of the Ozark Dome in Missouri. The fault has been described as a high-angle block fault resulting from vertical uplift of Proterozoic basement rocks, and also as a left-lateral, strike-slip or transpressive wrench fault associated with the Reelfoot rift. Recent mapping across the fault zone documents significant changes in the style of deformation along strike, including variations in the number and the spacing of fault strands, changes in the orientation of rocks within and adjacent to the fault zone, and changes in the direction of stratigraphic offsetmore » between different fault slices. These data are inconsistent with existing Ste. Genevieve models of monoclinal folding over basement upthrusts. Mesoscopic structural analysis of rocks in and near the fault zone indicates highly deformed noncylindrical folds, faults with normal, reverse, oblique, and strike-slip components of movement, and complex joint systems. Fabric orientation, calcite shear fibers, and slickensides indicate that the majority of these mesoscopic structures are kinematically related to left-lateral oblique slip with the southwest side up. Within the fault zone are highly fractured rocks, microscopic to coarse-grained carbonate breccia, and siliciclastic cataclasite. Microscopic deformation includes twinning in carbonate rocks, deformation banding, undulose extinction, and strain-induced polygonization in quartz, tectonic stylolites, extension veining, microfractures, and grain-scale cataclasis. Data are consistent with models relating the Ste. Genevieve fault zone to left-lateral oblique slip possibly associated with New Madrid tectonism.« less

Studies in geophysics: Active tectonics

NASA Technical Reports Server (NTRS)

1986-01-01

Active tectonics is defined within the study as tectonic movements that are expected to occur within a future time span of concern to society. Such movements and their associated hazards include earthquakes, volcanic eruptions, and land subsidence and emergence. The entire range of geology, geophysics, and geodesy is, to some extent, pertinent to this topic. The needs for useful forecasts of tectonic activity, so that actions may be taken to mitigate hazards, call for special attention to ongoing tectonic activity. Further progress in understanding active tectonics depends on continued research. Particularly important is improvement in the accuracy of dating techniques for recent geologic materials.

Late Tharsis tectonic activity and implications for Early Mars

NASA Astrophysics Data System (ADS)

Bouley, S.; Baratoux, D.; Paulien, N.; Missenard, Y.; Saint-Bezar, B.

2017-12-01

Constraining the timing of Tharsis volcanism is critical to understanding the planet's evolution including its climate, surface environment and mantle dynamics. The tectonic history of the Tharsis bulge was previously documented from the distribution and ages of related tectonic features [1]. Here we revisit the ages of 7493 Tharsis-related tectonic features based on their relationship with stratigraphic units defined in the new geological map [2]. Conversely to previous tectonic mapping [1], which suggested that Tharsis growth was nearly achieved during the Noachian, we find a protracted growth of Tharsis during the Hesperian. Faulting at Tempe Terra, Claritas and Coracis Fossae and Thaumasia Planum confirms that tectonic deformation started during the Noachian. Accumulated tectonic deformation was maximum in the Early Hesperian for compressional strain (Solis, Lunae and Ascuris Planum) and extended over time from Noachian to Amazonian for extensional strain (Noctis Labyrinthus and Fossae, Sinai Planum and Tractus, Ulysses and Fortuna fossae, Alba Patera). This new scenario is consistent with a protracted growth of Tharsis dome during the Hesperian and with the timing a large Tharsis-driven true polar wander post-dating the incision of Late Noachian/Hesperian valley networks[3]. References:[1] Anderson et al. JGR-Planets 106, E9, 20,563-20,585 (2001).[2] Tanaka, K.L. et al. Geologic map of Mars (2014). [3] Bouley et al. Nature doi:10.1038 (2016)

Tectonic signatures on active margins

NASA Astrophysics Data System (ADS)

Hogarth, Leah Jolynn

High-resolution Compressed High-Intensity Radar Pulse (CHIRP) surveys offshore of La Jolla in southern California and the Eel River in northern California provide the opportunity to investigate the role of tectonics in the formation of stratigraphic architecture and margin morphology. Both study sites are characterized by shore-parallel tectonic deformation, which is largely observed in the structure of the prominent angular unconformity interpreted as the transgressive surface. Based on stratal geometry and acoustic character, we identify three sedimentary sequences offshore of La Jolla: an acoustically laminated estuarine unit deposited during early transgression, an infilling or "healing-phase" unit formed during the transgression, and an upper transparent unit. The estuarine unit is confined to the canyon edges in what may have been embayments during the last sea-level rise. The healing-phase unit appears to infill rough areas on the transgressive surface that may be related to relict fault structures. The upper transparent unit is largely controlled by long-wavelength tectonic deformation due to the Rose Canyon Fault. This unit is also characterized by a mid-shelf (˜40 m water depth) thickness high, which is likely a result of hydrodynamic forces and sediment grain size. On the Eel margin, we observe three distinct facies: a seaward-thinning unit truncated by the transgressive surface, a healing-phase unit confined to the edges of a broad structural high, and a highly laminated upper unit. The seaward-thinning wedge of sediment below the transgressive surface is marked by a number of channels that we interpret as distributary channels based on their morphology. Regional divergence of the sequence boundary and transgressive surface with up to ˜8 m of sediment preserved across the interfluves suggests the formation of subaerial accommodation during the lowstand. The healing-phase, much like that in southern California, appears to infill rough areas in the

Viscoelastic deformation near active plate boundaries

NASA Technical Reports Server (NTRS)

Ward, S. N.

1986-01-01

Model deformations near the active plate boundaries of Western North America using space-based geodetic measurements as constraints are discussed. The first six months of this project were spent gaining familarity with space-based measurements, accessing the Crustal Dynamics Data Information Computer, and building time independent deformation models. The initial goal was to see how well the simplest elastic models can reproduce very long base interferometry (VLBI) baseline data. From the Crustal Dynamics Data Information Service, a total of 18 VLBI baselines are available which have been surveyed on four or more occasions. These data were fed into weighted and unweighted inversions to obtain baseline closure rates. Four of the better quality lines are illustrated. The deformation model assumes that the observed baseline rates result from a combination of rigid plate tectonic motions plus a component resulting from elastic strain build up due to a failure of the plate boundary to slip at the full plate tectonic rate. The elastic deformation resulting from the locked plate boundary is meant to portray interseismic strain accumulation. During and shortly after a large interplate earthquake, these strains are largely released, and points near the fault which were previously retarded suddenly catch up to the positions predicted by rigid plate models. Researchers judge the quality of fit by the sum squares of weighted residuals, termed total variance. The observed baseline closures have a total variance of 99 (cm/y)squared. When the RM2 velocities are assumed to model the data, the total variance increases to 154 (cm/y)squared.

Constraining fault activity by investigating tectonically-deformed Quaternary palaeoshorelines using a synchronous correlation method: the Capo D'Orlando Fault as a case study (NE Sicily, Italy)

NASA Astrophysics Data System (ADS)

Meschis, Marco; Roberts, Gerald P.; Robertson, Jennifer

2016-04-01

Long-term curstal extension rates, accommodated by active normal faults, can be constrained by investigating Late Quaternary vertical movements. Sequences of marine terraces tectonically deformed by active faults mark the interaction between tectonic activity, sea-level changes and active faulting throughout the Quaternary (e.g. Armijo et al., 1996, Giunta et al, 2011, Roberts et al., 2013). Crustal deformation can be calculated over multiple seismic cycles by mapping Quaternary tectonically-deformed palaeoshorelines, both in the hangingwall and footwall of active normal faults (Roberts et al., 2013). Here we use a synchronous correlation method between palaeoshorelines elevations and the ages of sea-level highstands (see Roberts et al., 2013 for further details) which takes advantage of the facts that (i) sea-level highstands are not evenly-spaced in time, yet must correlate with palaeoshorelines that are commonly not evenly-spaced in elevation, and (ii) that older terraces may be destroyed and/or overprinted by younger highstands, so that the next higher or lower paleoshoreline does not necessarily correlate with the next older or younger sea-level highstand. We investigated a flight of Late Quaternary marine terraces deformed by normal faulting as a result of the Capo D'Orlando Fault in NE Sicily (e.g. Giunta et al., 2011). This fault lies within the Calabrian Arc which has experienced damaging seismic events such as the 1908 Messina Straits earthquake ~ Mw 7. Our mapping and previous mapping (Giunta et al. (2011) demonstrate that the elevations of marine terraces inner edges change along the strike the NE - SW oriented normal fault. This confirms active deformation on the Capo D'Orlando Fault, strongly suggesting that it should be added into the Database of Individual Seismogenic Sources (DISS, Basili et al., 2008). Giunta et al. (2011) suggested that uplift rates and hence faults lip-rates vary through time for this examples. We update the ages assigned to

Tectonism

NASA Image and Video Library

2011-10-24

This image from NASA 2001 Mars Odyssey spacecraft shows evidence of tectonic stresses that deform and fracture rocks and planetary surfaces. Right angles seen here are a good indication that the feature was formed by tectonic stresses.

A mechanism for tectonic deformation on Venus

NASA Technical Reports Server (NTRS)

Phillips, Roger J.

1986-01-01

In the absence of identifiable physiographic features directly associated with plate tectonics, alternate mechanisms are sought for the intense tectonic deformation observed in radar images of Venus. One possible mechanism is direct coupling into an elastic lithosphere of the stresses associated with convective flow in the interior. Spectral Green's function solutions have been obtained for stresses in an elastic lithosphere overlying a Newtonian interior with an exponential depth dependence of viscosity, and a specified surface-density distribution driving the flow. At long wavelengths and for a rigid elastic/fluid boundary condition, horizontal normal stresses in the elastic lid are controlled by the vertical shear stress gradient and are directly proportional to the depth of the density disturbance in the underlying fluid. The depth and strength of density anomalies in the Venusian interior inferred by analyses of long wavelength gravity data suggest that stresses in excess of 100 MPa would be generated in a 10 km thick elastic lid unless a low viscosity channel occurring beneath the lid or a positive viscosity gradient uncouples the flow stresses. The great apparent depth of compensation of topographic features argues against this, however, thus supporting the importance of the coupling mechanism. If there is no elastic lid, stresses will also be very high near the surface, providing also that the viscosity gradient is negative.

Active tectonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1986-01-01

This study is part of a series of Studies in Geophysics that have been undertaken for the Geophysics Research Forum by the Geophysics Study Committee. One purpose of each study is to provide assessments from the scientific community to aid policymakers in decisions on societal problems that involve geophysics. An important part of such assessments is an evaluation of the adequacy of current geophysical knowledge and the appropriateness of current research programs as a source of information required for those decisions. The study addresses our current scientific understanding of active tectonics --- particularly the patterns and rates of ongoing tectonicmore » processes. Many of these processes cannot be described reasonably using the limited instrumental or historical records; however, most can be described adequately for practical purposes using the geologic record of the past 500,000 years. A program of fundamental research focusing especially on Quaternary tectonic geology and geomorphology, paleoseismology, neotectonics, and geodesy is recommended to better understand ongoing, active tectonic processes. This volume contains 16 papers. Individual papers are indexed separately on the Energy Database.« less

Generating topography through tectonic deformation of ice lithospheres: Simulating the formation of Ganymede's grooves

NASA Astrophysics Data System (ADS)

Bland, M. T.; McKinnon, W. B.

2010-12-01

Ganymede’s iconic topography offers clues to both the satellite’s thermal evolution, and the mechanics of tectonic deformation on icy satellites. Much of Ganymede’s surface consists of bright, young terrain, with a characteristic morphology dubbed “groove terrain”. As reviewed in Pappalardo et al. (2004), in Jupiter - The Planet, Satellites, and Magnetosphere (CUP), grooved terrain consists of sets of quasi-parallel, periodically-spaced, ridges and troughs. Peak-to-trough groove amplitudes are ~500 m, with low topographic slopes (~5°). Groove spacing is strongly periodic within a single groove set, ranging from 3-17 km; shorter wavelength deformation is also apparent in high-resolution images. Grooved terrain likely formed via unstable extension of Ganymede’s ice lithosphere, which was deformed into periodically-spaced pinches and swells, and accommodated by tilt-block normal faulting. Analytical models of unstable extension support this formation mechanism [Dombard and McKinnon 2001, Icarus 154], but initial numerical models of extending ice lithospheres struggled to produce large-amplitude, groove-like deformation [Bland and Showman 2007, Icarus 189]. Here we present simulations that reproduce many of the characteristics of Ganymede’s grooves [Bland et al. 2010, Icarus in press]. By more realistically simulating the decrease in material strength after initial fault development, our model allows strain to become readily localized into discrete zones. Such strain localization leads to the formation of periodic structures with amplitudes of 200-500 m, and wavelengths of 3-20 km. The morphology of the deformation depends on both the lithospheric thermal gradient, and the rate at which material strength decreases with increasing plastic strain. Large-amplitude, graben-like structures form when material weakening occurs rapidly with increasing strain, while lower-amplitude, periodic structures form when the ice retains its strength. Thus, extension can

Deformation bands, early markers of tectonic activity in front of a fold-and-thrust belt: Example from the Tremp-Graus basin, southern Pyrenees, Spain

NASA Astrophysics Data System (ADS)

Robert, Romain; Robion, Philippe; Souloumiac, Pauline; David, Christian; Saillet, Elodie

2018-05-01

Strain localization in a porous calcarenite facies of the Aren formation in the Tremp basin was studied. This Maastrichtian syn-tectonic formation exposed in front of the Boixols thrust, in the Central South Pyrenean Zone, hosts bedding perpendicular deformation bands. These bands are organized in two major band sets, striking East-West and N-020 respectively. Both populations formed during early deformation stages linked to the growth of the fold and thrust. A magnetic fabric study (Anisotropy of Magnetic Susceptibility, AMS) was carried out to constrain the shortening direction responsible for the deformation bands development during the upper Cretaceous-Paleocene N-S contraction in the region, which allowed us to define populations of Pure Compaction Bands (PCB) and Shear Enhanced Compaction Bands (SECB) regarding their orientations compared to the shortening direction. Both sets are formed by cataclastic deformation, but more intense in the case of SECBs, which are also thinner than PCBs. The initial pore space is both mechanically reduced and chemically filled by several cementation phases. We propose a geomechanical model based on the regional context of layer parallel shortening, thrusting and strike-slip tectonics considering the burial history of the formation, in order to explain the development of both types of bands at remarkably shallow depths.

Active tectonics of the Binalud Mountains, a key puzzle segment to describe Quaternary deformations at the northeastern boundary of the Arabia-Eurasia collision

NASA Astrophysics Data System (ADS)

Shabanian, Esmaeil; Bellier, Olivier; Siame, Lionel L.; Abbassi, Mohammad R.; Leanni, Laetitia; Braucher, Régis; Farbod, Yassaman; Bourlès, Didier L.

2010-05-01

In northeast Iran, the Binalud Mountains accommodate part of active convergence between the Arabian and Eurasian plates. This fault-bounded mountain range has been considered a key region to describe Quaternary deformations at the northeastern boundary of the Arabia-Eurasia collision. But, the lack of knowledge on active faulting hampered evaluating the geological reliability of tectonic models describing the kinematics of deformation in northeast Iran. Morphotectonic investigations along both sides of the Binalud Mountains allowed us to characterize the structural and active faulting patterns along the Neyshabur and Mashhad fault systems on the southwest and northeast sides of the mountain range, respectively. We applied combined approaches of morphotectonic analyses based on satellite imageries (SPOT5 and Landsat ETM+), STRM and site-scale digital topographic data, and field surveys complemented with in situ-produced 10Be exposure dating to determine the kinematics and rate of active faulting. Three regional episodes of alluvial surface abandonments were dated at 5.3±1.1 kyr (Q1), 94±5 kyr (Q3), and 200±14 kyr (S3). The geomorphic reconstruction of both vertical and right-lateral fault offsets postdating these surface abandonment episodes yielded Quaternary fault slip rates on both sides of the Binalud Mountains. On the Neyshabur Fault System, thanks to geomorphic reconstructions of cumulative offsets recorded by Q3 fan surfaces, slip rates of 2.7±0.8 mm/yr and 2.4±0.2 mm/yr are estimated for right-lateral and reverse components of active faulting, respectively. Those indicate a total slip rate of 3.6±1.2 mm/yr for the late Quaternary deformation on the southwest flank of the Binalud Mountains. Reconstructing the cumulative right-lateral offset recorded by S3 surfaces, a middle-late Quaternary slip rate of 1.6±0.1 mm/yr is determined for the Mashhad Fault System. Altogether, our geomorphic observations reveal that, on both sides of the Binalud Mountains

Recent tectonic activity on Pluto driven by phase changes in the ice shell

NASA Astrophysics Data System (ADS)

Hammond, Noah P.; Barr, Amy C.; Parmentier, Edgar M.

2016-07-01

The New Horizons spacecraft has found evidence for geologic activity on the surface of Pluto, including extensional tectonic deformation of its water ice bedrock see Moore et al. (2016). One mechanism that could drive extensional tectonic activity is global surface expansion due to the partial freezing of an ocean. We use updated physical properties for Pluto and simulate its thermal evolution to understand the survival of a possible subsurface ocean. For thermal conductivities of rock less than 3 W m-1 K-1, an ocean forms and at least partially freezes, leading to recent extensional stresses in the ice shell. In scenarios where the ocean freezes and the ice shell is thicker than 260 km, ice II forms and causes global volume contraction. Since there is no evidence for recent compressional tectonic features, we argue that ice II has not formed and that Pluto's ocean has likely survived to present day.

Copernican tectonic activities in the northwestern Imbrium region of the Moon

NASA Astrophysics Data System (ADS)

Daket, Yuko; Yamaji, Atsushi; Sato, Katsushi

2015-04-01

Mare ridges and lobate scarps are the manifestations of horizontal compression in the shallow part of the Moon. Conventionally, tectonism within mascon basins has been thought to originate from mascon loading which is syndepositional tectonics (e.g., Solomon and Head, 1980). However, Ono et al. (2009) have pointed out that the subsurface tectonic structures beneath some mare ridges in Serenitatis appeared to be formed after the deposition of mare strata. Watters et al. (2010) also reported Copernican lobate scarps. Those young deformations cannot be explained by the mascon loading and are possibly ascribed to global cooling, orbital evolution and/or regional factors. Since mare ridges are topographically larger than lobate scarps, they might have large contribution to the recent contraction. In this study, we estimated until when the tectonic activities of mare ridges lasted in the northwestern Imbrium region. In order to infer the timing of the latest ages of tectonic activities, we used craters dislocated by the thrust faults that run along to the mare ridges in the study area. The ages of dislocated craters indicate the oldest estimate of the latest tectonic activity of the faults, because those craters must have existed during the tectonic activities. The ages of craters are inferred by the degradation levels classified by Trask (1971). We found ~450 dislocated craters in the study area. About 40 of them are smaller than 100 meter in diameter. Sub-hundred-meter-sized craters that still maintain their morphology sharp are classified into Copernican Period. Those small dislocated craters are interspersed all over the region, indicating that the most of the mare ridges in the study area were tectonically active in Copernican Period. In addition, we also found two sub-hundred-meter-sized craters dislocated by a graben at the west of Promontorium Laplace, indicating horizontal extension existed at Copernican Period. Consequently, tectonic activities in the study

Tectonic and hydrological controls on multiscale deformations in the Levant: numerical modeling and theoretical analysis

NASA Astrophysics Data System (ADS)

Belferman, Mariana; Katsman, Regina; Agnon, Amotz; Ben Avraham, Zvi

2016-04-01

Understanding the role of the dynamics of water bodies in triggering deformations in the upper crust and subsequently leading to earthquakes has been attracting considerable attention. We suggest that dynamic changes in the levels of the water bodies occupying tectonic depressions along the Dead Sea Transform (DST) cause significant variations in the shallow crustal stress field and affect local fault systems in a way that eventually leads to earthquakes. This mechanism and its spatial and temporal scales differ from those in tectonically-driven deformations. In this study we present a new thermo-mechanical model, constructed using the finite element method, and extended by including a fluid flow component in the upper crust. The latter is modeled on a basis of two-way poroelastic coupling with the momentum equation. This coupling is essential for capturing fluid flow evolution induced by dynamic water loading in the DST depressions and to resolve porosity changes. All the components of the model, namely elasticity, creep, plasticity, heat transfer, and fluid flow, have been extensively verified and presented in the study. The two-way coupling between localized plastic volumetric deformations and enhanced fluid flow is addressed, as well as the role of variability of the rheological and the hydrological parameters in inducing deformations in specific faulting environments. Correlations with historical and contemporary earthquakes in the region are discussed.

Using the salt tectonics as a proxy to reveal post-rift active crustal tectonics: The example of the Eastern Sardinian margin

NASA Astrophysics Data System (ADS)

Lymer, Gaël; Vendeville, Bruno; Gaullier, Virginie; Chanier, Frank; Gaillard, Morgane

2017-04-01

The Western Tyrrhenian Basin, Mediterranean Sea, is a fascinating basin in terms of interactions between crustal tectonics, salt tectonics and sedimentation. The METYSS (Messinian Event in the Tyrrhenian from Seismic Study) project is based on 2100 km of HR seismic data acquired in 2009 and 2011 along the Eastern Sardinian margin. The main aim is to study the Messinian Salinity Crisis (MSC) in the Western Tyrrhenian Basin, but we also investigate the thinning processes of the continental crust and the timing of crustal vertical motions across this complex domain. Our first results allowed us to map the MSC seismic markers and to better constrain the timing of the rifting, which ended before the MSC across the upper and middle parts of the margin. We also evidenced that crustal activity persisted long after the end of rifting. This has been particularly observed on the upper margin, where several normal faults and a surprising compressional structure were recently active. In this study we investigate the middle margin, the Cornaglia Terrace, where the Mobile Unit (MU, mobile Messinian salt) accumulated during the MSC and acts as a décollement. Our goal is to ascertain whether or not crustal tectonics existed after the pre-MSC rift. This is a challenge where the MU is thick, because potential basement deformations could be first accommodated by the MU and therefore would not find any expression in the supra-salt layers (Upper Unit, UU and Plio-Quaternary, PQ). However our investigations clearly reveal interactions between crustal and salt tectonics along the margin. We thus evidence gravity gliding of the salt and its brittle sedimentary cover along basement slopes generated by the post-MSC tilting of some basement blocks bounded by crustal normal faults, formerly due to the rifting. Another intriguing structure also got our interest. It corresponds to a wedge-shaped of MU located in a narrow N-S half graben bounded to the west by a major, east-verging, crustal

Influence of increasing convergence obliquity and shallow slab geometry onto tectonic deformation and seismogenic behavior along the Northern Lesser Antilles zone

NASA Astrophysics Data System (ADS)

Laurencin, M.; Graindorge, D.; Klingelhoefer, F.; Marcaillou, B.; Evain, M.

2018-06-01

In subduction zones, the 3D geometry of the plate interface is one of the key parameters that controls margin tectonic deformation, interplate coupling and seismogenic behavior. The North American plate subducts beneath the convex Northern Lesser Antilles margin. This convergent plate boundary, with a northward increasing convergence obliquity, turns into a sinistral strike-slip limit at the northwestern end of the system. This geodynamic context suggests a complex slab geometry, which has never been imaged before. Moreover, the seismic activity and particularly the number of events with thrust focal mechanism compatible with subduction earthquakes, increases northward from the Barbuda-Anguilla segment to the Anguilla-Virgin Islands segment. One of the major questions in this area is thus to analyze the influence of the increasing convergence obliquity and the slab geometry onto tectonic deformation and seismogenic behavior of the subduction zone. Based on wide-angle and multichannel reflection seismic data acquired during the Antithesis cruises (2013-2016), we decipher the deep structure of this subduction zone. Velocity models derived from wide-angle data acquired across the Anegada Passage are consistent with the presence of a crust of oceanic affinity thickened by hotspot magmatism and probably affected by the Upper Cretaceous-Eocene arc magmatism forming the 'Great Arc of the Caribbean'. The slab is shallower beneath the Anguilla-Virgin Islands margin segment than beneath the Anguilla-Barbuda segment which is likely to be directly related to the convex geometry of the upper plate. This shallower slab is located under the forearc where earthquakes and partitioning deformations increase locally. Thus, the shallowing slab might result in local greater interplate coupling and basal friction favoring seismic activity and tectonic partitioning beneath the Virgin Islands platform.

Post-magmatic tectonic deformation of the outer Izu-Bonin-Mariana forearc system: initial results of IODP Expedition 352

NASA Astrophysics Data System (ADS)

Kurz, Walter; Ferré, Eric C.; Robertson, Alastair; Avery, Aaron; Christeson, Gail L.; Morgan, Sally; Kutterorf, Steffen; Sager, William W.; Carvallo, Claire; Shervais, John; Party IODP Expedition 352, Scientific

2015-04-01

IODP Expedition 352 was designed to drill through the entire volcanic sequence of the Bonin forearc. Four sites were drilled, two on the outer fore arc and two on the upper trench slope. Site survey seismic data, combined with borehole data, indicate that tectonic deformation in the outer IBM fore arc is mainly post-magmatic. Post-magmatic extension resulted in the formation of asymmetric sedimentary basins such as, for example, the half-grabens at sites 352-U1439 and 352-U1442 located on the upper trench slope. Along their eastern margins these basins are bounded by west-dipping normal faults. Sedimentation was mainly syn-tectonic. The lowermost sequence of the sedimentary units was tilted eastward by ~20°. These tilted bedding planes were subsequently covered by sub-horizontally deposited sedimentary beds. Based on biostratigraphic constraints, the minimum age of the oldest sediments is ~ 35 Ma; the timing of the sedimentary unconformities lies between ~ 27 and 32 Ma. At sites 352-U1440 and 352-U1441, located on the outer forearc, post-magmatic deformation resulted mainly in strike-slip faults possibly bounding the sedimentary basins. The sedimentary units within these basins were not significantly affected by post-sedimentary tectonic tilting. Biostratigraphic ages indicate that the minimum age of the basement-cover contact lies between ~29.5 and 32 Ma. Overall, the post-magmatic tectonic structures observed during Expedition 352 reveal a multiphase tectonic evolution of the outer IBM fore arc. At sites 352-U1439 and 352-U1442, shear with dominant reverse to oblique reverse displacement was localized along distinct subhorizontal cataclastic shear zones as well as steeply dipping slickensides and shear fractures. These structures, forming within a contractional tectonic regime, were either re-activated as or cross-cut by normal-faults as well as strike-slip faults. Extension was also accommodated by steeply dipping to subvertical mineralized veins and

Morphotectonic analysis and GNSS observations for assessment of relative tectonic activity in Alaknanda basin of Garhwal Himalaya, India

NASA Astrophysics Data System (ADS)

Sharma, Gopal; Champati ray, P. K.; Mohanty, S.

2018-01-01

Alaknanda basin in the Garhwal Himalaya, India, is a tectonically active region owing to ongoing crustal deformation, erosion, and depositional processes active in the region. Active tectonics in this region have greatly affected the drainage system and geomorphic expression of topography and provide an ideal natural set up to investigate the influence of tectonic activity resulting from the India-Eurasia collision. We evaluated active tectonics by using high resolution digital elevation model (DEM) based on eight geomorphic indices (stream length gradient index, valley floor width-to-height ratio, hypsometric integral, drainage basin asymmetry, transverse topography symmetry factor, mountain front sinousity index, bifurcation ratio, and basin shape index) and seismicity in eight subbasins of Alaknanda basin. The integrated product, relative tectonic activity index (TAI) map, was classified into three classes such as: 'highly active' with values ranging up to 2.0; 'moderately active' with values ranging from 2.0 to 2.25; and 'less active' with values > 2.25. Further, the results were compared with relatively high crustal movement rate of 41.10 mm/y computed through high precession Global Navigation Satellite System (GNSS) based continuous operating reference station (CORS) data. Thus, we concluded that this new quantitative approach can be used for better characterization and assessment of active seismotectonic regions of the Himalaya and elsewhere.

Development of a New Analog Test System Capable of Modeling Tectonic Deformation Incorporating the Effects of Pore Fluid Pressure

NASA Astrophysics Data System (ADS)

Zhang, M.; Nakajima, H.; Takeda, M.; Aung, T. T.

2005-12-01

Understanding and predicting the tectonic deformation within geologic strata has been a very important research subject in many fields such as structural geology and petroleum geology. In recent years, such research has also become a fundamental necessity for the assessment of active fault migration, site selection for geological disposal of radioactive nuclear waste and exploration for methane hydrate. Although analog modeling techniques have played an important role in the elucidation of the tectonic deformation mechanisms, traditional approaches have typically used dry materials and ignored the effects of pore fluid pressure. In order for analog models to properly depict the tectonic deformation of the targeted, large-prototype system within a small laboratory-scale configuration, physical properties of the models, including geometry, force, and time, must be correctly scaled. Model materials representing brittle rock behavior require an internal friction identical to the prototype rock and virtually zero cohesion. Granular materials such as sand, glass beads, or steel beads of dry condition have been preferably used for this reason in addition to their availability and ease of handling. Modeling protocols for dry granular materials have been well established but such model tests cannot account for the pore fluid effects. Although the concept of effective stress has long been recognized and the role of pore-fluid pressure in tectonic deformation processes is evident, there have been few analog model studies that consider the effects of pore fluid movement. Some new applications require a thorough understanding of the coupled deformation and fluid flow processes within the strata. Taking the field of waste management as an example, deep geological disposal of radioactive waste has been thought to be an appropriate methodology for the safe isolation of the wastes from the human environment until the toxicity of the wastes decays to non-hazardous levels. For the

An intramontane pull-apart basin in tectonic escape deformation: Elbistan Basin, Eastern Taurides, Turkey

NASA Astrophysics Data System (ADS)

Yusufoğlu, H.

2013-04-01

The Elbistan Basin in the east-Central Anatolia is an intramontane structural depression in the interior part of the Anatolide-Tauride Platform. The Neogene fill in and around Elbistan Basin develops above the Upper Devonian to lower Tertiary basement and comprises two units separated by an angular unconformity: (1) intensely folded and faulted Miocene shallow marine to terrestrial and lacustrine sediments and (2) nearly flat-lying lignite-bearing lacustrine (lower unit) and fluvial (upper unit) deposits of Plio-Quaternary Ahmetçik Formation. The former is composed of Lower-Middle Miocene Salyan, Middle-upper Middle Miocene Gövdelidağ and Upper Miocene Karamağara formations whereas the latter one is the infill of the basin itself in the present configuration of the Elbistan Basin. The basin is bound by normal faults with a minor strike-slip component. It commenced as an intramontane pull-apart basin and developed as a natural response to Early Pliocene tectonic escape-related strike-slip faulting subsequent to post-collisional intracontinental compressional tectonics during which Miocene sediments were intensely deformed. The Early Pliocene time therefore marks a dramatic changeover in tectonic regime and is interpreted as the beginning of the ongoing last tectonic evolution and deformation style in the region unlike to previous views that it commenced before that time. Consequently, the Elbistan Basin is a unique structural depression that equates the extensional strike-slip regime in east-Central Anatolia throughout the context of the neotectonical framework of Turkey across progressive collision of Arabia with Eurasia. Its Pliocene and younger history differs from and contrasts with that of the surrounding pre-Pliocene basins such as Karamağara Basin, on which it has been structurally superimposed.

Active Tectonics Around Almaty and along the Zailisky Alatau Rangefront

NASA Astrophysics Data System (ADS)

Grützner, C.; Walker, R. T.; Abdrakhmatov, K. E.; Mukambaev, A.; Elliott, A. J.; Elliott, J. R.

2017-10-01

The Zailisky Alatau is a >250 km long mountain range in Southern Kazakhstan. Its northern rangefront around the major city of Almaty has more than 4 km topographic relief, yet in contrast to other large mountain fronts in the Tien Shan, little is known about its Late Quaternary tectonic activity despite several destructive earthquakes in the historical record. We analyze the tectonic geomorphology of the rangefront fault using field observations, differential GPS measurements of fault scarps, historical and recent satellite imagery, meter-scale topography derived from stereo satellite images, and decimeter-scale elevation models from unmanned aerial vehicle surveys. Fault scarps ranging in height from 2 m to >20 m in alluvial fans indicate that surface rupturing earthquakes occurred along the rangefront fault since the Last Glacial Maximum. Minimum estimated magnitudes for those earthquakes are M6.8-7. Radiocarbon dating results from charcoal layers in uplifted river terraces indicate a Holocene slip rate of 1.2-2.2 mm/a. We find additional evidence for active tectonic deformation all along the Almaty rangefront, basinward in the Kazakh platform, and in the interior of the Zailisky mountain range. Our data indicate that the seismic hazard faced by Almaty comes from a variety of sources, and we emphasize the problems related to urban growth into the loess-covered foothills and secondary earthquake effects. With our structural and geochronologic framework, we present a schematic evolution of the Almaty rangefront that may be applicable to similar settings of tectonic shortening in the mountain ranges of Central Asia.

Episodic Cenozoic volcanism and tectonism in the Andes of Peru

USGS Publications Warehouse

Noble, D.C.; McKee, E.H.; Farrar, E.; Petersen, U.

1974-01-01

Radiometric and geologic information indicate a complex history of Cenozoic volcanism and tectonism in the central Andes. K-Ar ages on silicic pyroclastic rocks demonstrate major volcanic activity in central and southern Peru, northern Chile, and adjacent areas during the Early and Middle Miocene, and provide additional evidence for volcanism during the Late Eocene. A provisional outline of tectonic and volcanic events in the Peruvian Andes during the Cenozoic includes: one or more pulses of igneous activity and intense deformation during the Paleocene and Eocene; a period of quiescence, lasting most of Oligocene time; reinception of tectonism and volcanism at the beginning of the Miocene; and a major pulse of deformation in the Middle Miocene accompanied and followed through the Pliocene by intense volcanism and plutonism. Reinception of igneous activity and tectonism at about the Oligocene-Miocene boundary, a feature recognized in other circum-Pacific regions, may reflect an increase in the rate of rotation of the Pacific plate relative to fixed or quasifixed mantle coordinates. Middle Miocene tectonism and latest Tertiary volcanism correlates with and probably is genetically related to the beginning of very rapid spreading at the East Pacific Rise. ?? 1974.

Tectonic Deformation Pattern along the Longmen Shan Fault Zone in Eastern Tibet: Insights from Focal Mechanisms of the Wenchuan and Lushan Earthquake Sequences, Southwestern China

NASA Astrophysics Data System (ADS)

Yi, G.; Vallage, A.; Klinger, Y.; Long, F.; Wang, S.

2017-12-01

760 ML≥3.5 aftershocks of the 2008 Wenchuan earthquake, the 2013 Lushan mainshock and its 87 ML≥3.5 aftershocks were selected to obtain focal mechanism solutions from CAP waveform inversion method (Zhu and Helmberger, 1996), along with strain rosette (Amelung and King, 1997) and Areal strain (As) (Vallage et al., 2014), we aimed to analyze the tectonic deformation pattern along the Longmen Shan (LMS) fault zone, southwestern China. The As values show that 93% compressional earthquakes for the Lushan sequence are of pure thrust for the southern segment of the LMS fault zone, while only 50% compressional and nearly 40% of strike-slip and oblique-thrust events for the Wenchuan sequence reflect the strike-slip component increase on the central-northern segment of the LMS fault zone, meaning many different faults responsible for the Wenchuan aftershock activity. The strain rosettes with purely NW-trending compressional white lobe for the entire 87 aftershocks and 4 different classes of magnitudes are very similar to that of the Lushan mainshock. We infer that the geological structures for the southern segment are of thrust faulting under NW compressional deformation. The strain rosettes exhibit self-similarity in terms of orientation and shape for all classes, reflecting that the deformation pattern of the southern segment is independent with earthquake size, and suggesting that each class is representative of the overall deformation for the southern segment. We obtained EW-oriented pure compressional strain rosette of the entire 760 aftershocks and NW-oriented white lobe with small NE-oriented black lobe of the Wenchuan mainshock, and this difference may reflect different tectonic deformation pattern during the co-seismic and post-seismic stages. The deformation segmentation along the Wenchuan coseismic surface rupture is also evidenced from the different orientation of strain rosettes, i.e., NW for the southern area, NE for the central and NNW for the northern

Tectonic models for Yucca Mountain, Nevada

USGS Publications Warehouse

O'Leary, Dennis W.

2006-01-01

Performance of a high-level nuclear waste repository at Yucca Mountain hinges partly on long-term structural stability of the mountain, its susceptibility to tectonic disruption that includes fault displacement, seismic ground motion, and igneous intrusion. Because of the uncertainty involved with long-term (10,000 yr minimum) prediction of tectonic events (e.g., earthquakes) and the incomplete understanding of the history of strain and its mechanisms in the Yucca Mountain region, a tectonic model is needed. A tectonic model should represent the structural assemblage of the mountain in its tectonic setting and account for that assemblage through a history of deformation in which all of the observed deformation features are linked in time and space. Four major types of tectonic models have been proposed for Yucca Mountain: a caldera model; simple shear (detachment fault) models; pure shear (planar fault) models; and lateral shear models. Most of the models seek to explain local features in the context of well-accepted regional deformation mechanisms. Evaluation of the models in light of site characterization shows that none of them completely accounts for all the known tectonic features of Yucca Mountain or is fully compatible with the deformation history. The Yucca Mountain project does not endorse a preferred tectonic model. However, most experts involved in the probabilistic volcanic hazards analysis and the probabilistic seismic hazards analysis preferred a planar fault type model. ?? 2007 Geological Society of America. All rights reserved.

From Plate Tectonic to Continental Dynamics

NASA Astrophysics Data System (ADS)

Molnar, P. H.

2017-12-01

By the early 1970s, the basics of plate tectonics were known. Although much understanding remained to be gained, as a topic of research, plate tectonics no longer defined the forefront of earth science. Not only had it become a foundation on which to build, but also the methods used to reveal it became tools to take in new directions. For me as a seismologist studying earthquakes and active processes, the deformation of continents offered an obvious topic to pursue. Obviously examining the deformation of continents and ignoring the widespread geologic evidence of both ongoing and finite deformation of crust would be stupid. I was blessed with the opportunity to learn from and collaborate with two of the best, Paul Tapponnier and Clark Burchfiel. Continental deformation differed from plate tectonics both because deformation was widespread but more importantly because crust shortens (extends) horizontally and thickens (thins), processes that can be ignored where plate tectonics - the relative motion of rigid plates - occurs. Where a plate boundary passes into a continent, not only must the forces that move plates do work against friction or other dissipative processes, but where high terrain is created, they must also do work against gravity, to create gravitational potential energy in high terrain. Peter Bird and Kenneth Piper and Philip England and Dan McKenzie showed that a two-dimensional thin viscous sheet with vertically averaged properties enabled both sources of resistance to be included without introducing excessive complexity and to be scaled by one dimensionless number, what the latter pair called the Argand number. Increasingly over the past thirty years, emphasis has shifted toward the role played by the mantle lithosphere, because of both its likely strength and its negative buoyancy, which makes it gravitationally unstable. Despite progress since realizing that rigid plates (the essence of plate tectonics) provides a poor description of continental

Plains Tectonics on Venus

NASA Technical Reports Server (NTRS)

Banerdt, W. B.; McGill, G. E.; Zuber, M. T.

1996-01-01

Tectonic deformation in the plains of Venus is pervasive, with virtually every area of the planet showing evidence for faulting or fracturing. This deformation can be classified into three general categories, defined by the intensity and areal extent of the surface deformation: distributed deformation, concentrated deformation, and local fracture patterns.

The Interior Lowland Plains Unit of Mars: Evidence for a Possible Mud Ocean and Induced Tectonic Deformation

NASA Technical Reports Server (NTRS)

Tanaka, K. L.; Banerdt, W. B.

2000-01-01

We conclude from MOC and MOLA data that the northern plains of Mars were infilled by a sediment-rich, mud ocean. Evidence for subsidence within the north polar basin and reversed channel-floor gradients are consistent with tectonic deformation due to the sediment load.

Block Tectonic Motion on Venus

NASA Astrophysics Data System (ADS)

Byrne, P. K.; Ghail, R.; Sengor, A. M. C.; Klimczak, C.; Solomon, S. C.

2017-12-01

Despite close similarities in mass and bulk composition to Earth, Venus apparently shows no evidence for Earth-like plate tectonics, except perhaps for limited plume-induced subduction. We use Magellan radar data to survey numerous examples of low-lying areas infilled with plains lavas and delimited by networks of narrow belts of substantial tectonic deformation; such sites include those at Lavinia and Llorona Planitiæ and to the north of Helen Planitia. This deformation is locally extensional or shortening in style but very often also includes structures that denote substantial lateral motion. Cross-cutting relations suggest that this motion occurred both before and after the lavas were emplaced. Together, these observations imply that many of the belt-bounded areas have acted as relatively rigid blocks that experienced considerable horizontal movement relative to each other, in a manner similar to blocks that constitute parts of the Terran continental lithosphere. On Earth, continental deformation is enabled by the low strength of the lower crust and/or upper mantle. On Venus, the shallow brittle-ductile transition (BDT), a result of the planet's elevated surface temperature, likely acts in a similar way to decouple the upper and lower crust. Subcrustal lid rejuvenation, a recently proposed mechanism for renewal of the mantle portion of Venus' stagnant lithospheric lid through thinning and recycling, could drive the horizontal movement of these rigid blocks. It may be, then, that the blocks move as continental blocks do on Earth, with mantle motion transferred to the surface and manifest as narrow zones of tectonic deformation akin to, for example, the Tian Shan and Altin Tagh ranges that bound the Tarim Basin in northwestern China. The shallow BDT on Venus precludes the blocks from subducting, and so their fate is to shorten, lengthen, or retain their geometry at the expense of adjacent blocks. We suggest that this behavior is analogous to plate-tectonic

Crustal structure and tectonic deformation of the southern Ecuadorian margin

NASA Astrophysics Data System (ADS)

Calahorrano, Alcinoe; Collot, Jean-Yves; Sage, Françoise; Ranero, César R.

2010-05-01

Multichannel seismic lines acquired during the SISTEUR cruise (2000) provide new constraints on the structure and deformation of the subduction zone at the southern Ecuadorian margin, from the deformation front to the continental shelf of the Gulf of Guayaquil. The pre-stack depth migrated images allows to characterise the main structures of the downgoing and overriding plates and to map the margin stratigraphy in order to propose a chronology of the deformation, by means of integrating commercial well data and industry seismic lines located in the gulf area. The 100-km-long seismic lines show the oceanic Nazca plate underthrusting the South American plate, as well as the subduction channel and inter-plate contact from the deformation front to about 90 km landward and ~20 km depth. Based on seismic structure we identify four upper-plate units, consisting of basement and overlaying sedimentary sequences A, B and C. The sedimentary cover varies along the margin, being few hundreds of meters thick in the lower and middle slope, and ~2-3 km thick in the upper slope. Exceptionally, a ~10-km -thick basin, here named Banco Peru basin, is located on the upper slope at the southernmost part of the gulf. This basin seems to be the first evidence of the Gulf of Guayaquil opening resulting from the NE escaping of the North Andean Block. Below the continental shelf, thick sedimentary basins of ~6 to 8 km occupy most of the gulf area. Tectonic deformation across most of the upper-plate is dominated by extensional regime, locally disturbed by diapirism. Compression evidences are restricted to the deformation front and surrounding areas. Well data calibrating the seismic profiles indicate that an important portion of the total thickness of the sedimentary coverage of the overriding plate are Miocene or older. The data indicate the extensional deformation resulting from the NE motion of the North Andean Block and the opening of the Gulf of Guayaquil, evolves progressively in age

Glacier Ice Mass Fluctuations and Fault Instability in Tectonically Active Southern Alaska

NASA Technical Reports Server (NTRS)

SauberRosenberg, Jeanne M.; Molnia, Bruce F.

2003-01-01

Across southern Alaska the northwest directed subduction of the Pacific plate is accompanied by accretion of the Yakutat terrane to continental Alaska. This has led to high tectonic strain rates and dramatic topographic relief of more than 5000 meters within 15 km of the Gulf of Alaska coast. The glaciers of this area are extensive and include large glaciers undergoing wastage (glacier retreat and thinning) and surges. The large glacier ice mass changes perturb the tectonic rate of deformation at a variety of temporal and spatial scales. We estimated surface displacements and stresses associated with ice mass fluctuations and tectonic loading by examining GPS geodetic observations and numerical model predictions. Although the glacial fluctuations perturb the tectonic stress field, especially at shallow depths, the largest contribution to ongoing crustal deformation is horizontal tectonic strain due to plate convergence. Tectonic forces are thus the primary force responsible for major earthquakes. However, for geodetic sites located < 10-20 km from major ice mass fluctuations, the changes of the solid Earth due to ice loading and unloading are an important aspect of interpreting geodetic results. The ice changes associated with Bering Glacier s most recent surge cycle are large enough to cause discernible surface displacements. Additionally, ice mass fluctuations associated with the surge cycle can modify the short-term seismicity rates in a local region. For the thrust faulting environment of the study region a large decrease in ice load may cause an increase in seismic rate in a region close to failure whereas ice loading may inhibit thrust faulting.

Active deformation processes of the Northern Caucasus deduced from the GPS observations

NASA Astrophysics Data System (ADS)

Milyukov, Vadim; Mironov, Alexey; Rogozhin, Eugeny; Steblov, Grigory; Gabsatarov, Yury

2015-04-01

The Northern Caucasus, as a part of the Alpine-Himalayan mobile belt, is a zone of complex tectonics associated with the interaction of the two major tectonic plates, Arabian and Eurasian. The first GPS study of the contemporary geodynamics of the Caucasus mountain system were launched in the early 1990s in the framework of the Russia-US joint project. Since 2005 observations of the modern tectonic motion of the Northern Caucasus are carried out using the continuous GPS network. This network encompasses the territory of three Northern Caucasian Republics of the Russian Federation: Karachay-Cherkessia, Kabardino-Balkaria, and North Ossetia. In the Ossetian part of the Northern Caucasus the network of GPS survey-mode sites has been deployed as well. The GPS velocities confirm weak general compression of the Northern Caucasus with at the rate of about 1-2 mm/year. This horizontal motion at the boundary of the Northern Caucasus with respect to the Eurasian plate causes the higher seismic and tectonic activity of this transition zone. This result confirms that the source of deformation of the Northern Caucasus is the sub-meridional drift of the Arabian plate towards the adjacent boundary of the Eastern European part of the Eurasian lithospheric plate. The concept of such convergence implies that the Caucasian segment of the Alpine-Himalayan mobile belt is under compression, the layers of sedimentary and volcanic rocks are folded, the basement blocks are subject to shifts in various directions, and the upper crust layers are ruptured by reverse faults and thrusts. Weak deviation of observed velocities from the pattern corresponding to homogeneous compression can also be revealed, and numerical modeling of deformations of major regional tectonic structures, such as the Main Caucasus Ridge, can explain this. The deformation tensor deduced from the velocity field also exhibits the sub-meridional direction of the major compressional axes which coincides with the direction of

The effects of tectonic deformation and sediment allocation on shelf habitats and megabenthic distribution and diversity in southern California

NASA Astrophysics Data System (ADS)

Switzer, Ryan D.; Parnell, P. Ed; Leichter, James L.; Driscoll, Neal W.

2016-02-01

Landscape and seascape structures are typically complex and manifest as patch mosaics within characteristic biomes, bordering one another in gradual or abrupt ecotones. The underlying patch structure in coastal shelf ecosystems is driven by the interaction of tectonic, sedimentary, and sea level dynamic processes. Animals and plants occupy and interact within these mosaics. Terrestrial landscape ecological studies have shown that patch structure is important for ecological processes such as foraging, connectivity, predation, and species dynamics. The importance of patch structure for marine systems is less clear because far fewer pattern-process studies have been conducted in these systems. For many coastal shelf systems, there is a paucity of information on how species occupy shelf seascapes, particularly for seascapes imbued with complex patch structure and ecotones that are common globally due to tectonic activity. Here, we present the results of a study conducted along a myriameter-scale gradient of bottom and sub-bottom geological forcing altered by tectonic deformation, sea level transgression and sediment allocation. The resulting seascape is dominated by unconsolidated sediments throughout, but also exhibits increasing density and size of outcropping patches along a habitat patch gradient forced by the erosion of a sea level transgressive surface that has been deformed and tilted by tectonic forcing. A combination of sub-bottom profiling, multibeam bathymetry, and ROV surveys of the habitats and the demersal megafauna occupying the habitats indicate (1) significant beta diversity along this gradient, (2) biological diversity does not scale with habitat diversity, and (3) species occupy the patches disproportionately (non-linearly) with regard to the proportional availability of their preferred habitats. These results indicate that shelf habitat patch structure modulates species specific processes and interactions with other species. Further studies are

A 150-ka-long record for the volcano-tectonic deformation of Central Anatolian Volcanic Province

NASA Astrophysics Data System (ADS)

Karabacak, Volkan; Tonguç Uysal, I.; Ünal-İmer, Ezgi; Mutlu, Halim; Zhao, Jian-xin

2017-04-01

The Anatolian Block represents one of the most outstanding examples of intra-plate deformation related to continental collision. Deformation related to the convergence of the Afro-Arabian continent toward north gives rise to widespread and intense arc volcanism in the Central Anatolia. All the usual studies on dating the volcano-tectonic deformation of the region are performed entirely on volcanic events of the geological record resulted in eruptions. However, without volcanic eruption, magma migration and related fluid pressurization also generate crustal deformation. In the current study has been funded by the Scientific and Technological Research Council of Turkey with the project no. 115Y497, we focused on fracture systems and their carbonate veins around the Ihlara Valley (Cappadocia) surrounded by well-known volcanic centers with latest activities of the southern Central Anatolian Volcanic Province. We dated 37 samples using the Uranium-series technique and analyzed their isotope systematics from fissure veins, which are thought to be controlled by the young volcanism in the region. Our detailed fracture analyses in the field show that there is a regional dilatation as a result of a NW-SE striking extension which is consistent with the results of recent GPS studies. The Uranium-series results indicate that fracture development and associated carbonate vein deposition occurred in the last 150 ka. Carbon and oxygen isotope systematics have almost remained unchanged in the studied time interval. Although veins in the region were precipitated from fluids primarily of meteoric origin, fluids originating from water-rock interaction also contribute for the deposition of carbonate veins. The age distribution indicates that the crustal deformation intensified during 7 different period at about 4.7, 34, 44, 52, 83, 91, 149 ka BP. Four of these periods (4.7, 34, 91, 149 ka BP) correspond to the volcanic activities suggested in the previous studies. The three crustal

Plains tectonism on Venus: The deformation belts of Lavinia Planitia

NASA Technical Reports Server (NTRS)

Squyres, Steven W.; Jankowski, David G.; Simons, Mark; Solomon, Sean C.; Hager, Bradford H.; Mcgill, George E.

1993-01-01

High-resolution radar images from the Magellan spacecraft have revealed the first details of the morphology of the Lavinia Planitia region of Venus. A number of geologic units can be distinguished, including volcanic plains units with a range of ages. Transecting these plains over much of the Lavinia region are two types of generally orthogonal features that we interpret to be compressional wrinkle ridges and extensional grooves. The dominant tectonic features of Lavinia are broad elevated belts of intense deformation that transect the plains with complex geometry. They are many tens to a few hundred kilometers wide, as much as 1000 km long, and elevated hundreds of meters above the surrounding plains. Two classes of deformation belts are seen in the Lavinia region. 'Ridge belts' are composed of parallel ridges, each a few hundred meters in elevation, that we interpret to be folds. Typical fold spacings are 5-10 km. 'Fracture belts' are dominated instead by intense faulting, with faults in some instances paired to form narrow grabens. There is also some evidence for modest amounts of horizontal shear distributed across both ridge and fracture belts. Crosscutting relationships among the belts show there to be a range in belt ages. In western Lavinia, in particular, many ridge and fracture belts appear to bear a relationship to the much smaller wrinkle ridges and grooves on the surrounding plains: ridge morphology tends to dominate belts that lie more nearly parallel to local plains wrinkle ridges, and fracture morphology tends to dominate belts that lie more nearly parallel to local plains grooves. We use simple models to explore the formation of ridge and fracture belts. We show that convective motions in the mantle can couple to the crust to cause horizontal stresses of a magnitude sufficient to induce the formation of deformation belts like those observed in Lavinia. We also use the small-scale wavelengths of deformation observed within individual ridge belts to

Neotectonic activity and parameters of seismotectonic deformations of seismic belts in Northeast Asia

NASA Astrophysics Data System (ADS)

Imaeva, Lyudmila; Gusev, Georgy; Imaev, Valerii; Mel'nikova, Valentina

2017-10-01

The Arctic-Asian and Okhotsk-Chukotka seismic belts bordering the Kolyma-Chukotka crustal plate are the subject of our study aimed at reconstructing the stress-strain state of the crust and defining the types of seismotectonic deformation (STD) in the region. Based on the degrees of activity of geodynamic processes, the regional principles for ranking neotectonic structures were constrained, and the corresponding classes of the discussed neotectonic structures were substantiated. We analyzed the structural tectonic positions of the modern structures, their deep structure parameters, and the systems of active faults in the Laptev, Kharaulakh, Koryak, and Chukotka segments and Chersky seismotectonic zone, as well as the tectonic stress fields revealed by tectonophysical analysis of the Late Cenozoic faults and folds. From the earthquake focal mechanisms, the average seismotectonic strain tensors were estimated. Using the geological, geostructural, geophysical and GPS data, and corresponding average tensors, the directions of the principal stress axes were determined. A regularity in the changes of tectonic settings in the Northeast Arctic was revealed.

Active tectonics around the Yakutat indentor: New geomorphological constraints on the eastern Denali, Totschunda and Duke River Faults

NASA Astrophysics Data System (ADS)

Marechal, Anaïs; Ritz, Jean-François; Ferry, Matthieu; Mazzotti, Stephane; Blard, Pierre-Henri; Braucher, Régis; Saint-Carlier, Dimitri

2018-01-01

The Yakutat collision in SE Alaska - SW Yukon is an outstanding example of indentor tectonics. The impinging Yakutat block strongly controls the pattern of deformation inland. However, the relationship between this collision system and inherited tectonic structures such as the Denali, Totschunda, and Duke River Faults remains debated. A detailed geomorphological analysis, based on high-resolution imagery, digital elevation models, field observations, and cosmogenic nuclide dating, allow us to estimate new slip rates along these active structures. Our results show a vertical motion of 0.9 ± 0.3 mm/yr along the whole eastern Denali Fault, while the dextral component of the fault tapers to less than 1 mm/yr ∼80 km south of the Denali-Totschunda junction. In contrast, the Totschunda Fault accommodates 14.6 ± 2.7 mm/yr of right-lateral strike-slip along its central section ∼100 km south of the junction. Further south, preliminary observations suggest a slip rate comprised between 3.5 and 6.5 mm/yr along the westernmost part of the Duke River thrust fault. Our results highlight the complex partitioning of deformation inland of the Yakutat collision, where the role and slip rate of the main faults vary significantly over distances of ∼100 km or less. We propose a schematic model of present-day tectonics that suggests ongoing partitioning and reorganization of deformation between major inherited structures, relay zones, and regions of distributed deformation, in response to the radial stress and strain pattern around the Yakutat collision eastern syntaxis.

Glacio-Seismotectonics: Ice Sheets, Crustal Deformation and Seismicity

NASA Technical Reports Server (NTRS)

Sauber, Jeanne; Stewart, Iain S.; Rose, James

2000-01-01

The last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity. This growth has been driven largely by the emergence of postglacial rebound models (PGM) constrained by new field observations that incorporate increasingly realistic rheological, mechanical, and glacial parameters. In this paper, we highlight some of these recent field-based investigations and new PGMs, and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation. The emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern Canada and Fennoscandia. However, many of these models neglect important parameters, such as topography, lateral variations in lithospheric strength and tectonic strain built up during glaciation. In glaciated mountainous terrains, glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism. Such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields.

Fostering Inquiry and Scientific Investigation in Students by Using GPS Data to Explore Plate Tectonics and Volcanic Deformation

NASA Astrophysics Data System (ADS)

Olds, S. E.; Eriksson, S.

2007-12-01

The Education and Outreach program at UNAVCO has developed free instructional materials using authentic high-precision GPS data for secondary education and undergraduate students in Earth science courses. Using inquiry-based, data-rich activities, students investigate crustal deformation and plate motion using GPS data and learn how these measurements are important to scientific discovery and understanding natural hazards and the current state of prediction. Because this deformation is expressed on Earth's surface over familiar time scales and on easily visualized orders of magnitude, GPS data represent an effective method for illustrating the geomorphic effects of plate tectonics and, in essence, allow students to 'see' plates move and volcanoes deform. The activities foster student skills to critically assess different forms of data, to visualize abstract concepts, and to evaluate multiple lines of evidence to analyze scientific problems. The activities are scaffolded to begin with basic concepts about GPS data and analyzing simple plate motion and move towards data analyses for more complex motion and crustal deformation. As part of assessment, students can apply new knowledge to explore other geographic regions independently. Learning activities currently include exploring motion along the San Andreas Fault, monitoring volcano deformation and ground movement at the Yellowstone Caldera, and analyzing ground motion along the subduction zone in the Cascadia region. To support educators and their students in their investigations, UNAVCO has developed the Data for Educators portal; http://www.unavco.org/edu_outreach/data.html. This portal provides a Google-map displaying the locations of GPS stations, web links to numerical GPS data that illustrate specific Earth processes, and educational activities that incorporate this data. The GPS data is freely available in a format compatible with standard spreadsheet and graphing programs as well as visualization and

On the distinction of tectonic and nontectonic faulting in palaeoseismological research: a case study from the southern Marmara region of Turkey

NASA Astrophysics Data System (ADS)

Özaksoy, Volkan

2017-12-01

This study reports on spectacular deformation structures, including arrays of striated thrusts, discovered by excavation work in Holocene deposits in vicinity of a major neotectonic strike-slip fault in one of the tectonically most active regions of Turkey. The deformation structures were initially considered an evidence of sub-recent tectonic activity, but their detailed multidisciplinary study surprisingly revealed that the deformation of the clay-rich soil and its strongly weathered Jurassic substrate was of nontectonic origin, caused by argilliturbation. This phenomenon of vertisol self-deformation is well-known to pedologists, but may easily be mistaken for tectonic deformation by geologists less familiar with pedogenic processes. The possibility of argilliturbation thus needs to be taken into consideration in palaeoseismological field research wherever the deformed substrate consists of clay-rich muddy deposits. The paper reviews a range of specific diagnostic features that can serve as field criteria for the recognition of nontectonic deformation structures induced by argilliturbation in mud-dominated geological settings.

Evidences of Pleistocene tectonic deformations along the SE border of the Upper Rhine Graben (Freiburg area, Germany)

NASA Astrophysics Data System (ADS)

Brüstle, A.; Nivière, B.; Bertrand, G.; Gourry, J. C.; Carretier, S.; Fracassi, U.; Winter, T.

2003-04-01

The Upper Rhine Graben (URG) is a NNE-trending continental rift that was mostly active from Upper Eocene to Lower Miocene. However, the relatively well-preserved topography of its shoulders, at the scale of the whole basin, suggests a Pleistocene reactivation of its borders. We evaluate here such a possibility along its SE border, in the vincinity of Freiburg (Germany). Despite a continuous but diffuse seismic activity, evidences of near-surface deformations are not yet described. We coupled at the regional and local scales a multi-disciplinary approach, including morphological and geological analyses, to identify the markers of an assumed Pleistocene deformation. The imagery analysis reveals that the Oligocene structural pattern is yet well-marked in the topography by continuous escarpments, few tenth of kilometers long and from 20--30 to 300--500 m high. The correlation of boreholes allowed us to build isohypse and isopach maps of the Quaternary deposits and to propose a river system evolution scenario for the Quaternary. More interesting are the local depocenters located above the hanging wall of the faults and suggesting a Pleistocene tectonic reactivation. Thus, a minimum Pleistocene vertical offset of about 30 m can be illustrated above the main border fault. We then focused on the western Rhine river fault where very young deposits are suspected to have recorded a wechselian deformation. The morphological aspect of the scarp (location above the structural fault, linearity and continuity of the scarp, topographic tilting and presence of hanging valleys...), borehole data and electric tomography survey realized across the scarplet, located at toe of the main scarp, testify of a possible deformation. In particular, a ˜15 m vertical offset of the Wechselian deposits is illustrated in two localities, along the fault, where trenching will be performed in a near future to validate the ages of deformed deposits and obtain information on the strain scenario.

Late Pliocene-Quaternary evolution of outermost hinterland basins of the Northern Apennines (Italy), and their relevance to active tectonics

NASA Astrophysics Data System (ADS)

Sani, Federico; Bonini, Marco; Piccardi, Luigi; Vannucci, Gianfranco; Delle Donne, Dario; Benvenuti, Marco; Moratti, Giovanna; Corti, Giacomo; Montanari, Domenico; Sedda, Lorenzo; Tanini, Chiara

2009-10-01

We examine the tectonic evolution and structural characteristics of the Quaternary intermontane Mugello, Casentino, and Sansepolcro basins, in the Northern Apennines fold-and-thrust belt. These basins have been classically interpreted to have developed under an extensional regime, and to mark the extension-compression transition. The results of our study have instead allowed framing the formation of these basins into a compressive setting tied to the activity of backthrust faults at their northeastern margin. Syndepositional activity of these structures is manifested by consistent architecture of sediments and outcrop-scale deformation. After this phase, the Mugello and Sansepolcro basins experienced a phase of normal faulting extending from the middle Pleistocene until Present. Basin evolution can be thus basically framed into a two-phase history, with extensional tectonics superposed onto compressional structures. Analysis of morphologic features has revealed the occurrence of fresh fault scarps and interaction of faulting with drainage systems, which have been interpreted as evidence for potential ongoing activity of normal faults. Extensional tectonics is also manifested by recent seismicity, and likely caused the strong historical earthquakes affecting the Mugello and Sansepolcro basins. Qualitative comparison of surface information with depth-converted seismic data suggests the basins to represent discrete subsiding areas within the seismic belt extending along the axial zone of the Apennines. The inferred chronology of deformation and the timing of activity of normal faults have an obvious impact on the elaboration of seismic hazard models.

Influence of Tectonics on the Channel Pattern of Alaknanda River in Srinagar Valley (Garhwal Himalaya)

NASA Astrophysics Data System (ADS)

Datt, Devi

2017-04-01

This paper describes the results of a continuing investigation of tectonic influence on channel pattern and morphology of Alaknanda River in Lesser Garhwal Himalaya, Uttarakhand, India. Extensive field investigations using conventional methods supported by topographical sheets and remote sensing data (LISS IV), were undertaken.The results are classified into three sections :- tectonics, channel pattern and impact of tectonics on channel pattern. The channel length is divided into 8 meanders sets of 3 segments from Supana to Kirtinagar. Thereafter, a litho-tectonic map of the Srinagar valley was prepared. The style of active tectonics on deformation and characterization of fluvial landscape was investigated on typical strike-slip transverse faults near the zone of North Almora Thrust (NAT). NAT is a major tectonic unit of the Lesser Himalaya which passes through the northern margin from NW to SE direction.. The structural and lithological controls on the Alaknanda River system in Srinagar valley are reflected on distinct drainage patterns, abrupt change in flow direction, incised meandering, offset river channels, straight river lines, palaeo-channels, multi levels of terraces, knick points and pools in longitudinal profile. The results of the study show that the sinuosity index of the river is 1.35. Transverse faulting is very common along the NAT. An earlier generation of linear tectonic features were displaced by the latter phase of deformation. Significant deviations were observed in river channel at deformation junctions. Moreover, all 8 sets of meanders are strongly influenced by tectonic features. The meandering course is, thereby, correlated with tectonic features. It is shown that the river channel is strongly influenced by the tectonic features in the study area. Key Words: Tectonic, Meander, Channel pattern, deformation, Knick point.

Areas of Unsolved Problems in Caribbean Active Tectonics

NASA Astrophysics Data System (ADS)

Mann, P.

2015-12-01

I review some unsolved problems in Caribbean active tectonics. At the regional and plate scale: 1) confirm the existence of intraplate deformation zones of the central Caribbean plate that are within the margin of error of ongoing GPS measurements; 2) carry out field studies to evaluate block models versus models for distributed fault shear on the densely populated islands of Jamaica, Hispaniola, Puerto Rico, and the Virgin Islands; 3) carry out paleoseismological research of key plate boundary faults that may have accumulated large strains but have not been previously studied in detail; 4) determine the age of onset and far-field effects of the Cocos ridge and the Central America forearc sliver; 4) investigate the origin and earthquake-potential of obliquely-sheared rift basins along the northern coast of Venezuela; 5) determine the age of onset and regional active, tectonic effects of the Panama-South America collision including the continued activation of the Maracaibo block; and 6) validate longterm rates on active subduction zones with improving, tomographic maps of subducted slabs. At the individual fault scale: 1) determine the mode of termination of large and active strike -slip faults and application of the STEP model (Septentrional, Polochic, El Pilar, Bocono, Santa Marta-Bucaramanaga); 2) improve the understanding of the earthquake potential on the Enriquillo-Plantain Garden fault zone given "off-fault" events such as the 2010 Haiti earthquake; how widespread is this behavior?; and 3) estimate size of future tsunamis from studies of historic or prehistoric slump scars and mass transport deposits; what potential runups can be predicted from this information?; and 4) devise ways to keep rapidly growing, circum-Caribbean urban populations better informed and safer in the face of inevitable and future, large earthquakes.

The revised tectonic history of Tharsis

NASA Astrophysics Data System (ADS)

Bouley, Sylvain; Baratoux, David; Paulien, Nicolas; Missenard, Yves; Saint-Bézar, Bertrand

2018-04-01

Constraining the timing of the emplacement of the volcano-tectonic province of Tharsis is critical to understanding the evolution of mantle, surface environment and climate of Mars. The growth of Tharsis had exerted stresses on the lithosphere, which were responsible for tectonic deformation, previously mapped as radial or concentric faults. Insights into the emplacement history of Tharsis may be gained from an analysis of the characteristics and ages of these tectonic features. The number, total length, linear density of extensional or compressional faults in the Tharsis region and deformation rates are reported for each of the following 6 stages: Early and Middle Noachian (stage 1); Late Noachian (stage 2); Early Hesperian (stage 3); Late Hesperian (stage 4), Early Amazonian (stage 5) and Middle Amazonian to Late Amazonian (stage 6). 8571 Tharsis-related tectonic features (radial or concentric to the center of Tharsis) were assigned to one of these periods of time based on their relationship with stratigraphic units defined in the most recent geological map. Intense faulting at Tempe Terra, Claritas and Coracis Fossae and Thaumasia Planum confirms that tectonic deformation started during the Noachian. However, we report a peak in both compressive and extensive rates of deformation during the Early Hesperian whereas the quantitative indicators for compressional and extensional tectonics vary within less than one order of magnitude from the Late Noachian to the Late Hesperian. These observations indicate a protracted growth of Tharsis during the first quarter of Mars evolution and declining from 3 Gyrs ago.

Study of cataclastic deformation in compressive tectonic regime of a sandstone from south central Pyrenees, Spain: Timing of deformation bands occurrence during burial history and comparison with geomechanical models.

NASA Astrophysics Data System (ADS)

Robert, Romain; Robion, Philippe; David, Christian; Souloumiac, Pauline; Saillet, Elodie

2017-04-01

In high porosity sandstone lithologies, deformation bands (DBs) are characterized by changes in micro-structural characteristics inducing a localized change in the petrophysical properties of the rock. These DBs, which are generally tabular structures from millimeters to few centimeters thick, can be used at the field scale to decipher extensional or compactional tectonic regime. However, numerous parameters in addition to the tectonic regime may affect development of DBs, and particularly the evolution of porosity during burial history. The aim of this work is to understand the relationship between the DBs occurrence in tectonic shortening regime and the timing of grain cementation that occurs during burial for an analogue to siliciclastic reservoir. For that purpose, we have focused our analysis on the Aren syn-tectonic sandstone formation, maastrichtian in age, localized on the front of the Boixols thrust, on the southern side of the Sant Corneli anticline, in the south central Pyrenees (Spain). The outcrops are localized in the Tremp-Graus basin, all along a 30 km East-West trend where 10 different sites, in which deformation bands are observable, have been investigated and sampled. The structural geometry of the basin is constrained with 3 serial N-S oriented cross sections showing an increase of the shortening from West to East. Our field work strategy was to, 1) measure the orientation of the DBs in each site, 2) take cores both within the DBs and the host rock to conduct systematic thin section investigations, and 3) take oriented cores in order to study the magnetic fabric giving informations on the internal deformation linked to a set of deformation band and regional N-S shortening. Field data show a minimum of two sets of DBs on each site with variation of orientations and densities. These DBs are perpendicular to the strata which prove their early occurrence, recording the initial stages of local deformation and evolution of the Boixols fold and thrust

Venus tectonics - An overview of Magellan observations

NASA Technical Reports Server (NTRS)

Solomon, Sean C.; Smrekar, Suzanne E.; Bindschadler, Duane L.; Grimm, Robert E.; Kaula, William M.; Mcgill, George E.; Phillips, Roger J.; Saunders, R. S.; Schubert, Gerald; Squyres, Steven W.

1992-01-01

Magellan observations of the tectonic characteristics of highland regions on Venus are discussed with reference to competing theories for highland formation and evolution. Complex rigid terrain, or tessera, and the extent to which these elevated blocks of intensely deformed crust may be genetically related to highlands are then considered. Further, the tectonics of plains and lowland regions are examined, including deformation belts and coronae, and possible relations between such features and mantle dynamics. Implications of these observations for the global tectonics of Venus are discussed.

Glacial reorganization of topography in a tectonically active mountain range

NASA Astrophysics Data System (ADS)

Adams, Byron; Ehlers, Todd

2016-04-01

Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns, and not tectonic rock uplift rates. Alpine glaciers drastically altered the relief structure of the Olympic Mountains. The details of these relief changes are recorded in channel profiles as overdeepenings, reduced slopes, and associated knickpoints. We find the position of these relief changes within the orogen is dependent on the position of the Pleistocene ELA. While alpine glaciers overdeepened valleys in regions near the Pleistocene ELA (which has a tendency to increase relief), headward erosion of west and north flowing glacier systems captured significant area from opposing systems and caused drainage divide lowering. This divide lowering reduced relief throughout the range. We demonstrate similar topographic effects recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on

Lasting mantle scars lead to perennial plate tectonics.

