Inverse Faults Research Articles

GEOPHYSICAL MODELLING OF AN AREA OF CERRITOS, PEREIRA (RISARALDA)

A geophysical project was developed in Cerritos area, near Pereira city, where gravity, magnetic, electrical and seismic data were acquired over a 210.75 km 2 area. The data were processed and interpreted according the geological information acquired and also available; as result a free to confined aquifer was defined in the Plio-Pleistoce Pereira formation (Tqp), that is characterized by non-homogeneous lateral layers and constituted by a superior sequence of volcanic ashes and an inferior of volcano-clastic flows which reaches 750 m thick. The Pereira fm is controlled by the tectonic controlled Cartago and Barroso formations, with inverse faults that indicate uplift of the basement and variations of the Pereira formation thick, affecting the underwater circulation system and expressed by variations in the electric resistivity of the subsoil.

3D structural and geological modeling of the Kwatebala Cu–Co deposit, Tenke-Fungurume district, Democratic Republic of Congo

The Kwatebala Cu–Co deposit is one of the giant deposits of the Central African Copperbelt and is part of the Tenke-Fungurume district, the world's largest known resource of cobalt, located in the Democratic Republic of Congo. The application of 3D implicit geological modeling in the Cu–Co Kwatebala deposit defined not only the lithological and ore models but also a complex structural framework. A total of six groups of faults were defined and suggest the occurrence of two tectonic events subdivided into five local stages in the Kwatebala Cu–Co deposit. The hierarchy of these stages was correlated to the tectonic evolution data in the literature showing initial thrusts defining the allochthonous position of the deposit in a pre-Lufilian stage. Salt tectonics-related moves in the early stages of Lufilian orogenesis, defining the Kwatebala diapiric structure. Posterior inverse faults of high angle and northward dip are probably related to the circulation of saline hydrothermal fluids responsible for a later Cu–Co synorogenic mineralization. Two later groups of faults displace the ore bodies, the first being related to thrust faults dipping south related to the end of the Lufilian arc evolution and finally the northwest faults that cut all the other previous structures.

Geological setting of the barite-fluorite deposit at Jeżów Sudecki (Kaczawa Mts.)

From 1969 to 1993, investigation for the Ba-F mineralization was executed within the metamorphic Kaczawa complex, north of the Intra-Sudetic Fault in the Jeżów Sudecki-Dziwiszów area (Kaczawa Mts., Western Sudetes). The article presents unpublished results of those prospecting works. A small deposit of Ba-F with Zn, Pb, Cu-sulphides, on the SE slope of the Szybowisko hill near Jelenia Góra, was documented in 1994. The economic mineralization is developed in the Jeżów Sudecki fault, steep fracture zone running parallel to the Intra-Sudetic Fault, and was identified at a distance of 600 m along the strike of the fault (in the W–E direction) and up to a depth of 500 m along the dip (towards the south). Two (locally three) bifurcating veins were found. The average content of the main components is: BaSO4 – 63.18%, CaF2 – 8.60%. The Ba-F mineralization is associated with the Jeżów Sudecki fault, synchronous with the formation of the Intra-Sudetic Fault zone. Both of these faults are Variscan and fall steeply southward. Younger, alpine (?) inverse and transverse normal faults were formed after the intrusion of a rhyolite dyke into the Kaczawa complex rocks and after the formation of the barite deposit. The Ba-F mineralization developed in a multi-stage process and shows a pulsatory nature. Five mineral parageneses were distinguished in the deposit. The age of the Ba-F mineralization has not been definitively established.

Complete Diagnostic Length 2 Tests for Logic Networks under Inverse Faults of Logic Gates

It is proved that any Boolean function can be implemented by a logic network in the basis {x&y &z, x ⊕ y, 1} in such a way that this logic network admits a complete diagnostic test of length at most 2 with respect to inverse faults at the outputs of logic gates.

Upper Bound of the Circuits Unreliability in a Complete Finite Basis (in P3) with Arbitrary Faults of Elements

In this paper it is considered the implementation of ternary logic functions by the circuits of unreliable functional elements in an arbitrary complete finite basis. It is assumed that all the circuit elements pass to fault states independently of each other, and the faults can be arbitrary (for example, inverse or constant). Previously known class of ternary logic functions is extended, the circuits of these functions can be used to raise the reliability of the original circuits. With inverse faults at the outputs of basis elements it is constructively proved using functions of this class (we denote by G it) that a function which differs from any one of the variables can be implemented by a reliable circuit, and the probability of the inverse fault is bounded above by a constant. In particular if the basis under consideration contains at least one of the class G functions then for any function which differs from any one of the variables the constructed circuit is not only reliable, but this one is asymptotically optimal by reliability (we remind that function which is equal to one of the variables can be implemented absolutely reliably, not using functional element).

