Fault Kinematics Research Articles

Controls on Cu mineralization in central part of the Kerman porphyry copper belt, SE Iran:constraints from structural and spatial pattern analysis

The Sarduiyeh area in the central part of the Kerman Porphyry Copper Belt (KPCB), SE Iran, contains numerous Cu deposits and prospects. This area is bound by E-W trending major faults, which show the northern and southern borders of fault duplex. Minor faults (first, second or third orders) were identified in three trends of NW, N-S and NE. Analysis of the fault kinematics data revealed an extensional fault duplex pattern for this area. In this fault zone, Cu deposits are associated with faults that have a special trend. This proposed kinematic model for evolution of Sarduiyeh extensional fault duplex emphasizes that the main Cu deposits in the Sarduiyeh area are located within the dilatational zones related to NW-SE trending normal faults. In this study, the spatial pattern analysis conducted by Fry, Fractal, Fracture density and buffer zones methods support the conceptual model of district-scale mechanism of structural controls on final emplacement of Cu deposits. This investigation of Sarduiyeh Cu mineralization revealed that the NW-SE trending faults are effective in localization of Cu mineralization in the central part of KPCB.

Propagation and termination of a strike slip fault in an extensional domain: The westward growth of the North Anatolian Fault into the Aegean Sea

Geometry and kinematics of the active submarine faults over the North Aegean Trough, a complex and highly deforming boundary zone between the Eurasian and the Anatolian/Aegean micro-plates, were examined to investigate how a strike slip motion propagates through an extensional domain. The bathymetric and seismic reflection data analysis show, that the investigated area is affected from east to west, by three sets of active faults striking ENE-WSW, NE-SW and WNW-ESE. The ENE-WSW and NE-SW striking faults are right lateral strike slip faults and are considered strands of the northern branch of the North Anatolian Fault into the north Aegean Sea. The former set bounds the Saros basin and the latter set occupies the eastern and central part of the Sporades Basin in the eastern and western parts of the North Aegean Trough, respectively. The WNW-ESE striking faults are normal low angle faults and develop at the western parts of the Sporades Basin. It is suggested that the strike-slip fault system advances westwards and when it reaches the 23.8°E meridian, its right lateral motion is transferred to the WNW-ESE normal faults system, forming a 70 km wide normal faulting zone through which the shear is distributed. The interaction between the strike slip and normal faults probably started with the arrival of the northern branch of the North Anatolian Fault into the western part of the Sporades Basin since 430 ka BP (Marine Isotopic Stage, 12). The described fault architecture and their spatial distribution in the North Aegean Trough are consistent with: (i) the earthquake fault plane solutions and (ii) the stress and strain pattern prevailing across the area. Furthermore, all these three provide evidence that the northern branch of the North Anatolian Fault terminates at the western end of the NAT and does not continue to central Greece.

3-D kinematic restoration of the eastern Sudbury Igneous Complex, Canada, and its importance for Cu-Ni-PGE sulphide exploration

Kinematic restorations of deformed igneous terranes have rarely been attempted due to the general absence of (1) planar primary lithological contacts, (2) tightly constrained deformation kinematics, and (3) geometric constraints on lithologies and structures at depth. Because of the vast number of exploration drill holes, the deformed and layered 1.85 Ga Sudbury Igneous Complex (SIC) in Ontario, Canada, is reasonably well understood with respect to (1) and (3). We therefore explored the kinematics of folding and faulting in the eastern SIC and use the subsurface geometry of faults extracted from a model integrating surface mapping and drill core logs in an attempt to restore the geometry of part of the SIC. Specifically, we identified rotation magnitudes and the tilt axis of a kilometer-scale plunging fold, the West Bay Anticline, which appears to have folded the eastern part of the SIC. We combined a 3-D model of the faults and lithological contacts of the SIC, fault kinematics calculated from the inversion of brittle shear faults at surface, and limb rotations of the West Bay Anticline to kinematically restore the eastern part of the SIC. Results of restorations using simple shear and flexural-slip algorithms highlight the importance of slip on prominent, curved faults that displaced the SIC and facilitated its folding. Flexural slip appears to be the more plausible mechanism of the two, as it removed the curvature of, and displacement on, prominent faults. Flexural-slip restoration helps to estimate primary thickness variations of the SIC and the results show that thickened parts of the Main Mass of the SIC correspond spatially with known Cu-Ni-PGE sulfide deposits. This result demonstrates that 3-D restoration can be an important tool for mineral exploration in igneous terranes.

COST Action 625 Results: Monitoring of the Kaparelli fault, 2003-2006

Since November 2003 a collaborative group between Greek, Polish, and Slovak colleagues installed a dense network of non-permanent GPS stations and extensometers to monitor active faults in the eastern end of the Gulf of Corinth, central Greece. The network includes eleven GPS stations across the Kaparelli fault and the Asopos rift valley to the east and two TM-71 extensometers that were installed on the Kaparelli fault plane. The motions recorded by the TM-71 instruments show agreement with long-term fault kinematics. The GPS network has been measured in three campaigns (2004, 2005 & 2006) with very good accuracies (1-4 mm in the horizontal plane). Given that the total offset on the Kaparelli fault is small, and the geological data suggesting a segmented character of this fault, we expect in the near future to differentiate fault slip and strain accumulation among segments.