PubMed

Heron, Philip J; Pysklywec, Russell N; Stephenson, Randell

2016-06-10

Mid-ocean ridges, transform faults, subduction and continental collisions form the conventional theory of plate tectonics to explain non-rigid behaviour at plate boundaries. However, the theory does not explain directly the processes involved in intraplate deformation and seismicity. Recently, damage structures in the lithosphere have been linked to the origin of plate tectonics. Despite seismological imaging suggesting that inherited mantle lithosphere heterogeneities are ubiquitous, their plate tectonic role is rarely considered. Here we show that deep lithospheric anomalies can dominate shallow geological features in activating tectonics in plate interiors. In numerical experiments, we found that structures frozen into the mantle lithosphere through plate tectonic processes can behave as quasi-plate boundaries reactivated under far-field compressional forcing. Intraplate locations where proto-lithospheric plates have been scarred by earlier suturing could be regions where latent plate boundaries remain, and where plate tectonics processes are expressed as a 'perennial' phenomenon.

Continental deformation accommodated by non-rigid passive bookshelf faulting: An example from the Cenozoic tectonic development of northern Tibet

NASA Astrophysics Data System (ADS)

Zuza, Andrew V.; Yin, An

2016-05-01

Collision-induced continental deformation commonly involves complex interactions between strike-slip faulting and off-fault deformation, yet this relationship has rarely been quantified. In northern Tibet, Cenozoic deformation is expressed by the development of the > 1000-km-long east-striking left-slip Kunlun, Qinling, and Haiyuan faults. Each have a maximum slip in the central fault segment exceeding 10s to ~ 100 km but a much smaller slip magnitude (~< 10% of the maximum slip) at their terminations. The along-strike variation of fault offsets and pervasive off-fault deformation create a strain pattern that departs from the expectations of the classic plate-like rigid-body motion and flow-like distributed deformation end-member models for continental tectonics. Here we propose a non-rigid bookshelf-fault model for the Cenozoic tectonic development of northern Tibet. Our model, quantitatively relating discrete left-slip faulting to distributed off-fault deformation during regional clockwise rotation, explains several puzzling features, including the: (1) clockwise rotation of east-striking left-slip faults against the northeast-striking left-slip Altyn Tagh fault along the northwestern margin of the Tibetan Plateau, (2) alternating fault-parallel extension and shortening in the off-fault regions, and (3) eastward-tapering map-view geometries of the Qimen Tagh, Qaidam, and Qilian Shan thrust belts that link with the three major left-slip faults in northern Tibet. We refer to this specific non-rigid bookshelf-fault system as a passive bookshelf-fault system because the rotating bookshelf panels are detached from the rigid bounding domains. As a consequence, the wallrock of the strike-slip faults deforms to accommodate both the clockwise rotation of the left-slip faults and off-fault strain that arises at the fault ends. An important implication of our model is that the style and magnitude of Cenozoic deformation in northern Tibet vary considerably in the east

Deep seismic structure and tectonics of northern Alaska: Crustal-scale duplexing with deformation extending into the upper mantle

USGS Publications Warehouse

Fuis, G.S.; Murphy, J.M.; Lutter, W.J.; Moore, Thomas E.; Bird, K.J.; Christensen, N.I.

1997-01-01

Seismic reflection and refraction and laboratory velocity data collected along a transect of northern Alaska (including the east edge of the Koyukuk basin, the Brooks Range, and the North Slope) yield a composite picture of the crustal and upper mantle structure of this Mesozoic and Cenozoic compressional orogen. The following observations are made: (1) Northern Alaska is underlain by nested tectonic wedges, most with northward vergence (i.e., with their tips pointed north). (2) High reflectivity throughout the crust above a basal decollement, which deepens southward from about 10 km depth beneath the northern front of the Brooks Range to about 30 km depth beneath the southern Brooks Range, is interpreted as structural complexity due to the presence of these tectonic wedges, or duplexes. (3) Low reflectivity throughout the crust below the decollement is interpreted as minimal deformation, which appears to involve chiefly bending of a relatively rigid plate consisting of the parautochthonous North Slope crust and a 10- to 15-km-thick section of mantle material. (4) This plate is interpreted as a southward verging tectonic wedge, with its tip in the lower crust or at the Moho beneath the southern Brooks Range. In this interpretation the middle and upper crust, or all of the crust, is detached in the southern Brooks Range by the tectonic wedge, or indentor: as a result, crust is uplifted and deformed above the wedge, and mantle is depressed and underthrust beneath this wedge. (5) Underthrusting has juxtaposed mantle of two different origins (and seismic velocities), giving rise to a prominent sub-Moho reflector. Copyright 1997 by the American Geophysical Union.

Active transpressional tectonics in the Andean forearc of southern Peru quantified by 10Be surface exposure dating of an active fault scarp

NASA Astrophysics Data System (ADS)

Benavente, Carlos; Zerathe, Swann; Audin, Laurence; Hall, Sarah R.; Robert, Xavier; Delgado, Fabrizio; Carcaillet, Julien; Team, Aster

2017-09-01

Our understanding of the style and rate of Quaternary tectonic deformation in the forearc of the Central Andes is hampered by a lack of field observations and constraints on neotectonic structures. Here we present a detailed analysis of the Purgatorio fault, a recently recognized active fault located in the forearc of southern Peru. Based on field and remote sensing analysis (Pléiades DEM), we define the Purgatorio fault as a subvertical structure trending NW-SE to W-E along its 60 km length, connecting, on its eastern end, to the crustal Incapuquio Fault System. The Purgatorio fault accommodates right-lateral transpressional deformation, as shown by the numerous lateral and vertical plurimetric offsets recorded along strike. In particular, scarp with a 5 m cumulative throw is preserved and displays cobbles that are cut and covered by slickensides. Cosmogenic radionuclide exposure dating (10Be) of quartzite cobbles along the vertical fault scarp yields young exposure ages that can be bracketed between 0 to 6 ka, depending on the inheritance model that is applied. Our preferred scenario, which takes in account our geomorphic observations, implies at least two distinct rupture events, each associated with 3 and 2 m of vertical offset. These two events plausibly occurred during the last thousand years. Nevertheless, an interpretation invoking more tectonic events along the fault cannot be ruled out. This work affirms crustal deformation along active faults in the Andean forearc of southern Peru during the last thousand years.

Sedimentary environment and tectonic deformations of the Neoproterozoic Iron formation at the Wadi El-Dabbah greenstone sequence, Central Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Kiyokawa, S.; Suzuki, T.; Ikehara, M.; Horie, K.; Takehara, M.; Abd-Elmonem, H.; Dawoud, A. D. M.; El-Hasan, M. M.

2017-12-01

El-Dabbah area Central Eastern Desert of the Nubia Shield preserved Neoproterozoic lower green schist faces volcaniclastics greenstone sequence and covered strike-slip deformation related subaerial sedimentary sequence (Hammamat Group). The volcaniclastics greenstone sequence (El-Dabbah Formation) preserved several iron beds bearing well stratified sequence. Four tectonic deformation identified as this area; thrust deformation (D1), strike-slip deformation with transtension normal fault and strong left-lateral shear (D2), subaerial pull apart sediments basin formed strike-slip deformations (D3), and extensional deformation after the Hammamat Group sedimentation (D4). New age data from intrusions identified about 638 Ma white granite and about 660 Ma quartz porphyry. Based on the detail mapping, we reconstruct more than 5000m thick volcano sedimentary succession. At least, 10 iron rich sections were identified within 3500m thick volcano-sedimentary sequence. There are 14 iron formation sequence identified in this greenstone sequence. Each Iron sequences are bedded with greenish-black shales within massive volcaniclastics and lava flow. Iron formation is formed mostly fine grain magnetite deposited within volcanic mudstone and siltstone with gradual distribution. Timing of this iron sediment is identified within Sturtian glaciation (730-700Ma). However, there is no geological direct support evidence in the Snowball earth event at this greenstone sequence. The volcanic activities at this ocean already produced many Fe2+ to ocean water. Repeated iron precipitation occur during volcanic activity interphase period which produced oxidation of iron and produce oxyhydroxide with mud-silt sediment at bottom of ocean.

Drainage - Structure Correlation in tectonically active Regions: Case studies in the Bolivian and Colombian Andes

NASA Astrophysics Data System (ADS)

Zeilinger, Gerold; Parra, Mauricio; Kober, Florian

2017-04-01

It is widely accepted, that drainage patterns are often controlled by tectonics/climate and geology/rheology. Classical drainage patterns can be found 1) in fault-and-thrust belt, where rives follow the valleys parallel or cut perpendicular to strike trough the ridges, forming a trellis pattern, 2) at dome structures where the drainage form a radial pattern or 3) rectangular patterns in strongly fractured regions. In this study, we focus on fault-and-thrust belts, that undergone different phases of tectonic activity. According to classical models, the deformation is propagating into the foreland, hence being youngest at the frontal part and getting successively older towards the axis of the orogen. Drainage patterns in the more interior parts of the orogenic wedge should be then less influenced by the direction of structures, as landscape evolution is changing to a tectonic passive stage. This relationship might represent the transience and maturity of drainage pattern evolution. Here we study drainage patterns of the Bolivian and the eastern Colombian Andes by comparing the relative orientation of the drainage network with the orogen structural grain. The drainage is extracted from Digital Elevation Models (SRTM 30 m) and indexed by their Strahler Order. Order 1 channels have an upstream area of 1 km2. The direction of all segments is analyzed by linear directional mean function that results in the mean orientation of input channels with approx. 500 m average length. The orientation of structures for different structural domains is calculated using the same function on digitized faults and fold-axis. Rose diagrams show the length-weighted directional distribution of structures, of higher (>= 4) and of lower order (<= 3) channels. The structural trend in the Bolivian Andes is controlled by the orocline, where a predominant NW-SE trend turns into an N-S trend at 18°S and where the eastern orogen comprise from west to east, the Eastern Cordillera (EC), the

Tectonic History of the Terrestrial Planets

NASA Technical Reports Server (NTRS)

Solomon, Sean C.

1993-01-01

The topics covered include the following: patterns of deformation and volcanic flows associated with lithospheric loading by large volcanoes on Venus; aspects of modeling the tectonics of large volcanoes on the terrestrial planets; state of stress, faulting, and eruption characteristics of large volcanoes on Mars; origin and thermal evolution of Mars; geoid-to-topography ratios on Venus; a tectonic resurfacing model for Venus; the resurfacing controversy for Venus; and the deformation belts of Lavinia Planitia.

Syndepositional tectonics recorded by soft-sediment deformation and liquefaction structures (continental Lower Permian sediments, Southern Alps, Northern Italy): Stratigraphic significance

NASA Astrophysics Data System (ADS)

Berra, F.; Felletti, F.

2011-04-01

The Lower Permian succession of the Central Southern Alps (Lombardy, Northern Italy) was deposited in fault-controlled continental basins, probably related to transtensional tectonics. We focussed our study on the stratigraphic record of the Lower Permian Orobic Basin, which consists of a 1000 m thick succession of prevailing continental clastics with intercalations of ignimbritic flows and tuffs (Pizzo del Diavolo Formation, PDV) resting on the underlying prevailing pyroclastic flows of the Cabianca Volcanite. The PDV consists of a lower part (composed of conglomerates passing laterally to sandstones and distally to silt and shales), a middle part (pelitic, with carbonates) and an upper part (alternating sandstone, silt and volcanic flows). Syndepositional tectonics during the deposition of the PDV is recorded by facies distribution, thickness changes and by the presence of deformation and liquefaction structures interpreted as seismites. Deformation is recorded by both ductile structures (ball-and-pillow, plastic intrusion, disturbed lamination, convolute stratification and slumps) and brittle structures (sand dykes and autoclastic breccias). Both the sedimentological features and the geodynamic setting of the depositional basin confidently support the interpretation of the described deformation features as related to seismic shocks. The most significant seismically-induced deformation is represented by a slumped horizon (about 4 m thick on average) which can be followed laterally for more than 5 km. The slumped bed consists of playa-lake deposits (alternating pelites and microbial carbonates, associated with mud cracks and vertebrate tracks). The lateral continuity and the evidence of deposition on a very low-angle surface along with the deformation/liquefaction of the sediments suggest that the slump was triggered by a high-magnitude earthquake. The stratigraphic distribution of the seismites allows us to identify time intervals of intense seismic activity

Lasting mantle scars lead to perennial plate tectonics

PubMed Central

Heron, Philip J.; Pysklywec, Russell N.; Stephenson, Randell

2016-01-01

Mid-ocean ridges, transform faults, subduction and continental collisions form the conventional theory of plate tectonics to explain non-rigid behaviour at plate boundaries. However, the theory does not explain directly the processes involved in intraplate deformation and seismicity. Recently, damage structures in the lithosphere have been linked to the origin of plate tectonics. Despite seismological imaging suggesting that inherited mantle lithosphere heterogeneities are ubiquitous, their plate tectonic role is rarely considered. Here we show that deep lithospheric anomalies can dominate shallow geological features in activating tectonics in plate interiors. In numerical experiments, we found that structures frozen into the mantle lithosphere through plate tectonic processes can behave as quasi-plate boundaries reactivated under far-field compressional forcing. Intraplate locations where proto-lithospheric plates have been scarred by earlier suturing could be regions where latent plate boundaries remain, and where plate tectonics processes are expressed as a ‘perennial' phenomenon. PMID:27282541

Climate dominated topography in a tectonically active mountain range

NASA Astrophysics Data System (ADS)

Adams, B. A.; Ehlers, T. A.

2015-12-01

Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The broad spatial trend in channel steepness values suggests that the locus of high rock uplift rates is coincident with the rugged range core, in a similar position as high temperature and pressure lithologies, but not in the low lying foothills as has been previously suggested by low-temperature thermochronometry. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns. We demonstrate the same topographic effects are recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on topography makes the argument of mountain range steadiness untenable in significantly glaciated settings. Furthermore, our results suggest that most glaciated Cenozoic ranges are likely still in a mode of readjustment as fluvial systems change topography and erosion rates to equilibrate with rock uplift rates.

Sheet intrusions and deformation of Piton des Neiges, and their implication for the volcano-tectonics of La Réunion

NASA Astrophysics Data System (ADS)

Chaput, Marie; Famin, Vincent; Michon, Laurent

2017-10-01

To understand the volcano-tectonic history of Piton des Neiges (the dormant volcano of La Réunion), we measured in the field the orientation of sheeted intrusions and deformation structures, and interpreted the two datasets separately with a paleostress inversion. Results show that the multiple proposed rift zones may be simplified into three trends: (1) a N30°E, 5 km wide linear rift zone running to the south of the edifice, active in the shield building (≥ 2.48-0.43 Ma) and terminal stages (190-22 ka); (2) a curved N110 to N160°E rift zone, widening from 5 km to 10 km toward the NW flank, essentially active during the early emerged shield building (≥ 1.3 Ma); and (3) two sill zones, ≤ 1 km thick in total, in the most internal parts of the volcano, active in the shield building and terminal stages. In parallel, deformation structures reveal that the tectonics of the edifice consisted in three end-member stress regimes sharing common stress axes: (1) NW-SE extension affecting in priority the south of the edifice near the N30°E rift zone; (2) NNE-SSW extension on the northern half of the volcano near the N110-160°E rift zone; (3) compression occurring near the sill zones, with a NE-SW or NW-SE maximum principal stress. These three stress regimes are spatially correlated and mechanically compatible with the injection trends. Combined together, our data show that the emerged Piton des Neiges underwent sector spreading delimited by perpendicular rift zones, as observed on Piton de la Fournaise (the active volcano of La Réunion). Analogue experiments attribute such sector spreading to brittle edifices built on a weaker substratum. We therefore conclude that La Réunion volcanoes are both brittle, as opposed to Hawaiian volcanoes or Mount Etna whose radial spreading is usually attributed to a ductile body within the edifices.

Geodetic imaging of tectonic deformation with InSAR

NASA Astrophysics Data System (ADS)

Fattahi, Heresh

Precise measurements of ground deformation across the plate boundaries are crucial observations to evaluate the location of strain localization and to understand the pattern of strain accumulation at depth. Such information can be used to evaluate the possible location and magnitude of future earthquakes. Interferometric Synthetic Aperture Radar (InSAR) potentially can deliver small-scale (few mm/yr) ground displacement over long distances (hundreds of kilometers) across the plate boundaries and over continents. However, Given the ground displacement as our signal of interest, the InSAR observations of ground deformation are usually affected by several sources of systematic and random noises. In this dissertation I identify several sources of systematic and random noise, develop new methods to model and mitigate the systematic noise and to evaluate the uncertainty of the ground displacement measured with InSAR. I use the developed approach to characterize the tectonic deformation and evaluate the rate of strain accumulation along the Chaman fault system, the western boundary of the India with Eurasia tectonic plates. I evaluate the bias due to the topographic residuals in the InSAR range-change time-series and develope a new method to estimate the topographic residuals and mitigate the effect from the InSAR range-change time-series (Chapter 2). I develop a new method to evaluate the uncertainty of the InSAR velocity field due to the uncertainty of the satellite orbits (Chapter 3) and a new algorithm to automatically detect and correct the phase unwrapping errors in a dense network of interferograms (Chapter 4). I develop a new approach to evaluate the impact of systematic and stochastic components of the tropospheric delay on the InSAR displacement time-series and its uncertainty (Chapter 5). Using the new InSAR time-series approach developed in the previous chapters, I study the tectonic deformation across the western boundary of the India plate with Eurasia and

Morphological expression of active tectonics in the Southern Alps

NASA Astrophysics Data System (ADS)

Robl, Jörg; Heberer, Bianca; Neubauer, Franz; Hergarten, Stefan

2015-04-01

Evolving drainage pattern and corresponding metrics of the channels (e.g. normalized steepness index) are sensitive indicators for tectonic or climatic events punctuating the evolution of mountain belts and their associated foreland basins. The analysis of drainage systems and their characteristic properties represents a well-established approach to constrain the impact of tectonic and climatic drivers on mountainous landscapes in the recent past. The Southern Alps (SA) are one of the seismically most active zones in the periphery of northern Adria. Recent deformation is caused by the ongoing convergence of the Adriatic and European plate and is recorded by numerous earthquakes in the domain of the SA. Deformation in the SA is characterized by back-thrusting causing crustal thickening and should therefore result in uplift and topography formation. The vertical velocity field determined by GPS-data clearly indicates a belt of significant uplift in the south South alpine indenter between Lake Garda in the west and the Triglav in the east and strong subsidence of the foreland basin surrounding the Mediterranean Sea near Venice, although subsidence is often related to ongoing subduction of the Adriatic microplate underneath Appennines. Despite of these short term time series, timing, rates and drivers of alpine landscape evolution are not well constrained and the linkage between crustal deformation and topographic evolution of this highly active alpine segment remains unclear for the following reasons: (1) The eastern Southern Alps were heavily overprinted by the Pleistocene glaciations and tectonic signals in the alpine landscape are blurred. Only the transition zone to the southern foreland basin remained unaffected and allows an analysis of a glacially undisturbed topography. (2) The major part of this domain is covered by lithology (carbonatic rocks) which is unsuitable for low temperature geochronology and cosmogenic isotope dating so that exhumation and erosion

Tectonics of Europa

NASA Astrophysics Data System (ADS)

Kattenhorn, S. A.; Hurford, T. A.

2007-12-01

mechanical development of tectonic features. Hence, strike-slip faults are relatively common. Also, frictional shearing and heating has likely contributed to the construction of edifices along crack margins (i.e., ridges). If Europa has not recently expanded, crustal convergence (although elusive in Galileo images) is required to balance out new surface material created at spreading bands and may be accommodated locally along ridges or convergence bands. (3) Chains of concatenated curved cracks called cycloids provide convincing evidence of a subsurface ocean in that they must be the result of diurnal forcing of sufficient tidal amplitude to break the ice during a large portion of the Europan orbit, suggesting a tidally responding ocean beneath the ice shell. (4) Fracture mechanics reveals that the brittle portion of the ice shell is likely no more than a few km thick, but convection driven diapirism and crater morphologies necessitate a thicker shell overall (up to about 30 km). It is not known if fractures are able to penetrate this entire shell thickness. The brittle layer acts as a stagnant lid to plastic deformation in the ductile portion of the ice shell, resulting in localized brittle deformation. (5) Tectonic resurfacing has dominated the <70 my of visible geologic history. No evidence exists that Europa is currently tectonically active; however, this may be more a failing of the current state of the science rather than a lack of probability. A tectonically based answer to this question lies in a thorough analysis of geologically young surface fractures but would benefit from far more extensive coverage of the surface via a return mission to Europa.

Magnetostratigraphy of the Fenghuoshan Group in the Hoh Xil Basin and its tectonic implications for India-Eurasia collision and Tibetan Plateau deformation

NASA Astrophysics Data System (ADS)

Jin, Chunsheng; Liu, Qingsong; Liang, Wentian; Roberts, Andrew P.; Sun, Jimin; Hu, Pengxiang; Zhao, Xiangyu; Su, Youliang; Jiang, Zhaoxia; Liu, Zhifeng; Duan, Zongqi; Yang, Huihui; Yuan, Sihua

2018-03-01

Early Cenozoic plate collision of India and Eurasia was a significant geological event, which resulted in Tibetan Plateau (TP) uplift and altered regional and global atmospheric circulations. However, the timing of initial collision is debated. It also remains unclear whether the TP was deformed either progressively northward, or synchronously as a whole. As the largest basin in the hinterland of the TP, evolution of the Hoh Xil Basin (HXB) and its structural relationship with development of the Tanggula Thrust System (TTS) have important implications for unraveling the formation mechanism and deformation history of the TP. In this study, we present results from a long sedimentary sequence from the HXB that dates the Fenghuoshan Group to ∼72-51 Ma based on magnetostratigraphy and radiometric ages of a volcanic tuff layer within the group. Three depositional phases reflect different stages of tectonic movement on the TTS, which was initialized at 71.9 Ma prior to the India-Eurasia collision. An abrupt sediment accumulation rate increase from 53.9 Ma is a likely response to tectonic deformation in the plateau hinterland, and indicates that initial India-Eurasia collision occurred at no later than that time. This remote HXB tectonosedimentary response implies that compressional deformation caused by India-Eurasia collision likely propagated to the central TP shortly after the collision, which supports the synchronous deformation model for TP.

Interaction between active tectonics, erosion and diapirism, a case study from Habble-Rud in Southern Central Alborz (Northern Iran)

NASA Astrophysics Data System (ADS)

Jaberi, Maryam; Ghassemi, Mohammad R.; Shayan, Siavosh; Yamani, Mojtaba; Zamanzadeh, Seyed Mohammad

2018-01-01

The Alborz mountain chain is a region of active deformation within the Arabia-Eurasia continental collision zone. The southern part of central Alborz Mountains, in the north of Iran, represents complex tectonics because it is located at the border of two developing continental sedimentary basins between southern central Alborz and Central Iran. An arid and semi-arid climate, a large extent of Quaternary sediments, rugged topography, salt domes and faults with historical seismicity influence the Habble-Rud River catchment. In the present research, a number of tectonic geomorphologic indices were extracted from satellite imagery and 10 m DEM (digital elevation model) data in order to identify relative tectonic activity within the basin. The indices include: stream length-gradient index (Sl), drainage basin asymmetry (Af), index of mountain front sinuosity (Smf), hypsometric integral (Hi), index of drainage basin shape (Bs), ratio of valley-floor width to valley height (Vf), and fault density (Fd). Due to the presence of heterogeneous indices for all sections of the catchment causing large extension of Habble-Rud (3260 km2), all of the variables such as extremely erodible formations, faults and folds and salt tectonics on the Southern part; were put into a matrix table. As a new approach, the variables were put into the SAW (simple additive model) model as one of MADM (multi-attribute decision-making models) techniques. The study area was divided into four regions according to the values of SAW. These classes include very high (%11), high (48.3%), moderate (34.7%), and low activity (3.4%). The result of the model suggests that the study area is located on a changing tectonic trend in central Alborz from NW-SE to NE-SW. The regions with high relative tectonic activity in HR catchment correspond to the active Garmsar and Sorkhe-Kalout faults and diapirs.

Anisotropy and tectonic deformation in the Ordos basin revealed by an active source seismic experiment

NASA Astrophysics Data System (ADS)

Jun, W. S.; Wang, F.; Xu, T.

2016-12-01

With the purpose of exploring the Ordos block, western North China Craton, two controlled-source deep seismic transects were conducted across this region. The first one is a 650 km long profile oriented N-S; the second is 1530 km and is oriented E-W. The upper mantle P wave-velocity derived from these profiles features a 0.25 km/s difference between them. Being the E-W higher that the N-S. The results obtained from both seismic profiles indicate that the upper mantle beneath the Ordos block presents seismic anisotropy in terms of discrepancy in Pn-wave velocity, such as the apparent seismic velocities observed along the two reference profiles demonstrate. This result is consistent with SKS-wave splitting measurements in the interior of the Ordos block. This indicates that the compressive stress state in Ordos during the Mesozoic became an extensional stress state in the Cenozoic. The high-velocity anomaly in the uppermost mantle under the west-east profile suggests that the lithospheric mantle is still not water-rich. Unlike what happened in the NCC to east of the Taihang Mountains, where the lithosphere experienced its thinning and destruction since the Mesozoic, the lithosphere in the interior of Ordos has suffered less deformation and remained tectonically stable. Keywords: wide-angle seismic profiling, Pn phase, high-velocity anomaly, upper mantle anisotropy, Ordos block, North China Craton. ReferencesChen L., 2009. Lithospheric structure variations between the eastern and central North China Craton from S- and P-receiver function migration. Phys. Earth Planet. Inter. 173, 216-227. Gao S., Rudnick R.L., Xu W.L., et al., 2008. Recycling deep cratonic lithosphere and generation of intraplate magmatism in the North China Craton. Earth Planet. Sci. Lett. 270, 41-53. Xu T., Zhang Z.J., Gao E.G., et al., 2010. Segmentally iterative ray tracing in complex 2D and 3D heterogeneous block models. Bull. Seism. Soc. Am. 100, 841-850. Zhu R.X., Zheng T.Y., 2009. Destruction

Polyphase thrust tectonic in the Barberton greenstone belt

NASA Technical Reports Server (NTRS)

Paris, I. A.

1986-01-01

In the circa 3.5 by-old Barberton greenstone belt, the supracrustal rocks form a thick and strongly deformed thrust complex. Structural studies in the southern part of the belt have shown that 2 separate phases of over-thrusting (D sub 1 and D sub 2) successively dismembered the original stratigraphy. Thrust nappes were subsequently refolded during later deformations (D sub 3 and D sub 4). This report deals with the second thrusting event which, in the study region appears to be dominant, and (unlike the earlier thrusting), affects the entire supracrustal pile. The supracrustal rocks form a predominantly NE/SW oriented, SE dipping tectonic fan (the D sub 2 fan) in which tectonic slices of ophiolitic-like rocks are interleaved with younger sedimentary sequences of the Diepgezet and malalotcha groups. Structural and sedimentological data indicate that the D sub 2 tectonic fan was formed during a prolonged, multi-stage regional horizontal shortening event during which several types of internal deformation mechanisms were successively and/or simultaneously active. Movement appears to have been predominantly to the NW and to the N. During D sub 2, periods of quiescence and sedimentation followed periods of thrust propagation. Although the exact kinematics which led to the formation of this fan is not yet known, paleoenvironmental interpretations together with structural data suggest that D sub 2 was probably related to (an) Archean collision(s).

Deformation interplay at Hawaii Island

NASA Astrophysics Data System (ADS)

Shirzaei, M.; Walter, T. R.

2009-12-01

Volcanoes are known to be closely related to the tectonic environment, including vent locations and eruptions resulting from faults and earthquakes. Similarly, adjacent volcanoes interact with each other in time and space, as suggested for the Hawaiian volcanoes Kilauea and Mauna Loa. New satellite radar data imply even more complex deformation interplay in Hawaii than previously thought, involving magma chamber pressure changes, dike intrusions, slow earthquakes and ground subsidence. The affected regions are the Mauna Loa and Kilauea volcano summits, their active rift zones, the island’s unstable southeast flank and even the capital city of Hilo. Based on the data acquired by the European satellite ENVISAT, we present in this work a five-year spatio-temporal analysis of the deformation signals recorded between 2003 and 2008. The data suggests that most of the deformation sources are acting in chorus. The magma intrusion at the Mauna Loa chamber and the intrusion into the Kilauea rift dike are correlated in time while also interacting with gravity-driven flank movement events. Some of the events occur silently underneath the Kilauea south flank, such as slow earthquakes that may largely affect all of the active magmatic systems and reverse their sign of correlation. This study of the interplay between multiple deformations and inherently coupled systems provides a better understanding of Hawaiian volcano activity and may lead to new methods for assessing the hazards that arise during volcano-tectonic activities elsewhere.

Looking for very low tectonic deformation in GNSS time series impacted by strong hydrological signal in the Okavango Delta, Botswana

NASA Astrophysics Data System (ADS)

Pastier, Anne-Morwenn; Dauteuil, Olivier; Murray-Hudson, Michael; Makati, Kaelo; Moreau, Frédérique; Crave, Alain; Longuevergne, Laurent; Walpersdorf, Andrea

2017-04-01

Located in northern Botswana, the Okavango Delta is a vast wetland, fed from the Angolan highlands and constrained by a half-graben in the Kalahari depression. Since the 70's, the Okavango graben is usually considered as the terminus of the East African Rift System. But a recent geodetic study showed there has been no extension on the tectonic structure over the past 5 years, and recent geophysical studies began to call this hypothesis into question. The deformation in the area could instead be related to far-field deformation accommodation due to the motion of the Kalahari craton relative to the rest of the Nubian plate and to the opening of the Rift Valley. Getting to the vertical deformation isn't trivial. The GNSS time series show a strong annual deformation of the ground surface (3 cm of amplitude). On the vertical component, this periodic signal is so strong that it hides the tectonic long-term deformation, while this information would give a crucial insight on the geodynamic process at play. This periodic signal is related to the seasonal loading of water due to the rainy season. This hypothesis is corroborated by the modeling of the surface deformation based on the GRACE satellites data, interpreted as the variation of groundwater amount. In the Okavango Delta, the peak of water level isn't paced with the local precipitations, but is driven by a flood pulse coming from the Angolan Highlands. The migration of this massive water body isn't visible at first order in GRACE data. Yet, local precipitations are supposed to undergo too much evapotranspiration to be significant in the hydrological balance. Thus this later water body isn't supposed to produce a mass anomaly in GRACE time series. This paradox could highlight a relationship not yet defined between groundwater and local rainfall. The wide spatial resolution of GRACE data (about 300 km) doesn't allow a modeling accurate enough to give access to the slow tectonic deformation, nor to determine the

Applications of Morphochronology to the Active Tectonics of Tibet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryerson, F J; Tapponnier, P; Finkel, R C

2005-01-28

The Himalayas and the Tibetan Plateau were formed as a result of the collision of India and Asia, and provide an excellent opportunity to study the mechanical response of the continental lithosphere to tectonic stress. Geophysicists are divided in their views on the nature of this response advocating either (1) homogeneously distributed deformation with the lithosphere deforming as a fluid continuum or (2) deformation is highly localized with the lithosphere that deforms as a system of blocks. The resolution of this issue has broad implications for understanding the tectonic response of continental lithosphere in general. Homogeneous deformation is supported bymore » relatively low decadal, geodetic slip-rate estimates for the Altyn Tagh and Karakorum Faults. Localized deformation is supported by high millennial, geomorphic slip-rates constrained by both cosmogenic and radiocarbon dating on these faults. Based upon the agreement of rates determined by radiocarbon and cosmogenic dating, the overall linearity of offset versus age correlations, and on the plateau-wide correlation of landscape evolution and climate history, the disparity between geomorphic and geodetic slip-rate determinations is unlikely to be due to the effects of surface erosion on the cosmogenic age determinations. Similarly, based upon the consistency of slip-rates over various observation intervals, secular variations in slip-rate appear to persist no longer than 2000 years and are unlikely to provide reconciliation. Conversely, geodetic and geomorphic slip-rate estimates on the Kunlun fault, which does not have significant splays or associated thrust faults, are in good agreement, indicating that there is no fundamental reason why these complementary geodetic and geomorphic methods should disagree. Similarly, the geodetic and geomorphic estimates of shortening rates across the northeastern edge of the plateau are in reasonable agreement, and the geomorphic rates on individual thrust faults

Magnetic fabrics in tectonically inverted sedimentary basins: a review

NASA Astrophysics Data System (ADS)

García-Lasanta, Cristina; Román-Berdiel, Teresa; Casas-Sainz, Antonio; Oliva-Urcia, Belén; Soto, Ruth; Izquierdo-Llavall, Esther

2017-04-01

Magnetic fabric studies in sedimentary rocks were firstly focused on strongly deformed tectonic contexts, such as fold-and-thrust belts. As measurement techniques were improved by the introduction of high-resolution equipments (e.g. KLY3-S and more recent Kappabridge susceptometers from AGICO Inc., Czech Republic), more complex tectonic contexts could be subjected to anisotropy of magnetic susceptibility (AMS) analyses in order to describe the relationship between tectonic conditions and the orientation and shape of the resultant magnetic ellipsoids. One of the most common complex tectonic frames involving deformed sedimentary rocks are inverted extensional basins. In the last decade, multiple AMS studies revealed that the magnetic fabric associated with the extensional stage (i.e. a primary magnetic fabric) can be preserved despite the occurrence of subsequent deformational processes. In these cases, magnetic fabrics may provide valuable information about the geometry and kinematics of the extensional episode (i.e. magnetic ellipsoids with their minimum susceptibility axis oriented perpendicular to the deposit plane and magnetic lineation oriented parallel to the extension direction). On the other hand, several of these studies have also determined how the subsequent compressional stage can modify the primary extensional fabric in some cases, particularly in areas subjected to more intense deformation (with development of compression-related cleavage). In this contribution we present a compilation of AMS studies developed in sedimentary basins that underwent different degree of tectonic inversion during their history, in order to describe the relationship of this degree of deformation and the degree of imprint that tectonic conditions have in the previous magnetic ellipsoid (primary extension-related geometry). The inverted basins included in this synthesis are located in the Iberian Peninsula and show: i) weak deformation (W Castilian Branch and Maestrazgo basin

Distributed and localized horizontal tectonic deformation as inferred from drainage network geometry and topology: A case study from Lebanon

NASA Astrophysics Data System (ADS)

Goren, Liran; Castelltort, Sébastien; Klinger, Yann

2016-04-01

Partitioning of horizontal deformation between localized and distributed modes in regions of oblique tectonic convergence is, in many cases, hard to quantify. As a case study, we consider the Dead Sea Fault System that changes its orientation across Lebanon and forms a restraining bend. The oblique deformation along the Lebanese restraining bend is characterized by a complex suite of tectonic structures, among which, the Yammouneh fault, is believed to be the main strand that relays deformation from the southern section to the northern section of the Dead Sea Fault System. However, uncertainties regarding slip rates along the Yammouneh fault and strain partitioning in Lebanon still prevail. In the current work we use the geometry and topology of river basins together with numerical modeling to evaluate modes and rates of the horizontal deformation in Mount Lebanon that is associated with the Arabia-Sinai relative plate motion. We focus on river basins that drain Mount Lebanon to the Mediterranean and originate close to the Yammouneh fault. We quantify a systematic counterclockwise rotation of these basins and evaluate drainage area disequilibrium using an application of the χ mapping technique, which aims at estimating the degree of geometrical and topological disequilibrium in river networks. The analysis indicates a systematic spatial pattern whereby tributaries of the rotated basins appear to experience drainage area loss or gain with respect to channel length. A kinematic model that is informed by river basin geometry reveals that since the late Miocene, about a quarter of the relative plate motion parallel to the plate boundary has been distributed along a wide band of deformation to the west of the Yammouneh fault. Taken together with previous, shorter-term estimates, the model indicates little variation of slip rate along the Yammouneh fault since the late Miocene. Kinematic model results are compatible with late Miocene paleomagnetic rotations in western

Active Tectonics Around Pisagua, Northern Chile Gap: Seismological and Neotectonic Approaches

NASA Astrophysics Data System (ADS)

Comte, D.; Carrizo, D.; Peyrat, S.

2013-12-01

Northern Chile is a recognized mature seismic gap that is reaching the end of its megathrust cycle. Deformation associated with the convergence between the Nazca and the South American Plates is mainly absorbed along the interplate contact, but also partially accommodated along the upper plate. Even though distribution of the active deformation along this plate has been documented mainly in the backarc region, Late Cenozoic structures have been recognized along the forearc suggesting that some part of this deformation is also accommodated along the coastal region. Recent paleoseismological studies suggest that some of these structures are tectonically active and some could be potentially active, capable to generate shallow intraplate earthquakes (Mw˜7). However, seismological and geodetical evidences of the fault activation mechanisms are poorly documented, and the activation process remain not elucidate. Currently, Northern Chile seismic gap is monitored by regional seismic networks and partially studied by temporary local seismological experiments. Results of these studies suggest the presence of shallow seismicity along the forearc, but the relationships between upper plate faults and the seismicity has not been yet explored. We perform a detailed seismotectonic analysis of the subduction-forearc system in the central part of the Northern Chile seismic gap to establish relationships between the plate contact deformation and the upper plate faults. We present preliminary results of data recorded by a dense seismic network (three components continuous recording) deployed around Pisagua, between the coastline and the Central Depression, during several months. Pisagua region was chosen because the forearc faults exhibit an extraordinary well-preserved morphotectonic expression, and the upper part of the seismogenic interplate contact shows abundant continental intraplate seismicity that could be associated with the faults systems. The data recorded in this area

Evolution of Deformation Studies on Active Hawaiian Volcanoes

USGS Publications Warehouse

Decker, Robert W.; Okamura, Arnold; Miklius, Asta; Poland, Michael

2008-01-01

Everything responds to pressure, even rocks. Deformation studies involve measuring and interpreting the changes in elevations and horizontal positions of the land surface or sea floor. These studies are variously referred to as geodetic changes or ground-surface deformations and are sometimes indexed under the general heading of geodesy. Deformation studies have been particularly useful on active volcanoes and in active tectonic areas. A great amount of time and energy has been spent on measuring geodetic changes on Kilauea and Mauna Loa Volcanoes in Hawai`i. These changes include the build-up of the surface by the piling up and ponding of lava flows, the changes in the surface caused by erosion, and the uplift, subsidence, and horizontal displacements of the surface caused by internal processes acting beneath the surface. It is these latter changes that are the principal concern of this review. A complete and objective review of deformation studies on active Hawaiian volcanoes would take many volumes. Instead, we attempt to follow the evolution of the most significant observations and interpretations in a roughly chronological way. It is correct to say that this is a subjective review. We have spent years measuring and recording deformation changes on these great volcanoes and more years trying to understand what makes these changes occur. We attempt to make this a balanced as well as a subjective review; the references are also selective rather than exhaustive. Geodetic changes caused by internal geologic processes vary in magnitude from the nearly infinitesimal - one micron or less, to the very large - hundreds of meters. Their apparent causes also are varied and include changes in material properties and composition, atmospheric pressure, tidal stress, thermal stress, subsurface-fluid pressure (including magma pressure, magma intrusion, or magma removal), gravity, and tectonic stress. Deformation is measured in units of strain or displacement. For example, tilt

Active tectonic deformation along rejuvenated faults in tropical Borneo: Inferences obtained from tectono-geomorphic evaluation

NASA Astrophysics Data System (ADS)

Mathew, Manoj Joseph; Menier, David; Siddiqui, Numair; Kumar, Shashi Gaurav; Authemayou, Christine

2016-08-01

The island of Borneo is enveloped by tropical rainforests and hostile terrain characterized by high denudation rates. Owing to such conditions, studies pertaining to neotectonics and consequent geomorphic expressions with regard to surface processes and landscape evolution are inadequately constrained. Here we demonstrate the first systematic tectono-geomorphic evaluation of north Borneo through quantitative and qualitative morphotectonic analysis at sub-catchment scale, for two large drainage basins located in Sarawak: the Rajang and Baram basins. The extraction of morphometric parameters utilizing digital elevation models arranged within a GIS environment focuses on hypsometric curve analysis, distribution of hypsometric integrals through spatial autocorrelation statistics, relative uplift values, the asymmetry factor and the normalized channel steepness index. Hypsometric analysis suggests a young topography adjusting to changes in tectonic boundary conditions. Autocorrelation statistics show clusters of high values of hypsometric integrals as prominent hotspots that are associated with less eroded, young topography situated in the fold and thrust belts of the Interior Highlands of Borneo. High channel steepness and gradients (> 200 m0.9) are observed in zones corresponding to the hotspots. Relative uplift values reveal the presence of tectonically uplifted blocks together with relatively subsided or lesser uplifted zones along known faults. Sub-catchments of both basins display asymmetry indicating tectonic tilting. Stream longitudinal profiles demonstrate the presence of anomalies in the form of knickzones without apparent lithological controls along their channel reaches. Surfaces represented by cold spots of low HI values and low channel gradients observed in the high elevation headwaters of both basins are linked to isolated erosional planation surfaces that could be remnants of piracy processes. The implication of our results is that Borneo experiences

DELP Symposium: Tectonics of eastern Asia and western Pacific Continental Margin

NASA Astrophysics Data System (ADS)

Eastern Asia and the western Pacific make up a broad region of active plate tectonic interaction. The area is a natural laboratory for studying the processes involved in the origin and evolution of volcanic island arcs, marginal basins, accretionary prisims, oceanic trenches, accreted terranes, ophiolite emplacement, and intracontinental deformation. Many of our working concepts of plate tectonics and intraplate deformation were developed in this region, even though details of the geology and geophysics there must be considered of a reconnaissance nature.During the past few years researchers have accumulated a vast amount of new and detailed information and have developed a better understanding of the processes that have shaped the tectonic elements in this region. To bring together scientists from many disciplines and to present the wide range of new data and ideas that offer a broader perspective on the interrelations of geological, geochemical, geophysical and geodetic studies, the symposium Tectonics of Eastern Asia and Western Pacific Continental Margin was held December 13-16, 1988, at the Tokyo Institute of Technology in Japan, under the auspicies of DELP (Dynamics and Evolution of the Lithosphere Project).

Off-axis volcano-tectonic activity during continental rifting: Insights from the transversal Goba-Bonga lineament, Main Ethiopian Rift (East Africa)

NASA Astrophysics Data System (ADS)

Corti, Giacomo; Sani, Federico; Agostini, Samuele; Philippon, Melody; Sokoutis, Dimitrios; Willingshofer, Ernst

2018-03-01

The Main Ethiopian Rift, East Africa, is characterized by the presence of major, enigmatic structures which strike approximately orthogonal to the trend of the rift valley. These structures are marked by important deformation and magmatic activity in an off-axis position in the plateaus surrounding the rift. In this study, we present new structural data based on a remote and field analysis, complemented with analogue modelling experiments, and new geochemical analysis of volcanic rocks sampled in different portions of one of these transversal structures: the Goba-Bonga volcano-tectonic lineament (GBVL). This integrated analysis shows that the GBVL is associated with roughly E-W-trending prominent volcano-tectonic activity affecting the western plateau. Within the rift floor, the approximately E-W alignment of Awasa and Corbetti calderas likely represent expressions of the GBVL. Conversely, no tectonic or volcanic features of similar (E-W) orientation have been recognized on the eastern plateau. Analogue modelling suggests that the volcano-tectonic features of the GBVL have probably been controlled by the presence of a roughly E-W striking pre-existing discontinuity beneath the western plateau, which did not extend beneath the eastern plateau. Geochemical analysis supports this interpretation and indicates that, although magmas have the same sub-lithospheric mantle source, limited differences in magma evolution displayed by products found along the GBVL may be ascribed to the different tectonic framework to the west, to the east, and in the axial zone of the rift. These results support the importance of the heterogeneous nature of the lithosphere and the spatial variations of its structure in controlling the architecture of continental rifts and the distribution of the related volcano-tectonic activity.

Effect of basement structure and salt tectonics on deformation styles along strike: An example from the Kuqa fold-thrust belt, West China

NASA Astrophysics Data System (ADS)

Neng, Yuan; Xie, Huiwen; Yin, Hongwei; Li, Yong; Wang, Wei

2018-04-01

The Kuqa fold-thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, décollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E-W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, fold-thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core detachment fold-thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the fold-thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of

A global tectonic activity map with orbital photographic supplement

NASA Technical Reports Server (NTRS)

Lowman, P. D., Jr.

1981-01-01

A three part map showing equatorial and polar regions was compiled showing tectonic and volcanic activity of the past one million years, including the present. Features shown include actively spreading ridges, spreading rates, major active faults, subduction zones, well defined plates, and volcanic areas active within the past one million years. Activity within this period was inferred from seismicity (instrumental and historic), physiography, and published literature. The tectonic activity map was used for planning global geodetic programs of satellite laser ranging and very long base line interferometry and for geologic education.

Soft sediment deformation structures in a lacustrine sedimentary succession induced by volcano-tectonic activities: An example from the Cretaceous Beolgeumri Formation, Wido Volcanics, Korea

NASA Astrophysics Data System (ADS)

Ko, Kyoungtae; Kim, Sung Won; Lee, Hong-Jin; Hwang, In Gul; Kim, Bok Chul; Kee, Won-Seo; Kim, Young-Seog; Gihm, Yong Sik

2017-08-01

The Cretaceous Beolgeumri Formation is composed of laminated mudstones intercalated with sandstones, chert, and a bed of lapilli tuff that were deposited in a lacustrine environment at the terminal part of a regional strike-slip fault systems on the southwestern Korean Peninsula. The Beolgeumri Formation contains various types of soft sediment deformation (SSD) structures that are characterized by a wide extent (< 4 km), lateral continuity (< 200 m), and vertical repetition. The SSD structures can be classified into six categories based on their morphological features and deformation styles: 1) fold structures, 2) load structures, 3) water-escape structures, 4) rip-down structures, 5) boudin structures, and 6) synsedimentary fault structures. Field examination of SSD structures together with an analysis of the sedimentological records of the Beolgeumri Formation indicate that the SSD structures formed largely by liquefaction and/or fluidization triggered by ground shaking during earthquakes. To constrain the timing of the development of SSD structures in the Beolgeumri Formation, we conducted sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon age dating of block sized lithic clasts bearing volcaniclastic deposits that conformably underlie (the Mangryeongbong Tuff) and overlie (the Ttandallae Tuff) the Beolgeumri Formation. The Mangryeongbong and Ttandallae Tuffs have ages of 86.63 ± 0.83 Ma and 87.24 ± 0.36 Ma, respectively, indicating that the Beolgeumri Formation was deposited during a short interval between major volcanic eruptions. The large lithic clasts of volcaniclastic deposits suggest that the Beolgeumri Formation was deposited adjacent to an active volcanic edifice(s). Syndepositional magmatic activities are suggested by the occurrence of a lapilli tuff bed in the Beolgeumri Formation and an igneous intrusion (intermediate sill) that is crosscut by a sand dike, as well as the similar age results of the underlying and overlying volcaniclastic

Quaternary Tectonic Tilting Governed by Rupture Segments Controls Surface Morphology and Drainage Evolution along the South-Central Coast of Chile

NASA Astrophysics Data System (ADS)

Echtler, H. P.; Bookhagen, B.; Melnick, D.; Strecker, M.

2004-12-01

The Chilean coast represents one of the most active convergent margins in the Pacific rim, where major earthquakes (M>8) have repeatedly ruptured the surface, involving vertical offsets of several meters. Deformation along this coast takes place in large-scale, semi-independent seismotectonic segments with partially overlapping transient boundaries. They are possibly related to reactivated inherited crustal anisotropies; internal seismogenic deformation may be accommodated by structures that have developed during accretionary wedge evolution. Seismotectonic segmentation and the identification of large-scale rupture zones, however, are based on limited seismologic und geodetic observations over short timespans. In order to better define the long-term behavior and deformation rates of these segments and to survey the tectonic impact on the landscape on various temporal and spatial scales, we investigated the south-central coast of Chile (37-38S). There, two highly active, competing seismotectonic compartments influence the coastal and fluvial morphology. A rigorous analysis of the geomorphic features is a key for an assessment of the tectonic evolution during the Quaternary and beyond. We studied the N-S oriented Santa María Island (SMI), 20 km off the coast and only ~70km off the trench, in the transition between the two major Valdivia (46-37S) and Concepción (38-35S) rupture segments. The SMI has been tectonically deformed throughout the Quaternary and comprises two tilt domains with two topographic highs in the north and south that are being tilted eastward. The low-lying and flat eastern part of the island is characterized by a set of emergent Holocene strandlines related to coseismic uplift. We measured detailed surface morphology of these strandlines and E-W traversing ephemeral stream channels with a laser-total station and used these data to calibrate and validate high-resolution, digital imagery. In addition, crucial geomorphic markers were dated by the

Geology Field Camp at Southern Illinois University: Six weeks exploring four tectonic regimes

NASA Astrophysics Data System (ADS)

Friedman, S. A.; Conder, J. A.; Ferre, E. C.; Heij, G.

2013-12-01

Field Geology is typically the capstone course for an undergraduate Bachelor of Science degree in Geology. This type of course brings together the varied sub-disciplines and course topics students encounter in their undergraduate experience, and puts these in context of active Earth processes. At the same time, a significant fraction of Geology departments have dropped field geology from their offerings and students must choose from those programs still offering the course. Southern Illinois University has offered field geology for over 40 years, stationed in and around southwestern Montana. This field camp offers experiences with four distinct tectonic settings: thick-skin contractional, thin-skin contractional, extensional, and anorogenic. The most challenging projects of the course involve mapping and interpreting Laramide and Sevier compressionally deformed areas. The major difference between the two types of deformation is that Laramide ('thick-skinned') tectonics encompasses the mid-crust in deformation while Sevier ('thin-skinned') deformation is limited to the uppermost portion of the crust. This difference results in markedly different fold styles and other deformational structures encountered, requiring different approaches to understanding and constructing the deformational histories of the regions. Extensional tectonics are explored with a paleoseismology project at Hebgen Lake, in Grand Teton National Park where the students typically spend two days, and at the Bitterroot Shear Zone - the edge of a metamorphic core complex along the eastern boundary of the Idaho batholith. While recent work from EarthScope and elsewhere casts doubt on Yellowstone as a mantle plume, Yellowstone remains the classic example of a continental hotspot. During visits through the park, students distinguish between the recent volcanics and hydrothermal activity of Yellowstone and the nearby Eocene Absaroka volcanics. Expanding on the story of the Yellowstone hotspot, a visit is

Hydrothermal and tectonic activity in northern Yellowstone Lake, Wyoming

USGS Publications Warehouse

Johnson, S.Y.; Stephenson, W.J.; Morgan, L.A.; Shanks, Wayne C.; Pierce, K.L.

2003-01-01

Yellowstone National Park is the site of one of the world's largest calderas. The abundance of geothermal and tectonic activity in and around the caldera, including historic uplift and subsidence, makes it necessary to understand active geologic processes and their associated hazards. To that end, we here use an extensive grid of high-resolution seismic reflection profiles (???450 km) to document hydrothermal and tectonic features and deposits in northern Yellowstone Lake. Sublacustrine geothermal features in northern Yellowstone Lake include two of the largest known hydrothermal explosion craters, Mary Bay and Elliott's. Mary Bay explosion breccia is distributed uniformly around the crater, whereas Elliott's crater breccia has an asymmetric distribution and forms a distinctive, ???2-km-long, hummocky lobe on the lake floor. Hydrothermal vents and low-relief domes are abundant on the lake floor; their greatest abundance is in and near explosion craters and along linear fissures. Domed areas on the lake floor that are relatively unbreached (by vents) are considered the most likely sites of future large hydrothermal explosions. Four submerged shoreline terraces along the margins of northern Yellowstone Lake add to the Holocene record or postglacial lake-level fluctuations attributed to "heavy breathing" of the Yellowstone magma reservoir and associated geothermal system. The Lake Hotel fault cuts through northwestern Yellowstone Lake and represents part of a 25-km-long distributed extensional deformation zone. Three postglacial ruptures indicate a slip rate of ???0.27 to 0.34 mm/yr. The largest (3.0 m slip) and most recent event occurred in the past ???2100 yr. Although high heat flow in the crust limits the rupture area of this fault zone, future earthquakes of magnitude ???5.3 to 6.5 are possible. Earthquakes and hydrothermal explosions have probably triggered landslides, common features around the lake margins. Few high-resolution seismic reflection surveys have

Tectonic histories between Alba Patera and Syria Planum, Mars

USGS Publications Warehouse

Anderson, R.C.; Dohm, J.M.; Haldemann, A.F.C.; Hare, T.M.; Baker, V.R.

2004-01-01

Syria Planum and Alba Patera are two of the most prominent features of magmatic-driven activity identified for the Tharsis region and perhaps for all of Mars. In this study, we have performed a Geographic Information System-based comparative investigation of their tectonic histories using published geologic map information and Mars Orbiter Laser Altimetry (MOLA) data. Our primary objective is to assess their evolutional histories by focusing on their extent of deformation in space and time through stratigraphic, paleotectonic, topographic, and geomorphologic analyses. Though there are similarities among the two prominent features, there are several distinct differences, including timing deformational extent, and tectonic intensity of formation. Whereas Alba Patera displays a major pulse of activity during the Late Hesperian/Early Amazonian, Syria Planum is a long-lived center that displays a more uniform distribution of simple graben densities ranging from the Noachian to the Amazonian, many of which occur at greater distances away from the primary center of activity. The histories of the two features presented here are representative of the complex, long-lived evolutional history of Tharsis. ?? 2004 Elsevier Inc. All rights reserved.

The Yilgarn Craton western Australia: A tectonic synthesis

NASA Technical Reports Server (NTRS)

Fripp, R. E. P.

1986-01-01

The Yilgarn Craton in Western Australia is one of the larger contiguous preserved Archaean crustal fragments, with an area of about 650,000 square kilometres. Of this, by area, about 70% is granitoid and 30% greenstone. The Craton is defined by the Darling Fault on its western margin, by Proterozoic deformation belts on its southern and northwestern margins, and by unconformable younger sediments on its eastern and northeastern margins. A regional geotectonic synthesis at a scale of 1:500,000 is being prepared. This is based largely upon the 1:250,000 scale mapping of the Geological Survey of Western Australia together with interpretation using geophysical data, mainly airborne magnetic surveys. On a regional basis the granitoids are classied as pre-, syn- and post-tectonic with respect to greenstone belt deformation. The post-tectonic granitoids yield Rb-Sr isochrons of about 2.6 b.y., close to Rb-Sr ages for the greenstones themselves which are up to about 2.8 b.y. old, although data for the latter is sparse. Contacts between earlier granitoids and greenstones which are not obscured by the post-tectonic granitoids are most commonly tectonic contacts, intensely deformed and with mylonitic fabrics. The general concensus however is that there is a pre-tectonic, pre-greenhouse sialic gneiss preserved in places. A discussion follows.

A Digital Tectonic Activity Map of the Earth

NASA Technical Reports Server (NTRS)

Lowman, Paul; Masuoka, Penny; Montgomery, Brian; OLeary, Jay; Salisbury, Demetra; Yates, Jacob

1999-01-01

The subject of neotectonics, covering the structures and structural activity of the last 5 million years (i.e., post-Miocene) is a well-recognized field, including "active tectonics," focussed on the last 500,000 years in a 1986 National Research Council report of that title. However, there is a cartographic gap between tectonic maps, generally showing all features regardless of age, and maps of current seismic or volcanic activity. We have compiled a map intended to bridge this gap, using modern data bases and computer-aided cartographic techniques. The maps presented here are conceptually descended from an earlier map showing tectonic and volcanic activity of the last one million years. Drawn by hand with the National Geographic Society's 1975 "The Physical World" map as a base, the 1981 map in various revisions has been widely reproduced in textbooks and various technical publications. However, two decades of progress call for a completely new map that can take advantage of new knowledge and cartographic techniques. The digital tectonic activity map (DTM), presented in shaded relief (Fig. 1) and schematic (Fig. 2) versions, is the result. The DTM is intended to show tectonism and volcanism of the last one million years, a period long enough to be representative of global activity, but short enough that features such as fault scarps and volcanos are still geomorphically recognizable. Data Sources and Cartographic Methods The DTM is based on a wide range of sources, summarized in Table 1. The most important is the digital elevation model, used to construct a shaded relief map. The bathymetry is largely from satellite altimetry, specifically the marine gravity compilations by Smith and Sandwell (1996). The shaded relief map was designed to match the new National Geographic Society world physical map (1992), although drawn independently, from the digital elevation model. The Robinson Projection is used instead of the earlier Van der Grinten one. Although neither

Survey explores active tectonics in northeastern Caribbean

USGS Publications Warehouse

Carbó, A.; Córdoba, D.; Muñoz-Martín, A.; Granja, J.L.; Martín-Dávila, J.; Pazos, A.; Catalán, M.; Gómez, M.; ten Brink, Uri S.; von Hillebrandt, Christa; Payero, J.

2005-01-01

There is renewed interest in studying the active and complex northeastern Caribbean plate boundary to better understand subduction zone processes and for earthquake and tsunami hazard assessments [e.g., ten Brink and Lin, 2004; ten Brink et al., 2004; Grindlay et al., 2005]. To study the active tectonics of this plate boundary, the GEOPRICO-DO (Geological, Puerto Rico-Dominican) marine geophysical cruise, carried out between 28 March and 17 April 2005 (Figure 1), studied the active tectonics of this plate boundary.Initial findings from the cruise have revealed a large underwater landslide, and active faults on the seafloor (Figures 2a and 2c). These findings indicate that the islands within this region face a high risk from tsunami hazards, and that local governments should be alerted in order to develop and coordinate possible mitigation strategies.

Modeling the Evolution of Localized Strain in Orogenic Wedges: From Short-term Deformation to Long-term Tectonic States

NASA Astrophysics Data System (ADS)

Weiss, J. R.; Ito, G.; Brooks, B. A.; Olive, J. A. L.; Foster, J. H.; Howell, S. M.

2015-12-01

Some of the most destructive earthquakes on Earth are associated with active orogenic wedges. Despite a sound understanding of the basic mechanics that govern whole wedge structure over geologic time scales and a growing body of studies that have characterized the deformation associated with historic to recent earthquakes, first order questions remain about the linkage of the two sets of processes at the intermediate seismotectonic timescales. Numerical models have the power to test the effects of specific mechanical conditions on the evolution of observables at active orogenic wedges. Here we use a two-dimensional, continuum mechanics-based, finite difference method with a visco-elasto-plastic rheology coupled with surface processes to investigate the spatiotemporal distribution of deformation during wedge growth. The model simulates the contraction of a crustal layer overlying a weak base (décollement) against a rigid backstop and the spontaneous nucleation and evolution of fault zones due to cohesive, Mohr-Coulomb failure with strain weakening. Consistent with critical wedge theory, the average slope across the wedge is controlled by the relative frictional strengths of the wedge and décollement. Initial calculations predict changes in wedge deformation on short geologic timescales (103-105yrs) that involve episodes of widening as new, foreland-verging thrusts nucleate near the surface beyond the wedge toe and propagate down-dip to intersect the décollement. All the while, the wedge thickens via slip on older, internal fault zones. The aim of this study is to identify the parameters controlling the timescales of 1) episodic widening versus thickening and 2) nucleation and life-span of individual fault zones. These are initial steps needed to link earthquake observations to the long-term tectonic states inferred at various orogenic belts around the world.

Studying the active deformation of distributed plate boundaries by integration of GNSS networks

NASA Astrophysics Data System (ADS)

D'Agostino, Nicola; Avallone, Antonio; Cecere, Gianpaolo; D'Anastasio, Elisabetta

2013-04-01

In the last decade GNSS networks installed for different purposes have proliferated in Italy and now provide a large amount of data available to geophysical studies. In addition to the existing regional and nation-wide scientific GNSS networks developed by ASI (http://geodaf.mt.asi.it), INGV (http://ring.gm.ingv.it) and OGS (http://crs.inogs.it/frednet), a large number (> 400) of continuously-operating GPS stations have been installed in the framework of regional and national networks, both publicly-operated and commercial, developed to provide real-time positioning capability to surveyors. Although the quality of the data and metadata associated to these stations is generally lower with respect to the "scientific" CGPS stations, the increased density and redundancy in crustal motion information, resulting in more than 500 stations with more than 2.5 years of observations, significantly increase the knowledge of the active deformation of the Italian territory and provides a unique image of the crustal deformation field. The obtained GPS velocity field is analysed and various features ranging from the definition of strain distribution and microplate kinematics within the plate boundary, to the evaluation of tectonic strain accumulation on active faults are presented in this work. Undeforming, aseismic regions (Sardinia, Southern Apulia) provide test sites to evaluate the lower bound on the accuracy achievable to measure tectonic deformation. Integration of GNSS networks significantly improves the resolution of the strain rate field in Central Italy showing that active deformation is concentrated in a narrow belt along the crest of the Apennines, consistently with the distribution of the largest historical and recent earthquakes. Products derived from dense GPS velocity and strain rate fields include map of earthquake potential developed under the assumption that the rate of seismic moment accumulation measured from geodesy distributes into earthquake sizes that

Late Cenozoic tectonic activity of the Altyn Tagh range: Constraints from sedimentary records from the Western Qaidam Basin, NE Tibetan Plateau

NASA Astrophysics Data System (ADS)

Zhang, Tao; Fang, Xiaomin; Wang, Yadong; Song, Chunhui; Zhang, Weilin; Yan, Maodu; Han, Wenxia; Zhang, Dawen

2018-07-01

The Altyn Tagh range (ATR) is the northern geological boundary of the Tibetan Plateau and plays a key role in accommodating its Cenozoic lithospheric deformation. However, knowledge of the structural style and age of uplift of the ATR is limited and controversial. The Qaidam Basin, in the southeast side of the ATR, provides an outstanding field laboratory for understanding the history and mechanisms of ATR growth. This study presents a detailed sedimentological analysis of a 1040-m-thick late Cenozoic ( 17-5.0 Ma) sedimentary sequence from the western Qaidam Basin, together with the analysis of sedimentological data from nearby boreholes and sections. Our aims were to determine the spatiotemporal evolution of the sedimentary sequences in the study area and to explore their response to late Cenozoic tectonic activity in the ATR. The results show three major intervals of the sedimentary characteristics in the study area: >17-16 Ma, 10 Ma and <5 Ma, which are closely related to the development of unconformities and growth strata recorded by high-resolution seismic reflection profiles. Combining the results with a comprehensive provenance analysis and with published records of regional climate change and tectonic activity, we discuss the possible factors responsible for the variations in the sedimentary characteristics of the studied sections. We conclude that significant tectonic responses in the western Qaidam Basin during the late Cenozoic were caused by three stages of tectonic activity of the ATR, at >17-16 Ma, 16-10 Ma and 10 Ma, during which the ATR respectively experienced tectonic uplift, fast strike-slip motion and intense uplift.

Venus: Mantle convection, hotspots, and tectonics

NASA Technical Reports Server (NTRS)

Phillips, R. J.

1989-01-01

The putative paradigm that planets of the same size and mass have the same tectonic style led to the adaptation of the mechanisms of terrestrial plate tectonics as the a priori model of the way Venus should behave. Data acquired over the last decade by Pioneer Venus, Venera, and ground-based radar have modified this view sharply and have illuminated the lack of detailed understanding of the plate tectonic mechanism. For reference, terrestrial mechanisms are briefly reviewed. Venusian lithospheric divergence, hotspot model, and horizontal deformation theories are proposed and examined.

The nappes of the Lepontine dome: the influence of tectonic inheritance on their deformation style

NASA Astrophysics Data System (ADS)

Schenker, Filippo Luca; Ambrosi, Christian; Scapozza, Cristian; Czerki, Dorota; Castelletti, Claudio; Maino, Matteo; Gouffon, Yves

2017-04-01

The Lepontine dome exposes the tectonostratigraphy of the Central Alps, from bottom-to-top, the subpenninic gneissic nappes of the Leventina, Simano, Adula/Cima-Lunga and Maggia. These units were part of a post-Variscan gneissic crust, which was intensely intruded by several generations of granitoids forming laccoliths and dikes of different shapes and sizes within paragneisses, augengneisses and amphibolites. During the Alpine orogenic cycle this initial and complex geological architecture was reshaped into a fold and thrust belt. We present the effect of these initial rheological anomalies along the Leventina, Simano and Adula/Cima-Lunga units through the geological map of the Osogna sheet (Swiss National Map no. 1293,1:25'000) together with structural and metamorphic data. The geological map shows that the Simano and Adula/Cima-Lunga units have an internal and lateral lithological variation at different scales as illustrated by the geological cross-sections. All lithologies present a penetrative amphibolite-facies foliation, which can vary in intensity among the rock-types. On the foliation plane a mineral and stretching lineation is visible dipping NW or SE, depending on the plane dip direction. The kinematic analysis indicates a top-to-the NW shearing. Despite this consistent structural data showing a regional dominant fabric, the folds (generally with a fold-axis parallel to the lineation) show different styles, depending on the thickness and the rock-type of the folded horizon and matrix, do not form laterally continuous structures and often are not cylindrical. As a consequence, such structures are interpreted as local perturbation rather than structures of regional importance. Furthermore, the Leventina and the Simano boundary is locally incongruent with the tectonic contact of the published maps. The amphibolite and paragneisses, used in the past as nappe divider, result to be deformed magmatic xenoliths. Therefore we present evidence (i) of a bottom

Active Deformation of the Northern Cordillera Observed with GPS

NASA Astrophysics Data System (ADS)

Elliott, J.; Jiang, Y.; Leonard, L. J.; Hyndman, R. D.; Freymueller, J.; Mazzotti, S.

2017-12-01

The Northern Cordillera, which encompasses western Canada and eastern Alaska, is a complex tectonic puzzle. Past terrane accretions, the present collision of the Yakutat block, large-scale plate motions, and past and present glacier change have created a tectonic landscape that includes a major transform system, most of the highest peaks in North America, and far-flung ongoing distributed deformation. We present an updated GPS velocity field as well as a new integrated tectonic block model for the region. The style of deformation varies through the region. Surrounding the Yakutat collision, the model includes a number of small blocks that indicate rotations to the east, north, and west as material moves away from the collisional front. These small blocks also show evidence of internal deformation. Farther from the collisional front, blocks are larger and appear to behave more rigidly. In the south, northwestward motion resulting in a prominent band of coastal shear extends from Vancouver Island to Glacier Bay. In the Arctic, small southeastward motions in Alaska transition to easterly motion in Canada that extends to the Mackenize Mountains near the Cordillera-craton boundary. A number of faults and fault systems accommodate relative Pacific-North America plate motion in the region, although the significant majority is along the Fairweather-Queen Charlotte transform system and the St. Elias fold-and-thrust belt. Along the Fairweather-Queen Charlotte system, the motion is dominantly dextral with increasing oblique transpression to the south corresponding to a change in margin trend. At the northern end of the transform system, motion is distributed onto multiple faults. Roughly 75% of the Fairweather motion is transferred west into the St. Elias fold-and-thrust belt, which accommodates 30 mm/yr of convergence. The remaining 25% is transferred north towards the dextral Denali-Totschunda system. The eastern Denali fault presently plays a minor role in accommodating

Topographyc metrics in the southern sector of the Marche foothills: implication for active tectonic analysis

NASA Astrophysics Data System (ADS)

Materazzi, Marco; Aringoli, Domenico; Carducci, Tamara; Cavitolo, Paolo; Farabollini, Piero; Giacopetti, Marco; Pambianchi, Gilberto; Tondi, Emanuele; Troiani, Francesco

2016-04-01

Quantitative geomorphic analysis can be provided a useful contribution to the study of recent tectonics. Some parameters, that quantify the channels morphology, as the Stream Length-Gradient (SL) Index (Hack, 1973) and the Steepness (Ks) Index (Flint, 1974), are generally used to detect anomalies on the expected concave-up equilibrium stream-profile, which can result in local abrupt changes in stream gradient (i.e., knickpoints) and/or broad convexities on stream long-profiles extending for tens of kilometres (i.e., knickzones). The main goal of this work is the study of the morphological and morphometrical features in the southern sector of the Marche Region, with the aim to gain new knowledge on the influences of rock resistance and rock uplift on the fluvial and topographic system. The investigated area is situated in central Italy and it extends from the axial zone of the Umbria-Marche Apennines to the Adriatic Sea, including the southern sector of the Marche Region and belongs to the foredeep domain of the Apennines orogenic system, which has affected by tectonic activity up to very recent times. The rheology of outcropping deposits doesn't allow the strain to be easily recorded at the outcrop scale. The analyses have been aimed at to test the sensitivity of both SL and Ks for evaluating active crustal deformations, acting at different wavelengths on land surface, within a low tectonically active thrust-and-fold belt. Additional purpose was the understanding of the pattern of regional differential crustal activity in the topographic arrangement of the study area In this research project two sets of analysis were conducted. References Hack J.T. 1973. Stream-profile analysis and stream-gradient index. Journal of Research of the U.S. Geological Survey, 1, 421-429. Flint J.J. 1974. Stream gradient as a function of order, magnitude and discharge. Water Resources Research, 10, 969-973.

Indentation tectonics in northern Taiwan: insights from field observations and analog models

NASA Astrophysics Data System (ADS)

Lu, Chia-Yu; Lee, Jian-Cheng; Malavieille, Jacques

2017-04-01

In northern Taiwan, contraction, extension, transcurrent shearing, and block rotation are four major tectonic deformation mechanisms involved in the progressive deformation of this arcuate mountain belt. The recent evolution of the orogen is controlled not only by the oblique convergence between the Eurasian plate and the Philippine Sea plate but also by the corner shape of the plate boundary. Based on field observations, analyses, geophysical data (mostly GPS) and results of experimental models, we interpret the curved shape of northern Taiwan as a result of contractional deformation (involving imbricate thrusting and folding, backthrusting and backfolding). The subsequent horizontal and vertical extrusion, combined with increasing transcurrent & rotational deformation (bookshelf-type strike-slip faulting and block rotation) induced transcurrent/ rotational extrusion and extrusion related extensional deformation. A special type of extrusional folds characterizes that complex deformation regime. The tectonics in northern Taiwan reflects a single, regional pattern of deformation. The crescent-shaped mountain belt develops in response to oblique indentation by an asymmetric wedge indenter, retreat of Ryukyu trench and opening of the Okinawa trough. Three sets of analog sandbox models are presented to illustrate the development of tectonic structures and their kinematic evolution

Venus tectonics - Initial analysis from Magellan

NASA Technical Reports Server (NTRS)

Solomon, Sean C.; Head, James W.; Kaula, William M.; Schubert, Gerald; Mckenzie, Dan

1991-01-01

The styles of lithospheric deformation, the inferred mechanical properties of the lithosphere, and their implications for the tectonic history of Venus are discussed on the basis of radar imaging and altimetry data from Magellan. Observations of the planet plains reveal a superposition of different episodes of deformation and volcanism, strain both distributed and concentrated into zones of extension and shortening, and features reflecting a crustal response to mantle dynamic processes. Lithospheric shortening and crustal thickening are represented by ridge belts and mountain belts. The latter show the evidence for extension and collapse both during and following crustal compression. Venus displays quasi-circular coronae and broad rises with linear rift zones, associated with significant volcanism. Large-offset strike-slip faults have not been observed, although horizontal shear is accommodated across broad zones of crustal shortening. On Venus strain is distributed across zones that are one to a few hundred kilometers wide, and separated by stronger and less deformed blocks hundreds of kilometers in width, as in actively deforming continental regions on earth.