О надёжности схем в некоторых полных базисах (в P3) при инверсных неисправностях на выходах элементов

О надёжности схем в некоторых полных базисах (в P3) при инверсных неисправностях на выходах элементов

Полные диагностические тесты длины два для схем при инверсных неисправностях функциональных элементов

Полные диагностические тесты длины два для схем при инверсных неисправностях функциональных элементов

Asymptotically optimal reliable circuits in Rosser–Turkett basis (in P k )

In this paper we consider the realization of k-meaning logic functions with unreliable functional elements circuits in Rosser–Turkett basis. We assume that all the circuit elements are unreliable, they are exposed to inverse faults at the output, and pass to fault states independently. We propose an constructivemethod of synthesis of asymptotically optimal reliable circuits for almost any function of k-meaning logic.

Constraints on the source of resurgent doming inferred from analogue and numerical modeling — Implications on the current feeding system of the Yenkahe dome–Yasur volcano complex (Vanuatu)

Resurgence, defined as the post-collapse long-term uplift of a caldera floor, is commonly attributed to a renewed rise of magma. The Yenkahe dome (Vanuatu) exhibits a common morphology – elongated with a graben on top – among resurgent domes, and is also one of the most active structures of the kind. In this study, we performed a joint analysis based on analogue and finite element numerical models to (1) constrain the width and depth of the long-term deformation intrusive source of the Yenkahe dome and (2) discuss the close association between the Yenkahe dome and the active Yasur cone. We consider the resurgent deformation at the surface to be driven by the uplift of a magma reservoir roof in depth. As the edifice deformation response depends on the medium and the source properties, the mechanical behavior of the upper crust and the nature of the source are modeled using two very different sets of hypotheses. Analogue modeling uses silicone putty, an analogue for a large viscous magma body, intruding a sand–plaster mixture reproducing a Mohr–Coulomb behavior for the crust. Numerical models consider the vertical displacement of a rigid indenter, allowing the conservation of a flat-shaped roof, into an elastoplastic material. Numerical and analogue models show different resurgent dome structures at depth but similar dome and graben morphologies in the surface. Inverse faults – or equivalent shearing zones – delimiting the dome provide an explanation for the confined nature of resurgent doming and the persistent volcanic activity on the dome border represented by the Yasur volcano. Analogue and numerical models together provide an estimation range of 1–1.8km for the intrusive deformation source depth, and 1.3–2km for its width. The proposed association between the Yenkahe dome and the Yasur volcano is compatible with such a shallow depth of the magma reservoir, and argues for a discontinuous resurgence process.

Characterization of the hydrothermal system of the Tinguiririca Volcanic Complex, Central Chile, using structural geology and passive seismic tomography

A structural characterization of the hydrothermal–volcanic field associated with the Tinguiririca Volcanic Complex had been performed by combining passive seismic tomography and structural geology. This complex corresponds to a 20km long succession of N25°E oriented of eruptive centers, currently showing several thermal manifestations distributed throughout the area. The structural behavior of this zone is controlled by the El Fierro–El Diablo fault system, corresponding to a high angle reverse faults of Oligocene–Miocene age. In this area, a temporary seismic network with 16 short-period stations was setup from January to April of 2010, in the context of the MSc thesis of Lira (2010), covering an area of 200km2 that corresponds with the hydrothermal field of Tinguiririca Volcanic Complex (TVC), Central Chile, Southern Central Andes. Using P- and S- wave arrival times, a 3D seismic velocity tomography was performed. The preliminary locations of 2270 earthquakes have first been determined using an a priori 1D velocity model. Afterwards, a joint inversion of both, the 3D velocity model and final locations have been obtained. High Vp/Vs ratios are interpreted as zones with high hot fluid content and high fracturing. Meanwhile, low Vp/Vs anomalies could represent the magmatic reservoir and the conduit network associated to the fluid mobility. Based on structural information and thermal manifestations, these anomalies have been interpreted. In order to visualize the relation between local geology and the velocity model, the volume associated with the magma reservoir and the fluid circulation network has been delimited using an iso-value contour of Vp/Vs equal to 1.70. The most prominent observed feature in the obtained model is a large “V” shaped low-velocity anomaly extending along the entire study region and having the same vergency and orientation as the existing high-angle inverse faults, which corroborates that El Fierro–El Diablo fault system represents the local control for fluid mobility. This geometry coincides with surface hydrothermal manifestations and with available geochemical information of the area, which allowed us to generate a conceptual model of fluid circulation in the volcanic–hydrothermal system as well as define the location of the magmatic reservoir.