Testing the effects of topography, geometry, and kinematics on modeled thermochronometer cooling ages in the eastern Bhutan Himalaya

Abstract. In this study, reconstructions of a balanced geologic cross section in the Himalayan fold–thrust belt of eastern Bhutan are used in flexural–kinematic and thermokinematic models to understand the sensitivity of predicted cooling ages to changes in fault kinematics, geometry, topography, and radiogenic heat production. The kinematics for each scenario are created by sequentially deforming the cross section with ∼ 10 km deformation steps while applying flexural loading and erosional unloading at each step to develop a high-resolution evolution of deformation, erosion, and burial over time. By assigning ages to each increment of displacement, we create a suite of modeled scenarios that are input into a 2-D thermokinematic model to predict cooling ages. Comparison of model-predicted cooling ages to published thermochronometer data reveals that cooling ages are most sensitive to (1) the location and size of fault ramps, (2) the variable shortening rates between 68 and 6.4 mm yr−1, and (3) the timing and magnitude of out-of-sequence faulting. The predicted ages are less sensitive to (4) radiogenic heat production and (5) estimates of topographic evolution. We used the observed misfit of predicted to measured cooling ages to revise the cross section geometry and separate one large ramp previously proposed for the modern décollement into two smaller ramps. The revised geometry results in an improved fit to observed ages, particularly young AFT ages (2–6 Ma) located north of the Main Central Thrust. This study presents a successful approach for using thermochronometer data to test the viability of a proposed cross section geometry and kinematics and describes a viable approach to estimating the first-order topographic evolution of a compressional orogen.

A database of the coseismic effects following the 30 October 2016 Norcia earthquake in Central Italy

We provide a database of the coseismic geological surface effects following the Mw 6.5 Norcia earthquake that hit central Italy on 30 October 2016. This was one of the strongest seismic events to occur in Europe in the past thirty years, causing complex surface ruptures over an area of >400 km2. The database originated from the collaboration of several European teams (Open EMERGEO Working Group; about 130 researchers) coordinated by the Istituto Nazionale di Geofisica e Vulcanologia. The observations were collected by performing detailed field surveys in the epicentral region in order to describe the geometry and kinematics of surface faulting, and subsequently of landslides and other secondary coseismic effects. The resulting database consists of homogeneous georeferenced records identifying 7323 observation points, each of which contains 18 numeric and string fields of relevant information. This database will impact future earthquake studies focused on modelling of the seismic processes in active extensional settings, updating probabilistic estimates of slip distribution, and assessing the hazard of surface faulting.

Contributions of gravity and field data on the structural scheme updating of the Tellian domain and its foreland (Nefza-Bizerte region, northern Tunisia)

The Nefza-Bizerte region, eastern part of the Tunisian Alpine chain, covers the thrust sheets domain called the Tell and its Atlassic foreland. The deep structures under the Tellian thrust sheets are not enough explored. The structural interpretation of magmatic rocks, Triassic outcrops and the depressions are still a subject of discussion. In this work, we intend to investigate deep faults and their eventual role in magmatism and Triassic salt setting up and to explain the depression genesis. Analysis of the Bouguer anomaly map and its derivatives reveals the main gravity lineaments, organized in major NE- and NW-trending systems. The NE-trending system, dipping towards the NW, is the main component of the structural scheme and has controlled the tectonic evolution of this area. After the immobilization of the Tellian thrust sheets during the uppermost Langhian, the Tell and its Atlassic foreland were affected by the Tortonian compressive event with a NW-trending maximum horizontal stress. The reverse kinematics of the NE-trending deep-seated faults created at their front continental environments filled later by post-nappes Neogene deposits. After the early Pleistocene, a NNW-directed compressional stress regime deformed the post-nappes Neogene series and generated NW-trending grabens. This coexistence of compression-extension continues until present day.

Constraints on fault and crustal strength of the Main Ethiopian Rift from formal inversion of earthquake focal mechanism data

We evaluate the frictional strength of seismogenic faults in the Main Ethiopian Rift (MER) by inverting the available, well-constrained earthquake focal mechanisms. The regional stress field is given by − 119.6°/77.2°, 6.2°/7.6°, and 97.5°/10.2° for trend/plunge of σ1, σ2 and σ3, respectively agrees well with previous fault kinematic and focal mechanism inversions. We determine the coefficient of friction, μ, for 44 seismogenic faults by assuming the pore pressure to be at hydrostatic conditions. Slip on 36 seismogenic faults occurs with μ ≥ 0.4. Slip on the remaining eight faults is possible with low μ. In general, the coefficient of friction in the MER is compatible with a value of μ of 0.59 ± 0.16 (2σ standard deviation). The shear stresses range from 16 to 129 MPa, is similar to crustal shear stress observed in extensional tectonic regimes and global compilations of shear stresses from major fault zones. The maximum shear stress is observed in the ductile crust, below the seismologically determined brittle-ductile transition (BDT) zone. Below the BDT, the crust is assumed to be weak due to thermal modification and/or high pore fluid pressure. Our results indicate linearly increasing μ and shear stress with depth. We argue that in the MER upper crust is strong and deforms according to Coulomb frictional-failure criterion.