Reports on crustal movements and deformations. [bibliography

NASA Technical Reports Server (NTRS)

Cohen, S. C.; Peck, T.

1983-01-01

This Catalog of Reports on Crustal Movements and Deformation is a structured bibliography of scientific papers on the movements of the Earth crust. The catalog summarizes by various subjects papers containing data on the movement of the Earth's surface due to tectonic processes. In preparing the catalog we have included studies of tectonic plate motions, spreading and convergence, microplate rotation, regional crustal deformation strain accumulation and deformations associated with the earthquake cycle, and fault motion. We have also included several papers dealing with models of tectonic plate motion and with crustal stress. Papers which discuss tectonic and geologic history but which do not present rates of movements or deformations and papers which are primarily theoretical analyses have been excluded from the catalog. An index of authors cross-referenced to their publications also appears in the catalog. The catalog covers articles appearing in reviewed technical journals during the years 1970-1981. Although there are citations from about twenty journals most of the items come from the following publications: Journal of Geophysical Research, Tectonophysics, Geological Society of America Bulletin of the Seismological Society of America, Nature, Science, Geophysical Journal of the Royal Astronomical Society, Earth and Planetary Science Letters, and Geology.

Deformation geometry and timing of theWupoer thrust belt in the NE Pamir and its tectonic implications

NASA Astrophysics Data System (ADS)

Cheng, Xiaogan; Chen, Hanlin; Lin, Xiubin; Yang, Shufeng; Chen, Shenqiang; Zhang, Fenfen; Li, Kang; Liu, Zelin

2016-12-01

The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau's tectonic evolution. Here we present new findings on the deformation geometry and timing of the Wupoer thrust belt at the northeastern margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene (N2) and the underlying Miocene (N1) or Paleogene (Pg) strata associated with two other local unconformities between Lower Pleistocene (Q1) and N2 and between Middle Pleistocene (Q2-4) and Q1 strata. Results of structural restorations suggest that compressional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, combined with previous studies on the Kongur and Tarshkorgan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concurrent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a décollement along which both the extensional and compressional faults merged.

Geological timing and duration of methane seepage in different sedimentary and tectonic settings in the Lower Congo Basin

NASA Astrophysics Data System (ADS)

Wenau, S.; Spiess, V.

2016-12-01

Methane seepage sites have been investigated in the Lower Congo Basin using seismo-acoustic methods in combination with geological and geochemical sampling. Pockmarks were observed in different areas of the Lower Congo Basin that are affected by different styles of salt-tectonic deformation and sedimentary input. At the salt front in the southern part of the basin, methane seepage shifts continuously westwards as previously undeformed sediments are affected by westward moving salt. Older seepage sites to the East are cut off from methane supply in the process of continuing salt-tectonic deformation. The initiation of gas accumulation and seepage directly at the deformation front is expected in the late Miocene due to salt-induced uplift. In the northern part of the basin on the lower slope, methane seepage is focused along salt-tectonic faults connecting Pliocene fan deposits to the seafloor, breaching the hemipelagic seal. These sites show indications for continuing seepage for the last 640 kyrs. Such long term seepage activity may be due to the lack of polygonal faults in the hemipelagic seal, focusing gas migration on fewer, salt-tectonic faults. Westward of the salt front, seepage features include the Regab pockmark where a potential reservoir in an Early Pleistocene channel flank is connected to the seafloor feature via a seismic chimney. Seepage activity in this area is also documented to be continuous over geologic time scales by seafloor and sub-seafloor seepage indications such as chimneys, pockmarks and buried seepage features. The Lower Congo Basin thus documents the longevity of seepage processes in the context of various tectonic and sedimentary regimes on a passive continental margin. Indications of the duration of seepage activity at individual sites may be used for methane budgeting in combination with emission rates estimated for typical seepage sites.

Preliminary deformation model for National Seismic Hazard map of Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meilano, Irwan; Gunawan, Endra; Sarsito, Dina

Preliminary deformation model for the Indonesia’s National Seismic Hazard (NSH) map is constructed as the block rotation and strain accumulation function at the elastic half-space. Deformation due to rigid body motion is estimated by rotating six tectonic blocks in Indonesia. The interseismic deformation due to subduction is estimated by assuming coupling on subduction interface while deformation at active fault is calculated by assuming each of the fault‘s segment slips beneath a locking depth or in combination with creeping in a shallower part. This research shows that rigid body motion dominates the deformation pattern with magnitude more than 15 mm/year, except inmore » the narrow area near subduction zones and active faults where significant deformation reach to 25 mm/year.« less

Present-day Horizontal Mobility in the Serbian Part of the Pannonian Basin; Inferences from the Geometric Analysis of Deformations

NASA Astrophysics Data System (ADS)

Sušić, Zoran; Toljić, Marinko; Bulatović, Vladimir; Ninkov, Toša; Stojadinović, Uroš

2016-10-01

In tectonically complex environments, such as the Pannonian Basin surrounded by the Alps-Dinarides and Carpathians orogens, monitoring of recent deformations represents very challenging matter. Efficient quantification of active continental deformations demands the use of a multidisciplinary approach, including neotectonic, seismotectonic and geodetic methods. The present-day tectonic mobility in the Pannonian Basin is predominantly controlled by the northward movement of the Adria micro-plate, which has produced compressional stresses that were party accommodated by the Alps-Dinarides thrust belt and partly transferred towards its hinterland. Influence of thus induced stresses on the recent strain field, deformations and tectonic mobility in the southern segment of the Pannonian Basin has been investigated using GPS measurements of the horizontal mobility in the Vojvodina area (northern Serbia).

Kinematics and age of Early Tertiary trench parallel volcano-tectonic lineaments in southern Mexico: Tectonic implications

NASA Astrophysics Data System (ADS)

Martini, M.; Ferrari, L.; Lopez Martinez, M.; Cerca Martinez, M.; Serrano Duran, L.

2007-05-01

We present new geological, structural, and geochronological data that constrain the timing and geometry of Early Tertiary strike slip deformation in southwestern Mexico and its relation with the concurrent magmatic activity. Geologic mapping in Guerrero and Michoacan States documented two regional WNW trending volcano-tectonic lineaments sub parallel to the present trench. The southernmost lineament runs for ~140 km from San Miguel Totolapan area (NW Guerrero) to Sanchiqueo (SE Michoacan), and passes through Ciudad Altamirano. Its southeastern part is marked by the alignment of at least eleven silicic to intermediate major domes as well as by the course of the Balsas River. The northwestern part of the lineament is characterized by ductile left lateral shear zones in Early Tertiary plutonic rocks observed in the Rio Chiquito valley. Domes near Ciudad Altamirano are unaffected by ductile shearing and yielded a ~42 Ma 40Ar/39Ar age, setting a minimum age for this deformation. The northern volcano-tectonic lineament runs for ~190 km between the areas of Huitzuco in northern Guerrero and the southern part of the Tzitzio fold in eastern Michoacan. The Huautla, Tilzapotla, Taxco, La Goleta and Nanchititla silicic centers (all in the range 37-34 Ma) are emplaced along this lineament, which continues to the WNW trough a mafic dike swarm exposed north of Tiquicheo (37-35 Ma) and the Purungueo subvolcanic body (~42 Ma). These rocks, unaffected by ductile shearing, give a minimum age of deformation similar to the southern Totolapan-Sanquicheo lineament. Post ~42 Ma deformation is essentially brittle and is characterized by several left lateral and right lateral transcurrent faults with typical Riedel patterns. Other trench-parallel left lateral shear zones active in pre-Oligocene times were recently reported in western Oaxaca. The recognizing of Early Tertiary trench-parallel and left-lateral ductile shearing in internal areas of southern Mexico suggest a field of widely

Magma-tectonic interactions in an area of active extension; a review of recent observations, models and interpretations from Iceland

NASA Astrophysics Data System (ADS)

Pedersen, Rikke; Sigmundsson, Freysteinn; Drouin, Vincent; Rafn Heimisson, Elías; Parks, Michelle; Dumont, Stéphanie; Árnadóttir, Þóra; Masterlark, Timothy; Ófeigsson, Benedíkt G.; Jónsdóttir, Kristín; Hooper, Andrew

2016-04-01

The geological setting of Iceland provides rich opportunities of studying magma-tectonic interactions, as it constitutes Earth's largest part of the mid-oceanic ridge system exposed above sea level. A series of volcanic and seismic zones accommodate the ~2 cm/year spreading between the North-American and Eurasian plates, and the Icelandic hot-spot conveniently provides the means of exposing this oceanic crust-forming setting above sea-level. Both extinct and active plumbing system structures can be studied in Iceland, as the deeply eroded tertiary areas provide views into the structures of extinct volcanic systems, and active processes can be inferred on in the many active volcanic systems. A variety of volcanic and tectonic processes cause the Icelandic crust to deform continuously, and the availability of contemporaneous measurements of crustal deformation and seismicity provide a powerful data set, when trying to obtain insight into the processes working at depth, such as magma migration through the uppermost lithosphere, magma induced host rock deformation and volcanic eruption locations and styles. The inferences geodetic and seismic datasets allow on the active plate spreading processes and subsurface magma movements in Iceland will be reviewed, in particular in relation to the Northern Volcanic Zone (NVZ). There the three phases of a rifting cycle (rifting, post-rifting, inter-rifting) have been observed. The NVZ is an extensional rift segment, bounded to the south by the Icelandic mantle plume, and to the north by the Tjörnes transform zone. The NVZ has typically been divided into five partly overlapping en-echelon fissure swarms, each with a central main volcanic production area. Most recently, additional insight into controlling factors during active rifting has been provided by the Bárðarbunga activity in 2014-2015 that included a major rifting event, the largest effusive eruption in Iceland since 1783, and a gradual caldera collapse. It is evident

Evaluation of the deformation parameters of the northern part of Eg

NASA Astrophysics Data System (ADS)

Mohamed, Abdel-Monem S.; Radwan, Ali M.; Sharf, Mohamed; Hamimi, Zakaria; Hegazy, Esraa E.; Abou Aly, Nadia; Gomaa, Mahmoud

2016-06-01

The northern part of Egypt is a rapidly growing development accompanied by the increased levels of standard living particularly in its urban areas. From tectonic and seismic point of views, the northern part of Egypt is one of the interested regions. It shows an active geologic structure attributed to the tectonic movements of the African and Eurasian plates from one side and the Arabian plate from the other side. From historical point of view and recent instrumental records, the northern part of Egypt is one of the seismo-active regions in Egypt. The investigations of the seismic events and their interpretations had led to evaluate the seismic hazard for disaster mitigation, for the safety of the densely populated regions and the vital projects. In addition to the monitoring of the seismic events, the most powerful technique of Global Navigation Satellite System (GNSS) will be used in determining crustal deformation where a geodetic network covers the northern part of Egypt. Joining the GPS Permanent stations of the northern part of Egypt with the Southern part of Europe will give a clear picture about the recent crustal deformation and the African plate velocity. The results from the data sets are compared and combined in order to determine the main characteristics of the deformation and hazard estimation for specified regions. Final compiled output from the seismological and geodetic analysis will throw lights upon the geodynamical regime of these seismo-active regions. This work will throw lights upon the geodynamical regime and to delineate the crustal stress and strain fields in the study region. This also enables to evaluate the active tectonics and surface deformation with their directions from repeated geodetic observations. The results show that the area under study suffers from continuous seismic activity related to the crustal movements taken place along trends of major faults

Active tectonic deformation of the western Indian plate boundary: A case study from the Chaman Fault System

NASA Astrophysics Data System (ADS)

Crupa, Wanda E.; Khan, Shuhab D.; Huang, Jingqiu; Khan, Abdul S.; Kasi, Aimal

2017-10-01

Collision of the Eurasian and Indian plates has resulted in two spatially offset subduction zones, the Makran subduction zone to the south and the Himalayan convergent margin to the north. These zones are linked by a system of left-lateral strike-slip faults known as the Chaman Fault System, ∼1200 km, which spans along western Pakistan. Although this is one of the greatest strike-slip faults, yet temporal and spatial variation in displacement has not been adequately defined along this fault system. This study conducted geomorphic and geodetic investigations along the Chaman Fault in a search for evidence of spatial variations in motion. Four study areas were selected over the span of the Chaman Fault: (1) Tarnak-Rud area over the Tarnak-Rud valley, (2) Spinatizha area over the Spinatizha Mountain Range, (3) Nushki area over the Nushki basin, and (4) Kharan area over the northern tip of the Central Makran Mountains. Remote sensing data allowed for in depth mapping of different components and faults within the Kohjak group. Wind and water gap pairs along with offset rivers were identified using high-resolution imagery and digital-elevation models to show displacement for the four study areas. The mountain-front-sinuosity ratio, valley height-to-width-ratio, and the stream-length-gradient index were calculated and used to determine the relative tectonic activity of each area. These geomorphic indices suggest that the Kharan area is the most active and the Tarnak-Rud area is the least active. GPS data were processed into a stable Indian plate reference frame and analyzed. Fault parallel velocity versus fault normal distance yielded a ∼8-10 mm/yr displacement rate along the Chaman Fault just north of the Spinatizha area. InSAR data were also integrated to assess displacement rates along the fault system. Geodetic data support that ultra-slow earthquakes similar to those that strike along other major strike-slip faults, such as the San Andreas Fault System, are

Relationships between tectonism, volcano-tectonism and volcanism: the Ischia island (Italy) case.

NASA Astrophysics Data System (ADS)

Marotta, E.; de Vita, S.; Orsi, G.; Sansivero, F.

2005-12-01

The resurgent calderas of Ischia, Campi Flegrei and Pantelleria are characterized by differentially displaced blocks, and distribution of later eruption vents in a well defined sector of the resurgent area. These features suggest a simple shearing block resurgence mechanism. Moreover, the studies carried out on Ischia and Campi Flegrei evidenced a very complex structural pattern due to deformation related to the local stress regime induced by magmatism and volcanism and also to reactivation of regional structures. In order to better define the relationships among tectonic, volcano-tectonic and caldera resurgence mechanism, a structural study has been carried out at Ischia, where the Mt. Epomeo has been uplifted of about 900 m in the past 30 ka. The measures taken on 1,400 planar surfaces (faults, joints and fracture cleavages) show that the resurgent area is composed of differentially displaced blocks whose uplifting is maximum for the Mt. Epomeo and decreases southeastward. The resurgent area has a poligonal shape resulting from the reactivation of regional faults and by the activation of faults directly related to volcano-tectonism. The limit of the resurgent area is not defined towards the north, as beach deposits displaced at variable elevation by E-W and NW-SE trending faults, are exposed along the coastline. The western sector is bordered by inward-dipping, high-angle reverse faults, whose directions vary from N40E to NS and N50W from NW to SW of the block, testifying a compressional stress regime active in this area. These features are cut by late outward-dipping normal faults due to gravitational readjustment of the slopes. Vertical faults border the block at NE ad SW with right transtensive and left transpressive movements, respectively. The area located to the east of the most uplifted block, characterized by a tensile stress regime, has been deformed by N-S, N40-70E and N15W trending normal faults, with maximum elongation direction along N50W. The

A detection method of subrecent to recent tectonic activity in the anticlinal system of the northern Negev, Israel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zilberman, E.; Wachs, D.

Geomorphological and geophysical methods combined with borehole information were employed to search for possible subrecent small-scale vertical movement along the anticlinal fold belt of the central Negev, Israel. Such tectonic deformation might indicate displacement on the buried reverse faults underneath the anticlines. Variations in the thickness of the alluvial fill in the study area, which are in accordance with the fold structures, could be an indication of recent folding activity along the anticlinal system. In order to detect these thickness variations in the alluvial fill, seismic refraction and electrical resistivity measurements were carries out along the valley of Nahal Besor,more » which crosses the anticlinal belt. The thickness variations of the alluvial fill along the valley were not found to indicate any significant tectonic movement along the anticlines during the Pleistocene. The thickest alluvium was found overlying a karst bedrock, hence karst relief is suggested to be responsible for these variations.« less

Temporal evolution of continental lithospheric strength in actively deforming regions

USGS Publications Warehouse

Thatcher, W.; Pollitz, F.F.

2008-01-01

It has been agreed for nearly a century that a strong, load-bearing outer layer of earth is required to support mountain ranges, transmit stresses to deform active regions and store elastic strain to generate earthquakes. However the dept and extent of this strong layer remain controversial. Here we use a variety of observations to infer the distribution of lithospheric strength in the active western United States from seismic to steady-state time scales. We use evidence from post-seismic transient and earthquake cycle deformation reservoir loading glacio-isostatic adjustment, and lithosphere isostatic adjustment to large surface and subsurface loads. The nearly perfectly elastic behavior of Earth's crust and mantle at the time scale of seismic wave propagation evolves to that of a strong, elastic crust and weak, ductile upper mantle lithosphere at both earthquake cycle (EC, ???10?? to 103 yr) and glacio-isostatic adjustment (GIA, ???103 to 104 yr) time scales. Topography and gravity field correlations indicate that lithosphere isostatic adjustment (LIA) on ???106-107 yr time scales occurs with most lithospheric stress supported by an upper crust overlying a much weaker ductile subtrate. These comparisons suggest that the upper mantle lithosphere is weaker than the crust at all time scales longer than seismic. In contrast, the lower crust has a chameleon-like behavior, strong at EC and GIA time scales and weak for LIA and steady-state deformation processes. The lower crust might even take on a third identity in regions of rapid crustal extension or continental collision, where anomalously high temperatures may lead to large-scale ductile flow in a lower crustal layer that is locally weaker than the upper mantle. Modeling of lithospheric processes in active regions thus cannot use a one-size-fits-all prescription of rheological layering (relation between applied stress and deformation as a function of depth) but must be tailored to the time scale and tectonic

Active tectonics of the northern Mojave Desert: The 2017 Desert Symposium field trip road log

USGS Publications Warehouse

Miller, David; Reynolds, R.E.; Phelps, Geoffrey; Honke, Jeff; Cyr, Andrew J.; Buesch, David C.; Schmidt, Kevin M.; Losson, G.

2017-01-01

The 2017 Desert Symposium field trip will highlight recent work by the U.S. Geological Survey geologists and geophysicists, who have been mapping young sediment and geomorphology associated with active tectonic features in the least well-known part of the eastern California Shear Zone (ECSZ). This area, stretching from Barstow eastward in a giant arc to end near the Granite Mountains on the south and the Avawatz Mountains on the north (Fig. 1-1), encompasses the two major structural components of the ECSZ—east-striking sinistral faults and northwest-striking dextral faults—as well as reverseoblique and normal-oblique faults that are associated with topographic highs and sags, respectively. In addition, folds and stepovers (both restraining stepovers that form pop-up structures and releasing stepovers that create narrow basins) have been identified. The ECSZ is a segment in the ‘soft’ distributed deformation of the North American plate east of the San Andreas fault (Fig. 1-1), where it takes up approximately 20-25% of plate motion in a broad zone of right-lateral shear (Sauber et al., 1994) The ECSZ (sensu strictu) begins in the Joshua Tree area and passes north through the Mojave Desert, past the Owens Valley-to-Death Valley swath and northward, where it is termed the Walker Lane. It has been defined as the locus of active faulting (Dokka and Travis, 1990), but when the full history from about 10 Ma forward is considered, it lies in a broader zone of right shear that passes westward in the Mojave Desert to the San Andreas fault (Mojave strike-slip province of Miller and Yount, 2002) and passes eastward to the Nevada state line or beyond (Miller, this volume).We will visit several accessible highlights for newly studied faults, signs of young deformation, and packages of syntectonic sediments. These pieces of a complex active tectonic puzzle have yielded some answers to longstanding questions such as: How is fault slip transfer in this area accommodated

Tectonic state: its significance and characterization in the assessment of seismic effects associated with reservoir impounding

USGS Publications Warehouse

Castle, R.O.; Clark, M.M.; Grantz, A.; Savage, J.C.

1980-01-01

Any analysis of seismicity associated with the filling of large reservoirs requires an evaluation of the natural tectonic state in order to determine whether impoundment is the basic source, a mechanically unrelated companion feature, or a triggering stimulus of the observed seismicity. Several arguments indicate that the associated seismicity is usually a triggered effect. Among the elements of tectonic state considered here (existing fractures, accumulated elastic strain, and deformational style), deformational style is especially critical in forecasting the occurrence of impoundment-induced seismicity. The observational evidence indicates that seismicity associated with impounding generally occurs in areas that combine steeply dipping faults, relatively high strain rates, and either extensional or horizontal-shear strain. Simple physical arguments suggest: (1) that increased fluid pressures resulting from increased reservoir head should enhance the likelihood of seismic activity, whatever the tectonic environment; (2) that stress changes resulting from surface loading may increase the likelihood of crustal failure in areas of normal and transcurrent faulting, whereas they generally inhibit failure in areas of thrust faulting. Comparisons with other earthquake-producing artificial and natural processes (underground explosions, fluid injection, underground mining, fluid extraction, volcanic emissions) indicate that reservoir loading may similarly modify the natural tectonic state. Subsurface loading resulting from fluid extraction may be a particularly close analogue of reservoir loading; "seismotectonic" events associated with fluid extraction have been recognized in both seismically active and otherwise aseismic regions. Because the historic record of seismicity and surface faulting commonly is short in comparison with recurrence intervals of earthquake and fault-slip events, tectonic state is most reliably appraised through combined studies of historic

Plate tectonics beyond plate boundaries: the role of ancient structures in intraplate orogenesis

NASA Astrophysics Data System (ADS)

Heron, Philip; Pysklywec, Russell; Stephenson, Randell

2015-04-01

The development of orogens that occur at a distance from plate boundaries (i.e., `intraplate' deformation) cannot be adequately explained through conventional plate tectonic theory. Intraplate deformation infers a more complex argument for lithospheric and mantle interaction than plate tectonic theory allows. As a result, the origins of intraplate orogenesis are enigmatic. One hypothesis is the amalgamation of continental material (i.e., micro-plates) leaves inherent scars on the crust and mantle lithosphere. Previous studies into continent-continent collisions identify a number of scenarios from accretionary tectonics that affect the crust and mantle (namely, the development of a Rayleigh-Taylor instability, lithospheric underplating, lithospheric delamination, and lithospheric subduction). Any of these processes may weaken the lithosphere allowing episodic reactivation of faults within continental interiors. Hence, continental convergence (i.e., shortening) at a time after continental collision may cause the already weakened crust and mantle lithosphere to produce intraplate deformation. In order to better understand the processes involved in deformation away from plate boundaries, we present suites of continental shortening models (using the high-resolution thermal-mechanical modelling code SOPALE) to identify the preferred style of deformation. We model ancient structures by applying weak subduction scarring, changing the rheological conditions, and modifying the thermal structure within the lithosphere. To highlight the role of surface processes on plate and lithosphere deformation, the effect of climate-driven erosion and deposition on the tectonic structure of intraplate deformation is also addressed. We explore the relevance of the models to previously studied regions of intraplate orogenesis, including the Pyrenees in Europe, the Laramide orogen in North America, Tien Shan orogen in Central Asia, and Central Australia. The findings of the simulations with

The polyphased tectonic evolution of the Anegada Passage in the northern Lesser Antilles subduction zone

NASA Astrophysics Data System (ADS)

Laurencin, M.; Marcaillou, B.; Graindorge, D.; Klingelhoefer, F.; Lallemand, S.; Laigle, M.; Lebrun, J.-F.

2017-05-01

The influence of the highly oblique plate convergence at the northern Lesser Antilles onto the margin strain partitioning and deformation pattern, although frequently invoked, has never been clearly imaged. The Anegada Passage is a set of basins and deep valleys, regularly related to the southern boundary of the Puerto Rico-Virgin Islands (PRVI) microplate. Despite the publications of various tectonic models mostly based on bathymetric data, the tectonic origin and deformation of this Passage remains unconstrained in the absence of deep structure imaging. During cruises Antithesis 1 and 3 (2013-2016), we recorded the first deep multichannel seismic images and new multibeam data in the northern Lesser Antilles margin segment in order to shed a new light on the structure and tectonic pattern of the Anegada Passage. We image the northeastern extent of the Anegada Passage, from the Sombrero Basin to the Lesser Antilles margin front. Our results reveal that this northeastern segment is an EW trending left-stepping en échelon strike-slip system that consists of the Sombrero and Malliwana pull-apart basins, the Malliwana and Anguilla left-lateral faults, and the NE-SW compressional restraining bend at the Malliwana Hill. Reviewing the structure of the Anegada Passage, from the south of Puerto Rico to the Lesser Antilles margin front, reveals a polyphased tectonic history. The Anegada Passage is formed by a NW-SE extension, possibly related to the rotation or escape of PRVI block due to collision of the Bahamas Bank. Currently, it is deformed by an active WNW-ESE strike-slip deformation associated to the shear component of the strain partitioning resulting from the subduction obliquity.

Seismology: tectonic strain in plate interiors?

PubMed

Calais, E; Mattioli, G; DeMets, C; Nocquet, J-M; Stein, S; Newman, A; Rydelek, P

2005-12-15

It is not fully understood how or why the inner areas of tectonic plates deform, leading to large, although infrequent, earthquakes. Smalley et al. offer a potential breakthrough by suggesting that surface deformation in the central United States accumulates at rates comparable to those across plate boundaries. However, we find no statistically significant deformation in three independent analyses of the data set used by Smalley et al., and conclude therefore that only the upper bounds of magnitude and repeat time for large earthquakes can be inferred at present.

Quantitative morphometric analysis for the tectonic characterisation of northern Tunisia.

NASA Astrophysics Data System (ADS)

Camafort, Miquel; Pérez-Peña, José Vicente; Booth-Rea, Guillermo; Ranero, César R.; Gràcia, Eulàlia; Azañón, José Miguel; Melki, Fetheddine; Ouadday, Mohamed

2016-04-01

Northern Tunisia is characterized by low deformation rates and low to moderate seismicity. Although instrumental seismicity reaches maximum magnitudes of Mw 5.5, some historical earthquakes have occurred with catastrophic consequences in this region. Aiming to improve our knowledge of active tectonics in Tunisia, we carried out both a quantitative morphometric analysis and field study in the north-western region. We applied different morphometric tools, like river profiles, knickpoint analysis, hypsometric curves and integrals and drainage pattern anomalies in order to differentiate between zones with high or low recent tectonic activity. This analysis helps identifying uplift and subsidence zones, which we relate to fault activity. Several active faults in a sparse distribution were identified. A selected sector was studied with a field campaign to test the results obtained with the quantitative analysis. During the fieldwork we identified geological evidence of recent activity and a considerable seismogenic potential along El Alia-Teboursouk (ETF) and Dkhila (DF) faults. The ETF fault could be responsible of one of the most devastating historical earthquakes in northern Tunisia that destroyed Utique in 412 A.D. Geological evidence include fluvial terraces folded by faults, striated and cracked pebbles, clastic dikes, sand volcanoes, coseismic cracks, etc. Although not reflected in the instrumental seismicity, our results support an important seismic hazard, evidenced by the several active tectonic structures identified and the two seismogenic faults described. After obtaining the current active tectonic framework of Tunisia we discuss our results within the western Mediterranean trying to contribute to the understanding of the western Mediterranean tectonic context. With our results, we suggest that the main reason explaining the sparse and scarce seismicity of the area in contrast with the adjacent parts of the Nubia-Eurasia boundary is due to its extended

Soft sediment deformation associated with the East Patna Fault south of the Ganga River, northern India: Influence of the Himalayan tectonics on the southern Ganga plain

NASA Astrophysics Data System (ADS)

Verma, Aditya K.; Pati, Pitambar; Sharma, Vijay

2017-08-01

The geomorphic, tectonic and seismic aspects of the Ganga plain have been studied by several workers in the recent decades. However, the northern part of this tectonically active plain has been the prime focus in most of the studies. The region to the south of the Ganga River requires necessary attention, especially, regarding the seismic activities. The region lying immediately south of the Outer Himalayas (i.e. the Ganga plain) responds to the stress regime of the Himalayan Frontal Thrust Zone by movement along the existing basement faults (extending from the Indian Peninsula) and creating new surface faults within the sediment cover as well. As a result, several earthquakes have been recorded along these basement faults, such as the great earthquakes of 1934 and 1988 associated with the East Patna Fault. Large zones of ground failure and liquefaction in north Bihar (close to the Himalayan front), have been recorded associated with these earthquakes. The present study reports the soft sediment deformation structures from the south Bihar associated with the prehistoric earthquakes near the East Patna Fault for the first time. The seismites have been observed in the riverine sand bed of the Dardha River close to the East Patna Fault. Several types of liquefaction-induced deformation structures such as pillar and pocket structure, thixotropic wedge, liquefaction cusps and other water escape structures have been identified. The location of the observed seismites within the deformed zone of the East Patna Fault clearly indicates their formation due to activities along this fault. However, the distance of the liquefaction site from the recorded epicenters suggests its dissociation with the recorded earthquakes so far and hence possibly relates to any prehistoric seismic event. The occurrence of the earthquakes of a magnitude capable of forming liquefaction structure in the southern Ganga plain indicates the transfer of stress regime far from the Himalayan front into

Transposition of foliations and superposition of lineations during polyphase deformation in the Nevado-Filabride complex: tectonic implications

NASA Astrophysics Data System (ADS)

Ruiz-Fuentes, Alejandro; Aerden, Domingo G. A. M.

2018-01-01

Detailed structural analysis in a ca. 80 km2 area of the western Nevado-Filabride complex (Betic Cordillera) reveals a heterogeneous internal structure characterized by multiple cross-cutting foliations and lineations that locally transpose earlier ones. The large-scale geometry of these fabrics conflicts with continuous westward to south-westward tectonic transport related to thrusting or crustal extension, and mismatches a previously inferred extensional detachment in the area. Multiple crenulation lineations can be distinguished in the field and correlated with five foliation intersection axes (FIA1-5) preserved in garnet and plagioclase porphyroblasts of the western Sierra Nevada. These indicate crustal shortening in different directions associated with vertical foliation development and intermitted stages of gravitational collapse producing horizontal foliations. The large spread of lineation- and fold-axes trends in the Nevado-Filabride complex results from the mixed presence of multiple generations of these structures whose distinction is critical for tectonic models. The five principal FIA trends remarkably match successive vectors of relative Africa-Iberia plate motion since the Eocene, suggesting that deformation of the Nevado-Filabride took place during this period, although peak metamorphism in at least some of its parts was reached as late as the Middle Miocene.

Kinematics of the asal rift (djibouti) determined from the deformation of fieale volcano.

PubMed

De Chabalier, J B; Avouac, J P

1994-09-16

Because of its subaerial exposure the Asal rift segment provides an exceptional opportunity to quantify the deformation field of an active rift and assess the contribution of tectonics and volcanism to rifting processes. The present topography of the Asal rift results from the tectonic dismemberment during the last 100,000 years of a large central volcanic edifice that formed astride the rift zone 300,000 to 100,000 years ago. Three-dimensional deformation of this volcano has been quantified from the combined analysis of the topography and geology. The analysis indicates that spreading at 17 to 29 millimeters per year in a N40 degrees +/- 5 degrees E direction accounts for most of the separation between Arabia and Somalia. The small topographic subsidence relative to extension suggests that tectonic thinning of the crust has been balanced by injection and underplating of magmatic material of near crustal density. The methodology developed in this study could also be applied to quantify deformation in relatively inaccessible areas where the main available information is topography or bathymetry.

Deformation and evolution of an experimental drainage network subjected to oblique deformation: Insight from chi-maps

NASA Astrophysics Data System (ADS)

Guerit, Laure; Goren, Liran; Dominguez, Stéphane; Malavieille, Jacques; Castelltort, Sébastien

2017-04-01

The morphology of a fluvial landscape reflects a balance between its own dynamics and external forcings, and therefore holds the potential to reveal local or large-scale tectonic patterns. Commonly, particular focus has been cast on the longitudinal profiles of rivers as they constitute sensitive recorders of vertical movements, that can be recovered based on models of bedrock incision. However, several recent studies have suggested that maps of rescaled distance along channel called chi (χ), derived from the commonly observed power law relation between the slope and the drainage area , could reveal transient landscapes in state of reorganization of basin geometry and location of water divides. If river networks deforms in response to large amount of distributed strain, then they might be used to reconstruct the mode and rate of horizontal deformation away from major active structures through the use of the parameter χ. To explore how streams respond to tectonic horizontal deformation, we develop an experimental model for studying river pattern evolution over a doubly-vergent orogenic wedge growing in a context of oblique convergence. We use a series of sprinklers located about the experimental table to activate erosion, sediment transport and river development on the surface of the experimental wedge. At the end of the experiment, the drainage network is statistically rotated clockwise, confirming that rivers can record the distribution of motion along the wedge. However, the amount of rotation does not match with the imposed deformation, and thus we infer that stream networks are not purely passive markers. Based on the comparison between the observed evolution of the fluvial system and the predictions made from χ maps, we show that the plan-view morphology of the streams results from the competition between the imposed deformation and fluvial processes of drainage reorganization.

Multifaulting in a tectonic syntaxis revealed by InSAR: The case of the Ziarat earthquake sequence (Pakistan)

NASA Astrophysics Data System (ADS)

Pinel-Puysségur, B.; Grandin, R.; Bollinger, L.; Baudry, C.

2014-07-01

On 28-29 October 2008, within 12 h, two similar Mw = 6.4 strike-slip earthquakes struck Baluchistan (Pakistan), as part of a complex seismic sequence. Interferometric Synthetic Aperture Radar (InSAR) data reveal that the peak of surface displacement is near the Ziarat anticline, a large active fold affected by Quaternary strike-slip faulting. All coseismic interferograms integrate the deformation due to both earthquakes. As their causative faults ruptured close to each other, the individual signals cannot be separated. According to their focal mechanisms, each earthquake may have activated a NE-SW sinistral or a NW-SE dextral fault segment, which leads to four possible scenarios of fault orientations. A nonlinear inversion of the InSAR data set allows rejecting two scenarios. The best slip distributions on the two fault segments for the two remaining scenarios are determined by linear inversion. Stress-change modeling favors a scenario involving two abutting conjugate strike-slip faults. Two other fault segments accommodated left-lateral strike slip during the seismic sequence. The activated fault system includes multiple fault segments with different orientations and little surface expression. This may highlight, at a smaller scale, the distributed, possibly transient character of deformation within a broader right-lateral shear zone. It suggests that the activated faults delineate a small tectonic block extruding and subtly rotating within the shear zone. It occurs in the vicinity of the local tectonic syntaxis where orogenic structures sharply turn around a vertical axis. These mechanisms could participate in the long-term migration of active tectonic structures within this kinematically unstable tectonic syntaxis.

Pre-lithification tectonic foliation development in a clastic sedimentary sequence

NASA Astrophysics Data System (ADS)

Meere, Patrick; Mulchrone, Kieran; McCarthy, David; Timmermann, Martin; Dewey, John

2016-04-01

The current view regarding the timing of regionally developed penetrative tectonic fabrics in sedimentary rocks is that their development postdates lithification of those rocks. In this case fabric development is achieved by a number of deformation mechanisms including grain rigid body rotation, crystal-plastic deformation and pressure solution (wet diffusion). The latter is believed to be the primary mechanism responsible for shortening and the domainal structure of cleavage development commonly observed in low grade metamorphic rocks. In this study we combine field observations with strain analysis and modelling to fully characterise considerable (>50%) mid-Devonian Acadian crustal shortening in a Devonian clastic sedimentary sequence from south west Ireland. Despite these high levels of shortening and associated penetrative tectonic fabric there is a marked absence of the expected domainal cleavage structure and intra-clast deformation, which are expected with this level of deformation. In contrast to the expected deformation processes associated with conventional cleavage development, fabrics in these rocks are a product of translation, rigid body rotation and repacking of extra-formational clasts during deformation of an un-lithified clastic sedimentary sequence.

Fault kinematics and active tectonics of the Sabah margin: Insights from the 2015, Mw 6.0, Mt. Kinabalu earthquake

NASA Astrophysics Data System (ADS)

Wang, Y.; Wei, S.; Tapponnier, P.; WANG, X.; Lindsey, E.; Sieh, K.

2016-12-01

A gravity-driven "Mega-Landslide" model has been evoked to explain the shortening seen offshore Sabah and Brunei in oil-company seismic data. Although this model is considered to account simultaneously for recent folding at the edge of the submarine NW Sabah trough and normal faulting on the Sabah shelf, such a gravity-driven model is not consistent with geodetic data or critical examination of extant structural restorations. The rupture that produced the 2015 Mw6.0 Mt. Kinabalu earthquake is also inconsistent with the gravity-driven model. Our teleseismic analysis shows that the centroid depth of that earthquake's mainshock was 13 to 14 km, and its favored fault-plane solution is a 60° NW-dipping normal fault. Our finite-rupture model exhibits major fault slip between 5 and 15 km depth, in keeping with our InSAR analysis, which shows no appreciable surface deformation. Both the hypocentral depth and the depth of principal slip are far too deep to be explained by gravity-driven failure, as such a model would predict a listric normal fault connecting at a much shallower depth with a very gentle detachment. Our regional mapping of tectonic landforms also suggests the recent rupture is part of a 200-km long system of narrowly distributed active extension in northern Sabah. Taken together, the nature of the 2015 rupture, the belt of active normal faults, and structural consideration indicate that active tectonic shortening plays the leading role in controlling the overall deformation of northern Sabah and that deep-seated, onland normal faulting likely results from an abrupt change in the dip-angle of the collision interface beneath the Sabah accretionary prism.

Polyphase tectonics at the southern tip of the Manila trench, Mindoro-Tablas Islands, Philippines

NASA Astrophysics Data System (ADS)

Marchadier, Yves; Rangin, Claude

1990-11-01

The southern termination of the Manila trench within the South China Sea continental margin in Mindoro is marked by a complex polyphase tectonic fabric in the arc-trench gap area. Onshore Southern Mindoro the active deformation front of the Manila trench is marked by parallel folds and thrusts, grading southward to N50° W-trending left-lateral strike-slip faults. This transpressive tectonic regime, active at least since the Late Pliocene, has overprinted the collision of an Early Miocene volcanic arc with the South China Sea continental margin (San Jose platform). The collision is postdated by deposition of the Late Miocene-Early Pliocene elastics of the East Mindoro basin. The tectonic and geological framework of this arc, which overlies a metamorphic basement and Eocene elastics, suggests that it was built on a drifted block of the South China Sea continental margin.

Inventory of anthropogenic surface deformation measured by InSAR in the western U.S./Mexico and possible impacts on GPS measurements

NASA Astrophysics Data System (ADS)

Semple, A.; Pritchard, M. E.; Taylor, H.

2014-12-01

The western US and Mexico are deforming at several spatial scales that can be measured by ground and satellite observations like GPS and Interferometric Synthetic Aperture Radar (InSAR). Many GPS stations have been installed throughout this area to monitor ground deformation caused by large scale tectonic processes; however, several studies have noted that the data recorded at a GPS station can be contaminated by local, non-tectonic ground deformation. In this study, we use InSAR to examine deformation from various sources in the western US and Mexico. We chose this method due to the spatially large study area and the availability and temporal coverage of SAR imagery. We use SAR images acquired by the satellites Envisat, ERS-1 and ERS-2 over a time period from 1992-2010 to create several time series. Data from the ALOS satellite between 2006-2011 are also used in some areas. We use these time series analysis along with previously published results to observe and catalogue various sources of surface deformation in the western US and Mexico - from groundwater pumping, geothermal activity, mining, hydrocarbon production, and other sources. We then use these results to identify GPS stations that have potentially been contaminated by non-tectonic deformation signals. We document more than 150 distinct regions of non-tectonic and likely anthropogenic deformation. We have located 82 GPS stations within 20km of the center of at least one of the non-tectonic deformation signals we have identified. It is likely that the data from these 82 GPS stations have been contaminated by local anthropogenic deformation. Some examples of previously unpublished non-tectonic deformation we have seen in this study include but are not limited to, subsidence due to groundwater extraction in Jesus Garcia, Mexico, both uplift and subsidence due to natural gas extraction at Jonah Field in Sublette County, WY, and uplift due to a water recharge project in Tonopah, AZ.

Late-Paleozoic-Mesozoic deformational and deformation related metamorphic structures of Kuznetsk-Altai region

NASA Astrophysics Data System (ADS)

Zinoviev, Sergei

2014-05-01

Kuznetsk-Altai region is a part of the Central Asian Orogenic Belt. The nature and formation mechanisms of the observed structure of Kuznetsk-Altai region are interpreted by the author as the consequence of convergence of Tuva-Mongolian and Junggar lithospheric block structures and energy of collision interaction between the blocks of crust in Late-Paleozoic-Mesozoic period. Tectonic zoning of Kuznetsk-Altai region is based on the principle of adequate description of geological medium (without methods of 'primary' state recovery). The initial indication of this convergence is the crust thickening in the zone of collision. On the surface the mechanisms of lateral compression form a regional elevation; with this elevation growth the 'mountain roots' start growing. With an approach of blocks an interblock elevation is divided into various fragments, and these fragments interact in the manner of collision. The physical expression of collision mechanisms are periodic pulses of seismic activity. The main tectonic consequence of the block convergence and collision of interblock units is formation of an ensemble of regional structures of the deformation type on the basis of previous 'pre-collision' geological substratum [Chikov et al., 2012]. This ensemble includes: 1) allochthonous and autochthonous blocks of weakly deformed substratum; 2) folded (folded-thrust) systems; 3) dynamic metamorphism zones of regional shears and main faults. Characteristic of the main structures includes: the position of sedimentary, magmatic and PT-metamorphic rocks, the degree of rock dynamometamorphism and variety rock body deformation, as well as the styles and concentrations of mechanic deformations. 1) block terranes have weakly elongated or isometric shape in plane, and they are the systems of block structures of pre-collision substratum separated by the younger zones of interblock deformations. They stand out among the main deformation systems, and the smallest are included into the

Understanding and modeling volcanotectonic processes that generate surface deformation on active stratovolcanoes

NASA Astrophysics Data System (ADS)

Gudmundsson, A.

2005-05-01

Surface deformation on stratovolcanoes is the result of local stresses generated by various volcanotectonic processes. These processes include changes in fluid pressure in the associated geothermal fields and magma chambers, regional seismic or tectonic events, fault development, and dike injections. Here the focus is on magma-chamber pressure changes and dike injections. Surface deformation associated with magma-chamber pressure changes is normally referred to as inflation when the pressure increases, and as deflation when the pressure decreases. The processes that lead to inflation are primarily addition of new magma to the chamber and rapid exsolution of gas from the magma in the chamber. The processes that lead to deflation are primarily cooling (and contraction) of magma in the chamber, regional tectonic extension of the crust holding the chamber, and eruption and/or dike injection. Injection of dikes (including inclined sheets) is common in most active stratovolcanoes. However, no dike-fed eruptions can take place unless the local stress field within the volcano is favorable to feeder-dike formation. By contrast, if at any location - in any layer - in the stratovolcano the stress field is unfavorable to dike propagation, the dike becomes arrested and no eruption occurs. Detailed studies of dikes in stratovolcanoes worldwide indicate that most dikes become arrested and never reach the surface. However, arrested dikes may give rise to surface deformation, such as is commonly monitored during volcanic unrest periods. By definition, stratovolcanoes are composed of numerous alternating strata (layers) of pyroclastic material and lava flows. Commonly, these layers have widely different mechanical properties. In particular, some layers such as lava flows and welded pyroclastic flows may be stiff (with a high Young's modulus), whereas other layers, such as non-welded pyroclastic units, may be soft (with a low Young's modulus). Here I present new numerical models on

Holocene compression in the Acequión valley (Andes Precordillera, San Juan province, Argentina): Geomorphic, tectonic, and paleoseismic evidence

NASA Astrophysics Data System (ADS)

Audemard, M.; Franck, A.; Perucca, L.; Laura, P.; Pantano, Ana; Avila, Carlos R.; Onorato, M. Romina; Vargas, Horacio N.; Alvarado, Patricia; Viete, Hewart

2016-04-01

The Matagusanos-Maradona-Acequión Valley sits within the Andes Precordillera fold-thrust belt of western Argentina. It is an elongated topographic depression bounded by the roughly N-S trending Precordillera Central and Oriental in the San Juan Province. Moreover, it is not a piggy-back basin as we could have expected between two ranges belonging to a fold-thrust belt, but a very active tectonic corridor coinciding with a thick-skinned triangular zone, squeezed between two different tectonic domains. The two domains converge, where the Precordillera Oriental has been incorporated to the Sierras Pampeanas province, becoming the western leading edge of the west-verging broken foreland Sierras Pampeanas domain. This latter province has been in turn incorporated into the active deformation framework of the Andes back-arc at these latitudes as a result of enhanced coupling between the converging plates due to the subduction of the Juan Fernández ridge that flattens the Nazca slab under the South American continent. This study focuses on the neotectonics of the southern tip of this N-S elongated depression, known as Acequión (from the homonym river that crosses the area), between the Del Agua and Los Pozos rivers. This depression dies out against the transversely oriented Precordillera Sur, which exhibits a similar tectonic style as Precordillera Occidental and Central (east-verging fold-thrust belt). This contribution brings supporting evidence of the ongoing deformation during the Late Pleistocene and Holocene of the triangular zone bounded between the two leading and converging edges of Precordillera Central and Oriental thrust fronts, recorded in a multi-episodic lake sequence of the Acequión and Nikes rivers. The herein gathered evidence comprise Late Pleistocene-Holocene landforms of active thrusting, fault kinematics (micro-tectonic) data and outcrop-scale (meso-tectonic) faulting and folding of recent lake and alluvial sequences. In addition, seismically

The Pinjaur dun (intermontane longitudinal valley) and associated active mountain fronts, NW Himalaya: Tectonic geomorphology and morphotectonic evolution

NASA Astrophysics Data System (ADS)

Singh, Vimal; Tandon, S. K.

2008-12-01

The Himalayan orogenic belt, formed as a result of collision tectonic processes, shows abundant evidence of neotectonic activity, active tectonics, and the occurrence of historical earthquakes. Its frontal deformation zone is characterized, in some segments, by intermontane longitudinal valleys (duns). Such frontal segments of the Himalaya are marked by the occurrence of multiple mountain fronts. In one such segment of the foothills of the NW Himalaya, the Pinjaur dun is developed and marked by three mountain fronts: MF1A and MF1B associated with the southernmost Himalayan Frontal Thrust (HFT), MF2 associated with the Sirsa fault, and MF3 associated with the Barsar thrust along the southern margin of the relatively higher main part of the sub-Himalaya. Geomorphic responses to the tectonic activity of these and related structural features have been analyzed through the use of geomorphic indices, drainage density, stream longitudinal profiles, drainage anomalies, and hypsometric analysis. Also, fault and fold growth and their expression on landform development was studied using a combination of surface profiles and field observations. The values of valley floor width to height ratio ( Vf) for valleys associated with MF1 ranged between 0.07 and 0.74, and for valleys associated with MF2 ranged from 1.02-5.12. Vf for the four major valleys associated with MF1B ranged from 1.1-1.7. The asymmetry factor for 26 drainage basins related to MF1A indicate these have developed under the influence of a transverse structure. These results taken together with those obtained from the Hack profiles and SL index values, hypsometry, drainage density, and drainage anomalies suggest that the faults associated with the mountain fronts and related structures are active. Active tectonics and neotectonic activity have led to the formation of four surfaces in the Pinjaur dun. In addition, an important drainage divide separating the Sirsa and Jhajara drainage networks also developed in the

Late Pleistocene-Holocene Activity of the Strike-slip Xianshuihe Fault Zone, Tibetan Plateau, Inferred from Tectonic Landforms

NASA Astrophysics Data System (ADS)

Lin, A.; Yan, B.

2017-12-01

Knowledges on the activity of the strike-slip fault zones on the Tibetan Plateau have been promoted greatly by the interpretation of remote sensing images (Molnar and Tapponnier, 1975; Tapponnier and Molnar, 1977). The active strike-slip Xianshuihe-Xiaojiang Fault System (XXFS), with the geometry of an arc projecting northeastwards, plays an important role in the crustal deformation of the Tibetan Plateau caused by the continental collision between the Indian and Eurasian plates. The Xianshuihe Fault Zone (XFZ) is located in the central segment of the XXFS and extends for 370 km, with a maximum sinistral offset of 60 km since 13‒5 Ma. In this study, we investigated the tectonic landforms and slip rate along the central segment of the left-lateral strike-slip XFZ. Field investigations and analysis of ttectonic landforms show that horizontal offset has been accumulated on the topographical markers of different scales that developed since the Last Glacial Maximum (LGM). The central segment of the XFZ is composed of three major faults: Yalahe, Selaha, and Zheduotang faults showing a right-stepping echelon pattern, that is characterized by systematical offset of drainages, alluvial fans and terrace risers with typical scissoring structures, indicating a structural feature of left-lateral strike-slip fault. Based on the offset glacial morphology and radiocarbon dating ages, we estimate the Late Pleistocene-Holocene slip rate to be 10 mm/yr for the central segment of the XFZ, which is consistent with that estimated from the GPS observations and geological evidence as reported previously. Across the central segment of the XFZ, the major Selaha and Zheduotang faults participate a slip rate of 5.8 mm/yr and 3.4 mm/yr, respectively. Detailed investigations of tectonic landforms are essential for the understanding the activity of active faults. Our findings suggest that the left-lateral slipping of the XFZ partitions the deformation of eastward extrusion and northeastward

Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements

NASA Astrophysics Data System (ADS)

Doubre, Cécile; Déprez, Aline; Masson, Frédéric; Socquet, Anne; Lewi, Elias; Grandin, Raphaël; Nercessian, Alexandre; Ulrich, Patrice; De Chabalier, Jean-Bernard; Saad, Ibrahim; Abayazid, Ahmadine; Peltzer, Gilles; Delorme, Arthur; Calais, Eric; Wright, Tim

2017-02-01

Kinematics of divergent boundaries and Rift-Rift-Rift junctions are classically studied using long-term geodetic observations. Since significant magma-related displacements are expected, short-term deformation provides important constraints on the crustal mechanisms involved both in active rifting and in transfer of extensional deformation between spreading axes. Using InSAR and GPS data, we analyse the surface deformation in the whole Central Afar region in detail, focusing on both the extensional deformation across the Quaternary magmato-tectonic rift segments, and on the zones of deformation transfer between active segments and spreading axes. The largest deformation occurs across the two recently activated Asal-Ghoubbet (AG) and Manda Hararo-Dabbahu (MH-D) magmato-tectonic segments with very high strain rates, whereas the other Quaternary active segments do not concentrate any large strain, suggesting that these rifts are either sealed during interdyking periods or not mature enough to remain a plate boundary. Outside of these segments, the GPS horizontal velocity field shows a regular gradient following a clockwise rotation of the displacements from the Southeast to the East of Afar, with respect to Nubia. Very few shallow creeping structures can be identified as well in the InSAR data. However, using these data together with the strain rate tensor and the rotations rates deduced from GPS baselines, the present-day strain field over Central Afar is consistent with the main tectonic structures, and therefore with the long-term deformation. We investigate the current kinematics of the triple junction included in our GPS data set by building simple block models. The deformation in Central Afar can be described by adding a central microblock evolving separately from the three surrounding plates. In this model, the northern block boundary corresponds to a deep EW-trending trans-tensional dislocation, locked from the surface to 10-13 km and joining at depth the

Northwest Basin and Range tectonic deformation observed with the Global Positioning System, 1999-2003

USGS Publications Warehouse

Hammond, W.C.; Thatcher, W.

2005-01-01

We use geodetic velocities obtained with the Global Positioning System (GPS) to quantify tectonic deformation of the northwest Basin and Range province of the western United States. The results are based on GPS data collected in 1999 and 2003 across five new quasi-linear networks in northern Nevada, northeast California, and southeast Oregon. The velocities show ???3 mm/yr westward movement of northern Nevada with respect to stable North America. West of longitude 119??W the velocities increase and turn northwest, parallel to Sierra Nevada/Great Valley microplate motion, and similar to velocities previously obtained to the south. The observations are explained by a kinematic model with three domains that rotate around Euler poles in eastern Oregon and western Idaho. Northeast California experiences internal dextral shear deformation (11.2 ?? 3.6 nstrain/yr) subparallel to Pacific/North America motion. Relative motions of the domains imply 2-5 mm/yr approximately east-west extension in northwest Nevada and 1-4 mm/yr approximately north-south contraction near the California/Oregon border. The northward decreasing approximately east-west extension in northwest Nevada is consistent with the northern termination of Basin and Range deformation, faulting and characteristic topography. No significant extension is detected in the Oregon Basin and Range. The Oregon Cascade arc moves north at ???3.5 mm/yr and is possibly influenced by the approximately eastward motion of the Juan de Fuca plate. These results disagree with secular northwest trenchward motion of the Oregon forearc inferred from paleomagnetic rotations. South of latitude 43??, however, trenchward motion exists and is consistent with block rotations, approximately east-west Basin and Range extension, and northwest Sierra Nevada translation. Copyright 2005 by the American Geophysical Union.

Active Tectonics of the Far North Pacific Observed with GPS

NASA Astrophysics Data System (ADS)

Elliott, J.; Freymueller, J. T.; Jiang, Y.; Leonard, L. J.; Hyndman, R. D.; Mazzotti, S.

2017-12-01

The idea that the tectonics of the northeastern Pacific is defined by relatively discrete deformation along the boundary between the Pacific and North American plates has given way to a more complex picture of broad plate boundary zones and distributed deformation. This is due in large part to the Plate Boundary Observatory and several focused GPS studies, which have greatly increased the density of high-quality GPS data throughout the region. We will present an updated GPS velocity field in a consistent reference frame as well as a new, integrated block model that sheds light on regional tectonics and provides improved estimates of motion along faults and their potential seismic hazard. Crustal motions in southern Alaska are strongly influenced by the collision and flat-slab subduction of the Yakutat block along the central Gulf of Alaska margin. In the area nearest to the collisional front, small blocks showing evidence of internal deformation are required. East of the front, block motions show clockwise rotation into the Canadian Cordillera while west of the front there are counterclockwise rotations that extend along the Alaska forearc, suggesting crustal extrusion. Farther from the convergent margin, the crust appears to move as rigid blocks, with uniform motion over large areas. In western Alaska, block motions show a southwesterly rotation into the Bering Sea. Arctic Alaska displays southeasterly motions that gradually transition into easterly motion in Canada. Much of the southeastern Alaska panhandle and coastal British Columbia exhibit northwesterly motions. Although the relative plate motions are mainly accommodated along major faults systems, including the Fairweather-Queen Charlotte transform system, the St. Elias fold-and-thrust belt, the Denali-Totschunda system, and the Alaska-Aleutian subduction zone, a number of other faults accommodate lesser but still significant amounts of motion in the model. These faults include the eastern Denali/Duke River

Tectonic controls upon Kaveri River drainage, cratonic Peninsular India: Inferences from longitudinal profiles, morphotectonic indices, hanging valleys and fluvial records

NASA Astrophysics Data System (ADS)

Kale, Vishwas S.; Sengupta, Somasis; Achyuthan, Hema; Jaiswal, Manoj K.

2014-12-01

The Indian Peninsula is generally considered as a tectonically stable region, where ancient rocks, rivers and land surfaces predominate. In some parts of this ancient landscape, however, the role of tectonic landsculpting is strongly indicated by the presence of youthful topography and historical seismic activity. The present study is primarily focused on the middle domain of the Kaveri River, which displays such youthful features. The tectonic controls on this cratonic river were evaluated on the basis of the investigations of the longitudinal profiles, morphotectonic indices of active tectonics, and fluvial records. The presence of steep channel gradients, prominent knickpoints, hanging valleys, narrow bedrock gorges, and channel-in-channel morphology imply rapid erosion rates in the middle domain of the basin in response to active deformation, particularly in the reach defined by two major active faults - the Kollegal-Sivasamudram Fault and the Mekedatu Fault. Further, considering the remarkably low modern and long-term denudation rates and OSL ages of the alluvial deposits (30-40 ka), the tectonically-driven rejuvenation does not appear to be geologically recent as postulated by earlier workers.

Identifying active structures in the Kayak Island and Pamplona Zones: Implications for offshore tectonics of the Yakutat Microplate, Gulf of Alaska

NASA Astrophysics Data System (ADS)

Worthington, Lindsay L.; Gulick, Sean P. S.; Pavlis, Terry L.

Within the northern Gulf of Alaska, the Yakutat (YAK) microplate obliquely collides with and subducts beneath the North American (NA) continent at near-Pacific plate velocities. We investigate the extent that thin-skinned deformation on offshore structures located within the western portion of the unsubducted YAK block accommodates YAK-NA convergence. We compare faulting and folding observed on high-resolution and basin-scale multichannel seismic (MCS) reflection data with earthquake locations and surface ruptures observed on high-resolution bathymetric data. Holocene sediments overlying the Kayak Island fault zone (KIZ), previously interpreted as a region of active contraction, are relatively flat-lying, suggesting that active convergence within the KIZ is waning. Seismic reflection profiles east of KIZ show up to ˜200 m of undisturbed sediments overlying older folds in the Bering Trough, indicating that this area has been tectonically inactive since at least the last ˜1.3 Ma. Farther east, MCS profiles image active deformation in surface sediments along the eastern edge of the Pamplona zone (PZ) fold-and-thrust belt, that are collocated with a concentration of earthquake events that continues southwest to Khitrov Ridge and onshore through Icy Bay. These observations suggest that during the late Quaternary offshore shallow deformation style changed from distributed across the western Yakutat block to localized at the eastern edge of the PZ with extrusion of sediments southwest through the Khitrov Ridge area to the Aleutian Trench. This shallow deformation is interpreted as deformation of an accretionary complex above a shallow decollement.

Geomorphic indices indicated differential active tectonics of the Longmen Shan

NASA Astrophysics Data System (ADS)

Gao, M.; Xu, X.; Tan, X.

2012-12-01

The Longmen Shan thrust belt is located at the eastern margin of the Tibetan Plateau. It is a region of rapid active tectonics with high erosion rates and dense vegetation. The structure of the Longmen Shan region is dominated by northeast-trending thrusts and overturned folds that verge to the east and southeast (Burchfiel et al. 1995, Chen and Wilson 1996). The Longmen Shan thrust belt consists of three major faults from west to east: back-range fault, central fault, and frontal-range fault. The Mw 7.9 Wenchuan earthquake ruptured two large thrust faults along the Longmen Shan thrust belt (Xiwei et al., 2009). In this paper, we focus on investigating the spatial variance of tectonic activeness from the back-range fault to the frontal-range fault, particular emphasis on the differential recent tectonic activeness reflected by the hypsometry and the asymmetric factor of the drainage. Results from asymmetric factor indicate the back-rannge thrust fault on the south of the Maoxian caused drainage basins tilted on the hanging wall. For the north of the Maoxian, the strike-slip fault controlled the shapes of the drainage basins. Constantly river capture caused the expansion of the drainage basins which traversed by the fault. The drainages on the central fault and the frontal-range fault are also controlled by the fault slip. The drainage asymmetric factor suggested the central and southern segments of the Longmen Shan are more active than the northern segment, which is coherence with results of Huiping et al. (2010). The results from hypsometry show the back-range fault is the most active fault among the three major faults. Central fault is less active than the back-range fault but more active than the frontal-range fault. Beichuan is identified as the most active area along the central fault. Our geomorphic indices reflect an overall eastward decreasing of tectonic activeness of the Longmen Shan thrust belt.

Sand fairway mapping as a tool for tectonic restoration in orogenic belts

NASA Astrophysics Data System (ADS)

Butler, Rob

2016-04-01

geomorphology. The stratigraphic records are preserved in many parts of the Alpine-Mediterranean region. Examples are drawn from the Eo-Oligocene of the western Alps and the early Miocene of the Maghreb-Apennine system to illustrate how turbidite sedimentology, linked to studies of basin structure, can inform understanding of tectonic processes on regional and local scales. In both examples, sediment was delivered across deforming basin arrays containing contractional structures, sourced from beyond the immediate orogenic segments. The depositional systems show that multiple structures were active in parallel, rather than develop in any particular sequence. Both systems show that significant deformation occurs, emerging to the syn-orogenic surface ahead of the main orogenic wedge. The cycling of uplift and subsidence of "massifs" can be significantly more complex that the histories resolved from thermochronological data alone.

Fluvial archives, a valuable record of vertical crustal deformation

NASA Astrophysics Data System (ADS)

Demoulin, A.; Mather, A.; Whittaker, A.

2017-06-01

The study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms, but also for identifying the nature of crustal deformation and its history. In recent decades, geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens. Here, we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions (the effects of horizontal deformation are not addressed). Channel long profiles have received considerable attention in the literature, and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives, before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady-state characteristics. Then, we review the literature dealing with the transient response of rivers to tectonic perturbation, through the production of knickpoints propagating through the drainage network. Inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories. Finally, we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes. As well as the erosional imprint of tectonic forcing, sedimentary deposits, such as fluvial terrace staircases, are also considered as a classical component of tectonic geomorphology. We show that these studies have recently benefited from rapid advances in dating techniques, allowing more reliable reconstruction of incision histories and estimation of incision rates. The combination of progress in the understanding of transient river profiles and larger, more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace

Venus tectonics: initial analysis from magellan.

PubMed

Solomon, S C; Head, J W; Kaula, W M; McKenzie, D; Parsons, B; Phillips, R J; Schubert, G; Talwani, M

1991-04-12

Radar imaging and altimetry data from the Magellan mission have revealed a diversity of deformational features at a variety of spatial scales on the Venus surface. The plains record a superposition of different episodes of deformation and volcanism; strain is both areally distributed and concentrated into zones of extension and shortening. The common coherence of strain patterns over hundreds of kilometers implies that many features in the plains reflect a crustal response to mantle dynamic processes. Ridge belts and mountain belts represent successive degrees of lithospheric shortening and crustal thickening; the mountain belts also show widespread evidence for extension and collapse both during and following crustal compression. Venus displays two geometrical patterns of concentrated lithospheric extension: quasi-circular coronae and broad rises with linear rift zones; both are sites of significant volcanism. No long, large-offset strike-slip faults have been observed, although limited local horizontal shear is accommodated across many zones of crustal shortening. In general, tectonic features on Venus are unlike those in Earth's oceanic regions in that strain typically is distributed across broad zones that are one to a few hundred kilometers wide, and separated by stronger and less deformed blocks hundreds of kilometers in width, as in actively deforming continental regions on Earth.

Quantification of Fluvial Response to Tectonic Deformation and Climate in the Central Pontides, Turkey; Inferences from OSL Dating of Fluvial Terraces

NASA Astrophysics Data System (ADS)

McClain, K.; Yildirim, C.; Çiner, A.; Sahin, S.; Sarıkaya, A.; Ozturk, T.; Kıyak, N. G.; Ozcan, O.

2016-12-01

This study intends to improve the understanding of the topographic evolution and fluvial processes responding to tectonics and climate within the high-relief and deeply-incised Karabük Range of the Central Pontides, a large transpressional wedge at the northern margin of the Central Anatolian Plateau. Insight into these interactions can be obtained through the dating of fluvial sediment and understanding of geomorphic features. From Late Miocene to present, Anatolia's rapid counterclockwise movement, which increases in velocity towards the Hellenic Arc, has formed the North Anatolian Fault (NAF), a dextral transform fault along the Anatolia-Eurasia boundary. North of the transpressional zone of the NAF's massive restraining bend, an area that had experienced previous uplift due to the closure of the Intra-Pontide Ocean, the landscape experienced further uplift and the development of a detached flower structure. In the west side of this zone of transpression, the Filyos River deeply incises a gorge while bisecting the Karabük Range. This created an area with an abundance of indicators of tectonic deformation to map, such as hanging valleys, wind gaps, bedrock gorges, landslides, steep v-shaped channels, as well as an abundance of fluvial strath terraces. In particular, the village of Bolkuş lies among strath terraces of at least 8 ages within just 1.5 km of horizontal distance. In Bolkuş, we used optically stimulated luminescence dating (OSL dating) to estimate five deposition ages of fluvial strath terrace sediment, or their last exposure to daylight, leading to an estimation of incision and uplift rates over time. After collecting three samples from each terrace, with strath elevations of 246, 105.49, 43.6, 15.3 and 3.6 m.a.s.l., we determined corresponding ages of 841 ±76, 681 ±49, 386 ±18, 88 ±5.1 and 50.9 ±2.8 ka. These ages are older than expected for an area of active vertical deformation. Incision rates over time (highest/oldest terrace to lowest

An Integrated View of Tectonics in the North Pacific Derived from GPS

NASA Astrophysics Data System (ADS)

Elliott, J.; Freymueller, J.; Marechal, A.; Larsen, C.; Perea Barreto, M. A.

2015-12-01

Textbooks show a simple picture of the tectonics of the North Pacific, with discrete deformation along the boundary between the Pacific and North American plates along the Aleutian megathrust and Fairweather/Queen Charlotte fault system. Reality is much more complex, with a pattern of broadly distributed deformation. This is in part due to a number of studies and initiatives (such as PBO) in recent years that have greatly expanded the density of GPS data throughout the region. We present an overview of the GPS data acquired and various tectonic interpretations developed over the past decade and discuss a current effort to integrate the available data into a regional tectonic model for Alaska and northwestern Canada. Rather than discrete plate boundaries, we observe zones of concentrated deformation where the majority of the relative plate motion is accommodated. Within these zones, there are major fault systems, such as the Fairweather-Queen Charlotte transform and the Aleutian megathrust, where most of the deformation occurs along a main structure, but often motion is instead partitioned across multiple faults, such as the fold-and-thrust belt of the eastern St. Elias orogen. In zones of particular complexity, such as the eastern syntaxis of the St. Elias orogen, the deformation is better described by continuum deformation than localized strain along crustal structures. Strain is transferred far inboard, either by diffuse deformation or along fault system such as the Denali fault, and outboard of the main zones of deformation. The upper plate, if it can be called such, consists of a number of blocks and deforming zones while the lower plate is segmented between the Yakutat block and Pacific plate and is also likely undergoing internal deformation.

Neotectonic deformation model of the Northern Algeria from Paleomagnetic data

NASA Astrophysics Data System (ADS)

Derder, M. E. M.; Henry, B.; Maouche, S.; Amenna, M.; Bayou, B.; Djellit, H.; Ymel, H.; Gharbi, S.; Abtout, A.; Ayache, M.

2012-04-01

The seismic activity of the Western Mediterranean area is partly concentrated in northern Africa, particularly in northern Algeria, as it is shown by the strongest recent earthquakes of "Zemmouri" 21 May 2003 Mw=6.9 and the "El Asnam" 10 October 1980 Ms= 7.3. This seismicity is due to the tectonic activity related to the convergence between Africa and Eurasia plates since at least the Oligocene. The deformation is mostly compressional with associated folds, strike-slip faults and thrusts, and a direction of shortening between N-S and NNW-SSE. This convergence involves a tectonic transpression which is expressed by active deformation along the plate boundary. In northern Algeria, the seismicity is concentrated in a coastal E-W thin band zone (the Tell Atlas). Active structures define there NE-SW trending folds and NE-SW sinistral transpressive faults, which affect the intermountain and coastal Neogene to Quaternary sedimentary basins (e.g. " Cheliff "basin, " Mitidja "basin, …). These reverse faults are associated with NW-SE to E-W strike-slips deep faults. The active tectonics could be explained by a simple blocks rotation kinematics model. In order to test the validity of this kinematic model, three different paleomagnetic studies have been conducted. The first one concerned the "Cheliff" basin where sedimentary Neogene formations were extensively sampled (66 sites). The second study was carried out on Miocene andesite and dacite rocks cropping out along the northern coastal zone of the "Cheliff" basin ("Beni Haoua" area, 19 sites). The third study has been carried out on the Miocene magmatic rocks (rhyolites and basalts) cropping out north-eastern part of the "Mitidja" basin ("Cap Djinet" - "Boumerdes" area, 23 sites). The obtained results show existence of paleomagnetic clockwise rotations in all the studied areas and then validates the kinematics block rotation model. Accordingly, the deformation related to the convergence between the Africa and Eurasia

Geological constraints on the mechanism of tectonic tremor

NASA Astrophysics Data System (ADS)

Kirkpatrick, J. D.

2016-12-01

Observations of tectonic tremor in a wide variety of tectonic settings suggest that transitional behavior involving contemporaneous shear fracture and aseismic creep transients occurs in many major faults. Seismological and geophysical data indicate shear failure on critically stressed faults, likely under low effective stress conditions, are consistent characteristics, even though rock types and grain scale deformation mechanisms vary at these different locations. Geological observations could add additional insight into the specific failure mechanisms if the structures that form during tremor episodes can be identified. Exhumed shear zones often contain folded, boudinaged and/or dynamically recrystallized veins that record cyclical fracture and viscous deformation representing mixed bulk rheology. Examples from a Cretaceous transpressional continental shear zone in the Sierra Nevada, CA, include quartz-filled veins meters to tens of meters long with millimeters to centimeters of shear offset that preferentially developed along foliation planes in a high strain zone. Ambient temperatures during deformation were 400-600°C, and opening mode vein orientations and abundance suggest fluid pressure was near lithostatic at times. The orientation and spatial distribution of the veins indicate they formed under differential stress large enough for shear failure with pore pressures sufficiently high for the rocks to be critically stressed along mechanically weak foliation planes. Bulk deformation of the surrounding rock was accommodated viscously by crystal plastic deformation mechanisms. The mode of fracturing and overall behavior of the system was controlled by the local competition between the rates of stress recovery following fracture and stress drop, and pore pressure build up. The inferred mixed rheology recorded by the veins is phenomenologically similar to tremor. These shear fractures, and the conditions of failure they record, could be comparable to the

Tectonic Evolution of Jabal Tays Ophiolite Complex, Eastern Arabian Shield, Saudi Arabia

NASA Astrophysics Data System (ADS)

AlHumidan, Saad; Kassem, Osama; Almutairi, Majed; Al-Faifi, Hussain; Kahal, Ali

2017-04-01

Microstructural analysis is important for investigation of tectonic evaluation of Jable Tays area. Furthermore, the Jable Tays ophiolite complex is effected by Al Amar -Idsas fault. The nature of the Al Amar-Idsas fault is a part of the Eastern Arabian Shield, which was subjected to multiple interpretations. Through fieldwork investigation, microscopic examination, and microstructural analysis, we aim to understand the evolution and tectonic setting of the Jable Tays area. Finite-strain data displays that the Abt schist, the metavolcanics and the metagranites are highly to moderately deformed. The axial ratios in the XZ section range from 1.40 to 2.20. The long axes of the finite-strain ellipsoids trend NW- SE and W-E in the Jable Tays area while, their short axes are subvertical to subhorizontal foliations. The strain magnitude does not increase towards the tectonic contacts between the Abt schist and metavolcano-sedimentary. While majority of the obtained data indicate a dominant oblate with minor prolate strain symmetries in the Abt schist, metavolcano-sedimentary and metagranites. The strain data also indicate flattening with some constriction. We assume that the Abt schist and the metavolcano-sedimentry rocks have similar deformation behavior. The finite strain in the studied rocks accumulated during the metamorphism that effected by thrusting activity. Based on these results, we finally concluded that the contact between Abt schist and metavolcano-sedimentary rocks were formed during the progressive thrusting under brittle to semi-ductile deformation conditions by simple shear that also involved a component of vertical shortening, causing subhorizontal foliation in Jable Tays area.