A new 3D geological model and interpretation of structural evolution of the world-class Rio Tinto VMS deposit, Iberian Pyrite Belt (Spain)

A new 3D geological model and interpretation of structural evolution of the Rio Tinto world-class VMS deposit are presented in this work. The Rio Tinto volcanogenic massive sulfide (VMS) deposit is located in the Spanish segment of the Iberian Pyrite Belt and is hosted by felsic porphyritic volcanic rocks and tuffs. Computer generated 3D modeling of the different orebodies and host rocks has been carried out using data from around 3000 drill-core logs, allowing us to build 93 cross-sections and 6 plants (both 50m spacing). This has enabled us to recognize the geometry and relationships between the mineralization and the earliest Carboniferous transtensional tectonics through the development of an extensional pull-apart basin with two sub-basins separated by the NW-SE trending Eduardo Fault. The sub-basins, Cerro Colorado and San Dionisio, were limited by two E-W strike-slip faults, the Northern and Southern faults, and bounded in the east and west by the NW-SE-trending Nerva and Western faults, respectively. The generated pull-apart basin was first filled by a basaltic magmatism of mantle origin and later, following the deposition of the intermediate complex sedimentary unit, by rhyodacitic volcanic rocks of crustal origin. The evolution of the subsiding basins caused the development of an E-W oriented rollover anticline that affected these filling rocks.As a result of a counterclockwise rotation of the stress axes, the primitive pull-apart basin evolved into a basin affected by E-W transtensional sinistral shearing. Its northern and southern limits were favorable areas for increased hydrothermal fluid flow, which gave way to the huge concentration of VMS mineralization located near the limits. The Northern and, to a lesser degree, the Southern extensional faults thus become channel areas for feeding and discharging of the VMS and stockwork ores. The main mineralizing period was related to this stage. Subsequently, during the Variscan transpressional phase, the E-W extensional faults were reactivated as inverse faults, affecting the volcanic sequence of mafic to felsic composition and the intermediate complex sedimentary unit. Fault propagation folds developed above these faults, affecting the massive sulfides, the transition series and the Culm flysch sediments, with buttressing playing a significant role in the geometry of tectonically inverted structures. The VMS mineralization and cupriferous stockworks were folded and dismembered from the original conduits in the volcanic series, and a dextral reactivation of the NW-SE trending faults also developed.Finally, it should be emphasized that this new 3D geological model is an approach to provide a better insight into the 3D structure of the world-class VMS Rio Tinto deposit and could be a key-point for further studies providing a new tool to increase knowledge of the VMS mineralizations and exploration guidelines elsewhere in the IPB.

Synthesis of circuits admitting complete checking tests of constant length under inverse faults at outputs of elements

A method for synthesizing circuits of functional elements in a special basis which admit complete checking tests of length at most 4 under inverse faults at the outputs of functional elements is proposed.

Characteristics and occurrence of submarine canyon-associated landslides in the middle of the northern continental slope, South China Sea