Puzzling features of western Mediterranean tectonics explained by slab dragging

NASA Astrophysics Data System (ADS)

Spakman, Wim; Chertova, Maria V.; van den Berg, Arie.; van Hinsbergen, Douwe J. J.

2018-03-01

The recent tectonic evolution of the western Mediterranean region is enigmatic. The causes for the closure of the Moroccan marine gateway prior to the Messinian salinity crisis, for the ongoing shortening of the Moroccan Rif and for the origin of the seismogenic Trans-Alboran shear zone and eastern Betics extension are unclear. These puzzling tectonic features cannot be fully explained by subduction of the east-dipping Gibraltar slab in the context of the regional relative plate motion frame. Here we use a combination of geological and geodetic data, as well as three-dimensional numerical modelling of subduction, to show that these unusual tectonic features could be the consequence of slab dragging—the north to north-eastward dragging of the Gibraltar slab by the absolute motion of the African Plate. Comparison of our model results to patterns of deformation in the western Mediterranean constrained by geological and geodetic data confirm that slab dragging provides a plausible mechanism for the observed deformation. Our results imply that the impact of absolute plate motion on subduction is identifiable from crustal observations. Identifying such signatures elsewhere may improve the mantle reference frame and provide insights on subduction evolution and associated crustal deformation.

Elucidating tectonic events and processes from variably tectonized conglomerate clast detrital geochronology: examples from the Hongliuhe Formation in the southern Central Asian Orogenic Belt, NW China

NASA Astrophysics Data System (ADS)

Cleven, Nathan; Lin, Shoufa; Davis, Donald; Xiao, Wenjiao; Guilmette, Carl

2017-04-01

This work expands upon detrital zircon geochronology with a sampling and analysis strategy dating granitoid conglomerate clasts that exhibit differing degrees of internal ductile deformation. As deformation textures within clastic material reflect the variation and history of tectonization in the source region of a deposit, we outline a dating methodology that can provide details of the provenance's tectonomagmatic history from deformation-relative age distributions. The method involves bulk samples of solely granitoid clasts, as they are representative of the magmatic framework within the provenance. The clasts are classified and sorted into three subsets: undeformed, slightly deformed, and deformed. LA-ICPMS U-Pb geochronology is performed on zircon separates of each subset. Our case study, involving the Permian Hongliuhe Formation in the southern Central Asian Orogenic Belt, analyzes each of the three clast subsets, as well as sandstone detrital samples, at three stratigraphic levels to yield a profile of the unroofed provenance. The age spectra of the clast samples exhibit different, wider distributions than sandstone samples, considered an effect of proximity to the respective provenance. Comparisons of clast data to sandstone data, as well as comparisons between stratigraphic levels, yield indications of key tectonic processes, in addition to the typical characteristics provided by detrital geochronology. The clast data indicates a minimal lag time, implying rapid exhumation rates, whereas sandstone data alone would indicate a 90 m.y. lag time. Early Paleozoic arc building episodes appear as Ordovician peaks in sandstone data, and Silurian-Devonian peaks in clast data, indicating a younging of magmatism towards the proximal provenance. A magmatic hiatus starts in the Devonian, correlating with the latest age of deformed clasts, interpreted as timing of collisional tectonics. Provenance interpretation using the correlations seen between the clast and sandstone

Influence of pre-tectonic carbonate facies architecture on deformation patterns of syntectonic turbidites, an example from the central Mexican fold-thrust belt

NASA Astrophysics Data System (ADS)

Vásquez Serrano, Alberto; Tolson, Gustavo; Fitz Diaz, Elisa; Chávez Cabello, Gabriel

2018-04-01

The Mexican fold-thrust belt in central México excellently exposes relatively well preserved syntectonic deposits that overlay rocks with lateral lithostratigraphic changes across the belt. We consider the deformational effects of these changes by investigating the geometry, kinematics and strain distribution within syntectonic turbidites, which are deposited on top of Albian-Cenomanian shallow and deep water carbonate layers. Field observations and detailed structural analysis at different stratigraphic and structural levels of the Late Cretaceous syntectonic formation are compared with the deformation as a function of lithological and structural variations in the underlying carbonate units, to better understand the effect of these lithostratigraphic variations on deformation, kinematics, strain distribution and propagation of deformation. From our kinematic analyses, we conclude that the syntectonic strata are pervasively affected by folding in all areas and that deformation partitioning localized shear zones at the boundaries of this unit, particularly along the contact with massive carbonates. At the boundaries with massive platformal carbonates, the turbidites are strongly deformed by isoclinal folding with a pervasive sub-horizontal axial plane cleavage and 70-60% shortening. In contrast, contacts with thinly-bedded carbonate layers (basinal facies), do not show strain localization, and have horizontal shortening of 50-40% that is accommodated by buckle folds with a less pervasive, steeply dipping cleavage. The mechanical properties variations in the underlying pre-tectonic units as a function of changes in lithostratigraphy fundamentally control the deformation in the overlying syntectonic strata, which is an effect that could be expected to occur in any deformed sedimentary sequence with such variations.

Fault kinematics and tectonic stress in the seismically active Manyara Dodoma Rift segment in Central Tanzania Implications for the East African Rift

NASA Astrophysics Data System (ADS)

Macheyeki, Athanas S.; Delvaux, Damien; De Batist, Marc; Mruma, Abdulkarim

2008-07-01

The Eastern Branch of the East African Rift System is well known in Ethiopia (Main Ethiopian Rift) and Kenya (Kenya or Gregory Rift) and is usually considered to fade away southwards in the North Tanzanian Divergence, where it splits into the Eyasi, Manyara and Pangani segments. Further towards the south, rift structures are more weakly expressed and this area has not attracted much attention since the mapping and exploratory works of the 1950s. In November 4, 2002, an earthquake of magnitude Mb = 5.5 struck Dodoma, the capital city of Tanzania. Analysis of modern digital relief, seismological and geological data reveals that ongoing tectonic deformation is presently affecting a broad N-S trending belt, extending southward from the North Tanzanian Divergence to the region of Dodoma, forming the proposed "Manyara-Dodoma Rift segment". North of Arusha-Ngorongoro line, the rift is confined to a narrow belt (Natron graben in Tanzania) and south of it, it broadens into a wide deformation zone which includes both the Eyasi and Manyara grabens. The two-stage rifting model proposed for Kenya and North Tanzania also applies to the Manyara-Dodoma Rift segment. In a first stage, large, well-expressed topographic and volcanogenic structures were initiated in the Natron, Eyasi and Manyara grabens during the Late Miocene to Pliocene. From the Middle Pleistocene onwards, deformations related to the second rifting stage propagated southwards to the Dodoma region. These young structures have still limited morphological expressions compared to the structures formed during the first stage. However, they appear to be tectonically active as shown by the high concentration of moderate earthquakes into earthquake swarms, the distribution of He-bearing thermal springs, the morphological freshness of the fault scarps, and the presence of open surface fractures. Fault kinematic and paleostress analysis of geological fault data in basement rocks along the active fault lines show that recent

The tectonic and volcanic evolution of Venus: Catastrophic or gradual?

NASA Technical Reports Server (NTRS)

Solomon, Sean C.

1993-01-01

Radar imaging and altimetry data from the Magellan mission have yielded important new constraints on the tectonic and volcanic history of Venus and on its internal dynamics. The planet lacks global plate tectonics, but a number of chasm systems and corona moat structures have arcuate planforms, asymmetric topogrpahic profiles, and relief analogous to deep-sea trenches on Earth and may be products of limited lithospheric underthrusting or subduction. Several lines of evidence point to a crust and upper mantle stronger than would be predicted by simple extrapolation from Earth and the 450 K greater surface temperature; these include the unrelaxed depths of impact craters, apparently large values of elastic lithosphere thickness, and large ratios of gravity to topography. The density of impact craters indicates an averate crater retention age of about 500 My, but not more than 5% of the recognized craters have been volcanically embayed. This last observation has led to the proposal that Venus has been subjected to one or more global resurfacing events, the latest about 500 My ago, and that the volcanic flux during intervals between such events has been low. That more recent tectonic activity has been widespread, however, is indicated by the high relief and slopes of mountains, chasm walls, and plateau margins; the significant fraction (0.3) of impact craters deformed by younger faults; and the postformational vertical deformation of long channels. Interior dynamical scenarios advanced to account for episodic volcanic resurfacing include catastrophic overturn of a global lithosphere thickened by cooling or compositional buoyancy and strongly time-dependent mantle convective heat flux. Outgassing considerations and analogy with Earth and other terrestrial planets, however, suggests that such catastrophic models are unlikely. If the mantle of Venus cooled more efficiently than that of Earth because of, say, different boundary conditions, a different flow law, or a

The tectonics of Venus: An overview

NASA Technical Reports Server (NTRS)

Solomon, Sean C.

1992-01-01

While the Pioneer Venus altimeter, Earth-based radar observatories, and the Venera 15-16 orbital imaging radars provided views of large-scale tectonic features on Venus at ever-increasing resolution, the radar images from Magellan constitute an improvement in resolution of at least an order of magnitude over the best previously available. A summary of early Magellan observations of tectonic features on Venus was published, but data available at that time were restricted to the first month of mapping and represented only about 15 percent of the surface of the planet. Magellan images and altimetry are now available for more than 95 percent of the Venus surface. Thus a more global perspective may be taken on the styles and distribution of lithospheric deformation on Venus and their implications for the tectonic history of the planet.

Active Deformation in the Overriding Plate Associated with Temporal Changes of the Philippine Sea Plate Motion

NASA Astrophysics Data System (ADS)

Ishiyama, T.; Sato, H.; Van Horne, A.

2015-12-01

We present detailed geologic evidence linking changes over time in Philippine Sea plate (PHS) motion and intracontinental deformation in central and southwest (SW) Japan during the Pliocene and after. In the early Pliocene, subduction of the PHS plate under SW Japan restarted in a northerly direction after period of deceleration or cessation. Later, motion changed to a more westerly direction. Corresponding geological changes found in the overriding plate include unconformities in the forearc basins, changes in slip sense on faults, depocenter migration, re-organization of drainage systems and volcanism. Quaternary intraplate deformation is prominent north of the Median Tectonic Line (MTL) inactive segment, above a shallow flat slab. In contrast, less Quaternary tectonic activity is found north of the MTL active segment which lies over a steadily-slipping portion of the subducting slab that behaves as a less-deformed rigid block. Depocenters and active thrusting have migrated north/northwestward over the past 5 My above the shallow flat slab segment of the PHS. We reconstructed the Plio-Pleistocene migration history using Neogene stratigraphy and shallow seismic reflection profiles. We see shallow PHS slab contact with the lower continental crust in our deep seismic reflection profiles, which may explain its enhanced downward drag of the overriding plate and synchronous strong compression in the crust. We find evidence of more westerly PHS plate subduction since the middle Pleistocene in (1) unconformities in the Kumano forearc basin deposits in SW Japan, (2) drastic stream captures in Shikoku, and (3) concordant changes in fault slip sense from thrust to dextral slip along the MTL. Oblique subduction could have induced stronger horizontal stress in the overriding plate above the shallow flat slab which could account for the increasing geologic slip rate observed on active structures. During four repetitions of megathrust earthquake sequences since the 17th century

Interaction between crustal tectonics and salt deformation in the Eastern Sardinian margin, Western Tyrrhenian Sea: seismic data and analogue modelling

NASA Astrophysics Data System (ADS)

Vendeville, Bruno; Lymer, Gael; Gaullier, Virginie; Chanier, Frank; Maillard, Agnes; Sage, Françoise; Lofi, Johanna; Thinon, Isabelle

2014-05-01

The Tyrrhenian Basin opened by eastward migration of the Apennine subduction system. Rifting along the Eastern Sardinian margin started during the middle to late Miocene times and hence this timing partly overlapped the Messinian Salinity Crisis. The two "METYSS" cruises were conducted to use the deformation of the Messinian salt and its Plio-Quaternary overburden as a proxy for better delineating the tectonic history of the sub-salt basement. Many parts of the study area contain two of the most typical Messinian series of the Western Mediterranean: the Mobile Unit (MU; salt, mainly halite), overlain by the more competent Upper Unit (UU: alternating dolomitic marls and anhydrite). The brittle Plio-Quaternary cover overlies the UU. Usually, the presence of mobile salt is viewed as a nuisance for understanding crustal tectonics because salt's ability to act as a structural buffer between the basement and the cover. However, we illustrate, using examples from the Cornaglia Terrace, how we can use thin-skinned salt tectonics as indicators of vertical movements in the sub-salt, pre-Messinian basement. There, slip along N-S-trending crustal normal faults bounding basement troughs has been recorded by salt and overburden in two different manners: - First, post-salt basement faulting (typically after deposition of the Upper Unit and the early Pliocene), and some crustal-scale southward tilting, triggered along-strike (southward) thin-skinned, gliding of salt and overburden recorded by upslope extension and downslope shortening. - Second, and less obvious at first glance, there was some crustal activity along another basement trough, located East of the Baronie Ridge after deposition of the Messinian salt. This trough is narrow, trends N-S and is bounded by crustal faults. The narrow width of the trough allowed for only minor across-strike (E-W) gliding. The resulting geometry would suggest that nothing happened after Messinian times, but some structural features (confirmed

Strategic planning of INA-CORS development for public service and tectonic deformation study

NASA Astrophysics Data System (ADS)

Syetiawan, Agung; Gaol, Yustisi Ardhitasari Lumban; Safi'i, Ayu Nur

2017-07-01

GPS technology can be applied for surveying, mapping and research purposes. The simplicity of GPS technology for positioning make it become the first choice for survey compared with another positioning method. GPS can measure a position with various accuracy level based on the measurement method. In order to facilitate the GPS positioning, many organizations are establishing permanent GPS station. National Geodetic Survey (NGS) called it as Continuously Operating Reference Stations (CORS). Those devices continuously collect and record GPS data to be used by users. CORS has been built by several government agencies for particular purposes and scattered throughout Indonesia. Geospatial Information Agency (BIG) as a geospatial information providers begin to compile a grand design of Indonesia CORS (INA-CORS) that can be used for public service such as Real Time Kinematic (RTK), RINEX data request, or post-processing service and for tectonic deformation study to determine the deformation models of Indonesia and to evaluate the national geospatial reference system. This study aims to review the ideal location to develop CORS network distribution. The method was used is to perform spatial analysis on the data distribution of BIG and BPN CORS overlayed with Seismotectonic Map of Indonesia and land cover. The ideal condition to be achieved is that CORS will be available on each radius of 50 km. The result showed that CORS distribution in Java and Nusa Tenggara are already tight while on Sumatra, Celebes and Moluccas are still need to be more tighten. Meanwhile, the development of CORS in Papua will encounter obstacles toward road access and networking. This analysis result can be used as consideration for determining the priorities of CORS development in Indonesia.

The role of farfield tectonic stress in oceanic intraplate deformation, Gulf of Alaska

USGS Publications Warehouse

Reece, Robert S.; Gulick, Sean P. S.; Christesen, Gail L.; Horton, Brian K.; VanAvendonk, Harm J.; Barth, Ginger

2013-01-01

An integration of geophysical data from the Pacific Plate reveals plate bending anomalies, massive intraplate shearing and deformation, and a lack of oceanic crust magnetic lineaments in different regions across the Gulf of Alaska. We argue that farfield stress from the Yakutat Terrane collision with North America is the major driver for these unusual features. Similar plate motion vectors indicate that the Pacific plate and Yakutat Terrane are largely coupled along their boundary, the Transition Fault, with minimal translation. Our study shows that the Pacific Plate subduction angle shallows toward the Yakutat Terrane and supports the theory that the Pacific Plate and Yakutat Terranemaintain coupling along the subducted region of the Transition Fault. We argue that the outboard transfer of collisional stress to the Pacific Plate could have resulted in significant strain in the NE corner of the Pacific Plate, which created pathways for igneous sill formation just above the Pacific Plate crust in the Surveyor Fan. A shift in Pacific Plate motion during the late Miocene altered the Yakutat collision with North America, changing the stress transfer regime and potentially terminating associated strain in the NE corner of the Pacific Plate. The collision further intensified as the thickest portion of the Yakutat Terrane began to subduct during the Pleistocene, possibly providing the impetus for the creation of the Gulf of Alaska Shear Zone, a>200 km zone of intraplate strike-slip faults that extend from the Transition Fault out into the Pacific Plate. This study highlights the importance of farfield stress from complex tectonic regimes in consideration of large-scale oceanic intraplate deformation.

Probabilistic estimation of long-term volcanic hazard under evolving tectonic conditions in a 1 Ma timeframe

NASA Astrophysics Data System (ADS)

Jaquet, O.; Lantuéjoul, C.; Goto, J.

2017-10-01

Risk assessments in relation to the siting of potential deep geological repositories for radioactive wastes demand the estimation of long-term tectonic hazards such as volcanicity and rock deformation. Owing to their tectonic situation, such evaluations concern many industrial regions around the world. For sites near volcanically active regions, a prevailing source of uncertainty is related to volcanic hazard. For specific situations, in particular in relation to geological repository siting, the requirements for the assessment of volcanic and tectonic hazards have to be expanded to 1 million years. At such time scales, tectonic changes are likely to influence volcanic hazard and therefore a particular stochastic model needs to be developed for the estimation of volcanic hazard. The concepts and theoretical basis of the proposed model are given and a methodological illustration is provided using data from the Tohoku region of Japan.

Ground Deformation near active faults in the Kinki district, southwest Japan, detected by InSAR

NASA Astrophysics Data System (ADS)

Hashimoto, M.; Ozawa, T.

2016-12-01

The Kinki district, southwest Japan, consists of ranges and plains between which active faults reside. The Osaka plain is in the middle of this district and is surrounded by the Rokko, Arima-Takatsuki, Ikoma, Kongo and Median Tectonic Line fault zones in the clockwise order. These faults are considered to be capable to generate earthquakes of larger magnitude than 7. The 1995 Kobe earthquake is the most recent activity of the Rokko fault (NE-SW trending dextral fault). Therefore the monitoring of ground deformation with high spatial resolution is essential to evaluate seismic hazards in this area. We collected and analyzed available SAR images such as ERS-1/2, Envisat, JERS-1, TerraSAR-X, ALOS/PALSAR and ALOS-2/PALSAR-2 to reveal ground deformation during these 20 years. We made DInSAR and PSInSAR analyses of these images using ASTER-GDEM ver.2. We detected three spots of subsidence along the Arima-Takatsuki fault (ENE-WSW trending dextral fault, east neighbor of the Rokko fault) after the Kobe earthquake, which continued up to 2010. Two of them started right after the Kobe earthquake, while the easternmost one was observed after 2000. However, we did not find them in the interferograms of ALOS-2/PALSAR-2 acquired during 2014 - 2016. Marginal uplift was recognized along the eastern part of the Rokko fault. PS-InSAR results of ALOS/PALSAR also revealed slight uplift north of the Rokko Mountain that uplift by 20 cm coseismically. These observations suggest that the Rokko Mountain might have uplifted during the postseismic period. We found subsidence on the eastern frank of the Kongo Mountain, where the Kongo fault (N-S trending reverse fault) exits. In the southern neighbor of the Median Tectonic Line (ENE-WSW trending dextral fault), uplift of > 5 mm/yr was found by Envisat and ALOS/PALSAR images. This area is shifted westward by 4 mm/yr as well. Since this area is located east of a seismically active area in the northwestern Wakayama prefecture, this deformation

Ganges-Brahmaputra Delta: Balance of Subsidence, Sea level and Sedimentation in a Tectonically-Active Delta (Invited)

NASA Astrophysics Data System (ADS)

Steckler, M. S.; Goodbred, S. L.; Akhter, S. H.; Seeber, L.; Reitz, M. D.; Paola, C.; Nooner, S. L.; DeWolf, S.; Ferguson, E. K.; Gale, J.; Hossain, S.; Howe, M.; Kim, W.; McHugh, C. M.; Mondal, D. R.; Petter, A. L.; Pickering, J.; Sincavage, R.; Williams, L. A.; Wilson, C.; Zumberge, M. A.

2013-12-01

Bangladesh is vulnerable to a host of short and long-term natural hazards - widespread seasonal flooding, river erosion and channel avulsions, permanent land loss from sea level rise, natural groundwater arsenic, recurrent cyclones, landslides and huge earthquakes. These hazards derive from active fluvial processes related to the growth of the delta and the tectonics at the India-Burma-Tibet plate junctions. The Ganges and Brahmaputra rivers drain 3/4 of the Himalayas and carry ~1 GT/y of sediment, 6-8% of the total world flux. In Bangladesh, these two great rivers combine with the Meghna River to form the Ganges-Brahmaputra-Meghna Delta (GBMD). The seasonality of the rivers' water and sediment discharge is a major influence causing widespread flooding during the summer monsoon. The mass of the water is so great that it causes 5-6 cm of seasonal elastic deformation of the delta discerned by our GPS data. Over the longer-term, the rivers are also dynamic. Two centuries ago, the Brahmaputra River avulsed westward up to 100 km and has since captured other rivers. The primary mouth of the Ganges has shifted 100s of km eastward from the Hooghly River over the last 400y, finally joining the Brahmaputra in the 19th century. These avulsions are influenced by the tectonics of the delta. On the east side of Bangladesh, the >16 km thick GBMD is being overridden by the Burma Arc where the attempted subduction of such a thick sediment pile has created a huge accretionary prism. The foldbelt is up to 250-km wide and its front is buried beneath the delta. The main Himalayan thrust front is <100 km north, but adjacent to the GBMD is the Shillong Massif, a 300-km long, 2-km high block of uplifted Indian basement that is overthrusting and depressing GBMD sediments to the south. The overthrusting Shillong Massif may represent a forward jump of the Himalayan front to a new plate boundary. This area ruptured in a ~M8 1897 earthquake. Subsidence from the tectonics and differential

Statistical description of tectonic motions

NASA Technical Reports Server (NTRS)

Agnew, Duncan Carr

1993-01-01

This report summarizes investigations regarding tectonic motions. The topics discussed include statistics of crustal deformation, Earth rotation studies, using multitaper spectrum analysis techniques applied to both space-geodetic data and conventional astrometric estimates of the Earth's polar motion, and the development, design, and installation of high-stability geodetic monuments for use with the global positioning system.

Facies Analysis of the Tandoǧdu Travertines, Van, Eastern Anatolia, Turkey: implications for the active tectonic deformation behind the formation and evolution of the travertines

NASA Astrophysics Data System (ADS)

Yesilova, Cetin; Yesilova, Pelin; Aclan, Mustafa; Gülyüz, Nilay

2017-04-01

In this study, stratigraphic and sedimentologic characteristics of Tandoǧdu travertines exposing at the 13 km southwest of Başkale, Van were examined. In this respect, we shed light on their formation conditions and depositional environment by determining their morphological characteristics and analyzing their facies distribution. In addition, kinematic studies were conducted by collecting structural data from the structures hosting the travertines. Tandoǧdu travertines having bed type and ridge type travertines have 5 distinct lithofacies based on the studies conducted. These are: (1) crystalline crust facies, (2) coated bubble facies, (3) paper-thin raft type facies, (4) lithoclast - breccia facies and (5) paleosoil facies. According to the examination of their morphologies and lithofacies; lithofacies were developed depending on the temperature of fluids forming the travertines. Distal from the source field of the hydrothermal fluids, paper-thin raft type facies were developed in shallow pools. Proximal to the source field of the hydrothermal fluids, crystalline crust facies and coated bubble facies were deposited. Existence of breccia facies indicates the effects of active tectonism during the formation of travertines. Hot hydrothermal pools on the ridge type travertines prove the still active tectonic activities. On-going studies aim to date growth of the travertines by U-Th dating method which will also shed some light on the tectonic scenario behind the evolution of the travertines.

Structure and tectonic evolution of the southwestern Trinidad dome, Escambray complex, Central Cuba: Insights into deformation in an accretionary wedge

NASA Astrophysics Data System (ADS)

Despaigne-Díaz, Ana Ibis; García Casco, Antonio; Cáceres Govea, Dámaso; Wilde, Simon A.; Millán Trujillo, Guillermo

2017-10-01

The Trinidad dome, Escambray complex, Cuba, forms part of an accretionary wedge built during intra-oceanic subduction in the Caribbean from the Late Cretaceous to Cenozoic. The structure reflects syn-subduction exhumation during thickening of the wedge, followed by extension. Field mapping, metamorphic and structural analysis constrain the tectonic evolution into five stages. Three ductile deformation events (D1, D2 and D3) are related to metamorphism in a compressional setting and formation of several nappes. D1 subduction fabrics are only preserved as relict S1 foliation and rootless isoclinal folds strongly overprinted by the main S2 foliation. The S2 foliation is parallel to sheared serpentinised lenses that define tectonic contacts, suggesting thrust stacks and underthrusting at mantle depths. Thrusting caused an inverted metamorphic structure with higher-grade on top of lower-grade nappes. Exhumation started during D2 when the units were incorporated into the growing accretionary wedge along NNE-directed thrust faults and was accompanied by substantial decompression and cooling. Folding and thrusting continued during D3 and marks the transition from ductile to brittle-ductile conditions at shallower crustal levels. The D4-5 events are related to extension and contributed to the final exhumation (likely as a core complex). D4 is associated with a regional spaced S4 cleavage, late open folds, and numerous extension veins, whereas D5 is recorded by normal and strike-slip faults affecting all nappes. The P-t path shows rapid exhumation during D2 and slower rates during D3 when the units were progressively incorporated into the accretionary prism. The domal shape formed in response to tectonic denudation assisted by normal faulting and erosion at the surface during the final stages of structural development. These results support tectonic models of SW subduction of the Proto-Caribbean crust under the Caribbean plate during the latest Cretaceous and provide

Significant Centers of Tectonic Activity as Identified by Wrinkle Ridges for the Western Hemisphere of Mars

NASA Technical Reports Server (NTRS)

Anderson, R.C.; Haldemann, A. F. C.; Golombek, M. P.; Franklin, B. J.; Dohm, J. M.; Lias, J.

2000-01-01

The western hemisphere region of Mars has been the site of numerous scientific investigations regarding its tectonic evolution. For this region of Mars, the dominant tectonic region is the Tharsis province. Tharsis is characterized by an enormous system of radiating grabens and a circumferential system of wrinkle ridges. Past investigations of grabens associated with Tharsis have identified specific centers of tectonic activity. A recent structural analysis of the western hemisphere region of Mars which includes the Tharsis region, utilized 25,000 structures to determine the history of local and regional centers of tectonic activity based primarily on the spatial and temporal relationships of extensional features. This investigation revealed that Tharsis is more structurally complex (heterogeneous) than has been previously identified: it consists of numerous regional and local centers of tectonic activity (some are more dominant and/or more long lived than others). Here we use the same approach as Anderson et al. to determine whether the centers of tectonic activity that formed the extensional features also contributed to wrinkle ridge (compressional) formation.

The Investigation of Active Tectonism Offshore Cide-Sinop, Southern Black Sea by Seismic Reflection and Bathymetric Data

NASA Astrophysics Data System (ADS)

Alp, Y. I.; Ocakoglu, N.; Kılıc, F.; Ozel, A. O.

2017-12-01

The active tectonism offshore Cide-Sinop at the Southern Black Sea shelf area was first time investigated by multi-beam bathymetric and multi-channel seismic reflection data under the Research Project of The Scientific and Technological Research Council of Turkey (TUBİTAK-ÇAYDAG-114Y057). The multi-channel seismic reflection data of about 700 km length were acquired in 1991 by Turkish Petroleum Company (TP). Multibeam bathymetric data were collected between 2002-2008 by the Turkish Navy, Department of Navigation, Hydrography and Oceanography (TN-DNHO). Conventional data processing steps were applied as follows: in-line geometry definition, shot-receiver static correction, editing, shot muting, gain correction, CDP sorting, velocity analysis, NMO correction, muting, stacking, predictive deconvolution, band-pass filtering, finite-difference time migration, and automatic gain correction. Offshore area is represented by a quite smooth and large shelf plain with an approx. 25 km wide and the water depth of about -100 m. The shelf gently deepens and it is limited by the shelf break with average of -120 m contour. The seafloor morphology is charasterised by an erosional surface. Structurally, E-W trending strike-slip faults with generally compression components and reverse/thrust faults have been regionally mapped for the first time. Most of these faults deform all seismic units and reach the seafloor delimiting the morphological highs and submarine plains. Thus, these faults are intepreted as active faults. These results support the idea that the area is under the active compressional tectonic regime

Matrix deformation mechanisms in HP-LT tectonic mélanges — Microstructural record of jadeite blueschist from the Franciscan Complex, California

NASA Astrophysics Data System (ADS)

Wassmann, Sara; Stöckhert, Bernhard

2012-09-01

Exhumed high pressure-low temperature metamorphic mélanges of tectonic origin are believed to reflect high strain accumulated in large scale interplate shear zones during subduction. Rigid blocks of widely varying size are embedded in a weak matrix, which takes up the deformation and controls the rheology of the composite. The microfabrics of a highly deformed jadeite-blueschist from the Franciscan Complex, California, are investigated to help understand deformation mechanisms at depth. The specimen shows a transposed foliation with dismembered fold hinges and boudinage structures. Several generations of open fractures have been sealed to become veins at high-pressure metamorphic conditions. The shape of these veins, frequently restricted to specific layers, indicates distributed host rock deformation during and after sealing. Small cracks in jadeite and lawsonite are healed, with tiny quartz inclusions aligned along the former fracture surface. Large jadeite porphyroblasts show strain caps and strain shadows. Open fractures are sealed by quartz and new jadeite epitactically grown on the broken host. Monophase glaucophane aggregates consist of undeformed needles with a diameter between 0.1 and 2 μm, grown after formation of isoclinal folds. Only quartz microfabrics indicate some stage of crystal-plastic deformation, followed by annealing and grain growth. Aragonite in the latest vein generation shows retrogression to calcite along its rims. The entire deformation happened under HP-LT metamorphic conditions in the stability field of jadeite and quartz, at temperatures between 300 and 450 °C and pressures exceeding 1-1.4 GPa. The microfabrics indicate that dissolution precipitation creep was the predominant deformation mechanism, accompanied by brittle failure and vein formation at quasi-lithostatic pore fluid pressure. This indicates low flow strength and, combined with high strain rates expected for localized deformation between the plates, a very low viscosity

Extrusional Tectonics over Plate Corner: an Example in Northern Taiwan

NASA Astrophysics Data System (ADS)

Lu, Chia-Yu; Lee, Jian-Cheng; Li, Zhinuo; Lee, Ching-An; Yeh, Chia-Hung

2016-04-01

In northern Taiwan, contraction, transcurrent shearing, block rotation and extension are four essential tectonic deformation mechanisms involved in the progressive deformation of this arcuate collision mountain belt. The neotectonic evolution of the Taiwan mountain belt is mainly controlled not only by the oblique convergence between the Eurasian plate and the Philippine Sea plate but also the corner shape of the plate boundary. Based on field observations and analyses, and taking geophysical data (mostly GPS) and experimental modelling into account, we interpret the curved belt of northern Taiwan as a result of of contractional deformation (with compression, thrust-sheet stacking & folding, back thrust duplex & back folding) that induced vertical extrusion, combined with increasing transcurrent & rotational deformation (with transcurrent faulting, bookshelf-type strike-slip faulting and block rotation) that induced transcurrent/rotational extrusion and extension deformation which in turn induced extensional extrusion. As a consequence, a special type of extrusional folds was formed in association with contractional, transcurrent & rotational and extensional extrusions subsequently. The extrusional tectonics in northern Taiwan reflect a single, albeit complicated, regional pattern of deformation. The crescent-shaped mountain belt of Northeastern Taiwan develops in response to oblique indentation by an asymmetric wedge indenter, retreat of Ryukyu trench and opening of the Okinawa trough.

Extrusional Tectonics at Plate Corner: an Example in Northern Taiwan

NASA Astrophysics Data System (ADS)

Lu, C. Y.; Lee, J. C.; Li, Z.; Yeh, C. H.; Lee, C. A.

2015-12-01

In northern Taiwan, contraction, transcurrent shearing, block rotation and extension are four essential tectonic deformation mechanisms involved in the progressive deformation of this arcuate collision mountain belt. The neotectonic evolution of the Taiwan mountain belt is mainly controlled not only by the oblique convergence between the Eurasian plate and the Philippine Sea plate but also the corner shape of the plate boundary. Based on field observations and analyses, and taking geophysical data (mostly GPS) and experimental modelling into account, we interpret the curved belt of northern Taiwan as a result of of contractional deformation (with compression, thrust-sheet stacking & folding, back thrust duplex & back folding) that induced vertical extrusion, combined with increasing transcurrent & rotational deformation (with transcurrent faulting, bookshelf-type strike-slip faulting and block rotation) that induced transcurrent/rotational extrusion and extension deformation which in turn induced extensional extrusion. As a consequence, a special type of extrusional folds was formed in association with contractional, transcurrent & rotational and extensional extrusions subsequently. The extrusional tectonics in northern Taiwan reflect a single, albeit complicated, regional pattern of deformation. The crescent-shaped mountain belt of Northeastern Taiwan develops in response to oblique indentation by an asymmetric wedge indenter and opening of the Okinawa trough at plate corner.

Tectonic evolution of Western Ishtar Terra, Venus

NASA Astrophysics Data System (ADS)

Marinangeli, Lucia

1997-03-01

A detailed geological mapping based on Magellan data has been done in Western Ishtar Terra from 300-330 deg W to 65-75 deg N. The area studied comprises three main phisiografic provinces, Atropos Tessera, Akna Montes and North-Western Lakshmi Planum. The purposes of this study are (1) to recognize the tectonism of this area and investigate its type, direction, intensity, distribution and age relationships, (2) to define the link between the formation of the Akna mountain belt and the tectonic deformation in adjacent Tessera and Lakshmi Planum.

Impact of tectonic and volcanism on the Neogene evolution of isolated carbonate platforms (SW Indian Ocean)

NASA Astrophysics Data System (ADS)

Courgeon, S.; Jorry, S. J.; Jouet, G.; Camoin, G.; BouDagher-Fadel, M. K.; Bachèlery, P.; Caline, B.; Boichard, R.; Révillon, S.; Thomas, Y.; Thereau, E.; Guérin, C.

2017-06-01

Understanding the impact of tectonic activity and volcanism on long-term (i.e. millions years) evolution of shallow-water carbonate platforms represents a major issue for both industrial and academic perspectives. The southern central Mozambique Channel is characterized by a 100 km-long volcanic ridge hosting two guyots (the Hall and Jaguar banks) and a modern atoll (Bassas da India) fringed by a large terrace. Dredge sampling, geophysical acquisitions and submarines videos carried out during recent oceanographic cruises revealed that submarine flat-top seamounts correspond to karstified and drowned shallow-water carbonate platforms largely covered by volcanic material and structured by a dense network of normal faults. Microfacies and well-constrained stratigraphic data indicate that these carbonate platforms developed in shallow-water tropical environments during Miocene times and were characterized by biological assemblages dominated by corals, larger benthic foraminifera, red and green algae. The drowning of these isolated carbonate platforms is revealed by the deposition of outer shelf sediments during the Early Pliocene and seems closely linked to (1) volcanic activity typified by the establishment of wide lava flow complexes, and (2) to extensional tectonic deformation associated with high-offset normal faults dividing the flat-top seamounts into distinctive structural blocks. Explosive volcanic activity also affected platform carbonates and was responsible for the formation of crater(s) and the deposition of tuff layers including carbonate fragments. Shallow-water carbonate sedimentation resumed during Late Neogene time with the colonization of topographic highs inherited from tectonic deformation and volcanic accretion. Latest carbonate developments ultimately led to the formation of the Bassas da India modern atoll. The geological history of isolated carbonate platforms from the southern Mozambique Channel represents a new case illustrating the major

Pre-lithification tectonic foliation development in a clastic sedimentary rock sequence from SW Ireland

NASA Astrophysics Data System (ADS)

Meere, Patrick; Mulchrone, Kieran; McCarthy, David

2017-04-01

The current orthodoxy regarding the development of regionally developed penetrative tectonic cleavage fabrics in sedimentary rocks is that it postdates lithification of those rocks. It is well established that fabric development under these circumstances is achieved by a combination of grain rigid body rotation, crystal-plastic deformation and pressure solution. The latter is believed to be the primary mechanism responsible for the domainal nature of cleavage development commonly observed in low grade metamorphic rocks. While there have been advocates for the development of tectonic cleavages before host rock lithification these are currently viewed as essentially local aberrations without regional significance. In this study we combine new field observations with strain analysis, element mapping and modelling to characterise Acadian (>50%) crustal shortening in a Devonian clastic sedimentary sequence from the Dingle Peninsula of south west Ireland. Fabrics in these rocks reflect significant levels of tectonic shortening are a product of grain translation, rigid body rotation and repacking of intra- and extra-formational clasts during deformation of an unconsolidated clastic sedimentary sequence. There is an absence of the expected domainal cleavage structure and intra-clast deformation expected with conventional cleavage formation. This study requires geologists to consider the possibility such a mechanism contributing to tectonic strain in a wide range of geological settings and to look again at field evidence that indicates early sediment mobility during deformation.

Tectonics and volcanism in central Mexico - A Landsat Thematic Mapper perspective

NASA Technical Reports Server (NTRS)

Johnson, C. A.; Harrison, C. G. A.

1989-01-01

Digitally enhanced Landsat Thematic Mapper (TM) images were used to map neotectonic deformation in central Mexico. This region has been studied for decades using a variety of geological and geophysical techniques, but synoptic mapping of neotectonic activity and major fault zones there, and an evaluation of their regional relationship to the character and location of volcanism were not previously possible until the application of synoptic, high resolution satellite imagery. Interpretation of the TM images shows that the tectonic deformation is closely linked in time and space to the dominantly calc-alkaline volcanics of the Mexican Volcanic Belt (MVB). The eruptive style and distribution of the volcanics is clearly related to the deformation resulting from relative motions of three large crustal blocks south of the MVB. Therefore, zones of weakness within the crust of central Mexico, which may be inherited from earlier episodes of deformation, are a principal factor controlling the oblique orientation of the MVB relative to the Acapulco Trench.

The tectonic evolution of the Irtysh tectonic belt: New zircon U-Pb ages of arc-related and collisional granitoids in the Kalaxiangar tectonic belt, NW China

NASA Astrophysics Data System (ADS)

Hong, Tao; Klemd, Reiner; Gao, Jun; Xiang, Peng; Xu, Xing-Wang; You, Jun; Wang, Xin-Shui; Wu, Chu; Li, Hao; Ke, Qiang

2017-02-01

Precise geochronological constraints of the Irtysh tectonic belt situated between the Saur Island Arc and the Altay Terrane are crucial to a better understanding of the tectonic evolution of the Central Asian Orogenic Belt (CAOB). Recently, we discovered repeatedly deformed arc-related and collisional granitoids in the Kalaxiangar tectonic belt (KTB), which is located in the eastern part of the Irtysh tectonic belt. In this study, we report new whole-rock geochemical, zircon U-Pb and Hf isotopic data of the arc-related and collisional granitoids. Our data reveal that 1) arc-related granodioritic porphyries formed at ca. 382-374 Ma. Recrystallized zircon grains from a (ultra-)mylonitic granodiorite of the Laoshankou zone in the southern KTB display a U-Pb age of ca. 360 Ma; 2) syn-collisional granodioritic porphyries, which distribute along faults and parallel to the cleavage, were emplaced at ca. 367-356 Ma, with εHf(t) values varying from + 7.8 to + 14.2 and Hf model ages from 873 to 459 Ma; 3) a post-collisional A-type granodioritic porphyry, which crosscuts the NW-NNW trending schistosity of the metasedimentary country rocks at a low angle, has an age of ca. 324-320 Ma, while the εHf(t) values range from + 7.6 to + 14.4 with Hf model ages from 850 to 416 Ma; 4) post-collisional strike-slip A-type granite dykes, exposed along strike-slip faults, gave ages between 287 and 279 Ma, whereas the εHf(t) values range from + 4.9 to + 12.7 and the Hf model ages from 995 to 500 Ma; and 5) A-type biotite granite dykes, which intruded along conjugate tension joints, have ages of 274-271 Ma, and εHf(t) values from + 1.5 to + 13.2 with Hf model ages from 1196 to 454 Ma. Consequently, we propose that the collision between the Saur Island Arc and the Altay Terrane occurred in the Early Carboniferous (ca. 367-356 Ma) and the subsequent post-collisional tectonic process continued to the Late Carboniferous (ca. 324-320 Ma). It is further suggested that the Irtysh tectonic belt

Plate-tectonic boundary formation by grain-damage and pinning

NASA Astrophysics Data System (ADS)

Bercovici, David

2015-04-01

Shear weakening in the lithosphere is an essential ingredient for understanding how and why plate tectonics is generated from mantle convection on terrestrial planets. I present continued work on a theoretical model for lithospheric shear-localization and plate generation through damage, grain evolution and Zener pinning in two-phase (polycrystalline) lithospheric rocks. Grain size evolves through the competition between coarsening, which drives grain-growth, with damage, which drives grain reduction. The interface between phases controls Zener pinning, which impedes grain growth. Damage to the interface enhances the Zener pinning effect, which then reduces grain-size, forcing the rheology into the grain-size-dependent diffusion creep regime. This process thus allows damage and rheological weakening to co-exist, providing a necessary shear-localizing feedback. Moreover, because pinning inhibits grain-growth it promotes shear-zone longevity and plate-boundary inheritance. This theory has been applied recently to the emergence of plate tectonics in the Archean by transient subduction and accumulation of plate boundaries over 1Gyr, as well as to rapid slab detachment and abrupt tectonic changes. New work explores the saturation of interface damage at low interface curvature (e.g., because it is associated with larger grains that take up more of the damage, and/or because interface area is reduced). This effect allows three possible equilibrium grain-sizes for a given stress; a small-grain-size high-shear state in diffusion creep, a large grain-size low shear state in dislocation creep, and an intermediate state (often near the deformation map phase-boundary). The low and high grain-size states are stable, while the intermediate one is unstable. This implies that a material deformed at a given stress can acquire two stable deformation regimes, a low- and high- shear state; these are indicative of plate-like flows, i.e, the coexistence of both slowly deforming plates

Tectonic triggering of slump sheets in the Upper Cretaceous carbonate succession of the Porto Selvaggio area (Salento peninsula, southern Italy): Synsedimentary tectonics in the Apulian Carbonate Platform

NASA Astrophysics Data System (ADS)

Mastrogiacomo, G.; Moretti, M.; Owen, G.; Spalluto, L.

2012-08-01

Soft-sediment deformation structures crop out in the Upper Cretaceous carbonate succession in Porto Selvaggio cove in the western Salento peninsula, Apulian foreland, southern Italy. The deformed interval is about 13 m thick and occurs between shallow-water limestones and dolostones formed in peritidal and shallow subtidal environments. It comprises well-bedded grey mudstones interlayered with dark grey laminated microbioclastic wackestones characterized by couplets of closely spaced dark and bright laminae marked by the parallel orientation of calcareous microbioclasts and thin-shelled bivalves. The low biological diversity, scarcity of burrowing biota, and presence of a well preserved fish fauna provide evidence of anoxic conditions occurring in morphological depressions within the platform, and a stagnant, stratified water body affected by weak bottom currents, indicating the sudden development of a localised and short-lived intraplatform basin. Two soft-sediment deformation horizons (slump sheets) separated by undeformed limestones with similar facies occur in this part of the succession. The lower, thicker slump sheet (1.0-1.3 m thick) contains asymmetric and box folds. Well-developed décollement surfaces (locally containing thick brecciated zones) cut the folds, forming small-scale thrust-sheets and indicating mixed plastic to brittle behaviour. The upper, thinner slump sheet (0.25-0.35 m thick) contains only asymmetric folds, indicating plastic behaviour only. The differences in deformation style are attributed to differences in facies. Measurements of fold-axis orientations in the slump sheets show that they moved in similar directions, recording the development of a local, gently dipping palaeoslope. Autogenic (internal) trigger mechanisms are ruled out by a detailed consideration of facies. The slump sheets were triggered by allogenic, tectonic effects, either the weakening of sediment by seismic activity or the tectonically induced steepening of slopes

Study of the deformation in Central Afar using InSAR NSBAS chain

NASA Astrophysics Data System (ADS)

Deprez, A.; Doubre, C.; Grandin, R.; Saad, I.; Masson, F.; Socquet, A.

2013-12-01

The Afar Depression (East Africa) connects all three continental plates of Arabia, Somalia and Nubia plates. For over 20 Ma, the divergent motion of these plates has led to the formation of large normal faults building tall scarps between the high plateaus and the depression, and the development of large basins and an incipient seafloor spreading along a series of active volcano-tectonic rift segments within the depression. The space-time evolution of the active surface deformation over the whole Afar region remains uncertain. Previous tectonic and geodetic studies confirm that a large part of the current deformation is concentrated along these segments. However, the amount of extension accommodated by other non-volcanic basins and normal faulting remains unclear, despite significant micro-seismic activity. Due to the active volcanism, large transient displacements related to dyking sequence, notably in the Manda Hararo rift (2005-2010), increase the difficulty to characterize the deformation field over simple time and space scales. In this study, we attempt to obtain a complete inventory of the deformation within the whole Afar Depression and to understand the associated phenomena, which occurred in this singular tectonic environment. We study in particular, the behavior of the structures activated during the post-dyking stage of the rift segments. For this purpose, we conduct a careful processing of a large set of SAR ENVISAT images over the 2004-2010 period, we also use previous InSAR results and GPS data from permanent stations and from campaigns conducted in 1999, 2003, 2010, 2012 within a GPS network particularly dense along the Asal-Ghoubbet segment. In one hand, in the western part of Afar, the far-field response of the 2005-2010 dyke sequence appears to be the dominant surface motion on the mean velocity field. In an other hand, more eastward across the Asal-Ghoubbet rift, strong gradients of deformation are observed. The time series analysis of both In

Sedimentary record of seismic events in the Eocene Green River Formation and its implications for regional tectonics on lake evolution (Bridger Basin, Wyoming)

NASA Astrophysics Data System (ADS)

Törő, Balázs; Pratt, Brian R.

2016-10-01

, underfilled Wilkins Peak Member. Thus, these seismites are evidence for regional-scale changes in lacustrine sedimentation of Eocene Lake Gosiute in response to syndepositional tectonic activity. Analysis of synsedimentary deformation features is, therefore, a promising yet under-utilized tool to trace the tectonic evolution of lacustrine deposits of the Green River Formation and other tectonically active marine and non-marine basins.

Tectonics and volcanism of Eastern Aphrodite Terra, Venus - No subduction, no spreading

NASA Technical Reports Server (NTRS)

Hansen, Vicki L.; Phillips, Roger J.

1993-01-01

Eastern Aphrodite Terra, a deformed region with high topographic relief on Venus, has been interpreted as analogous to a terrestrial extensional or convergent plate boundary. However, analysis of geological and structural relations indicates that the tectonics of eastern Aphrodite Terra is dominated by blistering of the crust by magma diapirs. The findings imply that, within this region, vertical tectonism dominates over horizontal tectonism and, consequently, that this region is neither a divergent nor a convergent plate boundary.

Tectonic creep in the Hayward fault zone, California

USGS Publications Warehouse

Radbruch-Hall, Dorothy H.; Bonilla, M.G.

1966-01-01

Tectonic creep is slight apparently continuous movement along a fault. Evidence of creep has been noted at several places within the Hayward fault zone--a zone trending northwestward near the western front of the hills bordering the east side of San Francisco Bay. D. H. Radbruch of the Geological Survey and B. J. Lennert, consulting engineer, confirmed a reported cracking of a culvert under the University of California stadium. F. B. Blanchard and C. L. Laverty of the East Bay Municipal Utility District of Oakland studied cracks in the Claremont water tunnel in Berkeley. M. G. Bonilla of the Geological Survey noted deformation of railroad tracks in the Niles district of Fremont. Six sets of tracks have been bent and shifted. L. S. Cluff of Woodward-Clyde-Sherard and Associates and K. V. Steinbrugge of the Pacific Fire Rating Bureau noted that the concrete walls of a warehouse in the Irvington district of Fremont have been bent and broken, and the columns forced out of line. All the deformations noted have been right lateral and range from about 2 inches in the Claremont tunnel to about 8 inches on the railroad tracks. Tectonic creep almost certainly will continue to damage buildings, tunnels, and other structures that cross the narrow bands of active movement within the Hayward fault zone.

Geomorphologic, stratigraphic and sedimentologic evidences of tectonic activity in Sone-Ganga alluvial tract in Middle Ganga Plain, India

NASA Astrophysics Data System (ADS)

Sahu, Sudarsan; Saha, Dipankar

2014-08-01

The basement of the Ganga basin in the Himalayan foreland is criss-crossed by several faults, dividing the basin into several sub-blocks forming horsts, grabens, or half-grabens. Tectonic perturbations along basement faults have affected the fluvial regime and extent of sediment fill in different parts of the basin during Late Quaternary. The East Patna Fault (EPF) and the West Patna Fault (WPF), located in Sone-Ganga alluvial tract in the southern marginal parts of Middle Ganga Plain (MGP), have remained tectonically active. The EPF particularly has acted significantly and influenced in evolving the geomorphological landscape and the stratigraphic architecture of the area. The block bounded by the two faults has earlier been considered as a single entity, constituting a half-graben. The present investigation (by morpho-stratigraphic and sedimentologic means) has revealed the existence of yet another fault within the half-graben, referred to as Bishunpur-Khagaul Fault (BKF). Many of the long profile morphological characters (e.g., knick-zone, low width-depth ratio) of the Sone River at its lower reaches can be ascribed to local structural deformation along BKF. These basement faults in MGP lie parallel to each other in NE-SW direction.

On the breakup of tectonic plates by polar wandering

NASA Technical Reports Server (NTRS)

Liu, H.-S.

1974-01-01

The equations for the stresses in a homogeneous shell of uniform thickness caused by a shift of the axis of rotation are derived. The magnitude of these stresses reaches a maximum value of the order of 10 to the 9th power dyn/sq cm, which is sufficient for explaining a tectonic breakup. In order to deduce the fracture pattern according to which the breakup of tectonic plates can be expected the theory of plastic deformation of shells is applied. The analysis of this pattern gives an explanation of the existing boundary systems of the major tectonic plates as described by Morgan (1968), LePichon (1968) and Isacks et al. (1968).

Improving the detection of tectonic transients in Japan by accounting for Earth's deformation response to surface mass loading

NASA Astrophysics Data System (ADS)

Martens, H. R.; Simons, M.; Moore, A. W.; Owen, S. E.; Rivera, L. A.

2016-12-01

We explore the contributions of oceanic, atmospheric, and hydrologic mass loading to Global Navigation Satellite System (GNSS)-inferred observations of surface displacements in Japan. Surface mass loading (SML) generates mm- to cm-level deformation of the solid Earth on time scales of hours to years, which exceeds the measurement uncertainties of most GNSS position estimates. By improving the efficiency and accuracy of the prediction and empirical estimation of SML response, we aim to reduce the variance of GNSS time series and therefore enhance the ability to resolve subtle tectonic signals, such as aseismic transients associated with subduction zone processes. Using the GIPSY software in precise point positioning mode, we estimate time series of sub-daily receiver positions for the GNSS Earth Observation Network System (GEONET) in Japan. We also model the Earth's elastic deformation response to a variety of surface mass loads, including loads of atmospheric (e.g., ECMWF) and oceanic (e.g., TPXO8-Atlas, ECCO2) origin. We extract periodic signals, such as the ocean tides and seasonal variations in hydrological loading, using harmonic analysis. Deformation caused by non-periodic loads, such as non-tidal oceanic and atmospheric loads, can be predicted and removed to further reduce the variance. We seek to streamline the workflow for estimating SML-induced surface displacements from a variety of sources in order to account for loading signals in routine GNSS data processing, thereby improving the ability to assess the mechanics of plate boundaries.

Syn-deformational features of Carlin-type Au deposits

USGS Publications Warehouse

Peters, S.G.

2004-01-01

Syn-deformational ore deposition played an important role in some Carlin-type Au deposits according to field and laboratory evidence, which indicates that flow of Au-bearing fluids was synchronous with regional-scale deformation events. Gold-related deformation events linked to ore genesis were distinct from high-level, brittle deformation that is typical of many epithermal deposits. Carlin-type Au deposits, with brittle-ductile features, most likely formed during tectonic events that were accompanied by significant fluid flow. Interactive deformation-fluid processes involved brittle-ductile folding, faulting, shearing, and gouge development that were focused along illite-clay and dissolution zones caused by hydrothermal alteration. Alteration along these deformation zones resulted in increased porosity and enhancement of fluid flow, which resulted in decarbonated, significant dissolution, collapse, and volume and mass reduction. Carlin-type Au deposits commonly are hosted in Paleozoic and Mesozoic sedimentary rocks (limestone, siltstone, argillite, shale, and quartzite) on the margins of cratons. The sedimentary basins containing the host rocks underwent tectonic events that influenced the development of stratabound, structurally controlled orebodies. Published by Elsevier Ltd.

Relationships between plate convergence, the earthquake cycle, and long-term accumulation of net tectonic deformation at island arcs; not so simple as it seems

NASA Astrophysics Data System (ADS)

Taylor, F. W.; Lavier, L. L.; Bevis, M. G.; Thirumalai, K.; Frohlich, C. A.

2012-12-01

Over million-year time scales, what is the relationship between the meter-scale vertical displacements that occur in individual large subduction-zone earthquakes, and the observed topography and geology of island arcs? Because the geographic distribution of vertical displacements associated with the earthquake cycle sometimes mimics topography, it is tempting to assume that vertical deformation simply accrues as the coseismic part of the cycle that is preserved from one event to another. However, our research in the Central New Hebrides and Western Solomon arcs demonstrates that truly permanent tectonic deformation is a step farther removed from the earthquake cycle than we originally assumed. By precisely dating of coral reef terraces we are able to evaluate vertical deformation over time scales of 10,000 to 100,000 years. This analysis indicates that these arcs undergo episodes of hundreds of meters of subsidence and uplift over time scales of tens of thousands of years. Thus what remains in the geologic record is potentially providing invaluable information about more fundamental processes than the elastic earthquake cycle. These longer-term episodes of vertical motion may act in many arcs throughout the world, but evidence of them may be poorly preserved outside of tropical regions where corals along island coastlines provide a record of their occurrence.In our presentation we will describe the tectonic behavior observed in the Central New Hebrides and Western Solomons. We will speculate about some possible mechanisms that explain how the subduction process generates longer-term episodes of subsidence and uplift, and make suggestions about future observations that could better constrain the nature of these processes.

Thick-skinned tectonics closing the Rifian Corridor

NASA Astrophysics Data System (ADS)

Capella, Walter; Matenco, Liviu; Dmitrieva, Evelina; Roest, Wilmer M. J.; Hessels, Suzanne; Hssain, Mohamed; Chakor-Alami, Abdelwahid; Sierro, Francisco J.; Krijgsman, Wout

2017-07-01

Tectonic processes in the Gibraltar region are associated with Africa-Iberia convergence and the formation of the Betic-Rif orogenic system. The Late Miocene shortening recorded in the Rif orogen resulted in gradual shallowing and eventual closure of the Rifian Corridor, a narrow marine gateway connecting the Atlantic Ocean with the Mediterranean Sea. This closure is associated with paleoenvironmental changes that ultimately led to the Mediterranean Messinian Salinity Crisis. Here we present a structural analysis based on a combination of field kinematic data and interpretation of reflection seismic lines acquired for petroleum exploration to understand the deformational phases associated with the closure of the Rifian Corridor. We show the succession of three Late Miocene to present day events, an initial thin-skinned nappe thrusting, followed by regional subsidence and continued by thick-skinned contraction. The transition from in sequence thin-skinned tectonics during subduction to thick-skinned contraction during continental collision resulted in significant acceleration of tectonic uplift and associated exhumation. This is related to a change in the regional deformation linked to plate convergence, but possibly also coupled with deep lithospheric or dynamic topography processes. Such a mechanism is also common for other Mediterranean orogens during late stages of slab retreat, where accelerated tectonics resulted in rapid sedimentation and associated basins evolution. We conclude that the thick-skinned contraction in the Rif orogeny initiated in the late Tortonian, has created a cumulative uplift in the order of 1 km, and provided high enough uplift rates to close the Rifian Corridor.

GNSS activities for crustal deformation studies in Georgia (Caucasus)

NASA Astrophysics Data System (ADS)

Khazaradze, Giorgi; Machavariani, Kakhaber; Hahubia, Galaktion; Kachakhidze-Murphy, Nino; Kachakhidze, Manana

2017-04-01

The republic of Georgia is located in the Caucasus, between the Black and Caspian seas from the west and the east, and Greater and Lesser Caucasus mountains from the north and the south. Tectonically, the region belongs to the Alpine-Himalayan collisional zone, formed during the late Cenozoic period as a result of a collision between the Arabian and Eurasian plates. The deformation zone due to this collision is broad and extends from Zagros mountains in southern Iran to the Greater Caucasus in the north. The GPS studies conducted during the last decade suggest a convergence rate of 18 mm/yr between the Arabia and Eurasia plates. Although majority of this convergence occurs in the southern part of the deformation zone, important part of this convergence occurs in Georgia, implying an elevated seismic risk in the region. This is corroborated by a presence of significant historical and instrumental earthquakes in the country. As part of the project dealing with the detection of possible low frequency electromagnetic emissions proceeding earthquakes, we have installed a continuous GNSS station MTSK between Mtskheta and Tbilisi. The station consists of Leica GRX1200 GNSS receiver with an AS10 antenna. It is mounted on top of the building, anchored to the existing brick wall. The preliminary analysis of the time-series indicates the suitability of the new station for geodynamic studies, since the preliminary data shows clean time-series with low multipath signal. We are hopeful, with time the MTSK station can provide millimeter level precisions in the velocity estimates. The analysis of the data is performed using the Gamit/Globk software package from MIT and it is processed in conjunction with 23 continuous GNSS stations of the GEO-CORS network operated by National Agency of Public Registry of Georgia (geocors.napr.gov.ge). In addition, we analyze data form the stations located on Eurasia, Arabia and Africa plates. The principle objective of the given work is to monitor

Modelling ground deformation patterns associated with volcanic processes at the Okataina Volcanic Centre

NASA Astrophysics Data System (ADS)

Holden, L.; Cas, R.; Fournier, N.; Ailleres, L.

2017-09-01

The Okataina Volcanic Centre (OVC) is one of two large active rhyolite centres in the modern Taupo Volcanic Zone (TVZ) in the North Island of New Zealand. It is located in a complex section of the Taupo rift, a tectonically active section of the TVZ. The most recent volcanic unrest at the OVC includes the 1315 CE Kaharoa and 1886 Tarawera eruptions. Current monitoring activity at the OVC includes the use of continuous GPS receivers (cGPS), lake levelling and seismographs. The ground deformation patterns preceding volcanic activity the OVC are poorly constrained and restricted to predictions from basic modelling and comparison to other volcanoes worldwide. A better understanding of the deformation patterns preceding renewed volcanic activity is essential to determine if observed deformation is related to volcanic, tectonic or hydrothermal processes. Such an understanding also means that the ability of the present day cGPS network to detect these deformation patterns can also be assessed. The research presented here uses the finite element (FE) modelling technique to investigate ground deformation patterns associated with magma accumulation and diking processes at the OVC in greater detail. A number of FE models are produced and tested using Pylith software and incorporate characteristics of the 1315 CE Kaharoa and 1886 Tarawera eruptions, summarised from the existing body of research literature. The influence of a simple ring fault structure at the OVC on the modelled deformation is evaluated. The ability of the present-day continuous GPS (cGPS) GeoNet monitoring network to detect or observe the modelled deformation is also considered. The results show the modelled horizontal and vertical displacement fields have a number of key features, which include prominent lobe based regions extending northwest and southeast of the OVC. The results also show that the ring fault structure increases the magnitude of the displacements inside the caldera, in particular in the

Venusian tectonics: Convective coupling to the lithosphere?

NASA Technical Reports Server (NTRS)

Phillips, R. J.

1987-01-01

The relationship between the dominant global heat loss mechanism and planetary size has motivated the search for tectonic style on Venus. Prior to the American and Soviet mapping missions of the past eight years, it was thought that terrestrial style plate tectonics was operative on Venus because this planet is approximately the size of the Earth and is conjectured to have about the same heat source content per unit mass. However, surface topography mapped by the altimeter of the Pioneer Venus spacecraft did not show any physiographic expression of terrestrial style spreading ridges, trenches, volcanic arcs or transform faults, although the horizontal resolution was questionable for detection of at least some of these features. The Venera 15 and 16 radar missions mapped the northern latitudes of Venus at 1 to 2 km resolution and showed that there are significant geographic areas of deformation seemingly created by large horizontal stresses. These same high resolution images show no evidence for plate tectonic features. Thus a fundamental problem for venusian tectonics is the origin of large horizontal stresses near the surface in the apparent absence of plate tectonics.

Crustal architecture and tectonic evolution of the Cauvery Suture Zone, southern India

NASA Astrophysics Data System (ADS)

Chetty, T. R. K.; Yellappa, T.; Santosh, M.

2016-11-01

The Cauvery suture zone (CSZ) in southern India has witnessed multiple deformations associated with multiple subduction-collision history, with incorporation of the related accretionary belts sequentially into the southern continental margin of the Archaean Dharwar craton since Neoarchean to Neoproterozoic. The accreted tectonic elements include suprasubduction complexes of arc magmatic sequences, high-grade supracrustals, thrust duplexes, ophiolites, and younger intrusions that are dispersed along the suture. The intra-oceanic Neoarchean-Neoproterozoic arc assemblages are well exposed in the form of tectonic mélanges dominantly towards the eastern sector of the CSZ and are typically subjected to complex and multiple deformation events. Multi-scale analysis of structural elements with detailed geological mapping of the sub-regions and their structural cross sections, geochemical and geochronological data and integrated geophysical observations suggest that the CSZ is an important zone that preserves the imprints of multiple cycles of Precambrian plate tectonic regimes.

Active tectonics of northwestern U.S. inferred from GPS-derived surface velocities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert McCaffrey; Robert W. King; Suzette J. Payne

2013-02-01

Surface velocities derived from GPS observations from 1993 to 2011 at several hundred sites across the deforming northwestern United States are used to further elucidate the region's active tectonics. The new velocities reveal that the clockwise rotations, relative to North America, seen in Oregon and western Washington from earlier GPS observations, continue to the east to include the Snake River Plain of Idaho and south into the Basin and Range of northern Nevada. Regional-scale rotation is attributed to gravitationally driven extension in the Basin and Range and Pacific-North America shear transferred through the Walker Lane belt aided by potentially strongmore » pinning below the Idaho Batholith. The large rotating section comprising eastern Oregon displays very low internal deformation rates despite seismological evidence for a thin crust, warm mantle, organized mantle flow, and elevated topography. The observed disparity between mantle and surface kinematics suggests that either little stress acts between them (low basal shear) or that the crust is strong relative to the mantle. The rotation of the Oregon block impinges on Washington across the Yakima fold-thrust belt where shortening occurs in a closing-fan style. Elastic fault locking at the Cascadia subduction zone is reevaluated using the GPS velocities and recently published uplift rates. The 18 year GPS and 80 year leveling data can both be matched with a common locking model suggesting that the locking has been stable over many decades. The rate of strain accumulation is consistent with hundreds of years between great subduction events.« less

Active tectonics of the onshore Hengchun Fault using UAS DSM combined with ALOS PS-InSAR time series (Southern Taiwan)

NASA Astrophysics Data System (ADS)

Deffontaines, Benoit; Chang, Kuo-Jen; Champenois, Johann; Lin, Kuan-Chuan; Lee, Chyi-Tyi; Chen, Rou-Fei; Hu, Jyr-Ching; Magalhaes, Samuel

2018-03-01

Characterizing active faults and quantifying their activity are major concerns in Taiwan, especially following the major Chichi earthquake on 21 September 1999. Among the targets that still remain poorly understood in terms of active tectonics are the Hengchun and Kenting faults (Southern Taiwan). From a geodynamic point of view, the faults affect the outcropping top of the Manila accretionary prism of the Manila subduction zone that runs from Luzon (northern Philippines) to Taiwan. In order to better locate and quantify the location and quantify the activity of the Hengchun Fault, we start from existing geological maps, which we update thanks to the use of two products derived from unmanned aircraft system acquisitions: (1) a very high precision (< 50 cm) and resolution (< 10 cm) digital surface model (DSM) and (2) a georeferenced aerial photograph mosaic of the studied area. Moreover, the superimposition of the resulting structural sketch map with new Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) results obtained from PALSAR ALOS images, validated by Global Positioning System (GPS) and leveling data, allows the characterization and quantification of the surface displacements during the monitoring period (2007-2011). We confirm herein the geometry, characterization and quantification of the active Hengchun Fault deformation, which acts as an active left-lateral transpressive fault. As the Hengchun ridge was the location of one of the last major earthquakes in Taiwan (26 December 2006, depth: 44 km, ML = 7.0), Hengchun Peninsula active tectonics must be better constrained in order if possible to prevent major destructions in the near future.

Levelling Profiles and a GPS Network to Monitor the Active Folding and Faulting Deformation in the Campo de Dalias (Betic Cordillera, Southeastern Spain)

PubMed Central

Marín-Lechado, Carlos; Galindo-Zaldívar, Jesús; Gil, Antonio José; Borque, María Jesús; de Lacy, María Clara; Pedrera, Antonio; López-Garrido, Angel Carlos; Alfaro, Pedro; García-Tortosa, Francisco; Ramos, Maria Isabel; Rodríguez-Caderot, Gracia; Rodríguez-Fernández, José; Ruiz-Constán, Ana; de Galdeano-Equiza, Carlos Sanz

2010-01-01

The Campo de Dalias is an area with relevant seismicity associated to the active tectonic deformations of the southern boundary of the Betic Cordillera. A non-permanent GPS network was installed to monitor, for the first time, the fault- and fold-related activity. In addition, two high precision levelling profiles were measured twice over a one-year period across the Balanegra Fault, one of the most active faults recognized in the area. The absence of significant movement of the main fault surface suggests seismogenic behaviour. The possible recurrence interval may be between 100 and 300 y. The repetitive GPS and high precision levelling monitoring of the fault surface during a long time period may help us to determine future fault behaviour with regard to the existence (or not) of a creep component, the accumulation of elastic deformation before faulting, and implications of the fold-fault relationship. PMID:22319309

In search of transient subduction interfaces in the Dent Blanche-Sesia Tectonic System (W. Alps)

NASA Astrophysics Data System (ADS)

Angiboust, Samuel; Glodny, Johannes; Oncken, Onno; Chopin, Christian

2014-09-01

In this paper we study the Alpine metamorphic history of a major tectonic zone which formed during Alpine orogeny, the Dent Blanche Thrust (DBT). This contact, located in the Northern Western Alps, juxtaposes some ophiolitic metasediment-rich remnants of the Liguro-Piemontese ocean (Tsaté Complex) with a composite continental, km-sized complex (Dent Blanche Tectonic System, DBTS) of Adriatic affinity thrusted over the ophiolite. In order to better understand the geodynamic meaning of the DBT region and adjacent units, we have reconstructed the pressure-temperature-time-deformation (P-T-t-d) history of these two units using modern thermobarometric tools, Rb/Sr geochronology, and field relationships. We show that the Tsaté Complex is formed by a stack of km-thick calcschists-bearing tectonic slices having experienced variable maximum burial temperatures between 360 °C and 490 °C at depths of ca. 25-40 km. Associated deformation ages span a range between 37 Ma and 41 Ma. The Arolla gneissic mylonites at the base of the DBTS experienced high-pressure (12-14 kbar), top-to-NW deformation at ca. 450 °C between 43 and 48 Ma. A first age of ca. 58 Ma has been obtained for high-pressure ductile deformation in the Valpelline shear zone, atop Arolla gneisses. Some of the primary, peak metamorphic fabrics have been reworked and later backfolded during exhumation and collisional overprint (ca. 20 km depth, 37-40 Ma) leading to the regional greenschist-facies retrogression which is particularly prominent within Tsaté metasediments. We interpret the Dent Blanche Thrust, at the base of the Arolla unit, as a fossilized subduction interface active between 43 and 48 Ma. Our geochronological results on the shear zone lining the top of the Arolla unit, together with previous P-T-t estimates on equivalent blueschist-facies shear zones cutting the Sesia unit, indicate an older tectonic activity between 58 and 65 Ma. We demonstrate here that observed younger ages towards lowermost

Preliminary investigation on the deformation rates of the Nazimiye Fault (Eastern Turkey)

NASA Astrophysics Data System (ADS)

Sançar, Taylan

2016-04-01

The complex tectonic setting of the eastern Mediterranean is mainly shaped by the interaction between three major plates, Eurasian, African, and Arabian plates, with additional involvement from the smaller Anatolian Scholle. The internal deformation of the Anatolian Scholle is mainly accommodated along NW-striking dextral and NE-striking sinistral faults, which are explained by the Prandtl Cell model by Şengör (1979). Although some of these strike-slip faults, such as Tuzgölü, Ecemiş and Malatya-Ovacık faults, have long been documented, the Nazimiye Fault (NF) is only presented in very recent studies (Kara et al. 2013; Emre et al. 2012). The aim of the study is to understand intra-plate deformation of the Anatolian Scholle, by studying the morphotectonic structures along the NF. The study area located close to the eastern boundary of Anatolia, roughly on the wedge that is delimited by the North and East Anatolian shear zones and the Malatya-Ovacık Fault Zone. After the preliminary remote sensing analyses and field observations, I mapped the locations of the different terrace treads along the Pülümür River, which is strongly deflected by the activity of the NF. This dextral strike-slip fault, is not only characterized with the deformation of the Pülümür River, but also it shows many beheaded streams, pressure ridges, hot springs and travertines along its course. I sampled one of the alluvial fans for cosmogenic dating at the eastern section of the NF, where about 20 m of dextral offset was measured at the margins of the incised stream. Moreover, additional sampling was performed from different terrace levels along the Pülümür River, in order not only to estimate the min. horizontal rate, but also to quantify the vertical deformation. Moreover, I applied morphometric indices to understand the tectonic control on the local morphology along the NF. Transverse Topographic Symmetry Factor was used to show the relative degree of tectonic activity along the

Recent tectonic stress field, active faults and geothermal fields (hot-water type) in China

NASA Astrophysics Data System (ADS)

Wan, Tianfeng

1984-10-01

It is quite probable that geothermal fields of the hot-water type in China do not develop in the absence of recently active faults. Such active faults are all controlled by tectonic stress fields. Using the data of earthquake fault-plane solutions, active faults, and surface thermal manifestations, a map showing the recent tectonic stress field, and the location of active faults and geothermal fields in China is presented. Data collected from 89 investigated prospects with geothermal manifestations indicate that the locations of geothermal fields are controlled by active faults and the recent tectonic stress field. About 68% of the prospects are controlled by tensional or tensional-shear faults. The angle between these faults and the direction of maximum compressive stress is less than 45°, and both tend to be parallel. About 15% of the prospects are controlled by conjugate faults. Another 14% are controlled by compressive-shear faults where the angle between these faults and the direction maximum compressive stress is greater than 45°.

Investigation of Tectonic Boundaries in Taiwan Obtained with a Hierarchical Clustering of Dense GNSS Data

NASA Astrophysics Data System (ADS)

Takahashi, A.; Hashimoto, M.; Hu, J. C.; Fukahata, Y.

2017-12-01

Taiwan Island is composed of many geological structures. The main tectonic feature is the collision of the Luzon volcanic arc with the Eurasian continent, which propagates westward and generates complicated crustal deformation. One way to model crustal deformation is to divide Taiwan island into man rigid blocks that moves relatively each other along the boundaries (deformation zones) of the blocks. Since earthquakes tend to occur in the deformation zones, identification of such tectonic boundaries is important. So far, many tectonic boundaries have been proposed on the basis of geology, geomorphology, seismology and geodesy. However, which is the most significant boundary depends on disciplines and there is no way to objectively classify them. Here, we introduce an objective method to identify significant tectonic boundaries with a hierarchical representation proposed by Simpson et al. [2012].We apply a hierarchical agglomerative clustering algorithm to dense GNSS horizontal velocity data in Taiwan. One of the significant merits of the hierarchical representation of the clustering results is that we can consistently explore crustal structures from larger to smaller scales. This is because a higher hierarchy corresponds to a larger crustal structure, and a lower hierarchy corresponds to a smaller crustal structure. Relative motion between clusters can be obtained from this analysis.The first major boundary is identified along the eastern margin of the Longitudinal Valley, which corresponds to the separation of the Philippine Sea plate and the Eurasian continental margin. The second major boundary appears along the Chaochou fault and the Chishan fault in southwestern Taiwan. The third major boundary appears along the eastern margin of the coastal plane. The identified major clusters can be divided into several smaller blocks without losing consistency with geological boundaries. For example, the Fengshun fault, concealed beneath thick sediment layers, is identified

Miocene shale tectonics in the Moroccan margin (Alboran Sea)

NASA Astrophysics Data System (ADS)

Do Couto, D.; El Abbassi, M.; Ammar, A.; Gorini, C.; Estrada, F.; Letouzey, J.; Smit, J.; Jolivet, L.; Jabour, H.

2011-12-01

The Betic (Southern Spain) and Rif (Morocco) mountains form an arcuate belt that represents the westernmost termination of the peri-mediterranean Alpine mountain chain. The Miocene Alboran Basin and its subbasins is located in the hinterland of the Betic-Rif belt. It is considered to be a back-arc basin that developed during the coeval westward motion of the Alboran domain and the extensional collapse of previously thickened crust of the Betic-Rif belt. The Western Alboran Basin (WAB) is the major sedimentary depocenter with a sediment thickness in excess of 10 km, it is bordered by the Gibraltar arc, the volcanic Djibouti mounts and the Alboran ridge. Part of the WAB is affected by shale tectonics and associated mud volcanism. High-quality 2D seismic profiles acquired on the Moroccan margin of the Alboran Basin during the last decade reveal the multiple history of the basin. This study deals with the analysis of a number of these seismic profiles that are located along and orthogonal to the Moroccan margin. Seismic stratigraphy is calibrated from industrial wells. We focus on the interactions between the gravity-driven tectonic processes and the sedimentation in the basin. Our seismic interpretation confirms that the formation of the WAB began in the Early Miocene (Aquitanian - Burdigalian). The fast subsidence of the basin floor coeval to massive sedimentation induced the undercompaction of early miocene shales during their deposition. Downslope migration of these fine-grained sediments initiated during the deposition of the Langhian siliciclastics. This gravity-driven system was accompanied by continuous basement subsidence and induced disharmonic deformation in Mid Miocene units (i.e. not related to basement deformation). The development of shale-cored anticlines and thrusts in the deep basin is the result of compressive deformation at the front of the gravity-driven system and lasted for ca. 15 Ma. The compressive front has been re-activated by strong

Continental tectonics in the aftermath of plate tectonics

NASA Technical Reports Server (NTRS)

Molnar, Peter

1988-01-01

It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.

Activities for Plate Tectonics using GeoMapApp

NASA Astrophysics Data System (ADS)

Goodwillie, A. M.

2016-12-01

The concept of plate tectonics is a fundamental component of our understanding of how Earth works yet authentic, high-quality geoscience data related to plate tectonics may not be readily available to all students. To compound matters, when data is accessible, students may not possess the skills or resources necessary to explore and analyse it. As a result, much emphasis at federal and state level is now placed upon encouraging students to work with more data and more technology more often and more rigourously. Easy-to-use digital platforms offer much potential for promoting inquiry-based learning at all levels of education. GeoMapApp is one such tool. Developed at Columbia University's Lamont-Doherty Earth Observatory, GeoMapApp (http://www.geomapapp.org) is a free resource that integrates a wide range of research-grade geoscience data in one intuitive map-based interface. Simple strategies for data manipulation, visualisation and presentation allow uses to explore the data in meaningful ways. Layering and transparency capabilities further allow learners to use GeoMapApp to compare multiple data sets at once, and high-impact Save Session functionality allows a GeoMapApp project to be saved for sharing or later use. In this presentation, activities related to plate tectonics will be highlighted. One GeoMapApp activity helps students investigate plate boundaries by exploring earthquake and volcano locations. Another requires students to calculate the rate of seafloor spreading using crustal age data in various ocean basins. A third uses the GeoMapApp layering technique to explore the influence of geological forces in shaping the landscape. Each activity shown can be done by students on an individual basis, as pairs, or as groups. Educators report that student use of GeoMapApp fosters an increased sense of data "ownership" amongst students, promotes STEM skills, and provides them with access to authentic research-grade geoscience data using the same cutting

A study of tectonic activity in the Basin-Range Province and on the San Andreas Fault. No. 2: Lithospheric structure, seismicity, and contemporary deformation of the United States Cordillera

NASA Technical Reports Server (NTRS)

Smith, R. B.

1986-01-01

The structural evolution of the U.S. Cordillera has been influenced by a variety of tectonic mechanisms including passive margin rifting and sedimentation; arc volcanism; accretion of exotic terranes; intraplate magmatism; and folding and faulting associated with compression and extension processes that have profoundly influenced the lithospheric structure. As a result the Cordilleran crust is laterally inhomogeneous across its 2000 km east-west breadth. It is thin along the West Coast where it has close oceanic affinities. The crust thickens eastward beneath the Sierra Nevada, then thins beneath the Basin-Range. Crustal thickening continues eastward beneath the Colorado Plateau, the Rocky Mountains, and the Great Plains. The total lithospheric thickness attains 65 km in the Basin-Range and increases eastward beneath the Colorado Plateau. The upper-crust, including the crystalline basement of the Cordillera, has P sub G velocities of 6 km/s in the Basin-Range and Rio Grande Rift. Lower P sub G velocities of 5.4 to 5.7 km/s are associated with the youthful Yellowstone, Valles and Long Valley calderas and the Franciscan assemblage of the western coastal margin. Averaged crustal velocity reflects integrated tectonic evolution of the crust-thick silicic bodies, velocity reversals, and a thin crust produce low averaged velocities that are characteristic of a highly attenuated and thermally deformed crust.

Quantification of fluvial response to tectonic deformation in the Central Pontides, Turkey; inferences from OSL dating of fluvial terraces

NASA Astrophysics Data System (ADS)

McClain, Kevin; Yıldırım, Cengiz; Çiner, Attila; Akif Sarıkaya, M.; Şahin, Sefa; Özcan, Orkan; Güneç Kıyak, Nafiye; Öztürk, Tuǧba

2017-04-01

From Late Miocene to present, Anatolia's rapid counterclockwise movement, which increases in velocity towards the Hellenic Arc, has formed the North Anatolian Fault (NAF), a dextral transform fault along the Anatolia-Eurasia plate boundary and the northern margin of the Central Anatolian Plateau (CAP). A zone of transpression referred to as the Central Pontides exists between the broad restraining bend of the NAF and the Black Sea Basin, uplifting what is interpreted as a detached flower structure. Dating of Quaternary landforms in the eastern flank of the Central Pontides has helped to understand its recent deformation. However, in the western flank of the Central Pontides there is an absence of Quaternary studies, relatively quiet modern seismicity, and difficulties locating or observing fault scarps. This led us to use optically stimulated luminescence dating (OSL-dating) of fluvial terrace sediments and the study of geomorphic features to gain insight into the influence of climate and tectonics on landscape evolution of this area. In this area, the Filyos River crosses the Karabük Fault (reverse fault) and deeply incises a gorge through the Karabük Range before flowing towards the Black Sea. In the gorge an abundance of indicators of tectonic deformation were mapped, such as hanging valleys, wind gaps, bedrock gorges, landslides, steep V-shaped channels, tilted basins, as well as fluvial strath terraces. In particular, strath terraces of at least 8 levels within just 1.5 km of horizontal distance were examined. We used OSL-dating to estimate five deposition ages of fluvial strath terrace sediments, leading to an estimation of incision and uplift rates over time. Using three samples per terrace with strath elevations of 246 ± 0.2 m, 105.49 ± 0.2 m, 43.6 ± 0.2 m, 15.3 ± 0.2 m and 3.6 ± 0.2 m above the Filyos River, we determined corresponding ages of 841 ± 76 ka, 681 ± 49 ka, 386 ± 18 ka, 88 ± 5.1 ka and 50.9 ± 2.8 ka. Incision rates over time (oldest

Tectonic controls on nearshore sediment accumulation and submarine canyon morphology offshore La Jolla, Southern California

USGS Publications Warehouse

Le Dantec, Nicolas; Hogarth, Leah J.; Driscoll, Neal W.; Babcock, Jeffrey M.; Barnhardt, Walter A.; Schwab, William C.

2010-01-01

CHIRP seismic and swath bathymetry data acquired offshore La Jolla, California provide an unprecedented three-dimensional view of the La Jolla and Scripps submarine canyons. Shore-parallel patterns of tectonic deformation appear to control nearshore sediment thickness and distribution around the canyons. These shore-parallel patterns allow the impact of local tectonic deformation to be separated from the influence of eustatic sea-level fluctuations. Based on stratal geometry and acoustic character, we identify a prominent angular unconformity inferred to be the transgressive surface and three sedimentary sequences: an acoustically laminated estuarine unit deposited during early transgression, an infilling or “healing-phase” unit formed during the transgression, and an upper transparent unit. Beneath the transgressive surface, steeply dipping reflectors with several dip reversals record faulting and folding along the La Jolla margin. Scripps Canyon is located at the crest of an antiform, where the rocks are fractured and more susceptible to erosion. La Jolla Canyon is located along the northern strand of the Rose Canyon Fault Zone, which separates Cretaceous lithified rocks to the south from poorly cemented Eocene sands and gravels to the north. Isopach and structure contour maps of the three sedimentary units reveal how their thicknesses and spatial distributions relate to regional tectonic deformation. For example, the estuarine unit is predominantly deposited along the edges of the canyons in paleotopographic lows that may have been inlets along barrier beaches during the Holocene sea-level rise. The distribution of the infilling unit is controlled by pre-existing relief that records tectonic deformation and erosional processes. The thickness and distribution of the upper transparent unit are controlled by long-wavelength, tectonically induced relief on the transgressive surface and hydrodynamics.

New Insights on Mt. Etna's Crust and Relationship with the Regional Tectonic Framework from Joint Active and Passive P-Wave Seismic Tomography

NASA Astrophysics Data System (ADS)

Díaz-Moreno, A.; Barberi, G.; Cocina, O.; Koulakov, I.; Scarfì, L.; Zuccarello, L.; Prudencio, J.; García-Yeguas, A.; Álvarez, I.; García, L.; Ibáñez, J. M.

2018-01-01

In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g., those from Mt. Etna and the Aeolian Islands archipelago) testifies to the complexity of the tectonic and geodynamic setting. Despite the large number of studies that have focused on this area, the relationships among volcanism, tectonics, magma ascent, and geodynamic processes remain poorly understood. We present a tomographic inversion of P-wave velocity using active and passive sources. Seismic signals were recorded using both temporary on-land and ocean bottom seismometers and data from a permanent local seismic network consisting of 267 seismic stations. Active seismic signals were generated using air gun shots mounted on the Spanish Oceanographic Vessel `Sarmiento de Gamboa'. Passive seismic sources were obtained from 452 local earthquakes recorded over a 4-month period. In total, 184,797 active P-phase and 11,802 passive P-phase first arrivals were inverted to provide three different velocity models. Our results include the first crustal seismic active tomography for the northern Sicily area, including the Peloritan-southern Calabria region and both the Mt. Etna and Aeolian volcanic environments. The tomographic images provide a detailed and complete regional seismotectonic framework and highlight a spatially heterogeneous tectonic regime, which is consistent with and extends the findings of previous models. One of our most significant results was a tomographic map extending to 14 km depth showing a discontinuity striking roughly NW-SE, extending from the Gulf of Patti to the Ionian Sea, south-east of Capo Taormina, corresponding to the Aeolian-Tindari-Letojanni fault system, a regional deformation belt. Moreover, for the first time, we observed a high-velocity anomaly located in the south-eastern sector of the Mt. Etna region, offshore of the Timpe area, which is compatible with the plumbing system of an ancient shield volcano located offshore of Mt. Etna.

Recent uplift of the Atlantic Atlas (offshore West Morocco): Tectonic arch and submarine terraces

NASA Astrophysics Data System (ADS)

Benabdellouahed, M.; Klingelhoefer, F.; Gutscher, M.-A.; Rabineau, M.; Biari, Y.; Hafid, M.; Duarte, J. C.; Schnabel, M.; Baltzer, A.; Pedoja, K.; Le Roy, P.; Reichert, C.; Sahabi, M.

2017-06-01

Re-examination of marine geophysical data from the continental margin of West Morocco reveals a broad zone characterized by deformation, active faults and updoming offshore the High Atlas (Morocco margin), situated next to the Tafelney Plateau. Both seismic reflection and swath-bathymetric data, acquired during Mirror marine geophysical survey in 2011, indicate recent uplift of the margin including uplift of the basement. This deformation, which we propose to name the Atlantic Atlas tectonic arch, is interpreted to result largely through uplift of the basement, which originated during the Central Atlantic rifting stage - or even during phases of Hercynian deformation. This has produced a large number of closely spaced normal and reverse faults, ;piano key faults;, originating from the basement and affecting the entire sedimentary sequence, as well as the seafloor. The presence of four terraces in the Essaouira canyon system at about 3500 meters water depth and ;piano key faults; and the fact that these also affect the seafloor, indicate that the Atlantic Atlas is still active north of Agadir canyon. We propose that recent uplift is causing morphogenesis of four terraces in the Essaouira canyon system. In this paper the role of both Canary plume migration and ongoing convergence between the African and Eurasian plates in the formation of the Atlantic Atlas are discussed as possibilities to explain the presence of a tectonic arch in the region. The process of reactivation of passive margins is still not well understood. The region north of Agadir canyon represents a key area to better understand this process.

Late Pleistocene and Holocene uplift history of Cyprus: implications for active tectonics along the southern margin of the Anatolian microplate

USGS Publications Warehouse

Harrison, R.W.; Tsiolakis, E.; Stone, B.D.; Lord, A.; McGeehin, J.P.; Mahan, S.A.; Chirico, P.

2013-01-01

The nature of the southern margin of the Anatolian microplate during the Neogene is complex, controversial and fundamental in understanding active plate-margin tectonics and natural hazards in the Eastern Mediterranean region. Our investigation provides new insights into the Late Pleistocene uplift history of Cyprus and the Troodos Ophiolite. We provide isotopic (14C) and radiogenic (luminescence) dates of outcropping marine sediments in eastern Cyprus that identify periods of deposition during marine isotope stages (MIS) 3, 4, 5 and 6. Past sea-levels indicated by these deposits are c. 95±25 m higher in elevation than estimates of worldwide eustatic sea-level. An uplift rate of c. 1.8 mm/year and possibly as much as c. 4.1 mm/year in the past c. 26–40 ka is indicated. Holocene marine deposits also occur at elevations higher than those expected for past SL and suggest uplift rates of c. 1.2–2.1 mm/year. MIS-3 marine deposits that crop out in southern and western Cyprus indicate uniform island-wide uplift. We propose a model of tectonic wedging at a plate-bounding restraining bend as a mechanism for Late Pleistocene to Holocene uplift of Cyprus; uplift is accommodated by deformation and seismicity along the margins of the Troodos Ophiolite and re-activation of its low-angle, basal shear zone.

Tectonic map of the Circum-Pacific region, Pacific basin sheet

USGS Publications Warehouse

Scheibner, E.; Moore, G.W.; Drummond, K.J.; Dalziel, Corvalan Q.J.; Moritani, T.; Teraoka, Y.; Sato, T.; Craddock, C.

2013-01-01

George W. Moore (Arctic Region). Project coordination and final cartography was being carried out through the cooperation of the Office of the Chief Geologist of the U.S. Geological Survey, under the direction of General Chairman, George Gryc of Menlo Park, California. Project headquarters were located at 345 Middlefield Road, MS 952, Menlo Park, California 94025, U.S.A. The framework for the Circum-Pacific Map Project was developed in 1973 by a specially convened group of 12 North American geoscientists meeting in California. The project was officially launched at the First Circum-Pacific Conference on Energy and Mineral Resources, which met in Honolulu, Hawaii, in August 1974. Sponsors of the conference were the AAPG, Pacific Science Association (PSA), and the Coordinating Committee for Offshore Prospecting for Mineral Resources in Offshore Asian Areas (CCOP). The Circum-Pacific Map Project operates as an activity of the Circum-Pacific Council for Energy and Mineral Resources, a nonprofit organization that promotes cooperation among Circum-Pacific countries in the study of energy and mineral resources of the Pacific basin. Founded by Michel T. Halbouty in 1972, the Council also sponsors conferences, topical symposia, workshops and the Earth Science Series books. Tectonic Map Series: The tectonic maps distinguish areas of oceanic and continental crust. Symbols in red mark active plate boundaries, and colored patterns show tectonic units (volcanic or magmatic arcs, arc-trench gaps, and interarc basins) associated with active plate margins. Well-documented inactive plate boundaries are shown by symbols in black. The tectonic development of oceanic crust is shown by episodes of seafloor spreading. These correlate with the rift and drift sequences at passive continental margins and episodes of tectonic activity at active plate margins. The recognized episodes of seafloor spreading seem to reflect major changes in plate kinematics. Oceanic plateaus and other prominences of

Vertical tectonics at an active continental margin

NASA Astrophysics Data System (ADS)

Houlié, N.; Stern, T. A.

2017-01-01

Direct observations of vertical movements of the earth's surface are now possible with space-based GPS networks, and have applications to resources, hazards and tectonics. Here we present data on vertical movements of the Earth's surface in New Zealand, computed from the processing of GPS data collected between 2000 and 2015 by 189 permanent GPS stations. We map the geographical variation in vertical rates and show how these variations are explicable within a tectonic framework of subduction, volcanic activity and slow slip earthquakes. Subsidence of >3 mm/yr is observed along southeastern North Island and is interpreted to be due to the locked segment of the Hikurangi subduction zone. Uplift of 1-3 mm/yr further north along the margin of the eastern North Island is interpreted as being due to the plate interface being unlocked and underplating of sediment on the subduction thrust. The Volcanic Plateau of the central North Island is being uplifted at about 1 mm/yr, which can be explained by basaltic melts being injected in the active mantle-wedge at a rate of ∼6 mm/yr. Within the Central Volcanic Region there is a 250 km2 area that subsided between 2005 and 2012 at a rate of up to 14 mm/yr. Time series from the stations located within and near the zone of subsidence show a strong link between subsidence, adjacent uplift and local earthquake swarms.

Trench curvature and deformation of the subducting lithosphere

NASA Astrophysics Data System (ADS)

Schettino, Antonio; Tassi, Luca

2012-01-01

The subduction of oceanic lithosphere is generally accompanied by downdip and lateral deformation. The downdip component of strain is associated with external forces that are applied to the slab during its sinking, namely the gravitational force and the mantle resistance to penetration. Here, we present theoretical arguments showing that a tectonic plate is also subject to a predictable amount of lateral deformation as a consequence of its bending along an arcuate trench zone, independently from the long-term physical processes that have determined the actual curvature of the subduction zone. In particular, we show that the state of lateral strain and the lateral strain rate of a subducting slab depend from geometric and kinematic parameters, such as trench curvature, dip function and subduction velocity. We also demonstrate that the relationship between the state of lateral strain in a subducting slab and the geometry of bending at the corresponding active margin implies a small component of lateral shortening at shallow depths, and may include large extensional lateral deformation at intermediate depths, whereas a state of lateral mechanical equilibrium can only represent a localized exception. Our formulation overcomes the flaws of the classic 'ping-pong ball' model for the bending of the lithosphere at subduction zones, which lead to severe discrepancies with the observed geometry and style of deformation of the modern subducting slabs. A study of the geometry and seismicity of eight modern subduction zones is performed, to assess the validity of the theoretical relationship between trench curvature, slab dip function, and lateral strain rate. The strain pattern within the eight present-day slabs, which is reconstructed through an analysis of Harvard CMT solutions, shows that tectonic plates cannot be considered as flexible-inextensible spherical caps, whereas the lateral intraslab deformation which is accommodated through seismic slip can be explained in terms

Creep of phyllosilicates at the onset of plate tectonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amiguet, Elodie; Reynard, Bruno; Caracas, Razvan

Plate tectonics is the unifying paradigm of geodynamics yet the mechanisms and causes of its initiation remain controversial. Some models suggest that plate tectonics initiates when the strength of lithosphere is lower than 20-200 MPa, below the frictional strength of lithospheric rocks (>700 MPa). At present-day, major plate boundaries such as the subduction interface, transform faults, and extensional faults at mid-oceanic ridge core complexes indicate a transition from brittle behaviour to stable sliding at depths between 10 and 40 km, in association with water-rock interactions forming phyllosilicates. We explored the rheological behaviour of lizardite, an archetypal phyllosilicate of the serpentinemore » group formed in oceanic and subduction contexts, and its potential influence on weakening of the lithospheric faults and shear zones. High-pressure deformation experiments were carried out on polycrystalline lizardite - the low temperature serpentine variety - using a D-DIA apparatus at a variety of pressure and temperature conditions from 1 to 8 GPa and 150 to 400 C and for strain rates between 10{sup -4} and 10{sup -6} s{sup -1}. Recovered samples show plastic deformation features and no evidence of brittle failure. Lizardite has a large rheological anisotropy, comparable to that observed in the micas. Mechanical results and first-principles calculations confirmed easy gliding on lizardite basal plane and show that the flow stress of phyllosilicate is in the range of the critical value of 20-200 MPa down to depths of about 200 km. Thus, foliated serpentine or chlorite-bearing rocks are sufficiently weak to account for plate tectonics initiation, aseismic sliding on the subduction interface below the seismogenic zone, and weakening of the oceanic lithosphere along hydrothermally altered fault zones. Serpentinisation easing the deformation of the early crust and shallow mantle reinforces the idea of a close link between the occurrence of plate tectonics and

Mesozoic to Eocene ductile deformation of western Central Iran: From Cimmerian collisional orogeny to Eocene exhumation

NASA Astrophysics Data System (ADS)

Kargaranbafghi, Fariba; Neubauer, Franz; Genser, Johann; Faghih, Ali; Kusky, Timothy

2012-09-01

To advance our understanding of the Mesozoic to Eocene tectonics and kinematics of basement units exposed in the south-western Central Iran plateau, this paper presents new structural and thermochronological data from the Chapedony metamorphic core complex and hangingwall units, particularly from the Posht-e-Badam complex. The overall Paleogene structural characteristics of the area are related to an oblique convergent zone. The Saghand area represents part of a deformation zone between the Arabian and Eurasian plates, and can be interpreted to result from the Central Iran intracontinental deformation acting as a weak zone during Mesozoic to Paleogene times. Field and microstructural evidence reveal that the metamorphic and igneous rocks suffered a ductile shear deformation including mylonitization at the hangingwall boundary of the Eocene Chapedony metamorphic core complex. Comparison of deformation features in the mylonites and other structural features within the footwall unit leads to the conclusion that the mylonites were formed in a subhorizontal shear zone by NE-SW stretching during Middle to Late Eocene extensional tectonics. The Chapedony metamorphic core complex is characterized by amphibolite-facies metamorphism and development of S and S-L tectonic fabrics. The Posht-e-Badam complex was deformed by two stages during Cimmerian tectonic processes forming the Paleo-Tethyan suture.

Relation Between Crustal Deformations Caused by the 2000 Miyake-Kozu Seismovolcanic Activity and the 2000 Tokai Slow-Slip Event -- Which Crustal Deformation Occurred Earlier? --

NASA Astrophysics Data System (ADS)

Kawamura, M.; Yamaoka, K.

2006-12-01

The 2000 seismovolcanic activity between the Miyakejima and Kozushima islands, which are located south of the Japanese main island, and the 2000 slow-slip event, which was initiated on the plate boundary between the subducting Philippine Sea Plate and its overriding Eurasian (Amurian) Plate just beneath the Hamana Lake in the Tokai district, are typical overlapping geophysical processes in space and time around the Japanese islands. Which process affected the other one is an issue which is difficult to clear even now. It is important to resolve the issue in order to get insight into the tectonics of central Japan. For this purpose, we applied two statistical approaches, principal component analysis and mode rotation procedure, to the displacement field of central Japan to obtain the spatiotemporal crustal deformation structures characteristic of the above two processes. We divided time period into two spans: from 26th June, 1999 to 25th June, 2000 and from 26th June, 2000 to 26th June 2001. Secular and periodic components for each station were excluded beforehand by evaluating these components using the data of each station from 26th June, 1999 to 25th June, 2000. All of the spatial and temporal modes for the first half period didn't reveal any significant spatiotemporal changes accompanied by the two processes. This indicates that this time period didn't experience any nonstationary crustal deformations. On the contrary, the modes for the latter half period included the changes due to these processes. The 1st and 2nd modes corresponded to the spatiotemporal structures of the first and latter half periods of the Miyake-Kozu seismovolcanic activity, respectively. The 3rd mode, which was prominent later than the beginning of the Miyake-Kozu seismovolcanic activity, was characteristic of the structure of the Tokai slow-slip event. These results allow us to conclude that crustal deformation due to the Tokai slow-slip event was preceded by that due to the Miyake

Control of Precambrian basement deformation zones on emplacement of the Laramide Boulder batholith and Butte mining district, Montana, United States

USGS Publications Warehouse

Berger, Byron R.; Hildenbrand, Thomas G.; O'Neill, J. Michael

2011-01-01

What are the roles of deep Precambrian basement deformation zones in the localization of subsequent shallow-crustal deformation zones and magmas? The Paleoproterozoic Great Falls tectonic zone and its included Boulder batholith (Montana, United States) provide an opportunity to examine the importance of inherited deformation fabrics in batholith emplacement and the localization of magmatic-hydrothermal mineral deposits. Northeast-trending deformation fabrics predominate in the Great Falls tectonic zone, which formed during the suturing of Paleoproterozoic and Archean cratonic masses approximately 1,800 mega-annum (Ma). Subsequent Mesoproterozoic to Neoproterozoic deformation fabrics trend northwest. Following Paleozoic through Early Cretaceous sedimentation, a Late Cretaceous fold-and-thrust belt with associated strike-slip faulting developed across the region, wherein some Proterozoic faults localized thrust faulting, while others were reactivated as strike-slip faults. The 81- to 76-Ma Boulder batholith was emplaced along the reactivated central Paleoproterozoic suture in the Great Falls tectonic zone. Early-stage Boulder batholith plutons were emplaced concurrent with east-directed thrust faulting and localized primarily by northwest-trending strike-slip and related faults. The late-stage Butte Quartz Monzonite pluton was localized in a northeast-trending pull-apart structure that formed behind the active thrust front and is axially symmetric across the underlying northeast-striking Paleoproterozoic fault zone, interpreted as a crustal suture. The modeling of potential-field geophysical data indicates that pull-apart?stage magmas fed into the structure through two funnel-shaped zones beneath the batholith. Renewed magmatic activity in the southern feeder from 66 to 64 Ma led to the formation of two small porphyry-style copper-molybdenum deposits and ensuing world-class polymetallic copper- and silver-bearing veins in the Butte mining district. Vein orientations

Tectonic evolution, structural styles, and oil habitat in Campeche Sound, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Angeles-Aquino, F.J.; Reyes-Nunez, J.; Quezada-Muneton, J.M.

1994-12-31

Campeche Sound is located in the southern part of the Gulf of Mexico. This area is Mexico`s most important petroleum province. The Mesozoic section includes Callovian salt deposits; Upper Jurassic sandstones, anhydrites, limestones, and shales; and Cretaceous limestones, dolomites, shales, and carbonate breccias. The Cenozoic section is formed by bentonitic shales and minor sandstones and carbonate breccias. Campeche Sound has been affected by three episodes of deformation: first extensional tectonism, then compressional tectonism, and finally extensional tectonism again. The first period of deformation extended from the middle Jurassic to late Jurassic and is related to the opening of the Gulfmore » of Mexico. During this regime, tilted block faults trending northwest-southwest were dominant. The subsequent compressional regime occurred during the middle Miocene, and it was related to northeast tangential stresses that induced further flow of Callovian salt and gave rise to large faulted, and commonly overturned, anticlines. The last extensional regime lasted throughout the middle and late Miocene, and it is related to salt tectonics and growth faults that have a middle Miocene shaly horizon as the main detachment surface. The main source rocks are Tithonian shales and shaly limestones. Oolite bars, slope and shelf carbonates, and regressive sandstones form the main reservoirs. Evaporites and shales are the regional seals. Recent information indicates that Oxfordian shaly limestones are also important source rocks.« less

Rietveld analysis of X-ray powder diffraction patterns as a potential tool for the identification of impact-deformed carbonate rocks

NASA Astrophysics Data System (ADS)

Huson, S. A.; Foit, F. F.; Watkinson, A. J.; Pope, M. C.

2009-12-01

Previous X-ray powder diffraction (XRD) studies revealed that shock deformed carbonates and quartz have broader XRD patterns than those of unshocked samples. Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas, unshocked equivalent samples from 95 miles north of the crater and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater. Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenic belts. Whereas calcite subjected to significant shock intensities at the Sierra Madera impact crater can be differentiated from tectonically deformed calcite from the Mission Canyon Formation using Rietveld refined peak profiles, weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite. In contrast, Rietveld analysis readily distinguishes shocked Sierra Madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed Mission Canyon Formation dolomite.

Dynamics of Deformable Active Particles under External Flow Field

NASA Astrophysics Data System (ADS)

Tarama, Mitsusuke

2017-10-01

In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.

New insights on the recent and current deformation in Central-Eastern Iran, derived from a combined tectonic and GPS analysis

NASA Astrophysics Data System (ADS)

Walpersdorf, A.; Manighetti, I.; Tavakoli, F.; Mousavi, Z.; Vergnolle, M.; Jadidi, A.; Hatzfeld, D.; Aghamohammadi, A.; Djamour, Y.; Nankali, H.; Sedighi, M.; Lutz, L.

2012-04-01

We have studied the recent to current deformation in Iran and especially Central-Eastern Iran by tightly combining tectonic and GPS analyses. Based on morphotectonic analyses of satellite images, we have identified and mapped the major active faults that dissect the entire ≈ 4500 km x 2500 km2 region that extends from Eastern Turkey to Western Afghanistan/Pakistan and hence encompasses Iran, emphasizing their large-scale organization and kinematic relationships. Doing so, we have identified the major fault systems that control the tectonics of Iran, especially in its central-eastern part. We have also analyzed the 11 years GPS record on the 92 stations deployed in central-eastern Iran in the framework of the Iranian-French collaboration. The GPS analysis reveals that all major faults identified as seismogenic in central-eastern Iran are indeed currently active and slipping at fast rates. The northerly-trending East Lut, West Lut, Kuhbanan, Anar and Deshir faults have a current right-lateral slip rate of 5.7 ± 0.9, 4.7 ± 1.7, 2.3 ± 1.9, 2.7 ± 1.3 and 0.5 ± 0.2 mm/yr, respectively, while the ≈ EW-trending Doruneh and Sedeh faults have a left-lateral current slip rate of 3.1 ± 1.8 and 1.7 ± 0.2 mm/yr, respectively. The large regions bounded by the northerly-striking faults behave as fairly rigid blocks that are all found to move towards both the N13°E ARA-EUR convergence direction and the WNW, at fast rates, in the range 6.5-12.5 and 1-5 mm/yr, respectively. Combined with the available data on the studied faults, our tectonic and geodetic results suggest that a bookshelf faulting strain transfer mechanism has been and is still operating in central-eastern Iran. The coeval dextral motion of the two major, overlapping, North Anatolian-Main Recent and Caucasus-Kopeh Dagh-Herat fault lines that embrace central-eastern Iran, induces a large-scale regional sinistral shear on either side of the region, which forces the northerly-trending right-lateral faults and

Swinging motion of active deformable particles in Poiseuille flow

NASA Astrophysics Data System (ADS)

Tarama, Mitsusuke

2017-08-01

Dynamics of active deformable particles in an external Poiseuille flow is investigated. To make the analysis general, we employ time-evolution equations derived from symmetry considerations that take into account an elliptical shape deformation. First, we clarify the relation of our model to that of rigid active particles. Then, we study the dynamical modes that active deformable particles exhibit by changing the strength of the external flow. We emphasize the difference between the active particles that tend to self-propel parallel to the elliptical shape deformation and those self-propelling perpendicularly. In particular, a swinging motion around the centerline far from the channel walls is discussed in detail.

Extensional deformation of the Guadalquivir Basin: rate of WSW-ward tectonic displacement from Upper Tortonian sedimentary rocks

NASA Astrophysics Data System (ADS)

Roldán, Francisco J.; Azañón, Jose Miguel; Rodríguez-Fernández, Jose; María Mateos, Rosa

2016-04-01

The Guadalquivir Basin (Upper Tortonian-Quaternary sedimentary infilling) has been considered the foreland basin of the Betic Orogen built up during its collision with the Sudiberian margin. The basin is currently restricted to its westernmost sector, in the Cadiz Gulf, because the Neogene-Quaternary uplift of the Betic Cordillera has produced the emersion of their central and eastern parts. The upper Tortonian chronostratigraphic unit is the oldest one and it was indistinctly deposited on the South Iberian paleomargin and the External units from the Betic Cordillera. However, these rocks are undeformed on the Sudiberian paleomargin while they are deeply affected by brittle deformation on the External Betic Zone. Outcrops of Upper Tortonian sedimentary rocks on External Betic Zone are severely fragmented showing allocthonous characters with regard to those located on the Sudiberian paleomargin. This post- Upper Tortonian deformation is not well known in the External Zones of the Cordillera where the most prominent feature is the ubiquity of a highly deformed tecto-sedimentary unit outcropping at the basement of the Guadalquivir sedimentary infilling. This tecto-sedimentary unit belongs to the Mass Wasting Extensional Complex (Rodríguez-Fernández, 2014) formed during the collision and westward migration of the Internal Zone of the Betic Cordillera (15-8,5 Ma). In the present work, we show an ensemble of tectonic, geophysical and cartographic data in order to characterize the post-Upper Tortonian deformation. For this, seismic reflection profiles have been interpreted with the help of hidrocarbon boreholes to define the thickness of the Upper Tortonian sedimentary sequence. All these data provide an estimation of the geometrical and kinematic characteristics of the extensional faults, direction of movement and rate of displacement of these rocks during Messinian/Pliocene times. References Rodríguez-Fernández, J., Roldan, F. J., J.M. Azañón y Garcia-Cortes, A

Morphologic expression of Quaternary deformation in the northwestern foothills of the Ysyk-Köl basin, Tien Shan

NASA Astrophysics Data System (ADS)

Korjenkov, A. M.; Povolotskaya, I. E.; Mamyrov, E.

2007-03-01

The Tien Shan is one of the most active intracontinental mountain belts exhibiting numerous examples of Quaternary fault-related folding. To provide insight into the deformation of the Quaternary intermontane basins, the territory of the northwestern Ysyk-Köl region, where the growing Ak-Teke Anticline divided the piedmont apron of alluvial fans, is studied. It is shown that the Ak-Teke Hills are a sharply asymmetric anticline, which formed as a result of tectonic uplift and erosion related to motions along the South Ak-Teke Thrust Fault. The tectonic uplift gave rise to the local deviation of the drainage network in front of the northern limb of the fold. Optical (luminescent) dating suggests that the tectonic uplifting of the young anticline and the antecedent downcutting started 157 ka ago. The last upthrow of the high floodplain of the Toru-Aygyr River took place 1300 years ago. The structure of the South Ak-Teke Fault is examined by means of seismologic trenching and shallow seismic profiling across the fault. A laser tachymeter is applied to determine the vertical deformation of alluvial terraces in the Toru-Aygyr River valley at its intersection with the South Ak-Teke Fault. The rates of vertical deformation and an inferred number of strong earthquakes, which resulted in the upthrow of Quaternary river terraces of different ages, are calculated. The study territory is an example of changes in fluvial systems on growing folds in piedmont regions. As a result of shortening of the Earth’s crust in the mountainous belt owing to thrusting, new territories of previous sedimentation are involved in emergence. The tectonic activity migrates with time from the framing ridges toward the axial parts of intramontane basins.

Precise GPS/Acoustic Positioning of Seafloor Reference Points for Tectonic Studies

NASA Technical Reports Server (NTRS)

Spiess, F. N.; Chadwell, C.; Hildebrand, J. A.; Young, L. E.; Purcell, G. H., Jr.; Dragert, H.

1998-01-01

Global networks for crustal strain measurement provide important constraints for studies of tectonic plate motion and deformation. To date, crustal strain measurements have been possible only in terrestrial settings: on continental plates and island sites within oceanic plates.

Inherited crustal deformation along the East Gondwana margin revealed by seismic anisotropy tomography

NASA Astrophysics Data System (ADS)

Pilia, S.; Arroucau, P.; Rawlinson, N.; Reading, A. M.; Cayley, R. A.

2016-12-01

The mechanisms of continental growth are a crucial part of plate tectonic theory, yet a clear understanding of the processes involved remains elusive. Here we determine seismic Rayleigh wave phase anisotropy variations in the crust beneath the southern Tasmanides of Australia, a Paleozoic accretionary margin. Our results reveal a complex, thick-skinned pervasive deformation that was driven by the tectonic interaction between the proto-Pacific Ocean and the ancient eastern margin of Gondwana. Stress-induced effects triggered by the collision and entrainment of a microcontinent into the active subduction zone are evident in the anisotropy signature. The paleofracturing trend of failed rifting between Australia and Antarctica is also recorded in the anisotropy pattern as well as a tightly curved feature in central Tasmania. The observed patterns of anisotropy correlate well with recent geodynamic and kinematic models of the Tasmanides and provide a platform from which the spatial extent of deformational domains can be refined.

Current deformation in the Tibetan Plateau: a stress gauge in the large-scale India-Asia collision tectonics

NASA Astrophysics Data System (ADS)

Capitanio, F. A.

2017-12-01

The quantification of the exact tectonic forces budget on Earth has remained thus far elusive. Geodetic velocities provide relevant constraints on the current dynamics of the coupling between collision and continental tectonics, however in the Tibetan plateau these support contrasting, non-unique models. Here, we compare numerical models of coupled India-Asia plate convergence, collision and continent interiors tectonics to the geodetically-constrained motions in the Tibetan Plateau to provide a quantitative assessment of the driving forces of plate tectonics in the area. The models develop a range of long-term evolutions remarkably similar to the Asian tectonics in the Cenozoic, reproducing the current large-scale motions pattern under a range of conditions. Balancing the convergent margin forces, following subduction, and the far-field forcing along the trail of the subducting continent, the geodetic rates in the Tibetan Plateau can be matched. The comparisons support the discussion on the likely processes at work, allowing inferences on the drivers of plateau formation and its role on the plate margin-interiors tectonics. More in general, the outcomes highlight the unique role of the Tibetan Plateau as a pressure gauge for the tectonic forces on Earth.

Stability of active mantle upwelling revealed by net characteristics of plate tectonics.

PubMed

Conrad, Clinton P; Steinberger, Bernhard; Torsvik, Trond H

2013-06-27

Viscous convection within the mantle is linked to tectonic plate motions and deforms Earth's surface across wide areas. Such close links between surface geology and deep mantle dynamics presumably operated throughout Earth's history, but are difficult to investigate for past times because the history of mantle flow is poorly known. Here we show that the time dependence of global-scale mantle flow can be deduced from the net behaviour of surface plate motions. In particular, we tracked the geographic locations of net convergence and divergence for harmonic degrees 1 and 2 by computing the dipole and quadrupole moments of plate motions from tectonic reconstructions extended back to the early Mesozoic era. For present-day plate motions, we find dipole convergence in eastern Asia and quadrupole divergence in both central Africa and the central Pacific. These orientations are nearly identical to the dipole and quadrupole orientations of underlying mantle flow, which indicates that these 'net characteristics' of plate motions reveal deeper flow patterns. The positions of quadrupole divergence have not moved significantly during the past 250 million years, which suggests long-term stability of mantle upwelling beneath Africa and the Pacific Ocean. These upwelling locations are positioned above two compositionally and seismologically distinct regions of the lowermost mantle, which may organize global mantle flow as they remain stationary over geologic time.

The dynamic nature of relative sea level in Southeast Asia: tectonic effects and human impacts (Invited)

NASA Astrophysics Data System (ADS)

Hill, E.; Qiu, Q.; Feng, L.; Lubis, A.; Meltzner, A. J.; Tsang, L. L.; Daly, P.; McCaughey, J.; Banerjee, P.; Rubin, C. M.; Sieh, K.

2013-12-01

Tectonic changes can have significant effects on crustal deformation, the geoid, and relative sea level (RSL). Indeed, the tectonic impacts on RSL in some regions can be greater than those predicted as a result of climate change. In the case of earthquakes, these changes can occur suddenly, as coastlines uplift or subside by up to many meters. The changes can also occur over many decades as a result of interseismic or postseismic processes, or periodically in the form of transient slow-slip events. Although these effects are (mostly) recovered elastically over the course of the earthquake cycle, they are occurring in the context of ever-increasing populations living along affected coastlines, particularly the case in areas such as SE Asia. The societal effects of these tectonic-induced sea-level changes are therefore becoming increasingly significant, and important to consider in future projections for sea-level change. Additionally, tide-gauge and gravity measurements made in tectonically active areas cannot be interpreted without consideration and modeling of the tectonic setting. These facts highlight the need for accurate geodetic measurements of land-height change. Along the Sumatra subduction zone, a series of great earthquakes have occurred over the last decade, along with numerous moderate and smaller earthquakes. These, and their ensuing postseismic deformation, have reshaped regional coastlines. We will show visualization of land height changes using a decade of Sumatra GPS Array (SuGAr) data, and related tectonic models, that demonstrate dramatically the ups and downs of land elevation close to the earthquake sources. Vertical coseismic displacements as large as ~2.9 m have been recorded by the SuGAr (an uplift at Nias, during the 2005 Mw 8.6 earthquake), and vertical postseismic rates on the order of tens of mm/yr or greater (e.g., in northern Aceh, one station has been uplifting at a rate of ~34 mm/yr since the 2004 Mw 9.2 earthquake, while in southern

Deformation at longyao ground fissure and its surroundings, north China plain, revealed by ALOS PALSAR PS-InSAR

NASA Astrophysics Data System (ADS)

Yang, Chengsheng; Lu, Zhong; Zhang, Qin; Zhao, Chaoying; Peng, Jianbing; Ji, Lingyun

2018-05-01

The Longyao ground fissure (LGF) is the longest and most active among more than 1000 ground fissures on the North China Plain. There have been many studies on the formation mechanism of the LGF, due to its scientific importance and its potential for damage to the environment. These studies have been based on both regional tectonic analysis and numerical simulations. In order to provide a better understanding of the formation mechanism, the deformation of the crack and its surrounding environment should be taken into consideration. In this paper, PS-InSAR technology was employed to assess the ground deformation of LGF and its surrounding area, using L-band ALOS-1 PALSAR images from 2007 to 2011. The characteristics of ground deformation, relationships between fissure activity and surrounding faults and groundwater exploitation were analyzed. This study shows that the north side of Longyao fault (LF) is uplifting while the south side is subsiding. This provides the tectonic conditions responsible for the activity of the ground fissure. Local groundwater exploitation also plays an important role in the development of ground fissures. InSAR observations were modeled to infer the loading depth (-2.8 km) and the slip rate (31.1 mm/yr) of LF.

Crustal deformation: Earth vs Venus

NASA Technical Reports Server (NTRS)

Turcotte, D. L.

1989-01-01

It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate tectonics on Venus is debated, but there is certainly no evidence for the trenches associated with subduction on the earth. An essential question is what kind of tectonics can be expected if there is no plate tectonics on Venus. Mars and the Moon are reference examples. Volcanic constructs appear to play a dominant role on Mars but their role on Venus is not clear. On single plate planets and satellites, tectonic structures are often associated with thermal stresses. Cooling of a planet leads to thermal contraction and surface compressive features. Delamination has been propsed for Venus by several authors. Delamination is associated with the subduction of the mantle lithosphere and possibly the lower crust but not the upper crust. The surface manifestations of delamination are unclear. There is some evidence that delamination is occurring beneath the Transverse Ranges in California. Delamination will certainly lead to lithospheric thinning and is likely to lead to uplift and crustal thinning.

Subduction Related Crustal and Mantle Deformations and Their Implications for Plate Dynamics

NASA Astrophysics Data System (ADS)

Okeler, Ahmet

Ocean-continent convergence and subsequent continental collision are responsible for continental growth, mountain building, and severe tectonic events including volcanic eruptions and earthquake activity. They are also key driving forces behind the extensive thermal and compositional heterogeneities at crustal and mantle depths. Active subduction along the Calabrian Arc in southern Italy and the Hellenic Arc are examples of such collisional tectonics. The first part of this thesis examines the subduction related deformations within the crust beneath the southern Apennines. By modeling regional surface wave recordings of the largest temporary deployment in the southern Apennines, a lower-crustal/upper-mantle low-velocity volume extending down to 50 km beneath the mountain chain is identified. The magnitude (˜ 0.4 km/s slower) and anisotropic nature (˜ 10%) of the anomaly suggest the presence of hot and partially molten emplacement that may extend into the upper-crust towards Mt. Vulture, a once active volcano. Since the Apulian basement units are deformed during the compressional and consequent extensional events, our observations favor the "thick-skin" tectonic growth model for the region. In the deeper mantle, active processes are thermodynamically imprinted on the depth and strength of the phase transitions. This thesis examines more than 15000 SS precursors and provides the present-day reflectivity structure and topography associated with these phase transitions. Through case studies I present ample evidence for both slab penetration into the lower mantle (beneath the Hellenic Arc, Kurile Island and South America) and slab stagnation at the bottom of the Mantle Transition Zone (beneath the Tyrrhenian Sea and eastern China). Key findings include (1) thermal anomalies (˜ 200 K) at the base of the MTZ, which represent the deep source for Cenozoic European Rift Zone, Mount Etna and Mount Cameroon volcanism, (2) significant depressions (by 20-40 km) at the bottom

Geodynamics of Cenozoic deformation in central Asia

NASA Astrophysics Data System (ADS)

Liu, H.-S.

1981-04-01

This paper presents a study of the tectonic stresses in central Asia based on an interpretation of satellite gravity data for mantle convection and supplemented with published fault plane solutions of earthquakes. Northwest-southeast to north-south compressional stresses exist in the Tien Shan region where reverse faulting dominates. The maximum compressive stress is oriented approximately northeast-southwest in the regions of Altai and southern Mongolia. Farther north, compressive stress gives way to tensional stress which causes normal faulting in the Baikal rift system. It is also shown that all of the tectonic stresses in the Tibetan plateau and Himalayan frontal thrust are related to the convection-generated stress patterns inferred from satellite gravity data. These results suggest that the complex crustal deformation in central Asia can be convincingly described by the deformation of the lithosphere on top of the up- and down-welling asthenospheric material beneath it. This observational fact may not only upset the simple view of the fluid crustal model of the Tibetan plateau, but also provide some useful constraints for the future development of deformation theory of continental crust.

Geodynamics of Cenozoic deformation in central Asia

NASA Technical Reports Server (NTRS)

Liu, H.-S.

1981-01-01

This paper presents a study of the tectonic stresses in central Asia based on an interpretation of satellite gravity data for mantle convection and supplemented with published fault plane solutions of earthquakes. Northwest-southeast to north-south compressional stresses exist in the Tien Shan region where reverse faulting dominates. The maximum compressive stress is oriented approximately northeast-southwest in the regions of Altai and southern Mongolia. Farther north, compressive stress gives way to tensional stress which causes normal faulting in the Baikal rift system. It is also shown that all of the tectonic stresses in the Tibetan plateau and Himalayan frontal thrust are related to the convection-generated stress patterns inferred from satellite gravity data. These results suggest that the complex crustal deformation in central Asia can be convincingly described by the deformation of the lithosphere on top of the up- and down-welling asthenospheric material beneath it. This observational fact may not only upset the simple view of the fluid crustal model of the Tibetan plateau, but also provide some useful constraints for the future development of deformation theory of continental crust.

Geomorphology, active tectonics, and landscape evolution in the Mid-Atlantic region: Chapter

USGS Publications Warehouse

Pazzaglia, Frank J.; Carter, Mark W.; Berti, Claudio; Counts, Ronald C.; Hancock, Gregory S.; Harbor, David; Harrison, Richard W.; Heller, Matthew J.; Mahan, Shannon; Malenda, Helen; McKeon, Ryan; Nelson, Michelle S.; Prince, Phillip; Rittenour, Tammy M.; Spotilla, James; Whittecar, G. Richard

2015-01-01

In 2014, the geomorphology community marked the 125th birthday of one of its most influential papers, “The Rivers and Valleys of Pennsylvania” by William Morris Davis. Inspired by Davis’s work, the Appalachian landscape rapidly became fertile ground for the development and testing of several grand landscape evolution paradigms, culminating with John Hack’s dynamic equilibrium in 1960. As part of the 2015 GSA Annual Meeting, the Geomorphology, Active Tectonics, and Landscape Evolution field trip offers an excellent venue for exploring Appalachian geomorphology through the lens of the Appalachian landscape, leveraging exciting research by a new generation of process-oriented geomorphologists and geologic field mapping. Important geomorphologic scholarship has recently used the Appalachian landscape as the testing ground for ideas on long- and short-term erosion, dynamic topography, glacial-isostatic adjustments, active tectonics in an intraplate setting, river incision, periglacial processes, and soil-saprolite formation. This field trip explores a geologic and geomorphic transect of the mid-Atlantic margin, starting in the Blue Ridge of Virginia and proceeding to the east across the Piedmont to the Coastal Plain. The emphasis here will not only be on the geomorphology, but also the underlying geology that establishes the template and foundation upon which surface processes have etched out the familiar Appalachian landscape. The first day focuses on new and published work that highlights Cenozoic sedimentary deposits, soils, paleosols, and geomorphic markers (terraces and knickpoints) that are being used to reconstruct a late Cenozoic history of erosion, deposition, climate change, and active tectonics. The second day is similarly devoted to new and published work documenting the fluvial geomorphic response to active tectonics in the Central Virginia seismic zone (CVSZ), site of the 2011 M 5.8 Mineral earthquake and the integrated record of Appalachian

Rheological decoupling at the Moho and implication to Venusian tectonics.

PubMed

Azuma, Shintaro; Katayama, Ikuo; Nakakuki, Tomoeki

2014-03-18

Plate tectonics is largely responsible for material and heat circulation in Earth, but for unknown reasons it does not exist on Venus. The strength of planetary materials is a key control on plate tectonics because physical properties, such as temperature, pressure, stress, and chemical composition, result in strong rheological layering and convection in planetary interiors. Our deformation experiments show that crustal plagioclase is much weaker than mantle olivine at conditions corresponding to the Moho in Venus. Consequently, this strength contrast may produce a mechanical decoupling between the Venusian crust and interior mantle convection. One-dimensional numerical modeling using our experimental data confirms that this large strength contrast at the Moho impedes the surface motion of the Venusian crust and, as such, is an important factor in explaining the absence of plate tectonics on Venus.

From transpressional to transtensional tectonics in Northern Central America controlled by Cocos - Caribbean subduction coupling change

NASA Astrophysics Data System (ADS)

Alonso-Henar, Jorge; Alvarez-Gomez, José Antonio; Jesús Martinez-Diaz, José

2017-04-01

The Central American Volcanic Arc (CAVA) is located at the western margin of the Caribbean plate, over the Chortís Block, spanning from Guatemala to Costa Rica. The CAVA is associated to the subduction of the Cocos plate under the Caribbean plate at the Middle America Trench. Our study is focused in the Salvadorian CAVA segment, which is tectonically characterized by the presence of the El Salvador Fault Zone (ESFZ), part of the western boundary of a major block forming the Caribbean plate (the Chortis Block). The structural evolution of the western boundary of the Chortis Block, particularly in the CAVA crossing El Salvador remains unknown. We have done a kinematic analysis from seismic and fault slip data and combined our results with a review of regional previous studies. This approach allowed us to constrain the tectonic evolution and the forces that control the deformation in northern Central America. Along the active volcanic arc we identified active transtensional deformation. On the other hand, we have identified two deformation phases in the back arc region: A first one of transpressional wrenching close to simple shearing (Miocene); and a second one characterized by almost E-W extension. Our results reveal a change from transpressional to transtensional shearing coeval with a migration of the volcanism towards the trench in Late Miocene times. This strain change could be related with a coupled to decoupled transition on the Cocos - Caribbean subduction interface, which could be related to a slab roll-back of the Cocos Plate beneath the Chortis Block. The combination of different degrees of coupling on the subduction interface, together with a constant relative eastward drift of the Caribbean Plate, control the deformation style along the western boundary of the Chortis Block.

Active tectonics and earthquake potential of the Myanmar region

NASA Astrophysics Data System (ADS)

Wang, Yu; Sieh, Kerry; Tun, Soe Thura; Lai, Kuang-Yin; Myint, Than

2014-04-01

This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subduction and collision associated with the Sunda megathrust beneath and within the Indoburman range and Naga Hills accommodate most of the shortening across the transpressional plate boundary. The Sagaing fault system is the predominant locus of dextral motion associated with the northward translation of India. Left-lateral faults of the northern Shan Plateau, northern Laos, Thailand, and southern China facilitate extrusion of rocks around the eastern syntaxis of the Himalaya. All of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region.

Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana

USGS Publications Warehouse

Ruleman, Chester A.; Larsen, Mort; Stickney, Michael C.

2014-01-01

The catastrophic Hebgen Lake earthquake of 18 August 1959 (MW 7.3) led many geoscientists to develop new methods to better understand active tectonics in extensional tectonic regimes that address seismic hazards. The Madison Range fault system and adjacent Hebgen Lake–Red Canyon fault system provide an intermountain active tectonic analog for regional analyses of extensional crustal deformation. The Madison Range fault system comprises fault zones (~100 km in length) that have multiple salients and embayments marked by preexisting structures exposed in the footwall. Quaternary tectonic activity rates differ along the length of the fault system, with less displacement to the north. Within the Hebgen Lake basin, the 1959 earthquake is the latest slip event in the Hebgen Lake–Red Canyon fault system and southern Madison Range fault system. Geomorphic and paleoseismic investigations indicate previous faulting events on both fault systems. Surficial geologic mapping and historic seismicity support a coseismic structural linkage between the Madison Range and Hebgen Lake–Red Canyon fault systems. On this trip, we will look at Quaternary surface ruptures that characterize prehistoric earthquake magnitudes. The one-day field trip begins and ends in Bozeman, and includes an overview of the active tectonics within the Madison Valley and Hebgen Lake basin, southwestern Montana. We will also review geologic evidence, which includes new geologic maps and geomorphic analyses that demonstrate preexisting structural controls on surface rupture patterns along the Madison Range and Hebgen Lake–Red Canyon fault systems.

Seismic evidence for change of the tectonic regime in Messinian, northern Marmara Sea, Turkey

NASA Astrophysics Data System (ADS)

Alp, Hakan; Vardar, Denizhan; Alpar, Bedri; Ustaömer, Timur

2018-01-01

New Chirp seismic data collected from the northern margin of the Marmara Sea in June 2015 and previous Sparker seismic profiles recorded in 1999 suggest a change in tectonic regime in Messinian. New tectonic lineaments and fault segments were detected at offshore the Çekmece lagoons region that is located on one of the possible water corridors with the Paratethys. The faults only affect the older seismic unit (U1), which can be best outlined on the Chirp data. The E-W trending fault offshore Avcılar (OAF) borders the northern edge of a tightly folded sedimentary zone. The NNE-SSW trending fault, namely the Büyükçekmece Fault (BF), passing through the Büyükçekmece Bay, follows a buried valley. Its evolution must be related to the development of the Early Miocene - Early Pliocene Thrace-Eskişehir fault zone (TEFZ). BF and OAF indicate old tectonic activities in the region, which continued to the North Anatolian fault becoming the most dominant tectonic element in the region. The upper surface of the stratigraphic unit U1 and its terraces define the thickness of younger deposits (U2), which is thinner in the middle of the shelf. The morphology of the tightly folded zone controls those terraces, which correspond to the Bakırköy Formation and Kıraç member on land. The topmost parts of the terraces must have been eroded during sea level low-stands and cutting of the paleo-valleys. There is no evidence of any tectonic deformation or active fault in the younger seismic unit (U2).

Deformation Record Associated To The Valdoviño Fault (Variscan Orogeny, NW Iberia)

NASA Astrophysics Data System (ADS)

Llana-Funez, S.; Fernández, F. J.

2013-12-01

The Valdoviño Fault is a subvertical left-lateral strike-slip fault that exceeding a hundred kms in length formed in the late stages of the Variscan orogeny in NW Iberia. The fault cuts through the pile of allochthonous thrust sheets that conform the suture zone of the orogen and constitutes the eastern boundary of one of them, the Ordenes complex. In the section along the Atlantic coast, the fault core has a thickness of about 100 m in width with foliated rocks showing a subvertical attitude. It is formed by several rock types, beginning from the west these are: coarse grained foliated granitoids, tectonic breccia with fragments of high grade mafic rocks, fine-grained gneiss, serpentinites, fine-grained amphibolites and two-mica granites. The fault zone samples some of the lithologies found to the base of the Ordenes complex, emplaced and deformed prior to the nucleation of the Valdoviño Fault. Intense deformation produces extreme grain comminution particularly in felsic and basic rocks. Planolinear fabrics are predominant, with a subhorizontal lineation. The intensity of the deformation and the reduction in thickness of the various lithotypes is interpreted as indicative of the amount of strain accumulated during its tectonic history. Two types of tectonites stand out along the trace of the fault: the tectonic breccias at the coastal section (nucleated in basic rocks and in serpentinites) and the SC fabrics in syntectonic granitoids. Both evidence different deformation conditions during the activity of the fault. The band of tectonic breccias developed in basic rocks is a few meters thick and has a number of mm-thick ultracataclasites cutting sharply the breccia. The ultracataclasites show one straight side that cuts through the various components of the breccias (either earlier fault rocks as fragments of metabasites). The slipping surfaces all have a subvertical attitude consistent to the current orientation of the major fault. Earlier ultracataclastic bands

Drilling to investigate processes in active tectonics and magmatism

NASA Astrophysics Data System (ADS)

Shervais, J.; Evans, J.; Toy, V.; Kirkpatrick, J.; Clarke, A.; Eichelberger, J.

2014-12-01

Coordinated drilling efforts are an important method to investigate active tectonics and magmatic processes related to faults and volcanoes. The US National Science Foundation (NSF) recently sponsored a series of workshops to define the nature of future continental drilling efforts. As part of this series, we convened a workshop to explore how continental scientific drilling can be used to better understand active tectonic and magmatic processes. The workshop, held in Park City, Utah, in May 2013, was attended by 41 investigators from seven countries. Participants were asked to define compelling scientific justifications for examining problems that can be addressed by coordinated programs of continental scientific drilling and related site investigations. They were also asked to evaluate a wide range of proposed drilling projects, based on white papers submitted prior to the workshop. Participants working on faults and fault zone processes highlighted two overarching topics with exciting potential for future scientific drilling research: (1) the seismic cycle and (2) the mechanics and architecture of fault zones. Recommended projects target fundamental mechanical processes and controls on faulting, and range from induced earthquakes and earthquake initiation to investigations of detachment fault mechanics and fluid flow in fault zones. Participants working on active volcanism identified five themes: the volcano eruption cycle; eruption sustainability, near-field stresses, and system recovery; eruption hazards; verification of geophysical models; and interactions with other Earth systems. Recommended projects address problems that are transferrable to other volcanic systems, such as improved methods for identifying eruption history and constraining the rheological structure of shallow caldera regions. Participants working on chemical geodynamics identified four major themes: large igneous provinces (LIPs), ocean islands, continental hotspot tracks and rifts, and

Active Deformation along the Southern End of the Tosco-Abreojos Fault System: New Insights from Multibeam Swath Bathymetry

NASA Astrophysics Data System (ADS)

Michaud, François; Calmus, Thierry; Ratzov, Gueorgui; Royer, Jean-Yves; Sosson, Marc; Bigot-Cormier, Florence; Bandy, William; Mortera Gutiérrez, Carlos

2011-08-01

The relative motion of the Pacific plate with respect to the North America plate is partitioned between transcurrent faults located along the western margin of Baja California and transform faults and spreading ridges in the Gulf of California. However, the amount of right lateral offset along the Baja California western margin is still debated. We revisited multibeam swath bathymetry data along the southern end of the Tosco-Abreojos fault system. In this area the depths are less than 1,000 m and allow a finer gridding at 60 m cell spacing. This improved resolution unveils several transcurrent right lateral faults offsetting the seafloor and canyons, which can be used as markers to quantify local offsets. The seafloor of the southern end of the Tosco-Abreojos fault system (south of 24°N) displays NW-SE elongated bathymetric highs and lows, suggesting a transtensional tectonic regime associated with the formation of pull-apart basins. In such an active tectonic context, submarine canyon networks are unstable. Using the deformation rate inferred from kinematic predictions and pull-apart geometry, we suggest a minimum age for the reorganization of the canyon network.

River history and tectonics.

PubMed

Vita-Finzi, C

2012-05-13

The analysis of crustal deformation by tectonic processes has gained much from the clues offered by drainage geometry and river behaviour, while the interpretation of channel patterns and sequences benefits from information on Earth movements before or during their development. The interplay between the two strands operates at many scales: themes which have already benefited from it include the possible role of mantle plumes in the breakup of Gondwana, the Cenozoic development of drainage systems in Africa and Australia, Himalayan uplift in response to erosion, alternating episodes of uplift and subsidence in the Mississippi delta, buckling of the Indian lithospheric plate, and changes in stream pattern and sinuosity along individual alluvial channels subject to localized deformation. Developments in remote sensing, isotopic dating and numerical modelling are starting to yield quantitative analyses of such effects, to the benefit of geodymamics as well as fluvial hydrology. This journal is © 2012 The Royal Society

Remote sensing revealed drainage anomalies and related tectonics of South India

NASA Astrophysics Data System (ADS)

Ramasamy, SM.; Kumanan, C. J.; Selvakumar, R.; Saravanavel, J.

2011-03-01

Drainages have characteristic pattern and life histories with youthful stage in hilly areas, mature stage in plains and old stage in the coastal zones. The deviations from their normal life histories, especially aberrations in their flow pattern in the form of various drainage anomalies have been inferred to be the indications of dominantly the Eustatic and Isostatic changes. This, especially after the advent of Earth Observing Satellites, has attracted the geoscientists from all over the world, for studying such drainage anomalies. In this connection, a study has been undertaken in parts of South India falling south of 14° south latitude to comprehensively map some drainage anomalies like deflected drainages, eyed drainages and compressed meanders and to evolve the tectonic scenario therefrom. The mapping of such mega drainage anomalies and the related lineaments/faults from the satellite digital data and the integration of such lineaments/faults with the overall lineament map of South India showed that the study area is marked by active N-S block faults and NE-SW sinistral and NW-SE dextral strike slip faults. Such an architecture of active tectonic grains indicates that the northerly directed compressive force which has originally drifted the Indian plate towards northerly is still active and deforming the Indian plate.

Tectonic isolation from regional sediment sourcing of the Paradox Basin

NASA Astrophysics Data System (ADS)

Smith, T. M.; Saylor, J.; Sundell, K. E.; Lapen, T. J.

2017-12-01

The Appalachian and Ouachita-Marathon mountain ranges were created by a series of tectonic collisions that occurred through the middle and late Paleozoic along North America's eastern and southern margins, respectively. Previous work employing detrital zircon U-Pb geochronology has demonstrated that fluvial and eolian systems transported Appalachian-derived sediment across the continent to North America's Paleozoic western margin. However, contemporaneous intraplate deformation of the Ancestral Rocky Mountains (ARM) compartmentalized much of the North American western interior and mid-continent. We employ lithofacies characterization, stratigraphic thickness, paleocurrent data, sandstone petrography, and detrital zircon U-Pb geochronology to evaluate source-sink relationships of the Paradox Basin, which is one of the most prominent ARM basins. Evaluation of provenance is conducted through quantitative comparison of detrital zircon U-Pb distributions from basin samples and potential sources via detrital zircon mixture modeling, and is augmented with sandstone petrography. Mixing model results provide a measure of individual source contributions to basin stratigraphy, and are combined with outcrop and subsurface data (e.g., stratigraphic thickness and facies distributions) to create tectonic isolation maps. These maps elucidate drainage networks and the degree to which local versus regional sources influence sediment character within a single basin, or multiple depocenters. Results show that despite the cross-continental ubiquity of Appalachian-derived sediment, fluvial and deltaic systems throughout much of the Paradox Basin do not record their influence. Instead, sediment sourcing from the Uncompahgre Uplift, which has been interpreted to drive tectonic subsidence and formation of the Paradox Basin, completely dominated its sedimentary record. Further, the strong degree of tectonic isolation experienced by the Paradox Basin appears to be an emerging, yet common

Viscoelastic Lithosphere Response and Stress Memory of Tectonic Force History (Invited)

NASA Astrophysics Data System (ADS)

Kusznir, N. J.

2009-12-01

While great attention is often paid to the details of creep deformation mechanisms, brittle failure and their compositional controls when predicting the response of lithosphere to tectonic forces, the lithosphere’s elastic properties are usually neglected; a viscous rheology alone is often used to predict the resulting distribution of stress with depth or to determine lithosphere strength. While this may simplify geodynamic modelling of lithosphere response to tectonic processes, the omission of the elastic properties can often give misleading or false predictions. The addition of the elastic properties of lithosphere material in the form of a visco-elastic rheology results is a fundamentally different lithosphere response. This difference can be illustrated by examining the application of horizontal tectonic force to a section of lithosphere incorporating the brittle-visco-elastic response of each infinitesimal lithosphere layer with temperature and stress dependent viscous rheology. The transient response of a visco-elastic lithosphere to a constant applied tectonic force and the resulting distribution of stress with depth are substantially different from that predicted by a viscous lithosphere model, with the same lithosphere composition and temperature structure, subjected to a constant lateral strain rate. For visco-elastic lithosphere subject to an applied horizontal tectonic force, viscous creep in the lower crust and mantle leads to stress decay in these regions and to stress amplification in the upper lithosphere through stress redistribution. Cooling of lithosphere with a visco-elastic rheology results in thermal stresses which, as a consequence of stress dissipation by creep and brittle failure, results in a complex and sometimes counter-intuitive distribution of stress with depth. This can be most clearly illustrated for the cooling of oceanic lithosphere, however similar or more complex behaviour can be expected to occur for continental lithosphere

Analytical volcano deformation source models

USGS Publications Warehouse

Lisowski, Michael; Dzurisin, Daniel

2007-01-01

Primary volcanic landforms are created by the ascent and eruption of magma. The ascending magma displaces and interacts with surrounding rock and fluids as it creates new pathways, flows through cracks or conduits, vesiculates, and accumulates in underground reservoirs. The formation of new pathways and pressure changes within existing conduits and reservoirs stress and deform the surrounding rock. Eruption products load the crust. The pattern and rate of surface deformation around volcanoes reflect the tectonic and volcanic processes transmitted to the surface through the mechanical properties of the crust.