High-resolution and high-density 2-D multichannel seismic data, combined with high-precision multibeam bathymetric map, are utilized to investigate the characteristics and distribution of submarine landslides in the middle of the northern continental slope, South China Sea. In the region, a series of 19 downslope-extending submarine canyons are developed. The canyons are kilometers apart, and separated by inter-canyon sedimentary ridges. Numerous submarine landslides, bounded by headscarps and basal glide surfaces, are identified on the seismic profiles by their distorted to chaotic reflections. Listric faults and rotational blocks in head areas and compressional folds and inverse faults at the toes of the landslides are possibly developed. Three types of submarine landslides, i.e., creeps, slumps, and landslide complexes, are recognized. These landslides are mostly distributed in the head areas and on the flanks of the canyons. As the most widespread landslides in the region, creeps are usually composed of multiple laterally-coalesced creep bodies, in which the boundaries of singular component creep bodies are difficult to delineate. In addition, a total of 77 landslides are defined, including 61 singular slumps and 16 landslide complexes that consist of two or more component landslides. Statistics show that most landslides are of a small dimension (0.53–18.09 km² in area) and a short runout distance (less than 3.5 km). Regional and local slope gradients and rheological behavior of the displaced materials might play important roles in the generation and distribution of the submarine landslides. A conceptual model for the co-evolution of the canyons and the associated landslides in the study area is presented. In the model it is assumed that the canyons are initiated from gullies created by landslides on steeper sites of the continental slope. The nascent canyons would then experience successive retrogressive landsliding events to extend upslope; at the same time canyon downcutting or incision would steepen the canyon walls to induce more landslides.

On bases with unreliability coefficient 2

Consider the realization of Boolean functions by networks from unreliable functional components in a complete basis B ⊂ B3 (B3 is the set of all Boolean functions depending on the variables x1, x2, x3). It is assumed that all the components of the network are subject to inverse faults at the outputs independently of each other with probability ɛ ∈ (0, 1/2). In B3, we obtain all complete bases in which the following two conditions simultaneously hold: 1) any function can be realized by a network with unreliability asymptotically not greater than 2ɛ (ɛ → 0); 2) there exist functions (denote their set by K) that cannot be realized by networks with unreliability asymptotically less than 2ɛ, ɛ → 0. Such bases will be called bases with unreliability coefficient 2. It is also proved that the set K contains almost all functions.

Seismic activity in the Gulf of Mexico. A preliminary analysis

The southwestern corner of the Gulf of Mexico (around the Isthmus of Tehuantepec) is exposed to intense deep (> 100 km) seismic activity caused by the subduction of the Cocos Plate. Aside from this, the gulf has been considered a zone of low or no-seismicity. However, a sparse shallow seismic activity is observed across the Gulf of Mexico, even in the most distant areas from the plate boundaries. Some of these earthquakes have been strongly felt (e.g. 23/05/2007 and 10/09/2006), and the Jaltipan 1959 earthquake caused fatalities and severe destruction in central and southern Veracruz. In this study we analyze five relevant earthquakes that occurred since 2001. At the central Gulf of Mexico, focal mechanisms show inverse faults oriented approximately NW−SE with dip ~45o, suggesting a link to sediment loading and/or to salt tectonics. On the other hand, we analyzed in the southwestern corner of the gulf some clear examples of strike-slip faults and activity probably related to the Veracruz Fault. One anomalous earthquake, recorded in 2007 in the western margin of the gulf, shows a strike-slip mechanism indicating a transform regime probably related with the East Mexican Fault. The recent improvements of the Mexican Seismological broadband network have allowed the recording of small earthquakes distributed in the Gulf of Mexico. Although intermediate and large earthquakes in the region are infrequent, historic evidence indicates that magnitudes could reach Mw ~6.4. This fact should be taken in consideration to reassess the seismic hazard for industrial oil infrastructure in the region.

A method for synthesis of easily-testable circuits in some basis admitting single fault detection tests of constant length

A method of synthesis of irredundant circuits of functional elements in the basis {x&y, x⊕y, 1, \(\bar x\)(y ∨ z) ∨ x(y ∼ z)} realizing arbitrary Boolean functions and admitting unit verification tests of the length not exceeding 4 is proposed in the paper for inverse or constant (stuck-at) faults at outputs of gates.

Synthesis and Complexity of Asymptotically Optimal Circuits with Unreliable Gates

We consider the realization of Boolean functions by combinatorial circuits with unreliable gates computing the functions from a complete final basis B. We assume that all gates of the basis can have inverse faults on the outputs independently with probability e (e ∈ (0, 1/2)). We describe a set Mk (k ≥ 3) of Boolean functions, presence even by one of which in basis B guarantees the computing of almost all Boolean functions by asymptotically optimal circuits with unreliability e at e → 0. We prove that, for almost all functions, the complexity of asymptotically circuits with unreliable gates exceeds the complexity of the minimal circuits constructed from absolutely reliable gates by a multiplicative factor of 3(1 + b) for any b > 0.