Fault-based PSHA of an active tectonic region characterized by low deformation rates: the case of the Lower Rhine Graben

NASA Astrophysics Data System (ADS)

Vanneste, Kris; Vleminckx, Bart; Camelbeeck, Thierry

2016-04-01

The Lower Rhine Graben (LRG) is one of the few regions in intraplate NW Europe where seismic activity can be linked to active faults, yet probabilistic seismic hazard assessments of this region have hitherto been based on area-source models, in which the LRG is modeled as a single or a small number of seismotectonic zones with uniform seismicity. While fault-based PSHA has become common practice in more active regions of the world (e.g., California, Japan, New Zealand, Italy), knowledge of active faults has been lagging behind in other regions, due to incomplete tectonic inventory, low level of seismicity, lack of systematic fault parameterization, or a combination thereof. The past few years, efforts are increasingly being directed to the inclusion of fault sources in PSHA in these regions as well, in order to predict hazard on a more physically sound basis. In Europe, the EC project SHARE ("Seismic Hazard Harmonization in Europe", http://www.share-eu.org/) represented an important step forward in this regard. In the frame of this project, we previously compiled the first parameterized fault model for the LRG that can be applied in PSHA. We defined 15 fault sources based on major stepovers, bifurcations, gaps, and important changes in strike, dip direction or slip rate. Based on the available data, we were able to place reasonable bounds on the parameters required for time-independent PSHA: length, width, strike, dip, rake, slip rate, and maximum magnitude. With long-term slip rates remaining below 0.1 mm/yr, the LRG can be classified as a low-deformation-rate structure. Information on recurrence interval and elapsed time since the last major earthquake is lacking for most faults, impeding time-dependent PSHA. We consider different models to construct the magnitude-frequency distribution (MFD) of each fault: a slip-rate constrained form of the classical truncated Gutenberg-Richter MFD (Anderson & Luco, 1983) versus a characteristic MFD following Youngs

High-resolution numerical modeling of tectonic underplating in circum-Pacific subduction zones: toward a better understanding of deformation in the episodic tremor and slip region?

NASA Astrophysics Data System (ADS)

Menant, A.; Angiboust, S.; Gerya, T.; Lacassin, R.; Simoes, M.; Grandin, R.

2017-12-01

Study of now-exhumed ancient subduction systems have evidenced km-scale tectonic units of marine sediments and oceanic crust that have been tectonically underplated (i.e. basally accreted) from the downgoing plate to the overriding plate at more than 30-km depth. Such huge mass transfers must have a major impact, both in term of long-term topographic variations and seismic/aseismic deformation in subduction zones. However, the quantification of such responses to the underplating process remains poorly constrained. Using high-resolution visco-elasto-plastic thermo-mechanical models, we present with unprecedented details the dynamics of formation and destruction of underplated complexes in subductions zones. Initial conditions in our experiments are defined in order to fit different subduction systems of the circum-Pacific region where underplating process is strongly suspected (e.g. the Cascadia, SW-Japan, New Zealand, and Chilean subduction zones). It appears that whatever the subduction system considered, underplating of sediments and oceanic crust always occur episodically forming a coherent nappe stacking at depths comprised between 10 and 50 km. At higher depth, a tectonic mélange with a serpentinized mantle wedge matrix developed along the plates interface. The size of these underplated complexes changes according to the subduction system considered. For instance, a 15-km thick nappe stacking is obtained for the N-Chilean subduction zone after a series of underplating events. Such an episodic event lasts 4-5 Myrs and can be responsible of a 2-km high uplift in the forearc region. Subsequent basal erosion of these underplated complexes results in their only partial preservation at crustal and mantle depth, suggesting that, after exhumation, only a tiny section of the overall underplated material can be observed nowadays in ancient subduction systems. Finally, tectonic underplating in our numerical models is systematically associated with (1) an increasing

Late Quaternary tectonic activity and lake level change in the Rukwa Rift Basin

NASA Astrophysics Data System (ADS)

Delvaux, D.; Kervyn, F.; Vittori, E.; Kajara, R. S. A.; Kilembe, E.

1998-04-01

Interpretation of remotely sensed images and air photographs, compilation of geological and topographical maps, morphostructural and fault kinematic observations and 14C dating reveal that, besides obvious climatic influences, the lake water extent and sedimentation in the closed hydrological system of Lake Rukwa is strongly influenced by tectonic processes. A series of sandy ridges, palaeolacustrine terraces and palaeounderwater delta fans are related to an Early Holocene high lake level and subsequent progressive lowering. The maximum lake level was controlled by the altitude of the watershed between the Rukwa and Tanganyika hydrological systems. Taking as reference the present elevation of the palaeolacustrine terraces around Lake Rukwa, two orders of vertical tectonic movement are evidenced: i) a general uplift centred on the Rungwe Volcanic Province between the Rukwa and Malawi Rift Basins; and ii) a tectonic northeastward tilting of the entire Rukwa Rift Basin, including the depression and rift shoulders. This is supported by the observed hydromorphological evolution. Local uplift is also induced by the development of an active fault zone in the central part of the depression, in a prolongation of the Mbeya Range-Galula Fault system. The Ufipa and Lupa Border Faults, bounding the Rukwa depression on the southwestern and northeastern sides, respectively, exert passive sedimentation control only. They appear inactive or at least less active in the Late Quaternary than during the previous rifting stage. The main Late Quaternary tectonic activity is represented by dextral strike-slip movement along the Mbeya Range-Galula Fault system, in the middle of the Rukwa Rift Basin, and by normal dip-slip movements along the Kanda Fault, in the western rift shoulder.

Active deformation and seismicity in the Southern Alps (Italy): The Montello hill as a case study

NASA Astrophysics Data System (ADS)

Danesi, Stefania; Pondrelli, Silvia; Salimbeni, Simone; Cavaliere, Adriano; Serpelloni, Enrico; Danecek, Peter; Lovati, Sara; Massa, Marco

2015-06-01

The Montello anticline is a morphotectonic feature of the east pede-mountain of the South Alpine Chain in northern Italy, which lies ca. 40 km northwest of Venice, Italy. The purpose of this study is to characterize the present-day crustal deformation and seismotectonics of the Montello area through multi-parametric geophysical observations. We used new data obtained from the installation of a temporary network of 12 seismic stations and 6 GPS sites. The GPS observations indicate that there is ~ 1 mm/yr shortening across the Montello thrust. Sites located north of the Montello thrust front deviate from the ~ NNW-ward Adria-Eurasia convergence direction, as they are constrained by a relative rotation pole in northwestern Italy that has a NNE-ward motion trend. Over 18 months, seismographic recordings allowed us to locate 142 local seismic events with Ml 0.5-3.5 with good reliability (rms < 0.5). After cross-correlation analysis, we classified 42 of these events into six clusters, with cross-correlation thresholds > 0.80. The source focal solutions indicate that: (i) there is thrusting seismic activity on the basal, sub-horizontal, portion of the Montello structure; and (ii) strike-slip source kinematics prevail on the western edge of the Montello hill. Our observations on the source mechanisms and the measured crustal deformation confirm that the Montello thrust is tectonically active.

Maximum earthquake magnitudes in the Aegean area constrained by tectonic moment release rates

NASA Astrophysics Data System (ADS)

Ch. Koravos, G.; Main, I. G.; Tsapanos, T. M.; Musson, R. M. W.

2003-01-01

Seismic moment release is usually dominated by the largest but rarest events, making the estimation of seismic hazard inherently uncertain. This uncertainty can be reduced by combining long-term tectonic deformation rates with short-term recurrence rates. Here we adopt this strategy to estimate recurrence rates and maximum magnitudes for tectonic zones in the Aegean area. We first form a merged catalogue for historical and instrumentally recorded earthquakes in the Aegean, based on a recently published catalogue for Greece and surrounding areas covering the time period 550BC-2000AD, at varying degrees of completeness. The historical data are recalibrated to allow for changes in damping in seismic instruments around 1911. We divide the area up into zones that correspond to recent determinations of deformation rate from satellite data. In all zones we find that the Gutenberg-Richter (GR) law holds at low magnitudes. We use Akaike's information criterion to determine the best-fitting distribution at high magnitudes, and classify the resulting frequency-magnitude distributions of the zones as critical (GR law), subcritical (gamma density distribution) or supercritical (`characteristic' earthquake model) where appropriate. We determine the ratio η of seismic to tectonic moment release rate. Low values of η (<0.5) corresponding to relatively aseismic deformation, are associated with higher b values (>1.0). The seismic and tectonic moment release rates are then combined to constrain recurrence rates and maximum credible magnitudes (in the range 6.7-7.6 mW where the results are well constrained) based on extrapolating the short-term seismic data. With current earthquake data, many of the tectonic zones show a characteristic distribution that leads to an elevated probability of magnitudes around 7, but a reduced probability of larger magnitudes above this value when compared with the GR trend. A modification of the generalized gamma distribution is suggested to account

Temporal Variation of Tectonic Tremor Activity Associated with Nearby Earthquakes

NASA Astrophysics Data System (ADS)

Chao, K.; Van der Lee, S.; Hsu, Y. J.; Pu, H. C.

2017-12-01

Tectonic tremor and slow slip events, located downdip from the seismogenic zone, hold the key to recurring patterns of typical earthquakes. Several findings of slow aseismic slip during the prenucletion processes of nearby earthquakes have provided new insight into the study of stress transform of slow earthquakes in fault zones prior to megathrust earthquakes. However, how tectonic tremor is associated with the occurrence of nearby earthquakes remains unclear. To enhance our understanding of the stress interaction between tremor and earthquakes, we developed an algorithm for the automatic detection and location of tectonic tremor in the collisional tectonic environment in Taiwan. Our analysis of a three-year data set indicates a short-term increase in the tremor rate starting at 19 days before the 2010 ML6.4 Jiashian main shock (Chao et al., JGR, 2017). Around the time when the tremor rate began to rise, one GPS station recorded a flip in its direction of motion. We hypothesize that tremor is driven by a slow-slip event that preceded the occurrence of the shallower nearby main shock, even though the inferred slip is too small to be observed by all GPS stations. To better quantify what the necessary condition for tremor to response to nearby earthquakes is, we obtained a 13-year ambient tremor catalog from 2004 to 2016 in the same region. We examine the spatiotemporal relationship between tremor and 37 ML>=5.0 (seven events with ML>=6.0) nearby earthquakes located within 0.5 degrees to the active tremor sources. The findings from this study can enhance our understanding of the interaction among tremor, slow slip, and nearby earthquakes in the high seismic hazard regions.

Magmatic versus tectonic influence in the Eolian arc: the case of Vulcano and Lipari islands revisited

NASA Astrophysics Data System (ADS)

Ruch, Joel; Di Lorenzo, Riccardo; Vezzoli, Luigina Maria; De Rosa, Rosanna; Acocella, Valerio; Catalano, Stefano; Romagnoli, Gino

2014-05-01

The prevalent influence of magma versus tectonics for the edification and the evolution of volcanic zones is matter of debate. Here we focus on Vulcano and Lipari, two active volcanic islands located in the central sector of the Eolian arc (North of Sicily). Both systems are influenced by regional tectonics and affected by historical magmatic events taking place along a NS oriented structure, connecting both islands. We revisit and implement previous structural studies performed during the 1980's considering several new geophysical, geochemical and geodynamical findings. Four extensive structural campaigns have been performed on both islands and along the shorelines in 2012-2013 covering about 80% of the possible accessible outcrops. We collected ~500 measurements (e.g. faults, fractures and dikes) at 40 sites. Overall, most of the observed structures are oriented N-S and NNW-SSE, confirming previous studies, however, almost all features are strikingly dominated by an EW-oriented extensive regime, which is a novelty. These findings are supported by kinematic indicators and suggest a predominant dip-slip component (pitch from 80 and 130°) with alternating left and right kinematics. Marginal faulting in most recent formations have been observed, suggesting that the deformation may occur preferentially during transient deformation related to periods of magmatic activity, instead of resulting from continuous regional tectonic processes. Overall, fault and dike planes are characterized by a dominant eastward immersion, suggesting an asymmetric graben-like structure of the entire area. This may be explained by the presence of a topographic gradient connecting both islands to the deep Gioia basin to the East, leading to a preferential ample gravitational collapse. Finally, we propose a model in which the stress field rotates northward. It transits from a pure right lateral strike-slip regime along the Tindari fault zone (tectonic-dominant) to an extensive regime

Cenozoic intracontinental deformation of the Kopeh Dagh Belt, Northeastern Iran

NASA Astrophysics Data System (ADS)

Chu, Yang; Wan, Bo; Chen, Ling; Talebian, Morteza

2016-04-01

Compressional intracontinental orogens represent large tectonic zones far from plate boundaries. Since intracontinental mountain belts cannot be framed in the conventional plate tectonics theory, several hypotheses have been proposed to account for the formations of these mountain belts. The far-field effect of collision/subduction at plate margins is now well accepted for the origin and evolution of the intracontinental crust thickening, as exemplified by the Miocene tectonics of central Asia. In northern Iran, the Binalud-Alborz mountain belt witnessed the Triassic tectonothermal events (Cimmerian orogeny), which are interpreted as the result of the Paleotethys Ocean closure between the Eurasia and Central Iran blocks. The Kopeh Dagh Belt, located to the north of the Binalud-Alborz Belt, has experienced two significant tectonic phases: (1) Jurassic to Eocene rifting with more than 7 km of sediments; and (2) Late Eocene-Early Oligocene to Quaternary continuous compression. Due to the high seismicity, deformation associated with earthquakes has received more and more attention; however, the deformation pattern and architecture of this range remain poorly understood. Detailed field observations on the Cenozoic deformation indicate that the Kopeh Dagh Belt can be divided into a western zone and an eastern zone, separated by a series of dextral strike-slip faults, i.e. the Bakharden-Quchan Fault System. The eastern zone characterized by km-scale box-fold structures, associated with southwest-dipping reverse faults and top-to-the NE kinematics. In contrast, the western zone shows top-to-the SW kinematics, and the deformation intensifies from NE to SW. In the northern part of this zone, large-scale asymmetrical anticlines exhibit SW-directed vergence with subordinate thrusts and folds, whereas symmetrical anticlines are observed in the southern part. In regard to its tectonic feature, the Kopeh Dagh Belt is a typical Cenozoic intracontinental belt without ophiolites or

A methodology for studying tectonic subsidence variations: insights from the Fernie Formation of west-central Alberta

NASA Astrophysics Data System (ADS)

McCartney, Tannis Maureen

Tectonic subsidence curves for over 300 subsurface wells in west-central Alberta indicate that the Western Canada Foreland Basin was initiated at the same time the lower units of the Fernie Formation were being deposited. This evidence is further supported by sedimentological data and fits with the timing of the onset of deformation in the Cordillera and the initiation of the foreland basin in Montana. The volume of subsidence curves in this study required an innovative methodology. Subsidence calculations were performed using customized macros in a spreadsheet. The tectonic subsidence variations were displayed in a tectonic subsidence envelope, which showed the total variation in the subsidence curves, and three suites of maps: tectonic subsidence, tectonic subsidence residuals, and tectonic subsidence ratios. Collectively, the maps of the tectonic subsidence in the Fernie Formation show that there was a western influence on subsidence during deposition of the oldest members of the Fernie Formation.

Rifts never die: Structure of the Upper Rhine Graben, and bearing on young and recent tectonics

NASA Astrophysics Data System (ADS)

Behrmann, J. H.

2003-04-01

The Upper Rhine Graben (URG) is a 300 km long, NNE trending, low-strain, small-displacement continental rift of mid-Tertiary age. Its structure can be adequately retrodeformed in 3D if sinistrally transtensive strain and displacement paths along the major faults and associated contact deformation in the wall rocks are restored. The overall structure of the URG is characterised by low listric curvature of the principal faults and large (16-20 km) depth to a basal detachment zone. This deformation geometry and kinematics inhibits block rotation, minimises displacement on individual faults, and apparently leads to strain dissipation into intricate fault networks and/or "en masse" fracturing of large rock volumes, and propagation of dominantly brittle deformation deep into the continental crust. A net result of such deformation may be permanent reduction of tensional and shear strength on a crustal scale, making oblique rifts like the URG particularly prone to tectonic reactivation. Continued Quaternary and recent tectonic activity of the URG is documented by the following phenomena: (1) strong local differential subsidence and sedimentary basin filling, especially in the northern and southern parts of the rift. (2) Formation of morphological scarps at the locations of some major faults and offset of Quaternary stata at depth, especially in the southern (Freiburg-Basel) segment (3) Changes in relative elevation of reference points along precise levelling traverses. (4) Considerable microearthquake activity (> 50 events since 1995 in the Freiburg area), concentrated in the middle and upper crust on or in the vicinity of depth projections of faults. One possible conclusion to be drawn from the URG data and observations is that rifts can remain in a near-critical mechanical state very long after formation, even if plate-scale principal stresses have changed orientations and/or differential magnitudes. Rates of movement and seismicity are up to one order of magnitude lower

Analysis of Active Crustal Deformation in Chiayi Area, Southwestern Taiwan by Continues GPS network and numerical modeling

NASA Astrophysics Data System (ADS)

Chung, W. C.; Hu, J. C.

2012-04-01

Locating in the boundary between the Eurasia Plate and the Philippine Sea Plate, the island of Taiwan lies in a complex tectonic area. The fold-and-thrust belt in the southwestern Taiwan provides distinctive morphotectonic features reflecting the initial mountain building stage in Taiwan orogeny. Several devastating earthquakes have occurred in this region since 1900, the famous one is M7.1 Meishan earthquake in 1906. In addition, a seismic concentration zone is observed in Coastal plain in Chiayi counties, which no active faults have been reported in this region. The active deformation in SW Taiwan has been suggested to be related to active growing folding initiated by the blind thrust fault system. How surface deformation related to the subsurface active structures is a crucial topic for seismic hazard assessment in study area. The newly initiated blind fault system increases potential earthquake hazard in the southwestern alluvial plain where is densely populated. Thus we try to characterize the existence of blind fault-folding system beneath the coastal plain area by geodetic method. We derive a velocity field based on data at 55 continuous GPS (CGPS) stations from 2006 to 2010, and data at 97 campaign mode GPS over a time period between 2002 to 2010. The CGPS data used in this study were processed with the GAMIT/GLOBK software version 10.4. The crustal motion in this area shows the horizontal displacement about 30 mm/yr with the directions of 297° in the easternmost part of the Western Foothills, and crossing the main active structures, Chiushiunkeng-Chukou Fault and blind fault systems, the velocities significantly decrease to 3 mm/yr with the directions of 288° in the westernmost part in the coastal plan, with respect to Paisha station, S01R. The compressional strain rate dominates and the larger compressional strain rate is observed at the Foothill region, the east side of Chiushiunkeng- Chukou Fault. In some coordinate time-series of our CGPS sites, the

Active Beam Shaping System and Method Using Sequential Deformable Mirrors

NASA Technical Reports Server (NTRS)

Pueyo, Laurent A. (Inventor); Norman, Colin A. (Inventor)

2015-01-01

An active optical beam shaping system includes a first deformable mirror arranged to at least partially intercept an entrance beam of light and to provide a first reflected beam of light, a second deformable mirror arranged to at least partially intercept the first reflected beam of light from the first deformable mirror and to provide a second reflected beam of light, and a signal processing and control system configured to communicate with the first and second deformable mirrors. The first deformable mirror, the second deformable mirror and the signal processing and control system together provide a large amplitude light modulation range to provide an actively shaped optical beam.

Deformation of the Roberts Mountains Allochthon in north-central Nevada

USGS Publications Warehouse

Evans, James George; Theodore, Ted G.

1978-01-01

During the Antler orogeny in Late Devonian and Early Mississippian time, early and middle Paleozoic siliceous rocks, largely chert and sha1e, were thrust eastward for 90 to 160 km over coexisting carbonate rocks. Minor and major structures of two small areas of the allochthon at Battle Mountain and in the southern Tuscarora Mountains were studied in order to characterize the deformation and test the consistency of the movement plan with respect to the large eastward displacement. In the Battle Mountain area, the lower Paleozoic Scott Canyon and Valmy Formations were deformed in the Antler orogeny but were unaffected by later tectonism during late Paleozoic or early Mesozoic. In the southern Tuscarora Mountains area, the Ordovician and Silurian siliceous rocks deformed in the Antler Orogeny were deformed by later, possibly Mesozoic, folding and thrusting. Most of the minor folding visible in the allochthon is in the cheret, but proportionally more of the strain was taken up in the shale and argillite, both poorly exposed but predominant rock types. Most minor folds, concentric in form, plunge at small angles to the north-northeast and south-southwest with steeply dipping or vertical axial planes. The b-fabric axis, parallel to these folds, is identical apparently to the B-kinematic axis. The horizontal component of tectonic shortening of the allochthon, N. 70?-75? W. both in the Battle Mountain area and in the southern Tuscarora Mountains area, is therefore consistent with an eastward direction of movement of the allochthon. Folds with west- northwest trends locally present in the allochthon, may have formed in the direction of tectonic transport. In the southern Tuscarora Mountains, local strain in and below the allochthon was different from the prevailing strain in the allochthon, and tectonic shortening was locally at large angles to the accepted direction of movement of the allochthon.

Magmatic tectonic effects of high thermal regime at the site of active ridge subduction: the Chile Triple Junction model

NASA Astrophysics Data System (ADS)

Lagabrielle, Yves; Guivel, Christèle; Maury, René C.; Bourgois, Jacques; Fourcade, Serge; Martin, Hervé

2000-11-01

High thermal gradients are expected to be found at sites of subduction of very young oceanic lithosphere and more particularly at ridge-trench-trench (RTT) triple junctions, where active oceanic spreading ridges enter a subduction zone. Active tectonics, associated with the emplacement of two main types of volcanic products, (1) MORB-type magmas, and (2) calc-alkaline acidic magmas in the forearc, also characterize these plate junction domains. In this context, MORB-type magmas are generally thought to derive from the buried active spreading center subducted at shallow depths, whereas the origin of calc-alkaline acidic magmas is more problematic. One of the best constrained examples of ridge-trench interaction is the Chile Triple Junction (CTJ) located southwest of the South American plate at 46°12'S, where the active Chile spreading center enters the subduction zone. In this area, there is a clear correlation between the emplacement of magmatic products and the migration of the triple junction along the active margin. The CTJ lava population is bimodal, with mafic to intermediate lavas (48-56% SiO 2) and acidic lavas ranging from dacites to rhyolites (66-73% SiO 2). Previous models have shown that partial melting of oceanic crust plus 10-20% of sediments, leaving an amphibole- and plagioclase-rich residue, is the only process that may account for the genesis of acidic magmas. Due to special plate geometry in the CTJ area, a given section of the margin may be successively affected by the passage of several ridge segments. We emphasize that repeated passages will lead to the development of very high thermal gradients allowing melting of rocks of oceanic origin at temperatures of 800-900°C and low pressures, corresponding to depths of 10-20 km depth only. In addition, the structure of the CTJ forearc domain is dominated by horizontal displacements and tilting of crustal blocks along a network of strike-slip faults. The occurrence of such a deformed domain implies

Active Tectonics of Himalayan Faults/Thrusts System in Northern India on the basis of recent & Paleo earthquake Studies

NASA Astrophysics Data System (ADS)

Kumar, S.; Biswal, S.; Parija, M. P.

2016-12-01

The Himalaya overrides the Indian plate along a decollement fault, referred as the Main Himalayan Thrust (MHT). The 2400 km long Himalayan mountain arc in the northern boundary of the Indian sub-continent is one of the most seismically active regions of the world. The Himalayan Frontal Thrust (HFT) is characterized by an abrupt physiographic and tectonic break between the Himalayan front and the Indo-Gangetic plain. The HFT represents the southern surface expression of the MHT on the Himalayan front. The tectonic zone between the Main Boundary Thrust (MBT) and the HFT encompasses the Himalayan Frontal Fault System (HFFS). The zone indicates late Quaternary-Holocene active deformation. Late Quaternary intramontane basin of Dehradun flanked to the south by the Mohand anticline lies between the MBT and the HFT in Garhwal Sub Himalaya. Slip rate 13-15 mm/yr has been estimated on the HFT based on uplifted strath terrace on the Himalyan front (Wesnousky et al. 2006). An out of sequence active fault, Bhauwala Thrust (BT), is observed between the HFT and the MBT. The Himalayan Frontal Fault System includes MBT, BT, HFT and PF active fault structures (Thakur, 2013). The HFFS structures were developed analogous to proto-thrusts in subduction zone, suggesting that the plate boundary is not a single structure, but series of structures across strike. Seismicity recorded by WIHG shows a concentrated belt of seismic events located in the Main Central Thrust Zone and the physiographic transition zone between the Higher and Lesser Himalaya. However, there is quiescence in the Himalayan frontal zone where surface rupture and active faults are reported. GPS measurements indicate the segment between the southern extent of microseismicity zone and the HFT is locked. The great earthquake originating in the locked segment rupture the plate boundary fault and propagate to the Himalaya front and are registered as surface rupture reactivating the fault in the HFFS.

Time dependent deformation and stress in the lithosphere. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Yang, M.

1980-01-01

Efficient computer programs incorporating frontal solution and time stepping procedure were developed for the modelling of geodynamic problems. This scheme allows for investigating the quasi static phenomena including the effects of the rheological structure of a tectonically active region. From three dimensional models of strike slip earthquakes, it was found that lateral variation of viscosity affects the characteristics of surface deformations. The vertical deformation is especially informative about the viscosity structure in a strike slip fault zone. A three dimensional viscoelastic model of a thrust earthquake indicated that the transient disturbance on plate velocity due to a great plate boundary earthquake is significant at intermediate distances, but becomes barely measurable 1000 km away from the source.

Rheological decoupling at the Moho and implication to Venusian tectonics

PubMed Central

Azuma, Shintaro; Katayama, Ikuo; Nakakuki, Tomoeki

2014-01-01

Plate tectonics is largely responsible for material and heat circulation in Earth, but for unknown reasons it does not exist on Venus. The strength of planetary materials is a key control on plate tectonics because physical properties, such as temperature, pressure, stress, and chemical composition, result in strong rheological layering and convection in planetary interiors. Our deformation experiments show that crustal plagioclase is much weaker than mantle olivine at conditions corresponding to the Moho in Venus. Consequently, this strength contrast may produce a mechanical decoupling between the Venusian crust and interior mantle convection. One-dimensional numerical modeling using our experimental data confirms that this large strength contrast at the Moho impedes the surface motion of the Venusian crust and, as such, is an important factor in explaining the absence of plate tectonics on Venus. PMID:24638113

Tectonic evolution of the Qumran Basin from high-resolution 3.5-kHz seismic profiles and its implication for the evolution of the northern Dead Sea Basin

NASA Astrophysics Data System (ADS)

Lubberts, Ronald K.; Ben-Avraham, Zvi

2002-02-01

The Dead Sea Basin is a morphotectonic depression along the Dead Sea Transform. Its structure can be described as a deep rhomb-graben (pull-apart) flanked by two block-faulted marginal zones. We have studied the recent tectonic structure of the northwestern margin of the Dead Sea Basin in the area where the northern strike-slip master fault enters the basin and approaches the western marginal zone (Western Boundary Fault). For this purpose, we have analyzed 3.5-kHz seismic reflection profiles obtained from the northwestern corner of the Dead Sea. The seismic profiles give insight into the recent tectonic deformation of the northwestern margin of the Dead Sea Basin. A series of 11 seismic profiles are presented and described. Although several deformation features can be explained in terms of gravity tectonics, it is suggested that the occurrence of strike-slip in this part of the Dead Sea Basin is most likely. Seismic sections reveal a narrow zone of intensely deformed strata. This zone gradually merges into a zone marked by a newly discovered tectonic depression, the Qumran Basin. It is speculated that both structural zones originate from strike-slip along right-bending faults that splay-off from the Jordan Fault, the strike-slip master fault that delimits the active Dead Sea rhomb-graben on the west. Fault interaction between the strike-slip master fault and the normal faults bounding the transform valley seems the most plausible explanation for the origin of the right-bending splays. We suggest that the observed southward widening of the Dead Sea Basin possibly results from the successive formation of secondary right-bending splays to the north, as the active depocenter of the Dead Sea Basin migrates northward with time.

Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

NASA Astrophysics Data System (ADS)

Sauber, Jeanne M.; Molnia, Bruce F.

2004-07-01

Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes ( ML≥2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes ( Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake ( Ms=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass

Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

USGS Publications Warehouse

Sauber, J.M.; Molnia, B.F.

2004-01-01

Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes (ML???2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes (Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake (M s=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass

Recent and active tectonics of the external zone of the Northern Apennines (Italy)

NASA Astrophysics Data System (ADS)

Boccaletti, Mario; Corti, Giacomo; Martelli, Luca

2011-08-01

We present a comprehensive study of the recent and active tectonics of the external part of the Northern Apennines (Italy) by using morphotectonic, geological-structural, and stratigraphic analysis, compared with the current seismicity of the region. This analysis suggests that the external part of the Northern Apennines is characterised by presence of three major systems of Quaternary compressive structures corresponding to (1) the Apenninic watershed, (2) the Apennines-Po Plain margin (pede-Apenninic thrust front), and (3) the Emilia, Ferrara, and Adriatic Fold systems buried below the Po Plain. Geological data and interpreted seismic sections indicate a roughly N-S Quaternary deformation direction, with rates <2.5 mm/year. The shortening decreased since the Pliocene, when our data indicate compression in a NNW-SSE direction and rates up to 7 mm/year. The trend and kinematics of the structures affecting the Apennines-Po Plain margin and the Po Plain subsoil fit well the pattern of the current seismicity of the area, as well as recent GPS and geodetic levelling data, pointing to a current activity of these thrust systems controlled by an overall compressive stress field. Close to the Apenninic watershed, earthquake focal mechanisms indicate that shallow extension is associated to deep compression. The extensional events may be related to a secondary extensional stress field developing on the hangingwall of the thrust system affecting the Apenninic watershed; alternatively, this thrust system may have been recently deactivated and overprinted by active normal faulting. Deeper compressive events are related to the activity of both a major basement thrust that connects at surface with the pede-Apenninic thrust front and a major Moho structure.

MANTLE CONVECTION, PLATE TECTONICS, AND VOLCANISM ON HOT EXO-EARTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Summeren, Joost; Conrad, Clinton P.; Gaidos, Eric, E-mail: summeren@hawaii.edu

Recently discovered exoplanets on close-in orbits should have surface temperatures of hundreds to thousands of Kelvin. They are likely tidally locked and synchronously rotating around their parent stars and, if an atmosphere is absent, have surface temperature contrasts of many hundreds to thousands of Kelvin between permanent day and night sides. We investigated the effect of elevated surface temperature and strong surface temperature contrasts for Earth-mass planets on the (1) pattern of mantle convection, (2) tectonic regime, and (3) rate and distribution of partial melting, using numerical simulations of mantle convection with a composite viscous/pseudo-plastic rheology. Our simulations indicate thatmore » if a close-in rocky exoplanet lacks an atmosphere to redistribute heat, a {approx}>400 K surface temperature contrast can maintain an asymmetric degree 1 pattern of mantle convection in which the surface of the planet moves preferentially toward subduction zones on the cold night side. The planetary surface features a hemispheric dichotomy, with plate-like tectonics on the night side and a continuously evolving mobile lid on the day side with diffuse surface deformation and vigorous volcanism. If volcanic outgassing establishes an atmosphere and redistributes heat, plate tectonics is globally replaced by diffuse surface deformation and volcanism accelerates and becomes distributed more uniformly across the planetary surface.« less

Caribbean tectonics and relative plate motions

NASA Technical Reports Server (NTRS)

Burke, K.; Dewey, J. F.; Cooper, C.; Mann, P.; Pindell, J. L.

1984-01-01

During the last century, three different ways of interpreting the tectonic evolution of the Gulf of Mexico and the Caribbean have been proposed, taking into account the Bailey Willis School of a permanent pre-Jurassic deep sea basin, the Edward Suess School of a subsided continental terrain, and the Alfred Wegener School of continental separation. The present investigation is concerned with an outline of an interpretation which follows that of Pindell and Dewey (1982). An attempt is made to point out ways in which the advanced hypotheses can be tested. The fit of Africa, North America, and South America is considered along with aspects of relative motion between North and South America since the early Jurasic. Attention is given to a framework for reconstructing Caribbean plate evolution, the evolution of the Caribbean, the plate boundary zones of the northern and southern Caribbean, and the active deformation of the Caribbean plate.

Study of Deformation Bands in Ignimbrites in Shihtiping, Eastern Taiwan

NASA Astrophysics Data System (ADS)

Lin, S. T.; Huang, W. J.

2014-12-01

Shihtiping is located at the coast of eastern Taiwan, where rocks are the products of subaerial eruption by Chimei Volcano in late Miocene. The major lithology is ignimbrite along with pyroclasts in various sizes. Deformation bands ubiquitously appear in such loose, high-porosity, rocks. This study aims at documenting the occurrence of the deformation bands, understanding their formation mechanism and discussing their tectonic implications. There are two sets of deformation bands with orientations of N60°~80°E and N50°~70°W, respectively, in Shihtiping. The dip angles of both range from 70° to 90°. Commonly, the deformation bands are exposed as single trace or braided trace composed of several individuals. They can be traced easily because they are protruding owning to more weathering-resistant than the host rock. Thickness and separation of single deformation band are in the order of millimeter and millimeter to centimeter, respectively. Thickness of zone of deformation band ranges from few mm to tens of cm and total separation is commonly tens of cm. Based on microscopic examination, mineral assemblages in deformation bands usually include plagioclase, hornblende and augite. Although mineral assemblages are the same as host rock, clasts in deformation bands are rounder and smaller. Thus, it results in closed packing and porosity reduction within deformation bands. Summed up the observations, the deformation bands in Shihtiping were formed by cataclasis and can be classified as cataclastic band. They may reflect the regional paelostress state but not accompanied with any tectonic fault.

Deformation during terrane accretion in the Saint Elias orogen, Alaska

USGS Publications Warehouse

Bruhn, R.L.; Pavlis, T.L.; Plafker, G.; Serpa, L.

2004-01-01

The Saint Elias orogen of southern Alaska and adjacent Canada is a complex belt of mountains formed by collision and accretion of the Yakutat terrane into the transition zone from transform faulting to subduction in the northeast Pacific. The orogen is an active analog for tectonic processes that formed much of the North American Cordillera, and is also an important site to study (1) the relationships between climate and tectonics, and (2) structures that generate large- to great-magnitude earthquakes. The Yakutat terrane is a fragment of the North American plate margin that is partly subducted beneath and partly accreted to the continental margin of southern Alaska. Interaction between the Yakutat terrane and the North American and Pacific plates causes significant differences in the style of deformation within the terrane. Deformation in the eastern part of the terrane is caused by strike-slip faulting along the Fairweather transform fault and by reverse faulting beneath the coastal mountains, but there is little deformation immediately offshore. The central part of the orogen is marked by thrusting of the Yakutat terrane beneath the North American plate along the Chugach-Saint Elias fault and development of a wide, thin-skinned fold-and-thrust belt. Strike-slip faulting in this segment may he localized in the hanging wall of the Chugach-Saint Elias fault, or dissipated by thrust faulting beneath a north-northeast-trending belt of active deformation that cuts obliquely across the eastern end of the fold-and-thrust belt. Superimposed folds with complex shapes and plunging hinge lines accommodate horizontal shortening and extension in the western part of the orogen, where the sedimentary cover of the Yakutat terrane is accreted into the upper plate of the Aleutian subduction zone. These three structural segments are separated by transverse tectonic boundaries that cut across the Yakutat terrane and also coincide with the courses of piedmont glaciers that flow from

Recent developments in understanding the tectonic evolution of the Southern California offshore area: Implications for earthquake-hazard analysis

USGS Publications Warehouse

Fisher, M.A.; Langenheim, V.E.; Nicholson, C.; Ryan, H.F.; Sliter, R.W.

2009-01-01

During late Mesozoic and Cenozoic time, three main tectonic episodes affected the Southern California offshore area. Each episode imposed its unique structural imprint such that early-formed structures controlled or at least influenced the location and development of later ones. This cascaded structural inheritance greatly complicates analysis of the extent, orientation, and activity of modern faults. These fault attributes play key roles in estimates of earthquake magnitude and recurrence interval. Hence, understanding the earthquake hazard posed by offshore and coastal faults requires an understanding of the history of structural inheritance and modifi-cation. In this report we review recent (mainly since 1987) findings about the tectonic development of the Southern California offshore area and use analog models of fault deformation as guides to comprehend the bewildering variety of offshore structures that developed over time. This report also provides a background in regional tectonics for other chapters in this section that deal with the threat from offshore geologic hazards in Southern California. ?? 2009 The Geological Society of America.

Late Alpine to recent thick-skinned tectonics of the central Swiss Molasse Basin, Canton of Bern, Switzerland

NASA Astrophysics Data System (ADS)

Mock, Samuel; Allenbach, Robin; Wehrens, Philip; Reynolds, Lance; Kurmann-Matzenauer, Eva; Michael, Salomè; Herwegh, Marco

2017-04-01

The Swiss Molasse Basin (SMB) forms part of the North Alpine Foreland Basin. It is a typical peripheral foreland basin, which developed in Paleogene and Neogene times in response to flexural bending of the European lithosphere induced by the orogenic loading of the advancing Alpine thrust wedge. The tectonics of the SMB and the role of Paleozoic and Mesozoic structures are still poorly understood. It is widely accepted that during the main deformation phase of the Jura fold-and-thrust belt, the SMB was riding piggy-back above a major detachment horizon situated within Triassic evaporites. In recent years it has been observed that the Jura fold-and-thrust belt is today deforming in a thick-skinned tectonic style. As for the western and central SMB, most authors still argue in favor of a classical foreland type, thin-skinned style of deformation. Based on the geological 3D modeling of seismic interpretations, we present new insights into the structural configuration of the central SMB. Revised and new interpretations of 2D reflection seismic data from the 1960s to the 1980s reveal a major strike-slip fault zone affecting not only the Mesozoic and Cenozoic cover, but also the crystalline basement beneath. The fault zone reactivated late Paleozoic synsedimentary normal faults bounding a Permo-Carboniferous trough. Basement-involved thrusting observed in the southern part of the SMB seems to be controlled by the presence of slightly inverted Permo-Carboniferous troughs as well. These observations, combined with a compiled structural map and the distribution of recent earthquake hypocenters suggest a late stage, NNW-SSE directed, compressional thick-skinned and strike-slip dominated tectonic activity of the central SMB, post-dating the main deformation phase of the Jura fold-and-thrust belt. This still ongoing deformation might be related to the slab rollback of the European plate and the associated lower crustal delamination as recently suggested by Singer et al. (2014

First results of an INGV project for the integrated analysis of the active tectonics in SW Sicily

NASA Astrophysics Data System (ADS)

Mattia, Mario; Giovanni, Barreca; Carla, Bottari; Valentina, Bruno; Pierfrancesco, Burrato; Fabrizio, Cultrera; Luigi, Dardanelli; Sofia, De Gregorio; Luigi, Ferranti; Laura, Guzzetta; Paolo, Madonia; Carmelo, Monaco; Claudia, Pipitone; Fabrizio, Pepe; Francesco, Guglielmino

2017-04-01

We present the first results of a project financed by the "Struttura Terremoti" of INGV to study the potential sources of earthquakes in south-western Sicily, including the area hit by the 1968 Belice earthquake sequence and the archaeological area of Selinunte, affected by two earthquakes in historical times. We adopt in this project a multi-disciplinary approach, with the goal of addressing the following points: 1) define the active tectonic framework of south-western Sicily, 2) investigate and characterize on-shore and off-shore faults, potential sources of damaging earthquakes, and 3) evaluate the current deformation rates. To do this, we collected a new set of geodetic (GPS and InSAR) and geochemical data, and performed geological and geomorphological surveys on-land in the area between Mazara, Castelvetrano and Selinunte. We also acquired high-resolution Sparker seismic profiles off-shore Sciacca. Geological and geomorphological surveys have been focused around the 10 km long Castelvetrano-Campobello di Mazara (CCM) lineament, where previous research (Barreca et al., 2014) showed geodetic and geoarchaeological evidence of recent deformation. In particular, a detailed survey of Quaternary coastal forms and deposits was performed, in order to reconstruct the sequence of uplifted paleoshorelines and to search for differential motions between adjacent coastal sectors spanning the CCM. Preliminary observations indicate that the footwall of the CCM hosts a larger number, and a more elevated position of paleo-shorelines suggestive of syntectonic uplift . A grid of about 200 km of high-resolution reflection seismic profiles was recorded along the continental shelf in the offshore of Sciacca. Profiles are mostly oriented in the WNW-ESE direction, with tie lines acquired in ENE-WSW direction. The acoustic source used during seismic prospecting was a 1 kJ Sparker power supply with a multi-tips Sparker array. Preliminary seismic data interpretation indicates that a

Transient deformation from daily GPS displacement time series: postseismic deformation, ETS and evolving strain rates

NASA Astrophysics Data System (ADS)

Bock, Y.; Fang, P.; Moore, A. W.; Kedar, S.; Liu, Z.; Owen, S. E.; Glasscoe, M. T.

2016-12-01

Detection of time-dependent crustal deformation relies on the availability of accurate surface displacements, proper time series analysis to correct for secular motion, coseismic and non-tectonic instrument offsets, periodic signatures at different frequencies, and a realistic estimate of uncertainties for the parameters of interest. As part of the NASA Solid Earth Science ESDR System (SESES) project, daily displacement time series are estimated for about 2500 stations, focused on tectonic plate boundaries and having a global distribution for accessing the terrestrial reference frame. The "combined" time series are optimally estimated from independent JPL GIPSY and SIO GAMIT solutions, using a consistent set of input epoch-date coordinates and metadata. The longest time series began in 1992; more than 30% of the stations have experienced one or more of 35 major earthquakes with significant postseismic deformation. Here we present three examples of time-dependent deformation that have been detected in the SESES displacement time series. (1) Postseismic deformation is a fundamental time-dependent signal that indicates a viscoelastic response of the crust/mantle lithosphere, afterslip, or poroelastic effects at different spatial and temporal scales. It is critical to identify and estimate the extent of postseismic deformation in both space and time not only for insight into the crustal deformation and earthquake cycles and their underlying physical processes, but also to reveal other time-dependent signals. We report on our database of characterized postseismic motions using a principal component analysis to isolate different postseismic processes. (2) Starting with the SESES combined time series and applying a time-dependent Kalman filter, we examine episodic tremor and slow slip (ETS) in the Cascadia subduction zone. We report on subtle slip details, allowing investigation of the spatiotemporal relationship between slow slip transients and tremor and their

Quantitative thickness prediction of tectonically deformed coal using Extreme Learning Machine and Principal Component Analysis: a case study

NASA Astrophysics Data System (ADS)

Wang, Xin; Li, Yan; Chen, Tongjun; Yan, Qiuyan; Ma, Li

2017-04-01

The thickness of tectonically deformed coal (TDC) has positive correlation associations with gas outbursts. In order to predict the TDC thickness of coal beds, we propose a new quantitative predicting method using an extreme learning machine (ELM) algorithm, a principal component analysis (PCA) algorithm, and seismic attributes. At first, we build an ELM prediction model using the PCA attributes of a synthetic seismic section. The results suggest that the ELM model can produce a reliable and accurate prediction of the TDC thickness for synthetic data, preferring Sigmoid activation function and 20 hidden nodes. Then, we analyze the applicability of the ELM model on the thickness prediction of the TDC with real application data. Through the cross validation of near-well traces, the results suggest that the ELM model can produce a reliable and accurate prediction of the TDC. After that, we use 250 near-well traces from 10 wells to build an ELM predicting model and use the model to forecast the TDC thickness of the No. 15 coal in the study area using the PCA attributes as the inputs. Comparing the predicted results, it is noted that the trained ELM model with two selected PCA attributes yields better predication results than those from the other combinations of the attributes. Finally, the trained ELM model with real seismic data have a different number of hidden nodes (10) than the trained ELM model with synthetic seismic data. In summary, it is feasible to use an ELM model to predict the TDC thickness using the calculated PCA attributes as the inputs. However, the input attributes, the activation function and the number of hidden nodes in the ELM model should be selected and tested carefully based on individual application.

Early Paleozoic tectonic reactivation of the Shaoxing-Jiangshan fault zone: Structural and geochronological constraints from the Chencai domain, South China

NASA Astrophysics Data System (ADS)

Sun, Hanshen; Li, Jianhua; Zhang, Yueqiao; Dong, Shuwen; Xin, Yujia; Yu, Yingqi

2018-05-01

The Shaoxing-Jiangshan fault zone (SJFZ), as a fundamental Neoproterozoic block boundary that separates the Yangtze Block from the Cathaysia Block, is the key to understanding the evolution of South China from Neoproterozoic block amalgamation to early Paleozoic crustal reworking. New structural observations coupled with geochronological ages from the Chencai domain indicate that intense ductile deformation and metamorphism along the SJFZ occurred at ∼460-420 Ma, in response to the early Paleozoic orogeny in South China. To the east of the SJFZ, the deformation involves widespread generations of NE-striking foliation, intrafolial folds, and local development of sinistral-oblique shear zones. The shearing deformation occurred under amphibolite facies conditions at temperatures of >550 °C (locally even >650 °C). To the west of the SJFZ, the deformation corresponds to sinistral-oblique shearing along NE-striking, steep-dipping zones under greenschist facies conditions at temperatures of 400-500 °C. These deformation styles, as typical mid-crustal expressions of continental reworking, reflect tectonic reactivation of the pre-existing, deeply rooted Neoproterozoic block boundary in the early Paleozoic. We infer that the tectonic reactivation, possibly induced by oblique underthrusting of north Cathaysia, facilitated ductile shearing and burial metamorphic reactions, giving rise to the high-strain zones and high-grade metamorphic rocks. With respect to pre-existing mechanical weakness, our work highlights the role of tectonic reactivation of early structures in localizing later deformation before it propagates into yet undeformed domains.

The effect of pre-tectonic reaction and annealing extent on behaviour during subsequent deformation: Insights from paired shear zones in the lower crust of Fiordland, New Zealand

NASA Astrophysics Data System (ADS)

Piazolo, Sandra; Daczko, Nathan R.; Smith, James R.; Evans, Lynn

2015-04-01

The effect of pre-tectonic reaction and annealing extent on the rheology of lower crustal rocks during a subsequent deformation event was studied using field and detailed microstructural analyses combined with numerical simulations to examine. In the studied rocks (Pembroke granulite, South Island, New Zealand) granulite facies two-pyroxene-pargasite orthogneiss partially to completely reacted to garnet bearing granulite either side of felsic dykes. The metamorphic reaction not only changed the abundance of phases but also their shape and grain size distribution. The reaction is most advanced close to the dykes, whereas further away the reaction is incomplete. As a consequence, grain size and the abundance of the rheologically hard phase garnet decreases away from the felsic dykes. Aspect ratios of mafic clusters which may include garnet decrease from high in the host, to near equidimensional close to the dyke. Post-reaction deformation localized in those areas that experienced minor to moderate reaction extent producing two spaced "paired" shear zones within the garnet-bearing reaction zone at either side of the felsic dykes. Our study shows how rock flow properties are governed by the pre-deformation history of a rock in terms of reaction and coupled annealing extent. If the grain size is sufficiently reduced by metamorphic reaction, deformation localizes in the partially finer grained rock domains, where deformation dominantly occurs by grain size sensitive deformation flow. Even if the reaction produces a nominally stronger phase (e.g. garnet) than the reactants, a local switch in dominant deformation behaviour from a grain size insensitive to a grain size sensitive in reaction induced fine-grained portions of the rock may occur and result in significant strain localization.

Evaluating influence of active tectonics on spatial distribution pattern of floods along eastern Tamil Nadu, India

NASA Astrophysics Data System (ADS)

Selvakumar, R.; Ramasamy, SM.

2014-12-01

Flooding is a naturally recurrent phenomenon that causes severe damage to lives and property. Predictions on flood-prone zones are made based on intensity-duration of rainfall, carrying capacity of drainage, and natural or man-made obstructions. Particularly, the lower part of the drainage system and its adjacent geomorphic landforms like floodplains and deltaic plains are considered for analysis, but stagnation in parts of basins that are far away from major riverine systems is less unveiled. Similarly, uncharacteristic flooding in the upper and middle parts of drainage, especially in zones of an anomalous drainage pattern, is also least understood. Even though topographic differences are attributed for such anomalous spatial occurrence of floods, its genetic cause has to be identified for effective management practice. Added to structural and lithological variations, tectonic movements too impart micro-scale terrain undulations. Because active tectonic movements are slow-occurring, long-term geological processes, its resultant topographical variations and drainage anomalies are least correlated with floods. The recent floods of Tamil Nadu also exhibit a unique distribution pattern emphasizing the role of tectonics over it. Hence a detailed geoinformatics-based analysis was carried out to envisage the relationship between spatial distribution of flood and active tectonic elements such as regional arches and deeps, block faults, and graben and drainage anomalies such as deflected drainage, compressed meander, and eyed drainages. The analysis reveals that micro-scale topographic highs and lows imparted by active tectonic movements and its further induced drainage anomalies have substantially controlled the distribution pattern of flood.

Active tectonics in the Mygdonia basin (northern Greece): a combined seismological and remote-sensed geomorphology approach

NASA Astrophysics Data System (ADS)

Gkarlaouni, Charikleia; Andreani, Louis; Pennos, Chris; Gloaguen, Richard; Papadimitriou, Eleftheria; Kilias, Adamantios; Michail, Maria

2014-05-01

In Greek mainland, active extensional deformation resulted in the development of numerous seismogenic E- to SE-trending basins. The Mygdonia graben located in central Macedonia produced major historical earthquakes and poses a serious threat to the neighbouring city of Thessaloniki. Our aim is to determine which active seismic sources have the potential to generate strong events. Active tectonics shape the landscape, control the evolution of the fluvial network and cause the occurrence of strong and frequent earthquakes generated by fault populations. Thus, our approach combined both seismology and remote-sensed geomorphology. Seismological investigation and more especially relocation analysis was performed for recent seismicity in the area (2000-2012). Low magnitude earthquakes not exceeding 4.8 constitute the seismicity pattern for this period. Accurately determined focal parameters indicate that seismicity is not only localized along major fault zones. Smaller faults seem also to be activated. Temporal and spatial investigation show that seismicity is clustered and seismic bursts often migrate to adjacent faults. The hypocentral distribution of precisely determined microearthquake foci reveals the existence of high-angle (> 60º) normal faults dipping both south and north. This is consistent with fault plane solutions of stronger earthquakes. The largest amount of earthquakes is generated along the NW-SE sub-basin bounded from "Assiros-Analipsi" and "Lagina" fault zone, as well as in "Sochos" fault in the north which dips with approximately 70º-80º to the south. All these structures played an important role in the seismotectonic evolution of the area. We used geomorphic indices in order to analyse the landscapes of the Mygdonia region. Geomorphic indices were derived from DEM and computed using MATLAB scripts. We classified the landscapes according to their erosional stages using hypsometric integral and surface roughness. Both indices suggest stronger erosion

Surface deformation analysis over Vrancea seismogenic area through radar and GPS geospatial data

NASA Astrophysics Data System (ADS)

Zoran, Maria A.; Savastru, Roxana S.; Savastru, Dan M.; Serban, Florin S.; Teleaga, Delia M.; Mateciuc, Doru N.

2017-10-01

Time series analysis of GPS (Global Positioning Systems) and InSAR (Interferometric Synthetic Aperture Radar) data are important tools for Earth's surface deformation assessment, which can result from a wide range of geological phenomena like as earthquakes, landslides or ground water level changes. The aim of this paper was to identify several types of earthquake precursors that might be observed from geospatial data in Vrancea seismogenic region in Romania. Continuous GPS Romanian network stations and few field campaigns data recorded between 2005-2012 years revealed a displacement of about 5 or 6 millimeters per year in horizontal direction relative motion, and a few millimeters per year in vertical direction. In order to assess possible deformations due to earthquakes and respectively for possible slow deformations, have been used also time series Sentinel 1 satellite data available for Vrancea zone during October 2014 till October 2016 to generate two types of interferograms (short-term and medium- term). During investigated period were not recorded medium or strong earthquakes, so interferograms over test area revealed small displacements on vertical direction (subsidence or uplifts) of 5-10 millimeters per year. Based on GPS continuous network data and satellite Sentinel 1 results, different possible tectonic scenarios were developed. The localization of horizontal and vertical motions, fault slip, and surface deformation of the continental blocks provides new information, in support of different geodynamic models for Vrancea tectonic active region in Romania and Europe.

Inherited structures impact on co-seismic surface deformation pattern during the 2013 Balochistan, Pakistan, earthquake

NASA Astrophysics Data System (ADS)

Vallage, Amaury; Klinger, Yann; Grandin, Raphael; Delorme, Arthur; Pierrot-Deseilligny, Marc

2016-04-01

The understanding of earthquake processes and the interaction of earthquake rupture with Earth's free surface relies on the resolution of the observations. Recent and detailed post-earthquake measurements bring new insights on shallow mechanical behavior of rupture processes as it becomes possible to measure and locate surficial deformation distribution. The 2013 Mw 7.7 Balochistan earthquake, Pakistan, offers a nice opportunity to comprehend where and why surficial deformation might differs from at-depth localized slip. This earthquake ruptured the Hoshab fault over 200 km; the motion was mainly left lateral with a small and discontinuous vertical component in the southern part of the rupture. Using images with the finest resolution currently available, we measured the surface displacement amplitude and its orientation at the ground surface (including the numerous tensile cracks). We combined these measurements with the 1:500 scale ground rupture map to focus on the behavior of the frontal rupture in the area where deformation distributes. Comparison with orientations of inherited tectonic structures, visible in older rocks formation surrounding the actual 2013 rupture, shows the control exercised by such structures on co-seismic rupture distribution. Such observation raises the question on how pre-existing tectonic structures in a medium, mapped in several seismically active places around the globe; can control the co-seismic distribution of the deformation during earthquakes.

Workshop on the Tectonic Evolution of Greenstone Belts (supplement containing abstracts of invited talks and late abstracts)

NASA Technical Reports Server (NTRS)

1986-01-01

Topics addressed include: greenstone belt tectonics, thermal constaints, geological structure, rock components, crustal accretion model, geological evolution, synsedimentary deformation, Archean structures and geological faults.

Resolving the tectonic transition between ancestral North America and the northern Cordillera

NASA Astrophysics Data System (ADS)

Schaeffer, A. J.; Audet, P.; Lebedev, S.

2015-12-01

The northern Cordillera, situated in the Canadian northwest, is one of the most actively deforming regions in Canada and host to the highest earthquake activity in the country. Furthermore, it presents a largely contiguous snapshot through almost 4 Gyr of Earth's history across a zone <2000 km in linear extent. Deformation is thought to be driven by tectonic forces transferred from the Alaska-Pacific plate collision eastwards to the Cordilleran Deformation Front (CDF), where the westward edge of the Canadian Shield acts as a rigid backstop. Past studies in the southern Yukon indicate a sharp transition into the craton underlying the CDF and evidence of craton growth through shallow subduction. Further north the proximity of the craton edge to the CDF remains largely unresolved; based on studies of the southern Cordillera and Alaska, significant variations in lithospheric architecture are expected. Additionally, significant seismicity is observed further north off the Beaufort Shelf; however, its relationship to the regional stress fields and associated tectonic forcing is unclear. Despite the high seismicity levels across, detailed study of this region has been limited by insufficient coverage of seismological infrastructure, hindering resolution in past models. With the deployment of the USArray Transportable Array in Alaska over the last several years, combined with regional arrays such as the Yukon-Northwest Seismic Network (YNSN), Banks Island Seismic Network (BISN) and Mackenzie Mountains Experiment, new studies will leverage these datasets enabling more detailed imaging of the structure and seismicity across the region. Here we present a new high-resolution, vertically polarized shear speed and azimuthal model of northwestern Canada and Alaska, constrained by vertical component seismogram fits computed using the Automated Multimode Inversion of Surface, S, and multiple-S waveforms. With this new model, we aim to address key questions relating to the dynamics

Tectonic inheritance, reactivation and long term fault weakening processes

NASA Astrophysics Data System (ADS)

Holdsworth, Bob

2017-04-01

This talk gives a geological review of weakening processes in faults and their long-term effect on reactivation and tectonic inheritance during crustal deformation. Examples will be drawn from the Atlantic margins, N America, Japan and the Alps. Tectonic inheritance and reactivation are fundamentally controlled by the processes of stress concentration and shear localisation manifested at all scales in the continental lithosphere. Lithosphere-scale controls include crustal thickness, thermal age and the boundary conditions imposed by the causative plate tectonic processes during extension. At the other end of the scale range, grain-scale controls include local environmental controls (depth, stress, strain rate), rock composition, grainsize, fabric intensity and the presence of fluids or melt. Intermediate-scale geometric controls are largely related to the size, orientation and interconnectivity of pre-existing anisotropies. If reactivation of pre-existing structures occurs, it likely requires a combination of processes across all three scale ranges to be favourable. This can make the unequivocal recognition of inheritance and reactivation difficult. Large (e.g. crustal-scale) pre-existing structures are especially important due to their ability to efficiently concentrate stress and localise strain. For big faults (San Andreas, Great Glen, Median Tectonic Line), detailed studies of the associated exposed fault rocks indicate that reactivation is linked to the development of strongly anisotropic phyllosilicate-rich fault rocks that are weak (e.g. friction coefficients as low as 0.2 or less) under a broad range of deformation conditions. In the case of pre-existing regional dyke swarms (S Atlantic, NW Scotland) - which may themselves track deep mantle fabrics at depth - multiple reactivation of dyke margins is widespread and may preclude reactivation of favourably oriented local basement fabrics. In a majority of cases, pre-existing structures in the crust are

Diffuse Extension of the Southern Mariana Margin: Implications for Subduction Zone Infancy and Plate Tectonics

NASA Astrophysics Data System (ADS)

Martinez, F.; Stern, R. J.; Kelley, K. A.; Ohara, Y.; Sleeper, J. D.; Ribeiro, J. M.; Brounce, M. N.

2017-12-01

Opening of the southern Mariana margin takes place in contrasting modes: Extension normal to the trench forms crust that is passively accreted to a rigid Philippine Sea plate and forms along focused and broad accretion axes. Extension also occurs parallel to the trench and has split apart an Eocene-Miocene forearc terrain accreting new crust diffusely over a 150-200 km wide zone forming a pervasive volcano-tectonic fabric oriented at high angles to the trench and the backarc spreading center. Earthquake seismicity indicates that the forearc extension is active over this broad area and basement samples date young although waning volcanic activity. Diffuse formation of new oceanic crust and lithosphere is unusual; in most oceanic settings extension rapidly focuses to narrow plate boundary zones—a defining feature of plate tectonics. Diffuse crustal accretion has been inferred to occur during subduction zone infancy, however. We hypothesize that, in a near-trench extensional setting, the continual addition of water from the subducting slab creates a weak overriding hydrous lithosphere that deforms broadly. This process counteracts mantle dehydration and strengthening proposed to occur at mid-ocean ridges that may help to focus deformation and melt delivery to narrow plate boundary zones. The observations from the southern Mariana margin suggest that where lithosphere is weakened by high water content narrow seafloor spreading centers cannot form. These conditions likely prevail during subduction zone infancy, explaining the diffuse contemporaneous volcanism inferred in this setting.

Tertiary tectonic in the Tehuantepec Isthmus, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez, F.A.

1993-02-01

A microplate model in the basement was proposed according to photointerpretation of satellite imagery and supported with microtectonic studies in the Tehuantepec's Isthmus. The microplate is located in the northwestern part of the [open quotes]Sierra de Chiapas,[close quotes] and structurally has lineaments that correspond with sinestral wrench faults oriented northeast-southwest and dextral faults oriented northwest-southeast. In the front of the microplate, these faults are joined in an arc form. The microplate began its movement forward to the north in the middle Tertiary. This movement originated in a regional compressional stress that was younger to the north. The stress changed themore » orientation of the anticline axis from northwest-southeast to west-east. In its western limit, the stress produces a sinestral shear stress that built a rotational deformation in the [open quotes]Sierra Atravesada,[close quotes] and represents a superimposed tectonic block over an ancient (laramide) orogeny. This system has also produced other secondary transtensional effects oriented northwest-southeast, represented along the [open quotes]Depression Central del Istmo.[close quotes] The microplate has formed a tensional system opening the [open quotes]Superior, Inferior, and Mar Muerto[close quotes] lagoons. The microplate is strongly related with the relief, seismic activity, and the tectonics of the salt of the Tehuantepec's Isthmus.« less

Neotectonic deformation in Tunisia (North of the African plate)

NASA Astrophysics Data System (ADS)

Soumaya, Abdelkader; Ben Ayed, Noureddine; Kadri, Ali; Delvaux, Damien; Khayati Ammar, Hayet; Braham, Ahmed

2017-04-01

In Tunisia, at the extreme North of the African plate, the neotectonic context is largely influenced by the Eurasia-Africa convergence. The aim of this work is to characterize the neotectonic regime that affected this region during Quaternary. Field work investigations integrated with published data allowed to evidence a spatial-temporal variation of the tectonic stress regime during this period. The spatial repartition of the different types of Quaternary to historical deformation shows a North-South neotectonic zoning in Tunisia. After lower Pleistocene, the Tellian domain (Maghrebides) in the North and its Atlassic foreland in central Tunisia are affected by NNW-SSE compression. It generated E-W to NE-SW folds and reverse faults, well developed in the Plio-Quaternary molassic basins of Kechabta and Jendouba (Northern Tunisia). In the Atlas, the major E-W and N-S pre-existing faults have been reactivated with dextral and sinistral strike-slip kinematic respectively, associated to en-echelon folds (Kasserine, N-S Axis, Northern Chott belt...). After the Tyrrhenian, a submeridian compressional regime affected Northern Tunisia (e.g., Bizerte region) and was responsible for the E-W folding of marine strata. More to the South, in the Tunisian Sahel, transtensional tectonics with a NW-SE horizontal maximal compression (SHmax) deformed the Tyrrhenian marine series (Khénis, Skanès, Monastir…). During the Holocene and up to present-day times, N-S compressional tectonics reactivated the E-W pre-existing faults with a reverse movement in Northern Tunisia (Bulla Regia, Utica …), generating historical earthquakes. In Central Tunisia, the Aqueduct of Cherichira (built around AD 850) is displaced by a N-S normal fault. Similarly, a mosaic of a roman house is shifted by 10 cm, along a N-S sinistral normal fault. These deformations evidence a transtensional tectonic regime. During the Quaternary, all the NW-SE oriented grabens are subsiding (e.g., Bizerte Lake, Grombalia

Deformation Mechanisms of Darreh Sary Metapelites, Sanandaj‒Sirjan Zone, Iran

NASA Astrophysics Data System (ADS)

Hemmati, O.; Tabatabaei Manesh, S. M.; Nadimi, A. R.

2018-03-01

The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275-375, 375-500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed.

Tectonic evolution of the outer Izu-Bonin-Mariana fore arc system: initial results from IODP Expedition 352

NASA Astrophysics Data System (ADS)

Kurz, W.; Ferre, E. C.; Robertson, A. H. F.; Avery, A. J.; Kutterolf, S.

2015-12-01

During International Ocean Discovery Program (IODP) Expedition 352, a section through the volcanic stratigraphy of the outer fore arc of the Izu-Bonin-Mariana (IBM) system was drilled to trace magmatism, tectonics, and crustal accretion associated with subduction initiation. Structures within drill cores, borehole and site survey seismic data indicate that tectonic deformation in the outer IBM fore arc is mainly post-magmatic. Extension generated asymmetric sediment basins such as half-grabens at sites 352-U1439 and 352-U1442 on the upper trench slope. Along their eastern margins the basins are bounded by west-dipping normal faults. Deformation was localized along multiple sets of faults, accompanied by syn-tectonic pelagic and volcaniclastic sedimentation. The lowermost sedimentary units were tilted eastward by ~20°. Tilted beds were covered by sub-horizontal beds. Biostratigraphic constraints reveal a minimum age of the oldest sediments at ~ 35 Ma; timing of the sedimentary unconformities is between ~ 27 and 32 Ma. At sites 352-U1440 and 352-U1441 on the outer fore arc strike-slip faults are bounding sediment basins. Sediments were not significantly affected by tectonic tilting. Biostratigraphy gives a minimum age of the basement-cover contact between ~29.5 and 32 Ma. The post-magmatic structures reveal a multiphase tectonic evolution of the outer IBM fore arc. At sites 352-U1439 and 352-U1442, shear with dominant reverse to oblique reverse displacement was localized along subhorizontal fault zones, steep slickensides and shear fractures. These were either re-activated as or cut by normal-faults and strike-slip faults. Extension was also accommodated by steep to subvertical mineralized veins and extensional fractures. Faults at sites 352-U1440 and 352-U1441 show mainly strike-slip kinematics. Sediments overlying the igneous basement(maximum Late Eocene to Recent age), document ash and aeolian input, together with mass wasting of the fault-bounded sediment ponds.

Interpretation of remagnetization directions by Small Circle methods. Application to various tectonic problems

NASA Astrophysics Data System (ADS)

José Villalaín, Juan; Casas, Antonio; Calvín, Pablo; Soto-Marín, Ruth; Torres, Sara; Moussaid, Bennacer

2017-04-01

Secondary magnetizations have been used to constraint geological models in spite of the difficulties of dating the remanence age and the uncertainty in applying the valid tectonic correction, specially if the remagnetization is syntectonic. The fold test is the main tool used traditionally to identify and interpret remagnetization. In particular, the incremental fold test has been applied to attempt calculating the appropriate tectonic correction in synfolding remanences. However the fold test assumes symmetrical deformation giving erroneous solutions when dealing with asymmetrical folding. This strongly limits the use of the fold test because asymmetric tectonic evolution is very common in different geological processes. Therefore, it is necessary to use alternative techniques for analyzing remagnetization directions. In this sense, the use of small circles (SC) represents a very interesting option because it allows considering asymmetric deformations and degrees of freedom which fold test restricts. A SC is defined by a complete rotation of the in situ site mean paleomagnetic direction about the strike of bedding (i.e. the apical angle of its cone is the angle between the paleomagnetic vector and the strike of beds). In this presentation we analyze the use of SC for analysis of remagnetization directions in two phases: a) determination of the magnetic field direction at the remagnetization acquisition time by calculating the SC intersection (SCI) by methods described by Shipunov (1997) or Waldhör and Appel (2006). This obtained direction can be used to date the remagnetization by comparison with the APWP, but also as reference direction for restoration of the rotated remagnetization directions. And b) calculation of the bedding plane at the moment of the acquisition of the remagnetization (paleodip) by restoring the in situ remagnetization directions using each SC as described Villalaín et al. (2003), Henry et al. (2004) and Villalaín et al. (2015). In this

Contemporary tectonic deformation of the Basin and Range province, western United States: 10 years of observation with the Global Positioning System

USGS Publications Warehouse

Hammond, W.C.; Thatcher, W.

2004-01-01

We have estimated patterns and rates of crustal movement across 800 km of the Basin and Range at ???39?? north latitude with Global Positioning System surveys in 1992, 1996, 1998, and 2002. The total rate of motion tangent to the small circle around the Pacific-North America pole of rotation is 10.4 ?? 1.0 mm/yr, and motion normal to this small circle is 3.9 ?? 0.9 mm/yr compared to the east end of our network. On the Colorado Plateau the east end of our network moves by ???1-2 mm/yr westerly with respect to North America. Transitions in strain rates delimit six major tectonic domains within the province. These deformation zones coincide with areas of modern seismicity and are, from east to west, (1) east-west extension in the Wasatch Fault zone, (2) low rate east-west extension centered near the Nevada-Utah border, (3) low rate east-west contraction between 114.7??W and 117.9??W, (4) extension normal to and strike-slip motion across the N10??E striking Central Nevada Seismic Zone, (5) right lateral simple shear oriented N13??W inside the Walker Lane Belt, and (6) shear plus extension near the Sierra Nevada frontal faults. Concentration of shear and dilatational deformation across the three westernmost zones suggests that the Walker Lane Belt lithosphere is rheologically weak. However, we show that linear gradients in viscosity and gravitational potential energy can also effectively concentrate deformation. In the Basin and Range, gradients in gravitational potential are spatially anticorrelated with dilatational strain rates, consistent with the presence of horizontal variations in viscosity of the lithosphere.

Multi-type Tectonic Responses to Plate Motion Changes of Mega-Offset Transform Faults at the Pacific-Antarctic Ridge

NASA Astrophysics Data System (ADS)

Zhang, F.; Lin, J.; Yang, H.; Zhou, Z.

2017-12-01

Magmatic and tectonic responses of a mid-ocean ridge system to plate motion changes can provide important constraints on the mechanisms of ridge-transform interaction and lithospheric properties. Here we present new analysis of multi-type responses of the mega-offset transform faults at the Pacific-Antarctic Ridge (PAR) system to plate motion changes in the last 12 Ma. Detailed analysis of the Heezen, Tharp, and Udintsev transform faults showed that the extensional stresses induced by plate motion changes could have been released through a combination of magmatic and tectonic processes: (1) For a number of ridge segments with abundant magma supply, plate motion changes might have caused the lateral transport of magma along the ridge axis and into the abutting transform valley, forming curved "hook" ridges at the ridge-transform intersection. (2) Plate motion changes might also have caused vertical deformation on steeply-dipping transtensional faults that were developed along the Heezen, Tharp, and Udintsev transform faults. (3) Distinct zones of intensive tectonic deformation, resembling belts of "rift zones", were found to be sub-parallel to the investigated transform faults. These rift-like deformation zones were hypothesized to have developed when the stresses required to drive the vertical deformation on the steeply-dipping transtensional faults along the transform faults becomes excessive, and thus deformation on off-transform "rift zones" became favored. (4) However, to explain the observed large offsets on the steeply-dipping transtensional faults, the transform faults must be relatively weak with low apparent friction coefficient comparing to the adjacent lithospheric plates.

Lunar seismicity and tectonics

NASA Technical Reports Server (NTRS)

Lammlein, D. R.

1977-01-01

Results are presented for an analysis of all moonquake data obtained by the Apollo seismic stations during the period from November 1969 to May 1974 and a preliminary analysis of critical data obtained in the interval from May 1974 to May 1975. More accurate locations are found for previously located moonquakes, and additional sources are located. Consideration is given to the sources of natural seismic signals, lunar seismic activity, moonquake periodicities, tidal periodicities in moonquake activity, hypocentral locations and occurrence characteristics of deep and shallow moonquakes, lunar tidal control over moonquakes, lunar tectonism, the locations of moonquake belts, and the dynamics of the lunar interior. It is concluded that: (1) moonquakes are distributed in several major belts of global extent that coincide with regions of the youngest and most intense volcanic and tectonic activity; (2) lunar tides control both the small quakes occurring at great depth and the larger quakes occurring near the surface; (3) the moon has a much thicker lithosphere than earth; (4) a single tectonic mechanism may account for all lunar seismic activity; and (5) lunar tidal stresses are an efficient triggering mechanism for moonquakes.

Centimeter-scale surface deformation caused by the 2011 Mineral, Virginia, earthquake sequence at the Carter farm site—Subsidiary structures with a quaternary history

USGS Publications Warehouse

Harrison, Richard W.; Schindler, J. Stephen; Pavich, Milan J.; Horton, J. Wright; Carter, Mark W.

2016-08-25

non-tectonic model are considered: (1) tectonic, monoclinal flexuring along the Carter farm fault, probably aseismic, (2) tectonic, monoclinal flexuring related to a shallow (1–3 km) cluster of aftershocks (M2 to M3) that occurred approximately 1 to 1.5 km to the east of Carter farm, and (3) non-tectonic, differential response to seismic shaking between more-rigid quartz veins and soft residuum-saprolite under vertical motions that were created by Rayleigh surface waves radiating away from the August 23, 2011, hypocenter and propagating along strike of the Carter farm fault. These processes are not considered mutually exclusive, and all three support brittle deformation on the Carter farm fault during the Quaternary. In addition, abandoned stream valleys and active stream piracy are consistent with long-term uplift in vicinity of the Carter farm fault.

Drainage basin and topographic analysis of a tropical landscape: Insights into surface and tectonic processes in northern Borneo

NASA Astrophysics Data System (ADS)

Mathew, Manoj Joseph; Menier, David; Siddiqui, Numair; Ramkumar, Mu.; Santosh, M.; Kumar, Shashi; Hassaan, Muhammad

2016-07-01

We investigated the recent landscape development of Borneo through geomorphic analysis of two large drainage basins (Rajang and Baram basins). The extraction of morphometric parameters utilizing digital terrain data in a GIS environment, focusing on hydrography (stream length-gradient index, ratio of valley floor width to valley height, and transverse topographic symmetry factor) and topography (local relief and relief anomaly), was carried out in order to elucidate processes governing drainage and landscape evolution. Anomalously high and low values of stream length-gradient indices of main tributary streams associated with faults and multiple knick-points along the channel profiles are linked to deformation events. The development of deeply incised V-shaped valleys show enhanced incision capability of streams in response to steepening of hillslope gradients following tectonic inputs. Deflection of streams and probable dynamic reorganization of the drainage system through stream capture processes as feedbacks to tectonic uplift and orographic effect are observed. Local relief and relief anomaly maps highlight the presence of preserved elevation-accordant relict portions of landscapes characterized by low amplitude relief, nested between ridgelines in regions of complex folding. Our results reveal dynamic geomorphic adjustment of the landscape due to perturbations in tectonic and climatic boundary conditions. The implication is that the landscape of north Borneo experienced a tectonic phase of rapid uplift after 5 Ma and undergoes active folding of the Rajang Group thrust belts in the present-day. Active shortening combined with high rates of denudation in Sarawak, demonstrates transience emphasized by the drainage system attempting to adjust to tectonic and climatic forcing.

Soft sediment deformation structures in the Maastrichtian Ajali Formation Western Flank of Anambra Basin, Southern Nigeria

NASA Astrophysics Data System (ADS)

Olabode, Solomon Ojo

2014-01-01

Soft sediment deformation structures were recognized in the Maastrichtian shallow marine wave to tide influenced regressive sediments of Ajali Formation in the western flank of Anambra basin, southern Nigerian. The soft sediment deformation structures were in association with cross bedded sands, clay and silt and show different morphological types. Two main types recognised are plastic deformations represented by different types of recumbent folds and injection structure represented by clastic dykes. Other structures in association with the plastic deformation structures include distorted convolute lamination, subsidence lobes, pillars, cusps and sand balls. These structures are interpreted to have been formed by liquefaction and fluidization mechanisms. The driving forces inferred include gravitational instabilities and hydraulic processes. Facies analysis, detailed morphologic study of the soft sediment deformation structures and previous tectonic history of the basin indicate that the main trigger agent for deformation is earthquake shock. The soft sediment deformation structures recognised in the western part of Anambra basin provide a continuous record of the tectonic processes that acted on the regressive Ajali Formation during the Maastrichtian.

History and Evolution of Precambrian plate tectonics

NASA Astrophysics Data System (ADS)

Fischer, Ria; Gerya, Taras

2014-05-01

Plate tectonics is a global self-organising process driven by negative buoyancy at thermal boundary layers. Phanerozoic plate tectonics with its typical subduction and orogeny is relatively well understood and can be traced back in the geological records of the continents. Interpretations of geological, petrological and geochemical observations from Proterozoic and Archean orogenic belts however (e.g., Brown, 2006), suggest a different tectonic regime in the Precambrian. Due to higher radioactive heat production the Precambrian lithosphere shows lower internal strength and is strongly weakened by percolating melts. The fundamental difference between Precambrian and Phanerozoic tectonics is therefore the upper-mantle temperature, which determines the strength of the upper mantle (Brun, 2002) and the further tectonic history. 3D petrological-thermomechanical numerical modelling experiments of oceanic subduction at an active plate at different upper-mantle temperatures show these different subduction regimes. For upper-mantle temperatures < 175 K above the present day value a subduction style appears which is close to present day subduction but with more frequent slab break-off. At upper-mantle temperatures 175 - 250 K above present day values steep subduction continues but the plates are weakened enough to allow buckling and also lithospheric delamination and drip-offs. For upper-mantle temperatures > 250 K above the present day value no subduction occurs any more. The whole lithosphere is delaminating and due to strong volcanism and formation of a thicker crust subduction is inhibited. This stage of 200-250 K higher upper mantle temperature which corresponds roughly to the early Archean (Abbott, 1994) is marked by strong volcanism due to sublithospheric decompression melting which leads to an equal thickness for both oceanic and continental plates. As a consequence subduction is inhibited, but a compressional setup instead will lead to orogeny between a continental

Analysis of the Tectonic Lineaments in the Ganiki Planitia (V14) Quadrangle, Venus

NASA Technical Reports Server (NTRS)

Venechuk, E. M.; Hurwitz, D. M.; Drury, D. E.; Long, S. M.; Grosfils, E. B.

2005-01-01

The Ganiki Planitia quadrangle, located between the Atla Regio highland to the south and the Atalanta Planitia lowland to the north, is deformed by many tectonic lineaments which have been mapped previously but have not yet been assessed in detail. As a result, neither the characteristics of these lineaments nor their relationship to material unit stratigraphy is well constrained. In this study we analyze the orientation of extensional and compressional lineaments in all non-tessera areas in order to begin characterizing the dominant tectonic stresses that have affected the region.

Viscous relaxation as a prerequisite for tectonic resurfacing on Ganymede: Insights from numerical models of lithospheric extension

USGS Publications Warehouse

Bland, Michael T.; McKinnon, William B.

2018-01-01

Ganymede’s bright terrain formed during a near-global resurfacing event (or events) that produced both heavily tectonized and relatively smooth terrains. The mechanism(s) by which resurfacing occurred on Ganymede (e.g., cryovolcanic or tectonic), and the relationship between the older, dark and the younger, bright terrain are fundamental to understanding the geological evolution of the satellite. Using a two-dimensional numerical model of lithospheric extension that has previously been used to successfully simulate surface deformation consistent with grooved terrain morphologies, we investigate whether large-amplitude preexisting topography can be resurfaced (erased) by extension (i.e., tectonic resurfacing). Using synthetically produced initial topography, we show that when the total relief of the initial topography is larger than 25–50 m, periodic groove-like structures fail to form. Instead, extension is localized in a few individual, isolated troughs. These results pose a challenge to the tectonic resurfacing hypothesis. We further investigate the effects of preexisting topography by performing suites of simulations initialized with topography derived from digital terrain models of Ganymede’s surface. These include dark terrain, fresh (relatively deep) impact craters, smooth bright terrain, and a viscously relaxed impact crater. The simulations using dark terrain and fresh impact craters are consistent with our simulations using synthetic topography: periodic groove-like deformation fails to form. In contrast, when simulations were initialized with bright smooth terrain topography, groove-like deformation results from a wide variety of heat flow and surface temperature conditions. Similarly, when a viscously relaxed impact crater was used, groove-like structures were able to form during extension. These results suggest that tectonic resurfacing may require that the amplitude of the initial topography be reduced before extension begins. We emphasize that

Viscous relaxation as a prerequisite for tectonic resurfacing on Ganymede: Insights from numerical models of lithospheric extension

NASA Astrophysics Data System (ADS)

Bland, Michael T.; McKinnon, William B.

2018-05-01

Ganymede's bright terrain formed during a near-global resurfacing event (or events) that produced both heavily tectonized and relatively smooth terrains. The mechanism(s) by which resurfacing occurred on Ganymede (e.g., cryovolcanic or tectonic), and the relationship between the older, dark and the younger, bright terrain are fundamental to understanding the geological evolution of the satellite. Using a two-dimensional numerical model of lithospheric extension that has previously been used to successfully simulate surface deformation consistent with grooved terrain morphologies, we investigate whether large-amplitude preexisting topography can be resurfaced (erased) by extension (i.e., tectonic resurfacing). Using synthetically produced initial topography, we show that when the total relief of the initial topography is larger than 25-50 m, periodic groove-like structures fail to form. Instead, extension is localized in a few individual, isolated troughs. These results pose a challenge to the tectonic resurfacing hypothesis. We further investigate the effects of preexisting topography by performing suites of simulations initialized with topography derived from digital terrain models of Ganymede's surface. These include dark terrain, fresh (relatively deep) impact craters, smooth bright terrain, and a viscously relaxed impact crater. The simulations using dark terrain and fresh impact craters are consistent with our simulations using synthetic topography: periodic groove-like deformation fails to form. In contrast, when simulations were initialized with bright smooth terrain topography, groove-like deformation results from a wide variety of heat flow and surface temperature conditions. Similarly, when a viscously relaxed impact crater was used, groove-like structures were able to form during extension. These results suggest that tectonic resurfacing may require that the amplitude of the initial topography be reduced before extension begins. We emphasize that viscous

Geomorphology and Neogene tectonic evolution of the Palomares continental margin (Western Mediterranean)

NASA Astrophysics Data System (ADS)

Gómez de la Peña, Laura; Gràcia, Eulàlia; Muñoz, Araceli; Acosta, Juan; Gómez-Ballesteros, María; R. Ranero, César; Uchupi, Elazar

2016-10-01

The Palomares continental margin is located in the southeastern part of Spain. The margin main structure was formed during Miocene times, and it is currently part of the wide deformation zone characterizing the region between the Iberian and African plates, where no well-defined plate boundary occurs. The convergence between these two plates is here accommodated by several structures, including the left lateral strike-slip Palomares Fault. The region is characterized by sparse, low to moderate magnitude (Mw < 5.2) shallow instrumental earthquakes, although large historical events have also occurred. To understand the recent tectonic history of the margin we analyze new high-resolution multibeam bathymetry data and re-processed three multichannel seismic reflection profiles crossing the main structures. The analysis of seafloor morphology and associated subsurface structure provides new insights of the active tectonic features of the area. In contrast to other segments of the southeastern Iberian margin, the Palomares margin contains numerous large and comparatively closely spaced canyons with heads that reach near the coast. The margin relief is also characterized by the presence of three prominent igneous submarine ridges that include the Aguilas, Abubacer and Maimonides highs. Erosive processes evidenced by a number of scars, slope failures, gullies and canyon incisions shape the present-day relief of the Palomares margin. Seismic images reveal the deep structure distinguishing between Miocene structures related to the formation of the margin and currently active features, some of which may reactivate inherited structures. The structure of the margin started with an extensional phase accompanied by volcanic accretion during the Serravallian, followed by a compressional pulse that started during the Latemost Tortonian. Nowadays, tectonic activity offshore is subdued and limited to few, minor faults, in comparison with the activity recorded onshore. The deep Algero

Active crustal deformation of the El Salvador Fault Zone (ESFZ) using GPS data: Implications in seismic hazard assessment

NASA Astrophysics Data System (ADS)

Staller, Alejandra; Benito, Belen; Jesús Martínez-Díaz, José; Hernández, Douglas; Hernández-Rey, Román; Alonso-Henar, Jorge

2014-05-01

El Salvador, Central America, is part of the Chortis block in the northwestern boundary of the Caribbean plate. This block is interacting with a diffuse triple junction point with the Cocos and North American plates. Among the structures that cut the Miocene to Pleistocene volcanic deposits stands out the El Salvador Fault Zone (ESFZ): It is oriented in N90º-100ºE direction, and it is composed of several structural segments that deform Quaternary deposits with right-lateral and oblique slip motions. The ESFZ is seismically active and capable of producing earthquakes such as the February 13, 2001 with Mw 6.6 (Martínez-Díaz et al., 2004), that seriously affected the population, leaving many casualties. This structure plays an important role in the tectonics of the Chortis block, since its motion is directly related to the drift of the Caribbean plate to the east and not with the partitioning of the deformation of the Cocos subduction (here not coupled) (Álvarez-Gómez et al., 2008). Together with the volcanic arc of El Salvador, this zone constitutes a weakness area that allows the motion of forearc block toward the NW. The geometry and the degree of activity of the ESFZ are not studied enough. However their knowledge is essential to understand the seismic hazard associated to this important seismogenic structure. For this reason, since 2007 a GPS dense network was established along the ESFZ (ZFESNet) in order to obtain GPS velocity measurements which are later used to explain the nature of strain accumulation on major faults along the ESFZ. The current work aims at understanding active crustal deformation of the ESFZ through kinematic model. The results provide significant information to be included in a new estimation of seismic hazard taking into account the major structures in ESFZ.

Partitioning of deformation along a reactivated rifted margin: example of the northern Ligurian margin.

NASA Astrophysics Data System (ADS)

Sage, Françoise; Beslier, Marie-Odile; Gaullier, Virginie; Larroque, Christophe; Dessa, Jean-Xavier; Mercier de Lepinay, Bernard; Corradi, Nicola; Migeon, Sébastien; Katz, Hélène; Ruiz Constan, Ana

2013-04-01

The northern Ligurian margin, of Oligo-Miocene age, is currently undergoing compression related to microplate motions and/or to gravity spreading of the Alpine chain located immediately north of it. Active thrust faults and folds have previously been identified below the margin, together with a global uplift of the continental edge, since at least the Messinian. The seismicity that goes with the present-day margin contraction (e.g. Mw 6.9, 1887/02/23) extends to the axis of the adjacent oceanic basin (e.g. ML 6.0, 1963/07/19; ML 5.4, 2011/07/07). However, we do not know of any recent or active crustal contractional structure within this oceanic domain. In this study, we use new 12-channel high-resolution seismic data (FABLES seismic cruise, 2012, R/V Tethys II) in order to image the sedimentary cover of the Ligurian oceanic basin, up to ~3km below the seabed, including the Plio-Quaternary and the Messinian sediment down to the bottom of the Messinian salt layer. Because the Messinian event is well dated (5.96-5.32 Ma) and well identified in the seismic data, it forms a clear marker that we use to characterize the recent deformation related to both mobile salt motion and crustal tectonics. About 50 km south of the margin offshore of Italy, we identify huge and complex salt walls that elongate SW-NE. Such salt walls, which cannot be explained by salt tectonics only, are interpreted as evidence of deep-seated crustal deformation. They form en echelon structures that are well expressed in the seabed morphology, and do not correspond to any significant vertical throw at the base of the salt layer. This suggests that within the deep basin, mainly strike-slip faulting accommodates long-term crustal deformation. It thus offers a contrast with the margin where deformation is mainly marked by shortening and reverse faulting, with vertical throws of several hundred meters. This discrepancy in the tectonic styles between the margin and the adjacent oceanic basin suggests some

Seismicity and active tectonics in the Alboran Sea, Western Mediterranean: Constraints from an offshore-onshore seismological network and swath bathymetry data

NASA Astrophysics Data System (ADS)

Grevemeyer, Ingo; Gràcia, Eulàlia; Villaseñor, Antonio; Leuchters, Wiebke; Watts, Anthony B.

2015-12-01

Seismicity and tectonic structure of the Alboran Sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in Spain and Morocco, an area where the convergence between the African and Eurasian plates causes distributed deformation. Crustal structure derived from local earthquake data suggests that the Alboran Sea is underlain by thinned continental crust with a mean thickness of about 20 km. During the 5 months of offshore network operation, a total of 229 local earthquakes were located within the Alboran Sea and neighboring areas. Earthquakes were generally crustal events, and in the offshore domain, most of them occurred at crustal levels of 2 to 15 km depth. Earthquakes in the Alboran Sea are poorly related to large-scale tectonic features and form a 20 to 40 km wide NNE-SSW trending belt of seismicity between Adra (Spain) and Al Hoceima (Morocco), supporting the case for a major left-lateral shear zone across the Alboran Sea. Such a shear zone is in accord with high-resolution bathymetric data and seismic reflection imaging, indicating a number of small active fault zones, some of which offset the seafloor, rather than supporting a well-defined discrete plate boundary fault. Moreover, a number of large faults known to be active as evidenced from bathymetry, seismic reflection, and paleoseismic data such as the Yusuf and Carboneras faults were seismically inactive. Earthquakes below the Western Alboran Basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere.

Grabens on Io: Evidence for Extensional Tectonics

NASA Astrophysics Data System (ADS)

Hoogenboom, T.; Schenk, P.

2012-12-01

Io may well be the most geologically active body in the solar system. A variety of volcanic features have been identified, including a few fissure eruptions, but tectonism is generally assumed to be limited to compression driven mountain formation (Schenk et al., 2001). A wide range of structural features can also be identified including scarps, lineaments, faults, and circular depressions (pits and patera rims). Narrow curvilinear graben (elongated, relatively depressed crustal unit or block that is bounded by faults on its sides) are also scattered across Io's volcanic plains. These features are dwarfed by the more prominent neighboring volcanoes and mountains, and have been largely ignored in the literature. Although they are likely to be extensional in origin, their relationship to local or global stress fields is unknown. We have mapped the locations, length and width of graben on Io using all available Voyager and Galileo images with a resolution better than 5 km. We compare the locations of graben with existing volcanic centers, paterae and mountain data to determine the degree of correlation between these geologic features and major topographic variations (basins/swells) in our global topographic map of Io (White et al., 2011). Graben are best observed in > 1-2 km low-sun angle images. Approximately 300 images were converted from ISIS to ArcMap format to allow easy comparison with the geological map of Io (Williams et al., 2012) along with previous higher resolution structural mapping of local areas (e.g. Crown et al., 1992). We have located >45 graben to date. Typically 1-3 kilometers across, some of these features can stretch for over 500 kilometers in length. Their formation may be related to global tidal stresses or local deformation. Io's orbit is eccentric and its solid surface experiences daily tides of up to ˜0.1 km, leading to repetitive surface strains of 10-4 or greater. These tides flex and stress the lithosphere and can cause it to fracture

Determination of tectonic shortening rates from progressively deformed flights of terraces above the Chelungpu and Changhua thrust ramps, Taiwan

NASA Astrophysics Data System (ADS)

Yue, L.; Suppe, J.

2007-12-01

The Chelungpu and Changhua thrust ramps in central Taiwan show contrasting hanging-wall structural geometries that suggest different kinematics, even though they involve the same stratigraphic section and basal detachment. The Chelungpu thrust shows a classic fault-bend folding geometry, which predicts folding solely by kink-band migration, whereas the hanging wall of the Changhua thrust demonstrates the characteristic geometry of a shear fault-bend folding, which predicts a progressive limb rotation with minor kink-band migration. We test the kinematic predictions of classic and shear fault-bend folding theories by analyzing deformed flights of terraces and coseismic displacements in the Mw=7.6 Chi-Chi earthquake. The Chelungpu terraces shows differences in uplift magnitudes across active axial surfaces that closely approximate the assumptions of classical fault-bend folding, including constant fault-parallel displacement, implying conservation of bed length, and hanging-wall uplift rates that are proportional to the sine of the fault dip. This provides a basis for precise determination of total fault slip since the formation of each terrace and combined with terrace dating gives long- term fault-slip rates for the Chelungpu thrust system. An estimation of the long term fault-slip rate of the Chelungpu thrust in the north Hsinshe terrace yields 15 mm/yr over the last 55 ka, which is similar to the combined shortening rate of 16 mm/y on the Chelungpu and Chushiang thrusts in the south estimated by Simoes et al. in 2006. Evan the coseismic displacements of 3 to 9m in the Chi-Chi earthquake are approximately fault-parallel but have additional transient components that are averaged out over the timescale of terrace deformation, which represents 10-100 large earthquakes. In contrast, terrace deformation in the hanging wall of the Changhua thrust ramp shows progressive limb rotation, as predicted from its shear fault-bend folding geometry, which combined with terrace

Determination of tectonic shortening rates from progressively deformed flights of terraces above the Chelungpu and Changhua thrust ramps, Taiwan

NASA Astrophysics Data System (ADS)

Yue, L.; Suppe, J.

2004-12-01

The Chelungpu and Changhua thrust ramps in central Taiwan show contrasting hanging-wall structural geometries that suggest different kinematics, even though they involve the same stratigraphic section and basal detachment. The Chelungpu thrust shows a classic fault-bend folding geometry, which predicts folding solely by kink-band migration, whereas the hanging wall of the Changhua thrust demonstrates the characteristic geometry of a shear fault-bend folding, which predicts a progressive limb rotation with minor kink-band migration. We test the kinematic predictions of classic and shear fault-bend folding theories by analyzing deformed flights of terraces and coseismic displacements in the Mw=7.6 Chi-Chi earthquake. The Chelungpu terraces shows differences in uplift magnitudes across active axial surfaces that closely approximate the assumptions of classical fault-bend folding, including constant fault-parallel displacement, implying conservation of bed length, and hanging-wall uplift rates that are proportional to the sine of the fault dip. This provides a basis for precise determination of total fault slip since the formation of each terrace and combined with terrace dating gives long- term fault-slip rates for the Chelungpu thrust system. An estimation of the long term fault-slip rate of the Chelungpu thrust in the north Hsinshe terrace yields 15 mm/yr over the last 55 ka, which is similar to the combined shortening rate of 16 mm/y on the Chelungpu and Chushiang thrusts in the south estimated by Simoes et al. in 2006. Evan the coseismic displacements of 3 to 9m in the Chi-Chi earthquake are approximately fault-parallel but have additional transient components that are averaged out over the timescale of terrace deformation, which represents 10-100 large earthquakes. In contrast, terrace deformation in the hanging wall of the Changhua thrust ramp shows progressive limb rotation, as predicted from its shear fault-bend folding geometry, which combined with terrace

COMET-LICSAR: Systematic Deformation Monitoring of Fault Zones and Volcanoes with the Sentinel-1 Constellation

NASA Astrophysics Data System (ADS)

Spaans, K.; Wright, T. J.; Hooper, A. J.; Hatton, E. L.; González, P. J.; Bhattarai, S.; Biggs, J.; Crippa, P.; Ebmeier, S. K.; Elliott, J.; Gaddes, M.; Li, Z.; Parsons, B.; Qiu, Q.; McDougall, A.; Walters, R. J.; Weiss, J. R.; Ziebart, M.

2017-12-01

The Sentinel-1 constellation represents a major advance in our ability to monitor our planet's hazardous tectonic and volcanic zones. Here we present the latest progress from COMET (*), where we are now providing deformation results to the community for volcanoes and the tectonic belts (**). COMET now responds routinely to most significant continental earthquakes - Sentinel-1 allows us to do this within a few days for most earthquakes. For example, after the M7.8 Kaikoura (New Zealand) earthquake we supplied a processed interferogram to the community just 5 hours and 37 minutes after the Sentinel-1 acquisition. By the end of 2017, we will be producing interferogram products systematically for all earthquakes larger than M 6.0. For deformation data to be useful for preparedness, we need accuracy on the order of 1 mm/yr or better. This requires mass processing of long time series of radar acquisitions. We are currently (July 2017) processing interferograms systematically for the entire Alpine-Himalayan belt ( 9000 x 2000 km) using our LiCSAR chain, making interferograms and coherence products available to the community. By December 2017, we plan to process a wider tectonic area and the majority of subaerial volcanoes. We currently serve displacement and coherence grids, but plan to provide average deformation rates and time series. Results are available through our dedicated portal (**), and are being linked to the ESA G-TEP and EPOS during 2017. We will show the latest results for tectonics and volcanism, and discuss how these can be used to build value-added products, including (i) maps of tectonic strain (ii) maps of seismic hazard (iii) volcano deformation alerts. The accuracy of these products will improve as the number of data products acquired by Sentinel-1 increases, and as the time series lengthen. *http://comet.nerc.ac.uk**http://comet.nerc.ac.uk/COMET-LiCS-portal/

COMET-LICSAR: Systematic Deformation Monitoring of Fault Zones and Volcanoes with the Sentinel-1 Constellation

NASA Astrophysics Data System (ADS)

Spaans, K.; Wright, T. J.; Hooper, A. J.; Hatton, E. L.; González, P. J.; Bhattarai, S.; Biggs, J.; Crippa, P.; Ebmeier, S. K.; Elliott, J.; Gaddes, M.; Li, Z.; Parsons, B.; Qiu, Q.; McDougall, A.; Walters, R. J.; Weiss, J. R.; Ziebart, M.

2016-12-01

The Sentinel-1 constellation represents a major advance in our ability to monitor our planet's hazardous tectonic and volcanic zones. Here we present the latest progress from COMET (*), where we are now providing deformation results to the community for volcanoes and the tectonic belts (**). COMET now responds routinely to most significant continental earthquakes - Sentinel-1 allows us to do this within a few days for most earthquakes. For example, after the M7.8 Kaikoura (New Zealand) earthquake we supplied a processed interferogram to the community just 5 hours and 37 minutes after the Sentinel-1 acquisition. By the end of 2017, we will be producing interferogram products systematically for all earthquakes larger than M 6.0. For deformation data to be useful for preparedness, we need accuracy on the order of 1 mm/yr or better. This requires mass processing of long time series of radar acquisitions. We are currently (July 2017) processing interferograms systematically for the entire Alpine-Himalayan belt ( 9000 x 2000 km) using our LiCSAR chain, making interferograms and coherence products available to the community. By December 2017, we plan to process a wider tectonic area and the majority of subaerial volcanoes. We currently serve displacement and coherence grids, but plan to provide average deformation rates and time series. Results are available through our dedicated portal (**), and are being linked to the ESA G-TEP and EPOS during 2017. We will show the latest results for tectonics and volcanism, and discuss how these can be used to build value-added products, including (i) maps of tectonic strain (ii) maps of seismic hazard (iii) volcano deformation alerts. The accuracy of these products will improve as the number of data products acquired by Sentinel-1 increases, and as the time series lengthen. *http://comet.nerc.ac.uk**http://comet.nerc.ac.uk/COMET-LiCS-portal/

Plate Margin Deformation and Active Tectonics Along the Northern Edge of the Yakutat Terrane in the Saint Elias Orogen, Alaska and Yukon, Canada

NASA Technical Reports Server (NTRS)

Bruhn, Ronald L.; Sauber, Jeanne; Cotton, Michele M.; Pavlis, Terry L.; Burgess, Evan; Ruppert, Natalia; Forster, Richard R.

2012-01-01

The northwest directed motion of the Pacific plate is accompanied by migration and collision of the Yakutat terrane into the cusp of southern Alaska. The nature and magnitude of accretion and translation on upper crustal faults and folds is poorly constrained, however, due to pervasive glaciation. In this study we used high-resolution topography, geodetic imaging, seismic, and geologic data to advance understanding of the transition from strike-slip motion on the Fairweather fault to plate margin deformation on the Bagley fault, which cuts through the upper plate of the collisional suture above the subduction megathrust. The Fairweather fault terminates by oblique-extensional splay faulting within a structural syntaxis, allowing rapid tectonic upwelling of rocks driven by thrust faulting and crustal contraction. Plate motion is partly transferred from the Fairweather to the Bagley fault, which extends 125 km farther west as a dextral shear zone that is partly reactivated by reverse faulting. The Bagley fault dips steeply through the upper plate to intersect the subduction megathrust at depth, forming a narrow fault-bounded crustal sliver in the obliquely convergent plate margin. Since . 20 Ma the Bagley fault has accommodated more than 50 km of dextral shearing and several kilometers of reverse motion along its southern flank during terrane accretion. The fault is considered capable of generating earthquakes because it is linked to faults that generated large historic earthquakes, suitably oriented for reactivation in the contemporary stress field, and locally marked by seismicity. The fault may generate earthquakes of Mw <= 7.5.

Beyond plate tectonics - Looking at plate deformation with space geodesy

NASA Technical Reports Server (NTRS)

Jordan, Thomas H.; Minster, J. Bernard

1988-01-01

The requirements that must be met by space-geodetic systems in order to constrain the horizontal secular motions associated with the geological deformation of the earth's surface are explored. It is suggested that in order to improve existing plate-motion models, the tangential components of relative velocities on interplate baselines must be resolved to an accuracy of less than 3 mm/yr. Results indicate that measuring the velocities between crustal blocks to + or - 5 mm/yr on 100-km to 1000-km scales can produce geologically significant constraints on the integrated deformation rates across continental plate-boundary zones such as the western United States.

Soil radon measurements as a potential tracer of tectonic and volcanic activity.

PubMed

Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

2016-04-15

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

Soil radon measurements as a potential tracer of tectonic and volcanic activity

NASA Astrophysics Data System (ADS)

Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

2016-04-01

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

Soil radon measurements as a potential tracer of tectonic and volcanic activity

PubMed Central

Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

2016-01-01

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

Problems of the active tectonics of the Eastern Black Sea

NASA Astrophysics Data System (ADS)

Javakhishvili, Z.; Godoladze, T.; Dreger, D. S.; Mikava, D.; Tvaliashvili, A.

2016-12-01

The Black Sea Basin is the part of the Arabian Eurasian Collision zone and important unit for understanding the tectonic process of the region. This complex basin comprises two deep basins, separated by the mid-Black Sea Ridge. The basement of the Black Sea includes areas with oceanic and continental crust. It was formed as a "back-arc" basin over the subduction zone during the closing of the Tethys Ocean. In the past decades the Black Sea has been the subject of intense geological and geophysical studies. Several papers were published about the geological history, tectonics, basement relief and crustal and upper mantle structure of the basin. New tectonic schemes were suggested (e. g. Nikishin et al 2014, Shillington et al. 2008, Starostenko et al. 2004 etc.). Nevertheless, seismicity of the Black Sea is poorly studied due to the lack of seismic network in the coastal area. It is considered, that the eastern basin currently lies in a compressional setting associated with the uplift of the Caucasus and structural development of the Caucasus was closely related to the evolution of the Eastern Black Sea Basin. Analyses of recent sequence of earthquakes in 2012 can provide useful information to understand complex tectonic structure of the Eastern Black Sea region. Right after the earthquake of 2012/12/23, National Seismic monitoring center of Georgia deployed additional 4 stations in the coastal area of the country, close to the epicenter area, to monitor aftershock sequence. Seismic activity in the epicentral area is continuing until now. We have relocated approximately 1200 aftershocks to delineate fault scarf using data from Georgian, Turkish and Russian datacenters. Waveforms of the major events and the aftershocks were inverted for the fault plane solutions of the events. For the inversion were used green's functions, computed using new 1D velocity model of the region. Strike-slip mechanism of the major events of the earthquake sequence indicates extensional

Measuring Crustal Deformation in the American West.

ERIC Educational Resources Information Center

Jordan, Thomas H.; Minster, J. Bernard

1988-01-01

Suggests that there is a close relationship between deformation in the western United States and the large-scale motions of tectonic plates. Introduces very-long-baseline interferometry (VLBI) as one of the space-geodetic techniques, vector addition of the VLBI data and geological data, and a new geodetic network. (YP)

From thrusting to transpressional tectonics in the Aghdarband Basin (NE Iran): evidence for Cimmerian oblique convergence

NASA Astrophysics Data System (ADS)

Zanchi, Andrea; Balini, Marco; Ghassemi, Mohammad Reza; Zanchetta, Stefano

2010-05-01

The Aghdarband Basin, consisting of a strongly deformed arc-related Triassic marine succession, is a key-area for the study of the Cimmerian events, as it is unconformably covered by mid-Jurassic gently folded sediments entirely sealing the Cimmerian compressive structures. The basin developed during part of the Triassic in a highly mobile tectonic context suggested by abrupt facies variations and local unconformities. In addition, syn-sedimentary tectonic activity is testified by the occurrence of carbonate olistholiths in the deepest parts of the basin. The marine succession, spanning from Olenekian to lowermost Carnian, shows at the base continental conglomerates andsandstones, as well as basaltic lava flows, possibly of Early Triassic age. They are followed by the shallow water Sefid Kuh Limestone, in which an intraformational unconformity has been now identified. This unit is locally covered by deep-water limestones of the Nazarkardeh Fm. which interfinger with slope facies of the Sefid Kuh Limestone. The volcaniclastic sandstone layers of the Sina Fm follow up-section with a deep unconformity, marked in several places by deep erosion and tilting of the underlying units. The Sina Fm. is in turn unconformably covered by the coal bearing shales of the Miankhui Fm., with a Norian-Rhaetian age testified by plant megafossils, marking the end of marine sedimentation and of volcanic-arc activity. The Triassic units are overthrusted to the south by Upper Palaeozoic siliciclastic successions showing in some cases a LG metamorphic imprint. They largely include the Qara Geithan Fm. consisting of granitic rocks, acidic to basic volcanics, and locally also large blocks of Permian bioclastic limestones derived from the erosion of the Palaeotethys accretionary wedge, exposed south of Aghdarband. The whole succession of the Aghdarband Basin, including the unconformable Miankhui Fm., is deeply involved in a north-verging thrust stack which interacts in the northern part of the

Is There a Tectonic Component On The Subsidence Process In Morelia, Mexico?

NASA Astrophysics Data System (ADS)

Cabral-Cano, E.; Arciniega-Ceballos, A.; Diaz-Molina, O.; Garduno-Monroy, V.; Avila-Olivera, J.; Hernández-Madrigal, V.; Hernández-Quintero, E.

2009-12-01

Subsidence and faulting have affected cities in central Mexico for decades. This process causes substantial damages to the urban infrastructure, housing and large buildings, and is an important factor to be consider when planning urban development, land use zoning and hazard mitigation strategies. In Mexico, studies using InSAR and GPS based observations have shown that high subsidence areas are usually associated with the presence of thick lacustrine and fluvial deposits. In most cases the subsidence is closely associated with intense groundwater extraction that results in sediment consolidation. However, recent studies in the colonial city of Morelia in central Mexico show a different scenario, where groundwater extraction cannot solely explain the observed surface deformation. Our results indicate that a more complex interplay between sediment consolidation and tectonic forces is responsible for the subsidence and fault distribution within the city. The city of Morelia has experienced fault development recognized since the 80’s. This situation has led to the recognition of 9 NE-SW trending faults that cover most of its urbanized area. Displacement maps derived from differential InSAR analysis show that the La Colina fault is the highest subsiding area in Morelia with maximum annual rates over -35 mm/yr. However, lithological mapping and field reconnaissance clearly show basalts outcropping this area of high surface deformation. The subsurface characterization of the La Colina fault was carried out along 27 Ground Penetrating Radar (GPR) sections and 6 seismic tomography profiles. Assuming a constant, linear past behavior of the subsidence as observed by InSAR techniques, and based on the interpretation of the fault dislocation imaged by the shallow GPR and seismic tomography, it is suggested that the La Colina fault may have been active for the past 220-340 years and clearly pre-dates the intense water well extraction from the past century. These conditions

Magma-Tectonic Interactions in the Main Ethiopian Rift; Insights into Rifting Processes

NASA Astrophysics Data System (ADS)

Greenfield, T.; Keir, D.; Tessema, T.; Lloyd, R.; Biggs, J.; Ayele, A.; Kendall, J. M.

2017-12-01

We report observations made around the Bora-Tulu Moye volcanic field, in the Main Ethiopian Rift (MER). A network of seismometers deployed around the volcano for one and a half years reveals the recent state of the volcano. Accurate earthquake locations and focal mechanisms are combined with surface deformation and mapping of faults, fissures and geothermally active areas to reveal the interaction between magmatism and intra-rift faulting. More than 1000 earthquakes are detected and located, making the Bora-Tulu Moye volcanic field one of the most seismically active regions of the MER. Earthquakes are located at depths of less than 5 km below the surface and range between magnitudes of 1.5 - 3.5. Surface deformation of Bora-Tulu Moye is observed using satellite based radar interferometry (InSAR) recorded before and during the seismic deployment. Since 2004, deformation has oscillated between uplift and subsidence centered at the same spatial location but different depths. We constrain the source of the uplift to be at 7 km depth while the source of the subsidence is shallower. Micro-earthquake locations reveal that earthquakes are located around the edge of the observed deformation and record the activation of normal faults orientated at 025°. The spatial link between surface deformation and brittle failure suggest that significant hydrothermal circulation driven by an inflating shallow heat source is inducing brittle failure. Elsewhere, seismicity is focused in areas of significant surface alteration from hydrothermal processes. We use shear wave splitting using local earthquakes to image the stress state of the volcano. A combination of rift parallel and rift-oblique fast directions are observed, indicating the volcano has a significant influence on the crustal stresses. Volcanic activity around Bora-Tulu Moye has migrated eastwards over time, closer to the intra-rift fault system, the Wonji Fault Belt. How and why this occurs relates to changes in the melt

Reports on crustal movements and deformations

NASA Technical Reports Server (NTRS)

Cohen, S. C.; Peck, T.

1981-01-01

Studies of tectonic plate motions, regional crustal deformations, strain accumulation and release, deformations associated with earthquakes and fault motion, and micro-plate motion, were collected and are summarized. To a limited extent, papers dealing with global models of current plate motions and crustal stress are included. The data base is restricted to articles appearing in reveiwed technical journals during the years 1970-1980. The major journals searched include: Journal of Geophysical Research (solid earth), Tectonophysics, Bulletin of the Seismological Society of America, Geological Society of America Bulletin, Geophysical Journal of the Royal Astronomical Society, and the Journal of Geology.

Active tectonics on Lanzarote (Canary Islands) from the analysis of CGPS data

NASA Astrophysics Data System (ADS)

Riccardi, Umberto; Arnoso, Jose; Benavent, María Teresa; Velez, Emilio; Tammaro, Umberto; González Montesinos, Fuensanta

2017-04-01

We report on the analysis of about three years of CGPS data collected on a small network consisting in five permanent stations, with the largest baseline up to 40 km, spread over Timanfaya National Park in Lanzarote Island. The GPS stations are operated by different institutions, as follows: CAME is co-operated by the Institute of Geosciences (CSIC-UCM), DiSTAR and the Geodesy Research Group of University Complutense of Madrid (GRG-UCM), while LACV is operated by (CSIC-UCM and GRG-UCM). Stations HRIA, TIAS, YAIZ, belong to GRAFCAN (Cartographical Service of the Government of Canary Islands). Lanzarote is the most Northeast and the oldest island of the Canarian Archipelago (Spain), which is located on a transitional zone, a passive margin, between oceanic and continental crust. Due to some peculiarities in geochemistry and geochronology of the rocks as well as tectonics, the origin of the archipelago from a hot spot is still debated. In fact, the most recent Holocenic volcanism is scattered over the islands and the last eruption was a submarine one, occurred in October 2011 at El Hierro Island. The last eruption in Lanzarote was a 7 years voluminous eruptive cycle, occurred during the 18th century. Historical seismicity registered in the region, is customarily attributed to diffuse tectonic activity. This study is intended to contributing to shed light on the active tectonics on Lanzarote island and to separate between local and regional strain fields. With the aid of Gamit 10.6 software, we compute from the GPS observations the "ionofree" linear combinations in order to obtain the positions of the stations in ITRF2008 frame using daily sessions, and IGS precise ephemeris. The frame referencing of the network is realized by eleven IGS GPS stations. Then through a Kalman filtering procedure, implemented in GLOBK software, we obtain the final daily solutions by constraining the fiducial GPS stations to their ITRF2008 coordinates. For a reliable strain field retrieval

Late Cenozoic Deformation in the Western Tarim Basin, NW China

NASA Astrophysics Data System (ADS)

Thompson, J. A.; Burbank, D. W.; Chen, J.; Li, T.

2009-12-01

The Tian Shan in NW China is one of the most active regions of intracontinental deformation in the world, accommodating a large fraction (~40%) of the shortening from the Indo-Eurasian collision. The western Tarim Basin, situated between the southern Tian Shan and Pamir Mountains, manifests this deformation through a series of east-west trending fault-related folds that have formed during the late Cenozoic. Previous studies in this region have focused on the kinematics, style, and timing of detachment folds related to folding within the foreland basin of the southern Tian Shan. In contrast, this study focuses on the deformation caused by fault-propagation folding resulting from the northward movement of the Pamir. The rates of deformation are calculated using a combination of optically stimulated luminescence (OSL) ages, structural mapping and differential GPS surveys of fault scarps and deformed terrace surfaces crossing active folds. OSL dating provides the time since the sediment was last exposed to daylight, i.e., time since burial. Consequently, OSL is useful for dating the abandonment of terrace surfaces due to tectonic (fold growth) or climatic events. OSL quartz samples were collected from silt lenses within gravel topping the terraces. Most of the quartz OSL signals are weak, thus several grain sizes (silt (4-11 µm, 8-15 µm) and sand (90-125 µm)) were analyzed and different integrations of the shine-down curves were explored to calculate equivalent doses. The implications for different equivalent doses and ages on the calculation of rates of deformation are also addressed.

Α Deformation study in Central Greece using 20 years of GPS data

NASA Astrophysics Data System (ADS)

Marinou, Aggeliki; Papazissi, Kaliopi; Mitsakaki, Christiana; Paradissis, Demitris; Papanikolaou, Xanthos; Anastasiou, Demitris

2015-04-01

Central Greece is a region recognized for its intense tectonic activity with the main characterics being the extension in the North-South direction. This extension is revealed mainly in the form of large parallel grabens. Among these rifts is the Corinth Gulf, which is the most active tectonically, the basin between Parnassos and Kallidromo Mt, the Locris basin and the graben of North Evoikos Gulf, while in the south lays the Thebes basin and the South Evoikos Gulf. Since the late eighties the Laboratory of Higher Geodesy and the Dionysos Satellite Observatory of the National Technical University of Athens, in cooperation with several National and International Universities and Institutions have established, in various Greek areas, of high seismic activity, geodetic networks in order to monitor tectonic displacements. These geodetic networks were observed periodically using Satellite Geodesy techniques and in recent years almost entirely GPS. In this study all the available GPS data, referring to the broader area of Evia, Attiki and Viotia, for the years 1989 to 2008, are analyzed. The displacement field and its temporal changes for the area between the two major geological features, the Corinth Gulf and the Evoikos Gulf, are investigated. Αll the kinematic models that were used do not confirm that the area of study is deforming homogeneously, while an indication of a discontinuity has been detected.

Marine Terrace Deposits along the Mediterranean Coast on the Southeastern Turkey and Their Implications for Tectonic Uplift and Sea Level Change

NASA Astrophysics Data System (ADS)

Tari, U.; Tüysüz, O.; Blackwell, B. A. B.; Genç, Ş. C.; Florentin, J. A.; Mahmud, Z.; Li, G. L.; Blickstein, J. I. B.; Skinner, A. R.

2016-12-01

Tectonic movements among the African, Arabian and Anatolian Plates have deformed the eastern Mediterranean. These movements caused transtensional opening of the NE-trending Antakya Graben since the late Pliocene. Tectonic uplift coupled with Quaternary sealevel fluctuations has produced several stacked marine terraces along the Mediterranean coasts on the graben. Here, marine terrace deposits that sit on both flanks of the graben at elevations between 3 and 175 m were dated using electron spin resonance (ESR) method in order to calculate uplift rates. The ESR ages range from 12 ka in late MIS 2 to 457 ka in MIS 9-11, but most of the terraces contain molluscs reworked from several earlier deposits due to successive tectonic movements and sealevel fluctuations. By dating in situ fossils, along the basal contacts of the marine terraces, uplift rates were calculated on both sides of the Antakya Graben. Results indicate that these deposits were mainly uplifted by local active faults rather than regional movements.

Monitor the Surface Deformation in Metropolitan Taipei Basin by Using PS-InSAR Techniques

NASA Astrophysics Data System (ADS)

Chang, Yan-Ru; Tung, Hsin; Hu, Jyr-Ching

2015-04-01

Taipei is the most densely populated area and the center of politics and economics in Taiwan. However, the composite geohazards might occur in Taipei area, in which the active Shanchiao fault located in the western margin of Taipei basin and the active Tatun volcano group located 15 km to the north of the basin. Therefore, it is not only an important scientific topic but also a crucial social issue to better understand the assessment and mitigation of geological hazard in the metropolitan Taipei city. We use Persistent Scatterers interferometric synthetic aperture radar (PSInSAR) and small baseline methods to calculate the surface deformation rate with the constraints of continuous GPS and precise leveling measurements. The advantages of PSInSAR technique are wide, periodic, and stable in the temporal and spatial pattern of deformation. In this study C-band ERS-1/2 (1996/1-1999/9), ENVISAT (2003/1-2008/3) and L-band ALOS (2007/4-2011/6) SAR images are used to carry out the surface deformation in three periods. Based on the results of different periods of PS-InSAR, the slant range displacement (SRD) was variable via time which might be related to the deformation in different depth of loose deposits in Taipei basin. Previous study suggested that some factors influence the surface deformation change, including soil compaction, water-table change and tectonic movement. Consequently the assessment in activity of the Shanchiao fault, the induced deformation due to the fluctuation of the water table and the soil compaction should be removed. In general, the average SRD rate in the footwall and hanging wall of the Shanchiao Fault was about 12.2 mm/yr and 9.1 mm/yr, 1.5 mm/yr and 4.0 mm/yr, respectively with descending mode ERS-1/2 an ENVISAT radar images. For the ascending ALOS radar image, the average SRD rate in the footwall and hanging wall of the Shanchiao Fault was about -9.5 and -11.3 mm/yr, respectively. These results suggests that the slight uplift observed in the

Late Cretaceous fluvial systems and inferred tectonic history, central Utah

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawton, T.F.

1983-08-01

Upper Campanian nonmarine sedimentary rocks exposed between the Wasatch Plateau and the Green River in central Utah record a tectonic transition from thin-skinned deformation in the thrust belt to basement-cored uplift in the foreland region. Sandstones within the section consist of two distinct compositional suites, a lower quartzose petrofacies and an upper lithic petrofacies. The volcanic lithic grains of the Farrer and Tuscher Formations were derived from more distal arc sources to the southwest, and transported through the thrust belt somewhere west of the Kaiparowits region, where time-equivalent sedimentary rocks are also rich in volcanic lithic fragments. Disappearance of volcanicmore » lithics and appearance of pebbles at the top of the Tuscher Formation is interpreted to reflect a latest Campanian reorganization of drainage patterns that marked initial growth of the San Rafael swell and similar basement uplifts to the south of the swell. Contemporaneous fluvial systems that deposited the uppermost part of the Price River Formation in the Wasatch Plateau were apparently unaffected by the uplift and continued to flow northeast. Depositional patterns thus indicate that initial growth of the San Rafael swell was probably concurrent with late deformation in the thrust belt. Depositional onlap across the Mesaverde Group by a largely post-tectonic assemblage of fluvial and lacustrine strata (North Horn Formation) indicates a minimum late Paleocene age for growth of the San Rafael swell and deformation within the thrust belt.« less

The interpretation of crustal dynamics data in terms of plate interactions and active tectonics of the Anatolian plate and surrounding regions in the Middle East

NASA Technical Reports Server (NTRS)

Toksoz, M. Nafi; Reilinger, Robert

1992-01-01

A detailed study was made of the consequences of the Arabian plate convergence against Eurasia and its effects on the tectonics of Anatolia and surrounding regions of the eastern Mediterranean. A primary source of information is time rates of change of baseline lengths and relative heights determined by repeated SLR measurements. These SLR observations are augmented by a network of GPS stations in Anatolia, Aegea, and Greece, established and twice surveyed since 1988. The existing SLR and GPS networks provide the spatial resolution necessary to reveal the details of ongoing tectonic processes in this area of continental collision. The effort has involved examining the state of stress in the lithosphere and relative plate motions as revealed by these space based geodetic measurements, seismicity, and earthquake mechanisms as well as the aseismic deformations of the plates from conventional geodetic data and geological evidence. These observations are used to constrain theoretical calculations of the relative effects of: (1) the push of the Arabian plate; (2) high topography of Eastern Anatolia; (3) the geometry and properties of African-Eurasian plate boundary; (4) subduction under the Hellenic Arc and southwestern Turkey; and (5) internal deformation and rotation of the Anatolian plate.

Tectonic Plate Movement.

ERIC Educational Resources Information Center

Landalf, Helen

1998-01-01

Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)

Active deformation and evolution of the upper forearc slope of the central Ryukyu Arc, northwestern Pacific

NASA Astrophysics Data System (ADS)

Arai, K.; Inoue, T.; Sato, T.

2016-12-01

The Ryukyu Arc, which extend for over 1200 km along the east coast of Asia from Kyushu to Taiwan, and the associated Ryukyu Trench, are products of the subduction of the Philippine Sea Plate beneath the Eurasian Plate. The Okinawa Trough, a back-arc basin located landward of the Ryukyu Arc, formed in the Late Miocene (Gungor et al., 2012) or the Late Pliocene-Early Pleistocene (Sibuet et al., 1998); its formation is a key geologic event associated with complex tectonic movements and changes in the topographic configuration of the Ryukyu Arc. Geological Survey of Japan (GSJ), AIST has started the marine geological mapping project around Ryukyu Arc since the 2008 FY. Multi channel (16 ch) high-resolution seismic profiles were acquired during these cruises by the GI-gun (355cu. inch) or the Cluster-gun (30+30 cu. inch) systems. Survey area in the southeast off Okinawa Island is located on the upper forearc slope along the Ryukyu Trench. Seismic reflections of shelf and the upper forearc slope show no obvious deformation such as the fold and faults parallel to the Ryukyu Trench axis. In contrast, some active faults, which were perpendicular to the Ryukyu Trench axis (NW-SE direction), were observed. An acoustic basement, which is characterized distinct reflector had tilted southeastward (trenchward) and was unconformable overlain by the stratified sediments. These sediments divided into four seismic units. We present the geological history and tectonics of the central Ryukyu Arc.

Final report. [Mesozoic tectonic history of the northeastern Great Basin (Nevada)

NASA Technical Reports Server (NTRS)

Zamudio, Joe

1993-01-01

In eastern Nevada and western Utah is an extensive terrane that has experienced a complex tectonic history of Mesozoic deformation and superposed Tertiary extension. The Mesozoic tectonic history of this area has been the subject of controversy for the past twenty or more years. The debate has centered on whether major Mesozoic geologic structures were due to compressional or extensional tectonic regimes. The goal of our research was to decipher the deformational history of the area by combining detailed geologic mapping, remote sensing data analysis, and U-Pb and K-Ar geochronology. This study area includes the Dolly Varden Mountains and adjacent Currie Hills, located in the semi-arid environment of the northeastern Great Basin in Nevada. Vegetation cover in the Dolly Varden Mountains typically ranges from about 10 percent to 50 percent, with some places along drainages and on high, north-facing slopes where vegetation cover approaches 100 percent. Sagebrush is found at less vegetated lower elevations, whereas pinon pine and juniper are prevalent above 2,000 meters. A variety of geologic materials is exposed in the study area. A sequence of Late Paleozoic and Triassic sedimentary rocks includes limestone, dolomite, chert, sandstone, siltstone and shale. A two-phase granitic stock, called the Melrose, intruded these rocks, resulting in metamorphism along the intrusive contact. Tertiary volcanic rocks cover most of the eastern part of the Dolly Varden Mountains and low-lying areas in the Currie Hills.

In situ stress variations at the Variscan deformation front — Results from the deep Aachen geothermal well

NASA Astrophysics Data System (ADS)

Trautwein-Bruns, Ute; Schulze, Katja C.; Becker, Stephan; Kukla, Peter A.; Urai, Janos L.

2010-10-01

In 2004 the 2544 m deep RWTH-1 well was drilled in the city centre of Aachen to supply geothermal heat for the heating and cooling of the new student service centre "SuperC" of RWTH Aachen University. Aachen is located in a complex geologic and tectonic position at the northern margin of the Variscan deformation front at the borders between the Brabant Massif, the Hohes Venn/Eifel areas and the presently active rift zone of the Lower Rhine Embayment, where existing data on in situ stress show complex changes over short distances. The borehole offers a unique opportunity to study varying stress regimes in this area of complex geodynamic evolution. This study of the in situ stresses is based on the observation of compressive borehole breakouts and drilling-induced tensile fractures in electrical and acoustic image logs. The borehole failure analysis shows that the maximum horizontal stress trends SE-NW which is in accordance with the general West European stress trend. Stress magnitudes modelled in accordance to the Mohr-Coulomb Theory of Sliding Friction indicate minimum and maximum horizontal stress gradients of 0.019 MPa/m and 0.038 MPa/m, respectively. The occurrence of drilling-induced tensile failure and the calculated in situ stress magnitudes are consistent with a model of strike-slip deformation. The observed strike-slip faulting regime supports the extension of the Brabant Shear Zone proposed by Ahorner (1975) into the Aachen city area, where it joins the major normal faulting set of the Roer Valley Graben zone. This intersection of the inherited Variscan deformation grain and the Cenozoic deformation resulting in recent strike-slip and normal faulting activity proves the tectonically different deformation responses over a short distance between the long-lived Brabant Massif and the Cenozoic Rhine Rift System.

Active faulting Vs other surface displacing complex geomorphic phenomena. Case studies from a tectonically active area, Abruzzi Region, central Apennines, Italy

NASA Astrophysics Data System (ADS)

Lo Sardo, Lorenzo; Gori, Stefano; Falcucci, Emanuela; Saroli, Michele; Moro, Marco; Galadini, Fabrizio; Lancia, Michele; Fubelli, Giandomenico; Pezzo, Giuseppe

2016-04-01

could be possible to infer the genesis of the scarps as due to complex tectono-karstic phenomena. As for case (ii), our ongoing analyses are aimed to analyze the tectonic "significance" of some closed depressions, up to 4 km long and to 0,5-1 km large, that occur along the south-western slope of the Gran Sasso Range. All these small depression are NW-SE trending. As already described by Bosi et al. (1989), Galadini and Giuliani (1993), D'Agostino et al. (1998), Falcucci et al. (2015), these closed depressions are bounded by scarps carved onto the carbonate bedrock and, subordinately, onto early Quaternary slope deposits, reaching height of up to 5 m. These scarps are preferentially NE dipping, even if in few cases some SW dipping scarp are also present . The field work has permitted to attest that these scarps are related to shear planes that that displaced two subsequent of Early Pleistocene breccias formations (the Valle Valiano Fm. and Fonte Vedice Fm.; Bosi e Bertini, 1993; D'agostino et al., 1997). A paleoseismological trench was also performed across one of these scarps, attesting the activity of these shear planes also in recent times, providing indications result about the deformation style. Reference Bertini, T., & Bosi, C. (1993). La tettonica quaternaria della conca di Fossa (L'Aquila). Il Quaternario, 6(2), 293-314. Bertini, T., Bosi, C., & Galadini, F. (1989). La conca di Fossa-S. Demetrio dei Vestini. CNR, Centro di Studio per la Geologia Tecnica, ENEA, PAS in Elementi di tettonica pliocenicoquaternaria ed indizi di sismicita olocenica nell'Appennino laziale-abruzzese, Societa Geologica Italiana, L'Aquila, 26-58. Bosi, C., & Bertini, T. (1970). Geologia della media valle dell'Aterno. Memorie Società Geologica Italiana, 9(4), 719-777. D'Agostino, N., F. Speranza, & R. Funiciello., (1997) "Le Brecce Mortadella dell'Appennino Centrale: primi risultati di stratigrafia magnetica." Il Quaternario10.2: 385-388. D'Agostino, N., Chamot-Rooke, N., Funiciello, R

Tectonic significance of Kibaran structures in Central and Eastern Africa

NASA Astrophysics Data System (ADS)

Rumvegeri, B. T.

Tectonical movements of the Kibaran belt (1400-950 Ma) can be subdivided into two major deformation events, corresponding to tight, upright or recumbent folds, thrust faults, nappes and stretching lineation with a general plunging southwards. At the regional scale, the stretching lineation, associated with thrust faults and nappes is interpreted as an indication of a northwards moving direction. The shear zone with mafic-ultramafic rocks across Burundi, MW-Tanzania, SW-Uganda and NE-Zaïre is the suture zone of the Kibaran belt. Kibaran metamorphism is plurifacial and has four epizodes. The second, syn-D2, is the most important and constitutes the climax; it reached the granulite facies. The succession of tectonic, metamorphic and magmatic features suggests geotectonic evolution by subduction-collision.

Crustal Deformation at the Arabian Plate-Boundary observed by InSAR

NASA Astrophysics Data System (ADS)

Jonsson, S.; Cavalié, O.; Akoglu, A. M.; Wang, T.; Xu, W.; Feng, G.; Dutta, R.; Abdullin, A. K.

2013-12-01

The Arabian plate is bounded by a variety of active plate boundaries, with extension in the Red Sea and Gulf of Aden to the south, compression in Turkey and Iran to the north, and transform faults to the west and to the east. Internally, however, the Arabian plate has been shown to be tectonically rather stable, despite evidence of recent volcanism and earthquake faulting. We use InSAR observations to study recent tectonic and volcanic activity at several locations at the Arabian plate boundary as well within the plate itself. The region near the triple junction between the Arabian, Eurasian, and Anatolian plates has often been the focus of studies on continental deformation behavior and interseismic deformation. Here we use large-scale InSAR data processing to map the deformation near the triple junction and find the deformation to be focused on major faults with little intra-plate deformation. The eastern part of the East Anatolian Fault appears to have a very shallow locking depth with limited fault-normal deformation. Several major earthquakes that have occurred in recent years on the Arabian plate boundary, including the 2011 magnitude 7.1 Van earthquake in eastern Turkey. It occurred as a result of convergence of the Arabian plate towards Eurasia and caused significant surface deformation that we have analyzed with multiple coseismic InSAR, GPS, and coastal uplift observations. We use high-resolution Cosmo-Skymed and TerraSAR-X data to derive 3D coseismic displacements from offsets alone, as some of the interferograms are almost completely incoherent. By identifying point-like targets within the images, we were able to derive accurate pixel offsets between SAR sub-images containing such targets, which we used to estimate the 3D coseismic displacements. The derived 3D displacement field helped in constraining the causative northward dipping thrust-fault. The Qadimah fault is a recently discovered fault located on the Red Sea coast north of Jeddah and under the

Tunable deformation modes shape contractility in active biopolymer networks

NASA Astrophysics Data System (ADS)

Stam, Samantha; Banerjee, Shiladitya; Weirich, Kim; Freedman, Simon; Dinner, Aaron; Gardel, Margaret

Biological polymer-based materials remodel under active, molecular motor-driven forces to perform diverse physiological roles, such as force transmission and spatial self-organization. Critical to understanding these biomaterials is elucidating the role of microscopic polymer deformations, such as stretching, bending, buckling, and relative sliding, on material remodeling. Here, we report that the shape of motor-driven deformations can be used to identify microscopic deformation modes and determine how they propagate to longer length scales. In cross-linked actin networks with sufficiently low densities of the motor protein myosin II, microscopic network deformations are predominantly uniaxial, or dominated by sliding. However, longer-wavelength modes are mostly biaxial, or dominated by bending and buckling, indicating that deformations with uniaxial shapes do not propagate across length scales significantly larger than that of individual polymers. As the density of myosin II is increased, biaxial modes dominate on all length scales we examine due to buildup of sufficient stress to produce smaller-wavelength buckling. In contrast, when we construct networks from unipolar, rigid actin bundles, we observe uniaxial, sliding-based contractions on 1 to 100 μm length scales. Our results demonstrate the biopolymer mechanics can be used to tune deformation modes which, in turn, control shape changes in active materials.

Preliminary results on the tectonic activity of the Ovacık Fault (Malatya-Ovacık Fault Zone, Turkey): Implications of the morphometric analyses

NASA Astrophysics Data System (ADS)

Yazıcı, Müge; Zabci, Cengiz; Sançar, Taylan; Sunal, Gürsel; Natalin, Boris A.

2016-04-01

The Anatolian 'plate' is being extruded westward relative to the Eurasia along two major tectonic structures, the North Anatolian and the East Anatolian shear zones, respectively making its northern and eastern boundaries. Although the main deformation is localized along these two structures, there is remarkable intra-plate deformation within Anatolia, especially which are characterized by NE-striking sinistral and NW-striking dextral strike-slip faults (Şengör et al. 1985). The Malatya-Ovacık Fault Zone (MOFZ) and its northeastern member, the Ovacık Fault (OF), is a one of the NE-striking sinistral strike slip faults in the central 'ova' neotectonic province of Anatolia, located close to its eastern boundary. Although this fault zone is claimed to be an inactive structure in some studies, the recent GPS measurements (Aktuǧ et al., 2013) and microseismic activity (AFAD, 2013) strongly suggest the opposite. In order to understand rates and patterns of vertical ground motions along the OF, we studied the certain morphometric analyses such as hypsometric curves and integrals, longitudinal channel profiles, and asymmetry of drainage basins. The Karasu (Euphrates) and Munzur rivers form the main drainage systems of the study area. We extracted all drainage network from SRTM-based Digital Elevation Model with 30 m ground pixel resolution and totally identified 40 sub-drainage basins, which are inhomogeneously distributed to the north and to the south of the OF. Most of these basins show strong asymmetry, which are mainly tilted to SW. The asymmetry relatively decreases from NE to SW in general. The only exception is at the margins of the Ovacık Basin (OB), where almost the highest asymmetry values were calculated. On the other hand, the characteristics of hypsometric curves and the calculated hypsometric integrals do not show the similar systematic spatial pattern. The hypsometric curves with convex-shaped geometry, naturally indicating relatively young morphology

Rapid Measurement of Tectonic Deformation Using Structure-from-Motion

NASA Astrophysics Data System (ADS)

Pickering, A.; DeLong, S.; Lienkaemper, J. J.; Hecker, S.; Prentice, C. S.; Schwartz, D. P.; Sickler, R. R.

2016-12-01

Rapid collection and distribution of accurate surface slip data after earthquakes can support emergency response, help coordinate scientific response, and constrain coseismic slip that can be rapidly overprinted by postseismic slip, or eliminated as evidence of surface deformation is repaired or obscured. Analysis of earthquake deformation can be achieved quickly, repeatedly and inexpensively with the use of Structure-from-Motion (SfM) photogrammetry. Traditional methods of measuring surface slip (e.g. manual measurement with tape measures) have proven inconsistent and irreproducible, and sophisticated methods such as laser scanning require specialized equipment and longer field time. Here we present a simple, cost-effective workflow for rapid, three-dimensional imaging and measurement of features affected by earthquake rupture. As part of a response drill performed by the USGS and collaborators on May 11, 2016, geologists documented offset cultural features along the creeping Hayward Fault in northern California, in simulation of a surface-rupturing earthquake. We present several photo collections from smart phones, tablets, and DSLR cameras from a number of locations along the fault collected by users with a range of experience. Using professionally calibrated photogrammetric scale bars we automatically and accurately scale our 3D models to 1 mm accuracy for precise measurement in three dimensions. We then generate scaled 3D point clouds and extract offsets from manual measurement and multiple linear regression for comparison with collected terrestrial scanner data. These results further establish dense photo collection and SfM processing as an important, low-cost, rapid means of quantifying surface deformation in the critical hours after a surface-rupturing earthquake and emphasize that researchers with minimal training can rapidly collect three-dimensional data that can be used to analyze and archive the surface effects of damaging earthquakes.

Understanding thermally activated plastic deformation behavior of Zircaloy-4

NASA Astrophysics Data System (ADS)

Kumar, N.; Alomari, A.; Murty, K. L.

2018-06-01

Understanding micromechanics of plastic deformation of existing materials is essential for improving their properties further and/or developing advanced materials for much more severe load bearing applications. The objective of the present work was to understand micromechanics of plastic deformation of Zircaloy-4, a zirconium-based alloy used as fuel cladding and channel (in BWRs) material in nuclear reactors. The Zircaloy-4 in recrystallized (at 973 K for 4 h) condition was subjected to uniaxial tensile testing at a constant cross-head velocity at temperatures in the range 293 K-1073 K and repeated stress relaxation tests at 293 K, 573 K, and 773 K. The minimum in the total elongation was indicative of dynamic strain aging phenomenon in this alloy in the intermediate temperature regime. The yield stress of the alloy was separated into effective and athermal components and the transition from thermally activated dislocation glide to athermal regime took place at around 673 K with the athermal stress estimated to be 115 MPa. The activation volume was found to be in the range of 40 b3 to 160 b3. The activation volume values and the data analyses using the solid-solution models in literature indicated dislocation-solute interaction to be a potential deformation mechanism in thermally activated regime. The activation energy calculated at 573 K was very close to that found for diffusivity of oxygen in α-Zr that was suggestive of dislocations-oxygen interaction during plastic deformation. This type of information may be helpful in alloy design in selecting different elements to control the deformation behavior of the material and impart desired mechanical properties in those materials for specific applications.

Time-slice maps showing age, distribution, and style of deformation in Alaska north of 60° N.

USGS Publications Warehouse

Moore, Thomas E.; Box, Stephen E.

2016-08-29

The structural architecture of Alaska is the product of a complex history of tectonism that occurred along the Cordilleran and Arctic margins of North America through interactions with ancient and modern ocean plates and with continental elements derived from Laurentia, Siberia, and Baltica. To unravel the tectonic history of Alaska, we constructed maps showing the age, distribution, structural style, and kinematics of contractional and penetrative extensional deformation in Alaska north of latitude 60° N. at a scale of 1:5,000,000. These maps use the Geologic Map of the Arctic (Harrison and others, 2011) as a base map and follow the guidelines in the Tectonic Map of the Arctic project (Petrov and others, 2013) for construction, including use of the International Commission on Stratigraphy time scale (Cohen and others, 2013) divided into 20 time intervals. We find evidence for deformation in 14 of the 20 time intervals and present maps showing the known or probable extent of deformation for each time interval. Maps and descriptions of deformational style, age constraints, kinematics, and information sources for each deformational episode are discussed in the text and are reported in tabular form. This report also contains maps showing the lithologies and structural geology of Alaska, a terrane map, and the distribution of tectonically important units including post-tectonic sedimentary basins, accretionary complexes, ophiolites, metamorphic rocks.These new maps show that most deformational belts in Alaska are relatively young features, having developed during the late Mesozoic and Cenozoic. The oldest episode of deformation recognized anywhere in Alaska is found in the basement of the Farewell terrane (~1.75 Ga). Paleozoic and early Mesozoic deformational events, including Devonian deformation in the Arctic Alaska terrane, Pennsylvanian deformation in the Alexander terrane, Permian deformation in the Yukon Composite (Klondike orogeny) and Farewell terranes (Browns

Surface deformation monitored on the south eastern part of Uttarakhand State of India by the Persistent Scatterer Interferometry (PSI) techniques

NASA Astrophysics Data System (ADS)

Yhokha, A.; Chang, C.; Yen, J.; Goswami, P. K.; Ching, K.

2013-12-01

Persistent Scatterer Interferometry (PSI) is a useful tool in gathering the first basic information about the surface deformation, despite of different natural terrains, forested or mountainous region. This technique has been applied successfully by various worker in different field in extracting surface information in variety of terranes. The advantage of this techniques is that it has the ability of taking into account of only those return radar signal which are the brightest or the strongest in the surrounding background signal. Moreover, PS algorithms operate on a time series of interferograms all formed with respect to a single master SAR image that the noise terms of displacement for each PS pixel are much reduced. Keeping all these points in mind, we applied this technique in the Himalayan mountain, covering the south eastern part of the Uttarakhand state of India. So far lots of different work has been carried out in the Himalayan region, but less work has been done in regards to its surface deformation. The Himalayan mountain are well know for its segmented nature, different region undergoing different tectonic activity. In the similar manner, our PSI result in our study area also reveal two different set of deformation, with its eastern part revealing subsidence and the western part undergoing uplift, these two set of deformation is separated by a right later strike slip fault called, the Garampani-Kathgodam fault (G-KF). Apart from this obvious deformation, the western part also reveal differential deformation. Based on our result we have also tried to create a deformation model, to understand and to get better knowledge of the tectonic deformation setting.

Topography of the Central Alps in the light of Tertiary collisional tectonics

NASA Astrophysics Data System (ADS)

Rosenberg, Claudio; Garcia, Sebastian

2013-04-01

Collisional shortening in the Central Alps is partitioned very differently between the upper and lower plates along the strike of the orogen. North of the Insubric Line, the amount of post-nappe shortening accommodated in the wedge of accreted lower crustal material, increases westwards, whereas south of the Insubric Line, post-nappe shortening accommodated in the upper plate increases eastward (Rosenberg and Kissling, 2013). Taking the Bergell pluton as a time marker, the age of these deformations is inferred to be post 30 Ma. We investigate the present-day topography of the Central Alps, in order to test whether the systematic, along-strike changes, in the amounts of post-nappe shortening are associated to a systematic change in the topographic signature. In order to do so, the maximum and minimum elevations, and the local relief along a series of N-S sections are analysed and compared. The analysis of these topographic sections shows that the local relief varies following two along-strike trends: 1. North of the Insubric Line, i.e. in the wedge of accreted lower crust, the relief decreases from west to east, showing the transition from a highly incised topography in the west to a plateau-like topography in the East. 2. South of the Insubric Line, i.e. in the lower plate, the relief increases from East to West. These trends point to a positive correlation between the amount of shortening and the intensity of local relief. Linear correlations between local relief and uplift rate (e.g. Hurtez et al., 1999), and between local relief and shortening rates (Champagnac et al., 2012) have been inferred for different, tectonically active areas. Areas of larger finite shortening in the Central Alps, characterized by higher local relief, probably correspond to areas of higher shortening (and uplift) rates during Alpine collision. Considering the very slow, present-day, convergent movements across the Central Alps (Noquet and Calais, 2004) it is not clear whether the

Wrench tectonics in Abu Dhabi, United Arab Emirates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibrahim, M.; Mohamed, A.S.