Structure and tectonics of the central segment of the Eastern Cordillera of Colombia

In the Eastern Cordillera of Colombia, a new structural model constrained by field data, paleontologic determinations, and interpretations of seismic reflection profiles is proposed. The model implies 70 km of shortening, including reactivation of basement structures as inverse faults in both flanks of the chain. These faults propagated within the lower Cretaceous strata, inducing passively rooted and transported thrust sheets as the successive basement faults were reactivated. Two structural styles are identified in the western flank: (1) positive flower structures in a transpressive regime, which affected rocks older than upper Paleocene and were unconformably covered by post–late Paleocene sediments, and (2) compressive structures during the late Miocene–Recent Andean phase. Presently, WNW-ESE compression reactivates Late Paleocene structures, which locally affect Andean trends. In the western margin of the Eastern Cordillera, the Cambao thrust takes up most displacement, whereas the Bituima fault takes only a minor part. To the south, this relationship reverses, suggesting complementary behavior by the Bituima and Cambao faults, as well as a transfer zone. This suggestion explains the southward termination of the Guaduas syncline as a structure related to the Cambao fault, whereas the Bituima fault increases its displacement southward, generating the Girardot foldbelt that takes over the structural position of the Guaduas syncline.

GEOLOGIA ESTRUTURAL E IDADE 40Ar/39Ar DO DEPÓSITO DE OURO PAU-A-PIQUE, FAIXA MÓVEL AGUAPEÍ, SUDOESTE DO ESTADO DE MATO GROSSO

The ore is represented by quartz veins systems and disseminated in the metassedimentary rocks from the Aguapeí Group. These rocks was strongly deformed by the Sunsás-Aguapeí Orogeny (1.28- 0.95Ga). The geological mapping of Pau-a-Pique deposit revealed that gold ore in the regional scale was controlled by the Corredor ShearZone. This structure forms the contact between the metaconglomerate,which belongs to the Group Aguapeí, with a granite-gneissesfrom the Santa Helena Terrane. The brittle-ductil deformation had converted the host-rock in many kinds of mylonite facilitating hydrothermal fluid percolation. In local scale, ore is controlled by inverse faults subsidiary to Corredor Shear Zone, which form the contact between the metaconglomerate and an amphibole-biotite-chlorite mylonite schist layer. The petrographic study identified deformationand recovery microtextures in ore. 40 Ar/ 39 Ar ages from sericite of the hydrothermal veins in the Pau-a-Pique and Ellus deposits, north and south portions of the Corredor Shear Zone, suggest 908.1 ± 0.9Ma e 927 ± lMa ages for mineralization. These ages indicate hydrothermal fluids circulation in the Aguapeí Group metassedimentary rocks during the final stage of the Sunsás-Aguapeí Orogeny. Geochronological and structural data combined with petrographic studies suggest an epigenetic origin for studied deposits.

Dépliage 3-D des anticlinaux bordant le synclinal fermé de la vallée des Ponts, Jura central, Suisse

The Ponts valley syncline is a closed basin within the Neuchâtel Jura fold and thrust belt. This syncline, apparently uplifted to an altitude of around 1000m is closed in the SW by an anticline with an oblique WNW-ESE direction. The 3-D geometry of the entire structure is examined and unfolded in detail. This syncline is filled with an unexpectedly thick series (~400m) of Tertiairy Molasse, as revealed by the CS-AMT (controlled source audio-magneto-telluric) and a reflexion seismic line. The latter also documents internal compressional structures within the well layered upper freshwater Molasse series. The 3-D configuration of the top Malm limestones has been constructed for the entire area based on new detailed geologic and structural mapping, hundreds of dip measurements, as well as geophysical data. The Malm marker bed displays three distinct types of structures: 1) Thrust faults with shallow dips, vergent to the NW and/or SE that are associated with folds interpreted as fault bend folds; 2) high angle inverse faults, mostly with a SE vergence are interpreted as inverted normal faults, inherited from a modest Oligo-Miocene extensional phase in a NW-SE direction; and 3) tear faults with a dominant N-S direction, probably inherited from an Oligocene extensional phase in association with the opening of the Rhine and Bresse grabens. Tear faults accommodate important lateral changes in fold geometry during the Late Miocene main folding-and-thrusting phase. All deformations are easily explained in an entirely thin-skinned fashion, taking place above a thick detachment horizon within Triassic evaporite series.