1995-08-01

Recent studies of the geodynamics and tectonic history of the Arabian plate throughout geologic time have revealed that Wrench forces played an important role in the structural generation and deformation of Petroleum basins and reservoirs of the United Arab Emirates. The tectonic analysis of Abu Dhabi revealed that basin facies evolution were controlled by wrench tectonics, examples are the Pre-Cambrian salt basin, the Permo-Triassic and Jurassic basins. In addition, several sedimentary patterns were strongly influenced by wrench tectonics, the Lower Cretaceous Shuaiba platform margin and associated reservoirs is a good example. Wrench faults, difficult to identify by conventional methods, weremore » examined from a regional perspective and through careful observation and assessment of many factors. Subsurface structural mapping and geoseismic cross-sections supported by outcrop studies and geomorphological features revealed a network of strike slip faults in Abu Dhabi. Structural modelling of these wench forces including the use of strain ellipses was applied both on regional and local scales. This effort has helped in reinterpreting some structural settings, some oil fields were interpreted as En Echelon buckle folds associated with NE/SW dextral wrench faults. Several flower structures were interpreted along NW/SE sinistral wrench faults which have significant hydrocarbon potential. Synthetic and Antithetic strike slip faults and associated fracture systems have played a significant role in field development and reservoir management studies. Four field examples were discussed.« less

Late cretaceous extensional tectonics and associated igneous activity on the northern margin of the Gulf of Mexico Basin

NASA Technical Reports Server (NTRS)

Bowen, R. L.; Sundeen, D. A.

1985-01-01

Major, dominantly compressional, orogenic episodes (Taconic, Acadian, Alleghenian) affected eastern North America during the Paleozoic. During the Mesozoic, in contrast, this same region was principally affected by epeirogenic and extensional tectonism; one episode of comparatively more intense tectonic activity involving extensive faulting, uplift, sedimentation, intrusion and effusion produced the Newark Series of eposits and fault block phenomena. This event, termed the Palisades Disturbance, took place during the Late Triassic - Earliest Jurassic. The authors document a comparable extensional tectonic-igneous event occurring during the Late Cretaceous (Early Gulfian; Cenomanian-Santonian) along the southern margin of the cratonic platform from Arkansas to Georgia.

Challenges to Progress in Studies of Climate-Tectonic-Erosion Interactions

NASA Astrophysics Data System (ADS)

Burbank, D. W.

2016-12-01

Attempts to unravel the relative importance of climate and tectonics in modulating topography and erosion should compare relevant data sets at comparable temporal and spatial scales. Given that such data are uncommonly available, how can we compare diverse data sets in a robust fashion? Many erosion-rate studies rely on detrital cosmogenic nuclides. What time scales can such data address, and what landscape conditions do they require to provide accurate representations of long-term erosion rates? To what extent do large-scale, but infrequent erosional events impact long-term rates? Commonly, long-term erosion rates are deduced from thermochronologic data. What types of data are needed to test for consistency of rates across a given interval or change in rates through time? Similarly, spatial and temporal variability in precipitation or tectonics requires averaging across appropriate scales. How are such data obtained in deforming mountain belts, and how do we assess their reliability? This study describes the character and temporal duration of key variables that are needed to examine climate-tectonic-erosion interactions, explores the strengths and weaknesses of several study areas, and suggests the types of data requirements that will underpin enlightening "tests" of hypotheses related to the mutual impacts of climate, tectonics, and erosion.

Lithospheric structure of northwest Africa: Insights into the tectonic history and influence of mantle flow on large-scale deformation

NASA Astrophysics Data System (ADS)

Miller, Meghan S.; Becker, Thorsten

2014-05-01

Northwest Africa is affected by late stage convergence of Africa with Eurasia, the Canary Island hotspot, and bounded by the Proterozoic-age West African craton. We present seismological evidence from receiver functions and shear-wave splitting along with geodynamic modeling to show how the interactions of these tectonic features resulted in dramatic deformation of the lithosphere. We interpret seismic discontinuities from the receiver functions and find evidence for localized, near vertical-offset deformation of both crust-mantle and lithosphere-asthenosphere interfaces at the flanks of the High Atlas. These offsets coincide with the locations of Jurassic-aged normal faults that have been reactivated during the Cenozoic, further suggesting that inherited, lithospheric-scale zones of weakness were involved in the formation of the Atlas. Another significant step in lithospheric thickness is inferred within the Middle Atlas. Its location corresponds to the source of regional Quaternary alkali volcanism, where the influx of melt induced by the shallow asthenosphere appears restricted to a lithospheric-scale fault on the northern side of the mountain belt. Inferred stretching axes from shear-wave splitting are aligned with the topographic grain in the High Atlas, suggesting along-strike asthenospheric shearing in a mantle channel guided by the lithospheric topography. Isostatic modeling based on our improved lithospheric constraints indicates that lithospheric thinning alone does not explain the anomalous Atlas topography. Instead, an mantle upwelling induced by a hot asthenospheric anomaly appears required, likely guided by the West African craton and perhaps sucked northward by subducted lithosphere beneath the Alboran. This dynamic support scenario for the Atlas also suggests that the timing of uplift is contemporaneous with the recent volcanismin the Middle Atlas.

Role of tectonic inheritance in the instauration of Tunisian Atlassic fold-and-thrust belt: Case of Bouhedma - Boudouaou structures

NASA Astrophysics Data System (ADS)

Ghanmi, Mohamed Abdelhamid; Ghanmi, Mohamed; Aridhi, Sabri; Ben Salem, Mohamed Sadok; Zargouni, Fouad

2016-07-01

Tectonic inversion in the Bouhedma-Boudouaou Mountains was investigated through recent field work and seismic lines interpretation calibrated with petroleum well data. Located to the Central-Southern Atlas of Tunisia, this area signed shortened intra-continental fold-and-thrust belts. Two dissymmetric anticlines characterize Bouhedma - Boudouaou major fold. These structures show a strong virgation respectively from E-W to NNE-SSW as a response to the interference between both tectonic inversion and tectonic inheritance. This complex geometry is driven by Mesozoic rifting, which marked an extensional inherited regime. A set of late Triassic-Early Jurassic E-W and NW-SE normal faults dipping respectively to the North and to the East seems to widely affect the overall geodynamic evolution of this domain. They result in major thickness changes across the hanging wall and the footwall blocks in response with the rifting activity. Tectonic inversion is inferred from convergence between African and European plates since late Cretaceous. During Serravalian - Tortonian event, NW-SE trending paroxysm led to: 1) folding of pre-inversion and syn-inversion strata, 2) reactivation of pre-existing normal faults to reverse ones and 3) orogeny of the main structures with NE-SW and E-W trending. The compressional feature still remains active during Quaternary event (Post-Villafranchian) with N-S trending compression. Contraction during inversion generates folding and internal deformation as well as Fault-Propagation-Fold and folding related strike.

Modelling and visualizing distributed compressional plate deformation using GPlates2.0: The Arctic Eurekan Orogeny

NASA Astrophysics Data System (ADS)

Gion, Austin; Williams, Simon; Müller, Dietmar

2017-04-01

Present-day distributed plate deformation is being mapped and simulated in great detail, largely based on satellite observations. In contrast, the modelling of and data assimilation into deforming plate models for the geological past is still in its infancy. The recently released GPLates2.0 (www.gplates.org) software provides a framework for building plate models including diffuse deformation. Here we present an application example for the Eurekan orogeny, a Paleogene tectonic event driven by sea floor spreading in the Labrador Sea and Baffin Bay, resulting in compression between NW Greenland and the Canadian Arctic. The complexity of the region has prompted the development of countless tectonic models over the last 100 years. Our new tectonic model incorporates a variety of geological field and geophysical observations to model rigid and diffuse plate deformation in this region. Compression driven by Greenland's northward motion contemporaneous with sea floor spreading in the Labrador Sea, shortens Ellesmere Island in a "fan" like pattern, creating a series of thrust faults. Our model incorporates two phases of tectonic events during the orogeny from 63-35 Ma. Phase one from 63 to 55 Ma incorporates 85 km of Paleocene extension between Ellesmere Island and Devon Island with extension of 20 km between Axel Heiberg Island and Ellesmere Island and 85 km of left-lateral strike-slip along the Nares Strait/Judge Daly Fault System, matching a range of 50-100 km indicated by the offset of marker beds, facies contacts, and platform margins between the conjugate Greenland and Ellesmere Island margins. Phase two from 55 to 35 Ma captures 30 km of east-west shortening and 200 km of north-south shortening from Ellesmere Island to the Canadian Arctic Island margins. Our model extends the boundaries of the Eurekan Orogeny northward, considering its effect on the Lomonosov Ridge, Morris Jessup Rise, and the Yermak Plateau , favouring a model in which the Lomonosov Ridge moves

Deformation Styles Along the Southern Alaska Margin Constrained by GPS

NASA Astrophysics Data System (ADS)

Elliott, J.; Freymueller, J. T.; Larsen, C. F.

2009-12-01

The present-day deformation observed in southcentral and southeast Alaska and the adjacent region of Canada is controlled by two main factors: ~ 50 mm/yr relative motion between the Pacific plate and North America and the Yakutat block’s collision with and accretion to southern Alaska. Over 45 mm/yr of NW-SE directed convergence from the collision is currently accommodated within the St. Elias orogen. The Fairweather, St. Elias, and Chugach ranges show the spectacular consequences of the relative tectonic motions, but the details of the plate interactions have not been well understood. Here we present GPS data from a network of over 170 campaign sites across the region. We use the data to constrain block models and forward models that characterize the nature and extent of the tectonic deformation along the Pacific-Yakutat-North America boundary. Tectonics in southeast Alaska can be described by block motion, with the Pacific plate bounding the region to the west. The fastest block motions occur along the coastal regions. The Yakutat block has a velocity of 51 ± 2.7 mm/yr towards N22 ± 2.5 deg W relative to North America. This velocity has a magnitude almost identical to that of the Pacific plate, but the azimuth is more westerly. The northeastern edge of the Yaktuat block is deforming, represented in our model by two small blocks outboard of the Fairweather fault. East of that fault, the Fairweather block rotates clockwise relative to North America, resulting in transpression along the Duke River and Eastern Denali faults. There is a clear transfer of strain from the coastal region hundreds of kilometers eastward into the Northern Cordillera block, confirming earlier suggestions that the effects of the Yakutat collision are far-reaching along its eastern margin. In contrast, deformation along the leading edge of the Yakutat collision is relatively narrowly focused within the southern half of the St. Elias orogen. The current deformation front of the Yakutat

Philippine microplate tectonics and hydrocarbon exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallagher, J.J. Jr.

1986-07-01

Hydrocarbon traps in the Philippine Islands developed during a long, complex history of microplate tectonics. Carbonate and clastic stratigraphic traps formed during Mesozoic and early Cenozoic rifting and drifting. Hydrocarbons, generated in deep rift basins, migrated to the traps during drifting. Later Cenozoic compressional tectonic activity and concomitant faulting enhanced some traps and destroyed others. Seismic data offshore from Palawan Island reveal the early trap histories. Later trap histories can be interpreted from seismic, outcrop, and remote-sensing data. Understanding the microplate tectonic history of the Philippines is the key to interpreting trap histories.

Active Tectonics in the Central Chilean Andes: 3D Tomography Based on the Aftershock Sequence of the 28 August 2004 Shallow Crustal Earthquake

NASA Astrophysics Data System (ADS)

Comte, D.; Farias, M.; Charrier, R.; Gonzalez, A.

2008-12-01

Most of the seismological research in the Andes has been mainly oriented to the detection and understanding of the seismicity associated with megathrust earthquakes that characterize the subduction environment that governs the Andean tectonics. However, deployments of temporary networks have allowed the detection of intense crustal seismicity beneath the Chilean forearc-arc region. The temporary seismic network deployed along the Las Leñas and Pangal river valleys (34°25'S), between January and May 2004 permitted to better constrain the abundant shallow intra-continental seismicity previously detected in that region. Although most of the seismicity is randomly distributed in the region, several microearthquakes occur along the trace of the major El Fierro fault-system. This system is well recognized between 33°30' and 35°15'S and is located at or close to the eastern contact between Mesozoic and Cenozoic deposits in the Principal Cordillera and, locally, below active volcanoes, being considered to have participated in the extension and tectonic inversion of a widely extended (>600 km long) Cenozoic basin along the Principal Cordillera. Further south, at 35°S, a Mw=6.5 strike-slip shallow earthquake occurred on August 28, 2004, near of the headwater of the Teno river, close to the Planchon volcano. A 3D detailed Vp and Vs velocities determination was obtained along the 2004 earthquake aftershock area. The aftershocks are distributed along one branch of the El Fierro fault system, with a NNE-SSW direction and depths lower than 15 km. The rupture zone coincides with a sharp contrast in Vp and Vs, also in coincidence with the presence of hydrothermal fluids, gypsum diapers and the volcanic arc, suggesting rheological contrast controlling deformation. At the surface, this zone present an intense contractive deformation produced during the Neogene, which differs from what can be observed in other regions. Present day deformation related to seismicity has no

Tectonically Induced Anomalies Without Large Earthquake Occurrences

NASA Astrophysics Data System (ADS)

Shi, Zheming; Wang, Guangcai; Liu, Chenglong; Che, Yongtai

2017-06-01

In this study, we documented a case involving large-scale macroscopic anomalies in the Xichang area, southwestern Sichuan Province, China, from May to June of 2002, after which no major earthquake occurred. During our field survey in 2002, we found that the timing of the high-frequency occurrence of groundwater anomalies was in good agreement with those of animal anomalies. Spatially, the groundwater and animal anomalies were distributed along the Anninghe-Zemuhe fault zone. Furthermore, the groundwater level was elevated in the northwest part of the Zemuhe fault and depressed in the southeast part of the Zemuhe fault zone, with a border somewhere between Puge and Ningnan Counties. Combined with microscopic groundwater, geodetic and seismic activity data, we infer that the anomalies in the Xichang area were the result of increasing tectonic activity in the Sichuan-Yunnan block. In addition, groundwater data may be used as a good indicator of tectonic activity. This case tells us that there is no direct relationship between an earthquake and these anomalies. In most cases, the vast majority of the anomalies, including microscopic and macroscopic anomalies, are caused by tectonic activity. That is, these anomalies could occur under the effects of tectonic activity, but they do not necessarily relate to the occurrence of earthquakes.

Tectonics of the central Andes

NASA Technical Reports Server (NTRS)

Bloom, Arthur L.; Isacks, Bryan L.; Fielding, Eric J.; Fox, Andrew N.; Gubbels, Timothy L.

1989-01-01

Acquisition of nearly complete coverage of Thematic Mapper data for the central Andes between about 15 to 34 degrees S has stimulated a comprehensive and unprecedented study of the interaction of tectonics and climate in a young and actively developing major continental mountain belt. The current state of the synoptic mapping of key physiographic, tectonic, and climatic indicators of the dynamics of the mountain/climate system are briefly reviewed.

Global deformation on the surface of Venus

NASA Technical Reports Server (NTRS)

Bilotti, Frank; Connors, Chris; Suppe, John

1992-01-01

Large-scale mapping of tectonic structures on Venus shows that there is an organized global distribution to deformation. The structures we emphasize are linear compressive mountain belts, extensional rafted zones, and the small-scale but widely distributed wrinkle ridges. Ninety percent of the area of the planet's compressive mountain belts are concentrated in the northern hemisphere whereas the southern hemisphere is dominated by extension and small-scale compression. We propose that this striking concentration of fold belts in the northern hemisphere, along with the globe-encircling equatorial rift system, represents a global organization to deformation on Venus.

Research on the Crustal Deformation Characteristics in Beijing Using Insar and Gnss Technology

NASA Astrophysics Data System (ADS)

Hu, L.; Xing, C.; Dai, K.; Li, Y.; Li, Z.; Zhang, J.; Yan, R.; Xu, B.; Fan, Z.

2018-04-01

In this paper, we tried to reveal the characteristics of the crustal deformation in both the horizontal and vertical directions in Beijing using InSAR and GNSS observations. Regarding the serious land subsidence in Beijing plain, we also analysed the mechanism of the occurrence and development of the subsidence in combination with the tectonic settings. The GNSS results reveal that the crust in Beijing shows a significant left-lateral trend movement in the horizontal direction, while the vertical direction shows a gentle rise in the mountainous region and a significant subsidence in the plain area. The INSAR results shows a detailed subsidence area and the deformation characteristics were analyzed considering the fault activity. The foundation of geological structure dominates the subsiding in the Beijing Plain. The exploitation of groundwater exacerbates the level of subsidence and has new development. The active faults controlled the development of the subsiding in present days.

Complex Plate Tectonic Features on Planetary Bodies: Analogs from Earth

NASA Astrophysics Data System (ADS)

Stock, J. M.; Smrekar, S. E.

2016-12-01

We review the types and scales of observations needed on other rocky planetary bodies (e.g., Mars, Venus, exoplanets) to evaluate evidence of present or past plate motions. Earth's plate boundaries were initially simplified into three basic types (ridges, trenches, and transform faults). Previous studies examined the Moon, Mars, Venus, Mercury and icy moons such as Europa, for evidence of features, including linear rifts, arcuate convergent zones, strike-slip faults, and distributed deformation (rifting or folding). Yet, several aspects merit further consideration. 1) Is the feature active or fossil? Earth's active mid ocean ridges are bathymetric highs, and seafloor depth increases on either side; whereas, fossil mid ocean ridges may be as deep as the surrounding abyssal plain with no major rift valley, although with a minor gravity low (e.g., Osbourn Trough, W. Pacific Ocean). Fossil trenches have less topographic relief than active trenches (e.g., the fossil trench along the Patton Escarpment, west of California). 2) On Earth, fault patterns of spreading centers depend on volcanism. Excess volcanism reduced faulting. Fault visibility increases as spreading rates slow, or as magmatism decreases, producing high-angle normal faults parallel to the spreading center. At magma-poor spreading centers, high resolution bathymetry shows low angle detachment faults with large scale mullions and striations parallel to plate motion (e.g., Mid Atlantic Ridge, Southwest Indian Ridge). 3) Sedimentation on Earth masks features that might be visible on a non-erosional planet. Subduction zones on Earth in areas of low sedimentation have clear trench -parallel faults causing flexural deformation of the downgoing plate; in highly sedimented subduction zones, no such faults can be seen, and there may be no bathymetric trench at all. 4) Areas of Earth with broad upwelling, such as the North Fiji Basin, have complex plate tectonic patterns with many individual but poorly linked ridge

Offshore Tectonics of the St. Elias Mountains: Insights from Ocean Drilling and Seismic Stratigraphy on the Yakutat Shelf

NASA Astrophysics Data System (ADS)

Worthington, L. L.; Gulick, S. P. S.; Montelli, A.; Jaeger, J. M.; Zellers, S.; Walczak, M. H.; Mix, A. C.

2015-12-01

Ongoing collision of the Yakutat (YAK) microplate with North America (NA) in southern Alaska has driven orogenesis of the St. Elias Mountains and the advance of the offshore deformation front to the southeast. The offshore St. Elias fold-thrust belt records the complex interaction between collisional tectonics and glacial climate variability, providing insight for models of orogenesis and the evolution of glacial depocenters. Glacial erosion and deposition have provided sediment that constructed the upper continental shelf, much of which has been reincorporated into the orogenic wedge through offshore faulting and folding. We integrate core and downhole logging data from IODP Expedition 341 (Sites U1420 and U1421) drilled on the Yakutat shelf and slope with high-resolution and regional seismic profiles to investigate the coupled structural and stratigraphic evolution of the St. Elias margin. Site U1420 lies on the Yakutat shelf within the Bering Trough, a shelf-crossing trough that is within primary depocenter for Bering Glacier sediments. Two faults underlie the glacial packages and have been rendered inactive as the depositional environment has evolved, while faulting elsewhere on the shelf has initiated. Site U1421 lies on the current continental slope, within the backlimb of an active thrust that forms part of the modern YAK-NA deformation front. At each of these sites, we recovered glacigenic diamict (at depths up to ~1015 m at Site U1420), much of which is younger than 0.3 Ma. Age models within the trough indicated that initiation of active deformation away from the Bering Trough depocenter likely occurred since 0.3 Ma, suggesting that possible tectonic reorganization due to mass redistribution by glacial processes can occur at time scales on the order of 100kyr-1Myr.

Inferring tectonic activity using drainage network and RT model: an example from the western Himalayas, India

NASA Astrophysics Data System (ADS)

Sahoo, Ramendra; Jain, Vikrant

2017-04-01

Morphology of the landscape and derived features are regarded to be an important tool for inferring about tectonic activity in an area, since surface exposures of these subsurface processes may not be available or may get eroded away over time. This has led to an extensive research in application of the non-planar morphological attributes like river long profile and hypsometry for tectonic studies, whereas drainage network as a proxy for tectonic activity has not been explored greatly. Though, significant work has been done on drainage network pattern which started in a qualitative manner and over the years, has evolved to incorporate more quantitative aspects, like studying the evolution of a network under the influence of external and internal controls. Random Topology (RT) model is one of these concepts, which elucidates the connection between evolution of a drainage network pattern and the entropy of the drainage system and it states that in absence of any geological controls, a natural population of channel networks will be topologically random. We have used the entropy maximization principle to provide a theoretical structure for the RT model. Furthermore, analysis was carried out on the drainage network structures around Jwalamukhi thrust in the Kangra reentrant in western Himalayas, India, to investigate the tectonic activity in the region. Around one thousand networks were extracted from the foot-wall (fw) and hanging-wall (hw) region of the thrust sheet and later categorized based on their magnitudes. We have adopted the goodness of fit test for comparing the network patterns in fw and hw drainage with those derived using the RT model. The null hypothesis for the test was, the drainage networks in the fw are statistically more similar than those on the hw, to the network patterns derived using the RT model for any given magnitude. The test results are favorable to our null hypothesis for networks with smaller magnitudes (< 9), whereas for larger

North-South contraction of the mojave block and strike-slip tectonics in southern california.

PubMed

Bartley, J M; Glazner, A F; Schermer, E R

1990-06-15

The Mojave block of southern California has undergone significant late Cenozoic north-south contraction. This previously unappreciated deformation may account for part of the discrepancy between neotectonic and plate-tectonic estimates of Pacific-North American plate motion, and for part of the Big Bend in the San Andreas fault. In the eastern Mojave block, contraction is superimposed on early Miocene crustal extension. In the western Mojave block, contractional folds and reverse faults have been mistaken for extensional structures. The three-dimensional complexity of the contractional structures may mean that rigid-block tectonic models of the region based primarily on paleomagnetic data are unreliable.

Tectonic tremor activity associated with teleseismic and nearby earthquakes

NASA Astrophysics Data System (ADS)

Chao, K.; Obara, K.; Peng, Z.; Pu, H. C.; Frank, W.; Prieto, G. A.; Wech, A.; Hsu, Y. J.; Yu, C.; Van der Lee, S.; Apley, D. W.

2016-12-01

Tectonic tremor is an extremely stress-sensitive seismic phenomenon located in the brittle-ductile transition section of a fault. To better understand the stress interaction between tremor and earthquake, we conduct the following studies: (1) search for triggered tremor globally, (2) examine ambient tremor activities associated with distant earthquakes, and (3) quantify the temporal variation of ambient tremor activity before and after nearby earthquakes. First, we developed a Matlab toolbox to enhance the searching of triggered tremor globally. We have discovered new tremor sources in the inland faults in Kyushu, Kanto, and Hokkaido in Japan, southern Chile, Ecuador, and central Colombia in South America, and in South Italy. Our findings suggest that tremor is more common than previously believed and indicate the potential existence of ambient tremor in the triggered tremor active regions. Second, we adapt the statistical analysis to examine whether the long-term ambient tremor rate may affect by the dynamic stress of teleseismic earthquakes. We analyzed the data in Nankai, Hokkaido, Cascadia, and Taiwan. Our preliminary results did not show an apparent increase of ambient tremor rate after the passing of surface waves. Third, we quantify temporal changes in ambient tremor activity before and after the occurrence of local earthquakes under the southern Central Range of Taiwan with magnitudes of >=5.5 from 2004 to 2016. For a particular case, we found a temporal variation of tremor rate before and after the 2010/03/04 Mw6.3 earthquake, located about 20 km away from the active tremor source. The long-term increase in the tremor rate after the earthquake could have been caused by an increase in static stress following the mainshock. For comparison, clear evidence from seismic and GPS observations indicate a short-term increase in the tremor rate a few weeks before the mainshock. The increase in the tremor rate before the mainshock could correlate with stress changes

Hotspot evolution and Venusian tectonic style

NASA Technical Reports Server (NTRS)

Mcgill, George E.

1994-01-01

Because hotspots represent an important manifestation of heat loss on Venus, their geological evolution is of fundamental importance for any attempt to understand Venusian tectonics. Eistla Regio is an approximately 7500-km-long, moderately elevated region inferred to overlie one or more large mantle upwellings or hotspots. It also contains many shield volcanoes and coronae believed due to the rise of thermal plumes in the mantle. Central Eistla Regio includes two large volcanoes, Sappho and Anala, and several coronae in close proximity. Detailed mapping in this region results in two conclusions of tectonic significance: (1) Sappho and Anala occur near the intersection of two major extensional deformation zones, and (2) the coronae are older than the large volcanoes. Several of the coronae occur as a chain along Guor Linea, one of the major extensional deformation zones. Stratigraphic relationships indicate that the coronae began forming very soon after the emplacement of the widespread regional plains materials. Thus Central Eistla Regio was the site of a swarm of plumes that first formed coronae and then later formed shield volcanoes. The expected result of such a swarm would be thermal thinning of the elastic lithosphere with time. However, model results, geological observations, and gravity data suggest that the change from coronae to shield volcanoes was accompanied by a thickening of the lithosphere with time. This thickening is interpreted to be the result of global cooling of the lithosphere following the most recent episode of near-global resurfacing. The global cooling must have occurred faster than local heating of the lithosphere due to the impingement of thermal plumes.

Geomorphology of the Burnt River, eastern Oregon, USA: Topographic adjustments to tectonic and dynamic deformation

NASA Astrophysics Data System (ADS)

Morriss, Matthew Connor; Wegmann, Karl W.

2017-02-01

Eastern Oregon contains the deepest gorge in North America, where the Snake River cuts vertically down 2300 m. This deep gorge is known as Hells Canyon. A landscape containing such a topographic feature is likely undergoing relatively recent deformation. Study of the Burnt River, a tributary to the Snake River at the upstream end of Hells Canyon, yields data on active river incision in eastern Oregon, indicating that Quaternary faults are a first order control on regional landscape development. Through 1:24,000-scale geologic mapping, a 500,000-year record of fluvial incision along the Burnt River was constructed and is chronologically anchored by optically stimulated luminescence dating and tephrochronology analyses. A conceptual model of fluvial terrace formation was developed using these ages and likely applies to other non-glaciated catchments in eastern Oregon. Mapped terraces, inferred to have formed during glacial-interglacial cycles, provide constraints on rates of incision of the Burnt River. Incision through these terraces indicates that the Burnt River is down-cutting at 0.15 to 0.57 m kyr- 1. This incision appears to reflect a combination of local base-level adjustments tied to movement along the newly mapped Durkee fault and regional base-level control imposed by the downcutting of the Snake River. Deformation of terraces as young as 38.7 ± 5.1 ka indicates Quaternary activity along the Durkee fault, and when combined with topographic metrics (slope, relief, hypsometry, and stream-steepness), reveals a landscape in disequilibrium. Longer wavelength lithospheric dynamics (delamination and crustal foundering) that initiated in the Miocene may also be responsible for continued regional deformation of the Earth's surface.

The Mobile Margin of (Far) North America: GPS Constraints on Active Deformation in Alaska and the Role of the Yakutat Block

NASA Astrophysics Data System (ADS)

Elliott, J.; Freymueller, J. T.; Larsen, C. F.; Motyka, R. J.

2010-12-01

GPS data from southern Alaska and the northern Canadian Cordillera have helped redefine the region’s tectonic landscape. Instead of a comparatively simple interaction between the Pacific and North American plates, with relative motion accommodated on a single boundary fault, we find a margin made up of a number of small blocks and deformation zones with relative motion distributed across a variety of structures. Much of this complexity can be attributed to the Yakutat block, an allochthonous terrane that has been colliding with southern Alaska since the Miocene. We present a GPS-derived tectonic model for the Yakutat block collision and its effects on southern Alaska and eastern Canada. The Yakutat block moves NNW at a rate of 50 mm/a, resulting in ~ 45 mm/a of NW-directed convergence with southern Alaska. Along its eastern edge, the Yakutat block is deforming, represented in our model by two small northwesterly moving blocks outboard of the Fairweather fault. Part of the strain from the collision is transferred east of the Fairweather - Queen Charlotte fault system, causing the region inboard of the Fairweather fault to undergo a distinct clockwise rotation into the northern Canadian Cordillera. Further south, the region directly east of the Queen Charlotte fault displays a much slower clockwise rotation, suggesting that it is at least partially pulled along by the northern block motion. About 5% of the relative motion is transferred even further east, causing small northeasterly motions well into the northern Cordillera. The northwestern edge of the Yakutat block marks the main deformation front between that block and southern Alaska. Multiple narrow, northwesterly moving blocks bounded by N- to NW-dipping thrust faults are required to explain the GPS data between the Malaspina Glacier and the Bagley Ice Valley. These “blocks” may be more aptly termed crustal slivers or deformation zones due to their size and because their bounding faults may sole out into

The role of post-collisional strike-slip tectonics in the geological evolution of the late Neoproterozoic volcano-sedimentary Guaratubinha Basin, southern Brazil

NASA Astrophysics Data System (ADS)

Barão, Leonardo M.; Trzaskos, Barbara; Vesely, Fernando F.; de Castro, Luís Gustavo; Ferreira, Francisco J. F.; Vasconcellos, Eleonora M. G.; Barbosa, Tiago C.

2017-12-01

The Guaratubinha Basin is a late Neoproterozoic volcano-sedimentary basin included in the transitional-stage basins of the South American Platform. The aim of this study is to investigate its tectonic evolution through a detailed structural analysis based on remote sensing and field data. The structural and aerogeophysics data indicate that at least three major deformational events affected the basin. Event E1 caused the activation of the two main basin-bounding fault zones, the Guaratubinha Master Fault and the Guaricana Shear Zone. These structures, oriented N20-45E, are associated with well-defined right-lateral to oblique vertical faults, conjugate normal faults and vertical flow structures. Progressive transtensional deformation along the two main fault systems was the main mechanism for basin formation and the deposition of thick coarse-grained deposits close to basin-borders. The continuous opening of the basin provided intense intermediate and acid magmatism as well as deposition of volcaniclastic sediments. Event E2 characterizes generalized compression, recorded as minor thrust faults with tectonic transport toward the northwest and left-lateral activation of the NNE-SSW Palmital Shear Zone. Event E3 is related to the Mesozoic tectonism associated with the South Atlantic opening, which generated diabase dykes and predominantly right-lateral strike-slip faults oriented N10-50W. Its rhomboidal geometry with long axis parallel to major Precambrian shear zones, the main presence of high-angle, strike-slip or oblique faults, the asymmetric distribution of geological units and field evidence for concomitant Neoproterozoic magmatism and strike-slip movements are consistent with pull-apart basins reported in the literature.

Sedimentary masses and concepts about tectonic processes at underthrust ocean margins ( subduction).

USGS Publications Warehouse

Scholl, D. W.; von Huene, Roland E.; Vallier, T.L.; Howell, D.G.

1980-01-01

Tectonic processes associated with subduction of oceanic crust, but unrelated to the collision of thick crustal masses or microplates, are presumed by many geologists to significantly affect the formation and deformation of large sedimentary bodies at underthrust ocean margins. More geologists are familiar with the concept of subduction accretion than with other noncollision processes - for example, sediment subduction, subduction erosion, and subduction kneading. In our opinion, no single subduction-related tectonic process is the dominant or typical one that forges the geologic framework of modern underthrust ocean margins. It is likely, therefore, that the rock records of ancient underthrust margins are preserved in a multitude of structural and stratigraphic forms.-from Authors

Meso- and microscale vein structures in fore-arc basalts and boninites related to post-magmatic tectonic deformation in the outer Izu-Bonin-Mariana fore arc system: preliminary results from IODP Expedition 352

NASA Astrophysics Data System (ADS)

Quandt, Dennis; Micheuz, Peter; Kurz, Walter

2016-04-01

The International Ocean Discovery Program (IODP) Expedition 352 aimed to drill through the entire volcanic sequence of the Izu-Bonin-Mariana fore arc. Two drill sites are situated on the outer fore arc composed of fore arc basalts (FAB) whereas two more sites are located on the upper trench slope penetrating the younger boninites. First results from IODP Expedition 352 and preliminary post-cruise data suggest that FAB were generated by decompression melting during near-trench sea-floor spreading, and that fluids from the subducting slab were not involved in their genesis. Subduction zone fluids involved in boninite genesis appear to have been derived from progressively higher temperatures and pressures over time as the subducting slab thermally matured. Structures within the drill cores combined with borehole and site survey seismic data indicate that tectonic deformation in the outer Izu-Bonin-Mariana fore arc is mainly post-magmatic associated with the development of syn-tectonic sedimentary basins. Within the magmatic basement deformation was accommodated by shear along cataclastic fault zones and the formation of tension fractures, shear fractures and hybrid (tension and shear) fractures. Veins form by mineral filling of tension or hybrid fractures and show no or limited observable macroscale displacement along the fracture plane. (Low Mg-) Calcite and/or various types of zeolite are the major vein constituents, where the latter are considered to be alteration products of basaltic glass. Micrite contents vary significantly and are related to neptunian dikes. In boninites calcite develops mainly blocky shapes but veins with fibrous and stretched crystals also occur in places indicating antitaxial as well as ataxial growth, respectively. In FAB calcite forms consistently blocky crystals without any microscopic identifiable growth direction suggesting precipitation from a highly supersaturated fluid under dropping fluid pressure conditions. However, fluid pressure

Calculation of regional geomorphic indices to constrain the mechanisms of tectonic uplift and active deformation of the Island of Puerto Rico

NASA Astrophysics Data System (ADS)

Martinez, S.

2016-12-01

The island of Puerto Rico in the northern Caribbean covers an area of about 14,000 km2 and is 180 km long and 65 km wide and is densely populated by 3.4 million persons. The island is mountainous with an east-west-trending, central mountain range with its highest point of 1338 m in the geographic center of the island. Previous workers have suggested that the origin of this east-west, Central Cordillera is active uplift and folding of a large, east-west-trending anticline whose fold axis is coincident with the topographic crest of the Cordillera Central. The folding mechanism has been attributed by previous workers to obliquely-subducting slabs of the North American and Caribbean plates beneath the island. To test the hypothesis that this topographic and structural axis is also the axis of active topographic uplift, I created a knickpoint density map for the island based on over 50 different river systems to reveal areas of active uplift. The knickpoint map shows an excellent correlation with the proposed arch both in width and trend of the axis and supports the conclusion that the arch is the main axis of active uplift on the Island. I also calculated geomorphic indices for 21 different watersheds of the island that include the Hypsometric Integral and a Stream Length Gradient Index that both assess tectonic activity based on stream and watershed behaviors. The Hack index and Hypsometric Integral show that the most active area of uplift is located in the central and north-central parts of the island that include about one half of the length of the proposed, east-west-trending arch. The two topographically-elevated ends of the arch in the western and eastern parts of the island are less active, according to the indices. Lower values in these areas may be influenced by higher amounts of precipitations in these areas.

Marine forearc tectonics in the unbroken segment of the Northern Chile seismic gap

NASA Astrophysics Data System (ADS)

Geersen, J.; Behrmann, J.; Ranero, C. R.; Klaucke, I.; Kopp, H.; Lange, D.; Barckhausen, U.; Reichert, C. J.; Diaz-Naveas, J.

2016-12-01

While clearly occurring within the well-defined Northern Chile seismic gap, the 2014 Mw. 8.1 Iquique Earthquake only ruptured part of this gap, leaving large and possibly highly coupled areas untouched. These non-ruptured areas now may pose an elevated seismic hazard due to the transfer of stresses resulting from the 2014 rupture. Here we use recently collected multibeam bathymetric data, covering 90% of the North Chilean marine forearc, in combination with unpublished seismic reflection images to derive a tectonic map of the marine forearc in the unbroken segment of the seismic gap. In the entire study area we find evidence for widespread normal faulting. Seaward dipping normal faults locally extend close to the deformation front at the deep-sea trench under 8 km of water. Similar normal faults on the lower slope are neither observed further north (2014 Iquique earthquake area) nor further south (2007 Tocopilla earthquake area). On the upper continental slope, some of the normal faults dip towards the continent, defining N-S trending ridges that can be traced over tens of kilometers. The spatial variations in normal faulting do not correlate with obvious changes in the structural and tectonic setting of the subduction zone (e.g. plate convergence rate and direction, trench sediment thickness, subducting plate roughness). Thus, the permanent deformation recorded in the spatial distribution of faults may hold crucial information about the long-term seismic behavior of the Northern Chile seismic gap over multiple earthquake cycles. Although the structural interpretations cannot directly be translated into seismic hazard, the tectonic map serves to better understand deformation in the marine forearc in relation to the seismic cycle, historic seismicity, and the spatial distribution of plate-coupling.

Surface Deformation in Quetta Valley, Balochistan, Pakistan

NASA Astrophysics Data System (ADS)

Huang, J.; Shuhab, K.; Wulamu, A.; Crupa, W.; Khan, A. S.; Kakar, D. M.; Kasi, A.

2015-12-01

In February 2011, several ground fissures up to ~1.8 km in length appeared in the Quetta Valley, Balochsitan, Pakistan. It is not clear what caused the sudden occurrence of these fissures. The region is tectonically active and bounded to the west by several regional strike-slip faults including the north-south striking left-lateral Chaman fault system that slips at ~10 mm per year. Several large earthquakes have occurred recently in this area, one fatal 6.4 magnitude (Mw) earthquake occurred on October 28th, 2008. Some parts of Quetta Valley are subsiding; GPS data from two stations in Quetta that span mid-2006 - 2009 recorded subsidence rates of ~10 cm per year. Although subsidence in urban areas is generally attributed to groundwater depletion, it is not clear whether ground fissures are caused by water withdrawal or related to tectonics of the region. This study is designed to quantify and assess the source of surface deformation in Quetta Valley using InSAR, GPS, seismic and earthquake centroid moment tensor data. To detect and map the spatial-temporal features of the processes that led to the surface deformation, we used two time series, i.e., 15 European Remote Sensing (ERS-1/2) satellite images from 1992 - 1999 and 27 ENVISAT images spanning 2003 - 2010. A Differential Interferometric Synthetic Aperture Radar (DInSAR) Small Baseline Subset (SBAS) technique was used to investigate surface deformation. Eleven continuous-GPS stations within the InSAR antenna footprint were compared with the InSAR time series for quality control. Preliminary InSAR results revealed that the areas in and around the fissures are subsiding at 5 cm per year. Five seismic lines totaling ~60 km, acquired in 2003, were used to interpret faults beneath Holocene alluvium in the Quetta Valley. One of the blind faults is a north-south striking thrust fault mapped north into the Takatu range. However, a focal mechanism for the 2008 earthquake in this region indicated northwest

Impact of the slab dip change onto the deformation partitioning in the northern Lesser Antilles oblique subduction zone (Antigua-Virgin Islands)

NASA Astrophysics Data System (ADS)

Laurencin, Muriel; Marcaillou, Boris; Klingelhoefer, Frauke; Graindorge, David; Lebrun, Jean-Frédéric; Laigle, Mireille; Lallemand, Serge

2017-04-01

Marine geophysical cruises Antithesis (2013-2016) investigate the impact of the variations in interplate geometry onto margin tectonic deformation along the strongly oblique Lesser Antilles subduction zone. A striking features of this margin is the drastic increase in earthquake number from the quiet Barbuda-St Martin segment to the Virgin Islands platform. Wide-angle seismic data highlight a northward shallowing of the downgoing plate: in a 150 km distance from the deformation front, the slab dipping angle in the convergence direction decreases from 12° offshore of Antigua Island to 7° offshore of Virgin Islands. North-South wide-angle seismic line substantiates a drastic slab-dip change that likely causes this northward shallowing. This dip change is located beneath the southern tip of the Virgin Islands platform where the Anegada Passage entails the upper plate. Based on deep seismic lines and bathymetric data, the Anegada Passage is a 450 km long W-E trending set of pull-apart basins and strike-slip faults that extends from the Lesser Antilles accretionary prism to Puerto Rico. The newly observed sedimentary architecture within pull-apart Sombrero and Malliwana basins indicates a polyphased tectonic history. A past prominent NW-SE extensive to transtensive phase, possibly related to the Bahamas Bank collision, opened the Anegada Passage as previously published. Transpressive tectonic evidences indicate that these structures have been recently reactivated in an en-echelon sinistral strike-slip system. The interpreted strain ellipsoid is consistent with deformation partitioning. We propose that the slab northward shallowing increases the interplate coupling and the seismic activity beneath the Virgin Islands platform comparatively to the quiet Barbuda-St Martin segment. It is noteworthy that the major tectonic partitioning structure in the Lesser Antilles forearc is located above the slab dip change where the interplate seismic coupling increases.

Stress states in the Zagros fold-and-thrust belt from passive margin to collisional tectonic setting

NASA Astrophysics Data System (ADS)

Navabpour, Payman; Barrier, Eric

2012-12-01

The present-day Zagros fold-and-thrust belt of SW-Iran corresponds to the former Arabian passive continental margin of the southern Neo-Tethyan basin since the Permian-Triassic rifting, undergoing later collisional deformation in mid-late Cenozoic times. In this paper an overview of brittle tectonics and palaeostress reconstructions of the Zagros fold-and-thrust belt is presented, based on direct stress tensor inversion of fault slip data. The results indicate that, during the Neo-Tethyan oceanic opening, an extensional tectonic regime affectedthe sedimentary cover in Triassic-Jurassic times with an approximately N-S trend of the σ3 axis, oblique to the margin, which was followed by some local changes to a NE-SW trend during Jurassic-Cretaceous times. The stress state significantly changed to thrust setting, with a NE-SW trend of the σ1 axis, and a compressional tectonic regime prevailed during the continental collision and folding of the sedimentary cover in Oligocene-Miocene times. This compression was then followed by a strike-slip stress state with an approximately N-S trend of the σ1 axis, oblique to the belt, during inversion of the inherited extensional basement structures in Pliocene-Recent times. The brittle tectonic reconstructions, therefore, highlighted major changes of the stress state in conjunction with transitions between thin- and thick-skinned structures during different extensional and compressional stages of continental deformation within the oblique divergent and convergent settings, respectively.

Flower-strucutre deformation pattern of theTian Shan mountains as revealed by Late Quaternary geological and modern Geodesy slip rates

NASA Astrophysics Data System (ADS)

Wu, C.; Zhang, P.; Zheng, W.; Wang, H.; Zhang, Z.; Ren, Z.; Zheng, D.; Yu, J.; Wu, G.

2017-12-01

The deformation pattern and strain distribution of the Tian Shan is a hot issue.Previous studies mainly focus on the thrust-fold systems on both sides of Tian Shan, the strike-slip faults within the mountains are rarely reported. The understanding about the deformation characteristics of Tian Shan is not complete for lacking information of these strike-slip faults.Our studies show the NEE trending structures of Maidan fault and Nalati fault in the southwestern Tian Shan are all active during the Holence. These faults are characterized by sinistral strike-slip and thrust movement. The minimum average sinistral strike-slip rate of the Maidan fault is 1.07 ± 0.13 mm/yr. During the late Quaternary, the average shortening rate and sinistral strike-slip rate of the Nalati fault are 2.1 ±0.4 mm/yr and 2.56 ±0.25 mm/yr, respectively . In the interior of the Tian Shan area, two groups of strike-slip faults were developed. The NEE trending faults with sinistral strike-slipmovement, and the NWW trending faults with dextral strike-slip movement show the shape of "X"in geometrical structure. The piedmont thrust faults and the thrust strike-slip faults in the interior mountain constitute the tectonic framework of Tian Shan. Threegroups of active fault systems are the main seismogenic and geological structures, which control the current tectonic deformation pattern of Tian Shan (Figure 1). GPS observation data also showthe similar deformation characteristics with the geological results (Figures 2, 3). In addition to the crustal shortening, there is a certain strike-slip shear movement in the interior of the Tian Shan.The strike-slip rate defined by the geological and GPS data is approximately consistent with each other near the same longitude. We suggest the two groups of strike-slip faults in the interior of mountains is a set of conjugate structures. The whole Tian Shan forms a large flower-structure in a profile view. The complete tectonic deformation of the Tian Shan

Insights on fluid-rock interaction evolution during deformation from fracture network geochemistry at reservoir-scale

NASA Astrophysics Data System (ADS)

Beaudoin, Nicolas; Koehn, Daniel; Lacombe, Olivier; Bellahsen, Nicolas; Emmanuel, Laurent

2015-04-01

Fluid migration and fluid-rock interactions during deformation is a challenging problematic to picture. Numerous interplays, as between porosity-permeability creation and clogging, or evolution of the mechanical properties of rock, are key features when it comes to monitor reservoir evolution, or to better understand seismic cycle n the shallow crust. These phenomenoms are especially important in foreland basins, where various fluids can invade strata and efficiently react with limestones, altering their physical properties. Stable isotopes (O, C, Sr) measurements and fluid inclusion microthermometry of faults cement and veins cement lead to efficient reconstruction of the origin, temperature and migration pathways for fluids (i.e. fluid system) that precipitated during joints opening or faults activation. Such a toolbox can be used on a diffuse fracture network that testifies the local and/or regional deformation history experienced by the rock at reservoir-scale. This contribution underlines the advantages and limits of geochemical studies of diffuse fracture network at reservoir-scale by presenting results of fluid system reconstruction during deformation in folded structures from various thrust-belts, tectonic context and deformation history. We compare reconstructions of fluid-rock interaction evolution during post-deposition, post-burial growth of basement-involved folds in the Sevier-Laramide American Rocky Mountains foreland, a reconstruction of fluid-rock interaction evolution during syn-depostion shallow detachment folding in the Southern Pyrenean foreland, and a preliminary reconstruction of fluid-rock interactions in a post-deposition, post-burial development of a detachment fold in the Appenines. Beyond regional specification for the nature of fluids, a common behavior appears during deformation as in every fold, curvature-related joints (related either to folding or to foreland flexure) connected vertically the pre-existing stratified fluid system

The interplay between rheology and pre-existing structures in the lithosphere and its influence on intraplate tectonics: Insights from scaled physical analogue models.

NASA Astrophysics Data System (ADS)

Santimano, T. N.; Adiban, P.; Pysklywec, R.

2017-12-01

The primary controls of deformation in the lithosphere are related to its rheological properties. In addition, recent work reveals that inherited zones of weakness in the deep lithosphere are prevalent and can also define tectonic activity. To understand how deformation is genetically related to rheology and/or pre-existing structures, we compare a set of physical analogue models with the presence and absence of a fault in the deep lithosphere. The layered lithosphere scaled models of a brittle upper crust, viscous lower crust and viscous mantle lithosphere are deformed in a convergent setting. Deformation of the model is recorded using high spatial and temporal stereoscopic cameras. We use Particle Image Velocimetry (PIV) to acquire a time-series dataset and study the velocity field and subsequently strain in the model. The finished model is also cut into cross-section revealing the finite internal structures that are then compared to the topography of the model. Preliminary results show that deformation in models with an inherited fault in the mantle lithosphere is accommodated by displacement along the fault plane that propagates into the overlying viscous lower crust and brittle upper crust. Here, the majority of the deformation is localized along the fault in a brittle manner. This is in contrast to the model absent of a fault that also displays significant amounts of deformation. In this setting, ductile deformation is accommodated by folding and thickening of the viscous layers and flexural shearing of the brittle upper crust. In these preliminary experiments, the difference in the strength profile between the mantle lithosphere and the lower crust is within the same order of magnitude. Future experiments will include models where the strength difference is an order of magnitude. This systematic study aids in understanding the role of rheology and deep structures particularly in transferring stress over time to the surface and is therefore fundamental in

Interdisciplinary approach to exploit the tectonic memory in the continental crust of collisional belts.

NASA Astrophysics Data System (ADS)

Gosso, G.; Marotta, A. M.; Rebay, G.; Regorda, A.; Roda, M.; Spalla, M. I.; Zanoni, D.; Zucali, M.

2015-12-01

Collisional belts result by thoroughly competing thermo-mechanical disaggregation and coupling within both continental and oceanic lithospheric slices, during construction of tectono-metamorphic architectures. In multiply reworked metamorphics, tectonic units may be contoured nowadays on the base of coherent thermo-baric and structural time-sequences rather than simply relying on lithologic affinities. Sequences of equilibrium assemblages and related fabric imprints are an approach that appears as a more reliable procedure, that enables to define tectonic units as the volume of crustal slices that underwent corresponding variations during the dynamics of an active margin and takes into account a history of physical imprints. The dimensions of these tectonic units may have varied over time and must be reconstructed combining the tracers of structural and metamorphic changes of basement rocks, since such kind of tectono-metamorphic units (TMUs) is a realistic configuration of the discrete portions of orogenic crust that experienced a coherent sequence of metamorphic and textural variations. Their translational trajectories, and bulk shape changes during deformation, cannot simply be derived from the analysis of the geometries and kinematics of tectonic units, but are to be obtained by adding the reconstruction of quantitative P-T-d-t paths making full use of fossil mineral equilibria. The joint TMU field-and-laboratory definition is an investigation procedure that bears a distinct thermo-tectonic connotation, that, through modelling, offers the opportunity to test the physical compatibilities of plate-scale interconnected variables, such as density, viscosity, and heat transfer, with respect to what current interpretative geologic histories may imply. Comparison between predictions from numerical modelling and natural data obtained by this analytical approach can help to solve ambiguities on geodynamic significance of structural and thermal signatures, also as a

Gravity and magnetic anomalies of the Cyprus arc and tectonic implications

NASA Astrophysics Data System (ADS)

Ergün, M.; Okay, S.; Sari, C.; Oral, E. Z.

2003-04-01

In present day, eastern Mediterranean is controlled by the collision of the African and Eurasian plates and displacements of Arabian, Anatolian and Aegean micro-plates. The boundary between African and Eurasian plates is delineated by the Hellenic arc and Pliny-Strabo trench in the west and the Cyprus arc and a diffuse fault system of the Eastern Anatolian Fault zone in the east. The available gravity and magnetic data from the easternmost Mediterranean allow to subdivide this basin into three provinces: the northeastern Mediterranean north of the Cyprus Arc; the Levant Basin south of the Cyprus Arc and east of the line that roughly continues the Suez rift trend toward the Gulf of Antalya, between Cyprus and Anaximander Mountains; and the Mediterranean Ridge, Herodotus Basin west of this line. High anomalies observed in Cyprus and the sea region at the south is prominent in the gravity data. The Bouguer gravity anomaly reaches its maximum values over Cyprus, where it is most probably caused by high dense Troodos ophiolites. The uplifted oceanic crust causes high Bouguer anomaly also seen in the vicinity of Eratosthenes Seamount. Another result obtained from gravity data is that the crust under Herodotos and Rhodes basins is somehow oceanic and Anaximander, Eratosthenes and Cyprus are continental fragments. There are no linear magnetic anomalies in the Mediterranean. But there are magnetic anomalies over the Eratosthenes seamount and as well as from Cyprus to the Antalya basin due to the ophiolitic bodies. In Cyprus, the last compressional deformations were defined near the Miocene/Pliocene boundary. The extensional deformation associated with the Antalya basin appears to be separated by a zone of the Florence rise and Anaximander Mountains affected by differential tectonic movements. Eratosthenes Seamount is a positive crustal feature in the process of collision with Cyprus along an active margin; there is clearly a potential tectonic relationship to the onland

The Eocene-Miocene tectonic evolution of the Rif chain (Morocco): new data from the Jebha area

NASA Astrophysics Data System (ADS)

D'Assisi Tramparulo, Francesco; Ciarcia, Sabatino; El Ouaragli, Bilal; Vitale, Stefano; Najib Zaghloul, Mohamed

2016-04-01

Keywords: structural analysis, tectonics, shear bands, Miocene, Jebha Fault The Jebha area, located in the Central Rif, is a key sector to understand the orogenic evolution of the Rif chain. Here, the left lateral Jebha-Chrafate transfer fault, allowed, in the Miocene time, the westward migration of the internal thrust front. The structural analysis of the area revealed a complex tectonic history. The Eocene orogenic pulse produced the tectonic stacking of the Ghomaride thrust sheets. During the late Aquitanian and Langhian, under a dominant ENE-WSW shortening, imbrication of several Internal Dorsale Calcaire slices occurred. The following orogenic stage, characterized by a main SE tectonic transport, allowed the External Dorsale Calcaire to overthrust the Maghrebian Flysch Basin Units by means of a dominant thin-skinned tectonics. Synchronously with the buttressing following the collision of the allochthonous wedge against the External Rif domain, an out-of-sequence thrusting stage involved the Ghomaride and Dorsale Calcaire Units and a general back-thrusting deformed the entire tectonic pile. A renewal of the NE-SW shortening produced strike-slip faults and SW-verging folds and finally a radial extension affected the whole chain.

Investigating Environmental Tectonics in Northern Alpine Foreland of Europe

NASA Astrophysics Data System (ADS)

Cloetingh, Sierd; Ziegler, Peter; Cornu, Tristan; Ustaszewski, K.; Schmid, S.; Dezes, P.; Hinsch, R.; Decker, K.; Lopes Cardozo, G.; Granet, M.; Bertrand, G.; Behrmann, J.; Michon, L.; Pagnier, H.; van Wees, J. D.; Rozsa, S.; Heck, B.; Verdun, J.; Kahle, H. G.; Fracassi, U.; Winter, T.; Burov, E.

Until now, research on neotectonics and related seismicity has mostly focused on active plate boundaries characterized by a generally high level of earthquake activity. Current seismic hazard estimates for intraplate areas are commonly based on probabilistic analyses of historical and instrumental earthquake data. The accuracy of these hazard estimates is limited by the nature of the data (e.g., ambiguous historical sources), and by the restriction of available earthquake catalogues to time scales of only few hundred years. Both of these are geologically insignificant and unsuitable for describing tectonic processes causing earthquakes. This is especially relevant to intraplate regions, where faults show low slip rates resulting in long average recurrence times for large earthquakes (103 to 106 yrs), such as the devastating Basel earthquake of 1356, with an estimated magnitude of 6.5. The Alpine orogen and the intraplate sedimentary basins and rifts of its northern foreland are associated with a much higher level of neotectonic activity than hitherto assumed. Seismicity and stress indicator data, combined with geodetic and geomorphologic observations, demonstrate that the Northern Alpine foreland is being actively deformed [Cloetingh, 2000; Ziegler et al., 2002; Behrmann et al., 2003]. This has major implications for the assessment of their natural hazards and environmental degradation. The northwest European lithosphere has undergone a polyphase evolution, in which the interplay between upper mantle thermal perturbations [Goes et al., 2000; Ritter et al., 2001] and stress-induced intraplate deformation [Muller et al., 1992; Ziegler et al., 2002] played an important role. A number of recent findings point to an important role of lithospheric folding in thermally weakened lithosphere of the northwestern European foreland [Cloetingh et al., 1999].

The Role of the Mantle on Structural Reactivation at the Plate Tectonics Scale (Invited)

NASA Astrophysics Data System (ADS)

Vauchez, A. R.; Tommasi, A.

2009-12-01

During orogeny, rifting, and in major strike-slip faults, the lithospheric mantle undergoes solid-state flow to accommodate the imposed strain. This deformation occurs mostly through crystal plasticity processes, like dislocation creep, and results in the development of a crystallographic preferred orientation (CPO) of olivine and pyroxene. Because these minerals, especially olivine, display strongly anisotropic physical properties, their preferred orientation confers anisotropic properties at the scale of the rock. When the deformation event comes to its end, the CPO are "frozen" and remain stable for millions or even billions years if no other deformation subsequently affects the lithospheric mantle. This means that anisotropic properties preserving a memory of previous deformation events may subsist in the continental mantle over very long periods of time. One of the main consequences of a well-developed olivine CPO is an anisotropic mantle viscosity and hence a deformation dependant on the orientation of the tectonic solicitations relative to the orientation of the olivine CPO inherited from the past orogenic events. The most obvious expression of this anisotropic mechanical behaviour is the influence of the inherited tectonic fabric on continental rifting. Most continental rifts that lead to successful continental breakup, like in the early Atlantic or the western Indian systems, formed parallel to ancient collisional belts. Moreover, the early stages of deformation in these systems are characterized by a transtensional strain regime involving a large component of strike-slip shearing parallel to the inherited fabric. The link between the lithospheric mantle fabric and the rift structure is further supported by seismic anisotropy measurements in major rifts (e.g., the East-African Rift) or at passive continental margins (e.g., the Atlantic Ocean) that show fast split S-waves polarized in a direction parallel to both the inherited fabric and the trend of the

Tectonic stages in Southern Greater Caucasus and Adjara Trialeti belt in Georgia: new results on timing and structures of inverted basins

NASA Astrophysics Data System (ADS)

Candaux, Zoé; Sosson, Marc; Adamia, Shota; Sadradze, Nino; Alania, Victor; Enukidze, Onise; Chabukiani, Alexandre

2017-04-01

The Greater Caucasus mountain belt is the result of a long live subduction process and collisions of continental microplates (e.g. Dercourt et al., 1986; Barrier and Vrielynck, 2008). The northward subduction of Tethys beneath Eurasian plate initiated a back-arc basin: the Greater Caucasus basin (e.g. Adamia et al., 1981; Zonenshain and Le Pichon, 1986; Roberston et al., 1996; Stephenson and Schellart, 2010 among others). It took place from Middle Jurassic to Late Cretaceous. First compression stage started at the end of Cretaceous in the Lesser Caucasus (e.g. Rolland et al., 2010; Sosson et al. 2010, 2016) and Palaeocene-early Eocene in Crimean Mountains (northwestern continuation of the Greater Caucasus) (Sheremet et al., 2016). In southern Greater Caucasus (Georgian area) the age of deformation during the beginning of the collision is still a subject of debate: Oligocene-Lower Miocene at the frontal part (e.g. Adamia et al. 2010) or Eocene (Mosar et al., 2010). The deformation continues at Miocene, Pliocene and actual time in Kura and Rioni foreland basins (Forte et al., 2010; 2013; Mosar et al., 2010). The different timing is interpreted to be the result of the Taurides-Anatolides-South Armenian microcontinent collision with Eurasia, followed by the collision with Arabia. During the first collision, during Paleocene-Eocene, the so-called Adjara-Trialeti basin opened north of the volcanic arc. One question is if this local extension affect the timing of compression observed in the Greater Caucasus or not. In Georgia, we investigated new structural analyses, and considered unconformities and growth strata at the frontal part of deformations in Kura and Rioni forelands basins (in front of the Greater Caucasus). Our results evidence different tectonic stages and their timing. In Adjara-Trialeti, Kura and south Rioni basins deformation starts at Middle-Late Miocene. In northern Rioni basin Upper Cretaceous-Lower Paleocene compression is evidenced. The structures

Quaternary Tectonic and Climatic Processes shaping the Central Andean hyperarid forearc (southern Peru)

NASA Astrophysics Data System (ADS)

Audin, Laurence; Benavente, Carlos; Zerathe, Swann; Saillard, Marianne; Hall, Sarah R.; Farber, Daniel L.

2015-04-01

Understanding the forearc structure and processes related to Quaternary evolution and uplift of the Western Andean Cordillera remains an outstanding scientific issue. Models of Andean Plateau evolution based on Tertiary volcanic stratigraphy since 5Ma suggest that the deformation was focused along the eastern margin of the plateau and that minimal uplift occurred along the Pacific margin. On the contrary, new tectonic data and Quaternary surface 10Be dating highlight the presence of recently active deformation, incision and alluvial processes within the upper Andean forearc together with a regional uplift of the coastal zone. Additionally, the high obliquity observed in the northern Arica Bend region makes it an ideal target to discuss whether partitioning of the oblique convergence is accommodated by the neotectonic features that dissect the Quaternary forearc. Our goals are both to decipher the Quaternary tectonic and climatic processes shaping the hyperarid forearc along strike and across strike. Finally, we aim to quantify the respective influence of these factors in the overall uplift of the Western Andes. Indeed, sequences of pediment surfaces, landslide products, paleolake deposits and marine terraces found along the oblique Peruvian margin are a unique set of datable markers that can be used to quantify the rates of Quaternary processes. In this study, we focus on the southern Peru hyperarid Atacama area where regional surfaces and tectonic markers (scarps, folds, temporary streams and paleolake levels offsets…) are well preserved for the Quaternary timescale. Numerous landsliding events align on the major fault segments and reflect Plio-Pleistocene climatic and tectonic activity together with filled and strath terraces. As the present day sea-level is one of the highest levels recorded for Quaternary time span, any emerged marine terrace is preserved by tectonic coastal uplift. In particular, the geomorphic and chronologic correlation between marine and

Active crustal deformation of the El Salvador Fault Zone by integrating geodetic, seismological and geological data: application in seismic hazard assessment

NASA Astrophysics Data System (ADS)

Staller, A.; Benito, B.; Martínez-Díaz, J.; Hernández, D.; Hernández-Rey, R.

2013-05-01

El Salvador, Central America, is part of the Chortis block in the northwestern boundary of the Caribbean plate. This block is interacting with a diffuse triple junction point with the Cocos and North American plates. Among the structures that cut the Miocene to Pleistocene volcanic deposits stands out the El Salvador Fault Zone (ESFZ): It is oriented in N90-100E direction, and it is composed of several structural segments that deform Quaternary deposits with right-lateral and oblique slip motions. The ESFZ is seismically active and capable of producing earthquakes such as the February 13, 2001 with Mw 6.6 (Martínez-Díaz et al., 2004), that seriously affected the population, leaving many casualties. This structure plays an important role in the tectonics of the Chortis block, since its motion is directly related to the drift of the Caribbean plate to the east and not with the partitioning of the deformation of the Cocos subduction (here not coupled) (Álvarez-Gómez et al., 2008). Together with the volcanic arc of El Salvador, this zone constitutes a weakness area that allows the motion of forearc block toward the NW. The geometry and the degree of activity of the ESFZ are not studied enough. However their knowledge is essential to understand the seismic hazard associated to this important seismogenic structure. For this reason, since 2007 a GPS dense network was established along the ESFZ (ZFESNet) in order to obtain GPS velocity measurements which are later used to explain the nature of strain accumulation on major faults along the ESFZ. The current work aims at understanding active crustal deformation of the ESFZ through kinematic model. The results provide significant information to be included in a new estimation of seismic hazard taking into account the major structures in ESFZ.

Potential seismic hazards and tectonics of the upper Cook Inlet basin, Alaska, based on analysis of Pliocene and younger deformation

USGS Publications Warehouse

Haeussler, Peter J.; Bruhn, Ronald L.; Pratt, Thomas L.

2000-01-01

The Cook Inlet basin is a northeast-trending forearc basin above the Aleutian subduction zone in southern Alaska. Folds in Cook Inlet are complex, discontinuous structures with variable shape and vergence that probably developed by right-transpressional deformation on oblique-slip faults extending downward into Mesozoic basement beneath the Tertiary basin. The most recent episode of deformation may have began as early as late Miocene time, but most of the deformation occurred after deposition of much of the Pliocene Sterling Formation. Deformation continued into Quaternary time, and many structures are probably still active. One structure, the Castle Mountain fault, has Holocene fault scarps, an adjacent anticline with flower structure, and historical seismicity. If other structures in Cook Inlet are active, blind faults coring fault-propagation folds may generate Mw 6–7+ earthquakes. Dextral transpression of Cook Inlet appears to have been driven by coupling between the North American and Pacific plates along the Alaska-Aleutian subduction zone, and by lateral escape of the forearc to the southwest, due to collision and indentation of the Yakutat terrane 300 km to the east of the basin.

Plate motions and deformations from geologic and geodetic data

NASA Technical Reports Server (NTRS)

Jordan, T. H.

1986-01-01

Research effort on behalf of the Crustal Dynamics Project focused on the development of methodologies suitable for the analysis of space-geodetic data sets for the estimation of crustal motions, in conjunction with results derived from land-based geodetic data, neo-tectonic studies, and other geophysical data. These methodologies were used to provide estimates of both global plate motions and intraplate deformation in the western U.S. Results from the satellite ranging experiment for the rate of change of the baseline length between San Diego and Quincy, California indicated that relative motion between the North American and Pacific plates over the course of the observing period during 1972 to 1982 were consistent with estimates calculated from geologic data averaged over the past few million years. This result, when combined with other kinematic constraints on western U.S. deformation derived from land-based geodesy, neo-tectonic studies, and other geophysical data, places limits on the possible extension of the Basin and Range province, and implies significant deformation is occurring west of the San Andreas fault. A new methodology was developed to analyze vector-position space-geodetic data to provide estimates of relative vector motions of the observing sites. The algorithm is suitable for the reduction of large, inhomogeneous data sets, and takes into account the full position covariances, errors due to poorly resolved Earth orientation parameters and vertical positions, and reduces baises due to inhomogeneous sampling of the data. This methodology was applied to the problem of estimating the rate-scaling parameter of a global plate tectonic model using satellite laser ranging observations over a five-year interval. The results indicate that the mean rate of global plate motions for that interval are consistent with those averaged over several million years, and are not consistent with quiescent or greatly accelerated plate motions. This methodology was also

Crustal Structure and Deformation of the Yakutat Microplate: New Insights From STEEP Marine Seismic Reflection Data

NASA Astrophysics Data System (ADS)

Lowe, L. A.; Gulick, S. P.; Christeson, G.; van Avendonk, H.; Reece, R.; Elmore, R.; Pavlis, T.

2008-12-01

In fall 2008, we will conduct an active source marine seismic experiment of the offshore Yakutat microplate in the northern Gulf of Alaska. The survey will be conducted aboard the academic research vessel, R/V Marcus Langseth, collecting deep-penetrating multi-channel seismic reflection survey using an 8-km, 640 channel hydrophone streamer and a 6600 cu. in., 36 airgun array. The survey is the concluding data acquisition phase for the ST. Elias Erosion and tectonics Project (STEEP), a multi-institution NSF-Continental Dynamics project investigating the interplay of climate and tectonics in the Chugach-St. Elias Mountains in southern Alaska. The experiment will also provide important site survey information for possible future Integrated Ocean Drilling Program investigations. Two profiles coincident with wide-angle refraction data (see Christeson, et al., this session) will image structural changes across the Dangerous River Zone from east to west and the Transition Fault from south to north. We will also image the western portion of the Transition Fault to determine the nature of faulting along this boundary including whether or not the Pacific Plate is underthrusting beneath the Yakutat microplate as part of this collision. Our westernmost profile will image the Kayak Island Zone, typically described as the northern extension of the Aleutian megathrust but which may be a forming suture acting as a deformation backstop for the converging Yakutat and North American plates. Profiles across the Pamplona Zone, the current Yakutat-North America deformation front, will further constrain relative timing of structural development and the depth of deformation on the broad folds and thrust faults that comprise the area. This new dataset will allow further insight into regional tectonics of the St. Elias region as well as provide more detail regarding the development of the south Alaskan margin during major Plio-Pleistocene glacial- interglacial periods.

Tectonic evolution of the Gaoua region, Burkina Faso: Implications for mineralization

NASA Astrophysics Data System (ADS)

Baratoux, L.; Metelka, V.; Naba, S.; Ouiya, P.; Siebenaller, L.; Jessell, M. W.; Naré, A.; Salvi, S.; Béziat, D.; Franceschi, G.

2015-12-01

The interpretation of high-resolution airborne geophysical data integrated with field structural and lithological observations were employed in the creation of a litho-structural framework for the Gaoua region, Burkina Faso. The granite-greenstone domain of Paleoproterozoic age was affected by multiple deformation and mineralization events. The early tectonic phase is characterized by the emplacement of voluminous tholeiitic and calc-alkaline lavas, probably in a volcanic arc setting. The copper mineralization in Gongondy, Dienemera and Mt Biri is concentrated in a diorite/andesite breccia, and is interpreted as porphyry-copper style formed at an early stage of the evolution of the area. Evidence for the first deformation event D1Ga corresponding to N-S shortening was only found in the E-W trending mafic unit bordering the Gaoua batholith to the south. A second deformation phase D2Ga occurred under greenschist facies conditions and lead to a development of more or less penetrative metamorphic foliation and its subsequent folding under overall E-W compression. At later stages, the D2Ga switched to a transcurrent regime characterized by intense N-S to NW-trending steeply dipping shear zones. The first significant gold mineralization event is related to this transcurrent tectonic phase. During subsequent D3Ga, intense network of brittle to brittle-ductile NW and NE faults developed. Economic gold concentrations are attributed to the D3Ga event and are associated with the remobilization of early disseminated low grade gold concentrations. Significant deposits in the area are Nassara, Gomblora, Batié West and Kampti. The last deformation event D4Ga resulted in E-W trending thrust faults and crenulation cleavage planes, under overall N-S compression. No mineralization events related to this stage have been seen.

Transient radon signals driven by fluid pressure pulse, micro-crack closure, and failure during granite deformation experiments

NASA Astrophysics Data System (ADS)

Girault, Frédéric; Schubnel, Alexandre; Pili, Éric

2017-09-01

In seismically active fault zones, various crustal fluids including gases are released at the surface. Radon-222, a radioactive gas naturally produced in rocks, is used in volcanic and tectonic contexts to illuminate crustal deformation or earthquake mechanisms. At some locations, intriguing radon signals have been recorded before, during, or after tectonic events, but such observations remain controversial, mainly because physical characterization of potential radon anomalies from the upper crust is lacking. Here we conducted several month-long deformation experiments under controlled dry upper crustal conditions with a triaxial cell to continuously monitor radon emission from crustal rocks affected by three main effects: a fluid pressure pulse, micro-crack closure, and differential stress increase to macroscopic failure. We found that these effects are systematically associated with a variety of radon signals that can be explained using a first-order advective model of radon transport. First, connection to a source of deep fluid pressure (a fluid pressure pulse) is associated with a large transient radon emission increase (factor of 3-7) compared with the background level. We reason that peak amplitude is governed by the accumulation time and the radon source term, and that peak duration is controlled by radioactive decay, permeability, and advective losses of radon. Second, increasing isostatic compression is first accompanied by an increase in radon emission followed by a decrease beyond a critical pressure representing the depth below which crack closure hampers radon emission (150-250 MPa, ca. 5.5-9.5 km depth in our experiments). Third, the increase of differential stress, and associated shear and volumetric deformation, systematically triggers significant radon peaks (ca. 25-350% above background level) before macroscopic failure, by connecting isolated cracks, which dramatically enhances permeability. The detection of transient radon signals before rupture

Transient radon signals driven by fluid pressure pulse, micro-crack closure, and failure during granite deformation experiments

NASA Astrophysics Data System (ADS)