Fault Slip and GPS Velocities Across the Shan Plateau Define a Curved Southwestward Crustal Motion Around the Eastern Himalayan Syntaxis

AbstractCharacterizing the 700 km wide system of active faults on the Shan Plateau, southeast of the eastern Himalayan syntaxis, is critical to understanding the geodynamics and seismic hazard of the large region that straddles neighboring China, Myanmar, Thailand, Laos, and Vietnam. Here we evaluate the fault styles and slip rates over multi‐timescales, reanalyze previously published short‐term Global Positioning System (GPS) velocities, and evaluate slip‐rate gradients to interpret the regional kinematics and geodynamics that drive the crustal motion. Relative to the Sunda plate, GPS velocities across the Shan Plateau define a broad arcuate tongue‐like crustal motion with a progressively northwestward increase in sinistral shear over a distance of ~700 km followed by a decrease over the final ~100 km to the syntaxis. The cumulative GPS slip rate across the entire sinistral‐slip fault system on the Shan Plateau is ~12 mm/year. Our observations of the fault geometry, slip rates, and arcuate southwesterly directed tongue‐like patterns of GPS velocities across the region suggest that the fault kinematics is characterized by a regional southwestward distributed shear across the Shan Plateau, compared to more block‐like rotation and indentation north of the Red River fault. The fault geometry, kinematics, and regional GPS velocities are difficult to reconcile with regional bookshelf faulting between the Red River and Sagaing faults or localized lower crustal channel flows beneath this region. The crustal motion and fault kinematics can be driven by a combination of basal traction of a clockwise, southwestward asthenospheric flow around the eastern Himalayan syntaxis and gravitation or shear‐driven indentation from north of the Shan Plateau.

Strain Partitioning and Present‐Day Fault Kinematics in NW Tibet From Envisat SAR Interferometry

AbstractAn 8 year archive of Envisat synthetic aperture radar (SAR) data over a 300 × 500 km2 wide area in northwestern Tibet is analyzed to construct a line‐of‐sight map of the current surface velocity field. The resulting velocity map reveals (1) a velocity gradient across the Altyn Tagh fault, (2) a sharp velocity change along a structure following the base of the alluvial fans in southern Tarim, and (3) a broad velocity gradient, following the Jinsha suture. The interferometric synthetic aperture radar velocity field is combined with published GPS data to constrain the geometry and slip rates of a fault model consisting of a vertical fault plane under the Altyn Tagh fault and a shallow flat décollement ending in a steeper ramp on the Tarim side. The solutions converge toward 0.7 mm/yr of pure thrusting on the décollement‐ramp system and 10.5 mm/yr of left‐lateral strike‐slip movement on the Altyn Tagh fault, below a 17 km locking depth. A simple elastic dislocation model across the Jinsha suture shows that data are consistent with 4–8 mm/yr of left‐lateral shear across this structure. Interferometric synthetic aperture radar processing steps include implementing a stepwise unwrapping method starting with high‐quality interferograms to assist in unwrapping noisier interferograms, iteratively estimating long‐wavelength spatial ramps, and referencing all interferograms to bedrock pixels surrounding sedimentary basins. A specific focus on atmospheric delay estimation using the ERA‐Interim model decreases the uncertainty on the velocity across the Tibet border by a factor of 2.

Seismicity assessment of Fukushima region, fault kinematics and calculation of PGA value for Idosawa fault in Hamadori area, Japan

In depth assessment of seismicity distribution for a particular region like Fukushima, prefecture is key towards reliable seismic hazard analysis for the area. Assessment of seismicity becomes more challenging for those areas lying close to mega subduction zone like in this study. Development of accurate input data like seismicity and faults data can reduce bias in the results and can improve quality of analysis. To assess the influence of seismicity on hazard analysis, two approaches known as Gutenberg–Richter law and the Gumbel’s extreme asymptotic distributions are employed. It is found that b value calculated through Gutenberg–Richter law has shown better b value of 1.0 according to tectonics of the Fukushima area. However, Gumbel’s approach which uses maximum earthquake of each years have shown b value of 0.6 and used for calculating future earthquake potential. Comparison of earthquake distribution in both cases has shown that in areas where we have rich seismicity data Gutenberg–Richter law is found much applicable as compared to Gumbel’s approach. Fault kinematics is done through software called FaultKin6 developed by (Rick Allmendinger) which resulted that Idosawa fault is a normal fault based on the fact that P axis is greater than 45° showing extension in N–S direction for Idosawa fault. Resultantly, it is tried to highlight the need to take normal faults in seismic hazard analysis probabilistically in design when they exist within stress field of big subduction zone. Peak ground acceleration is calculated by using PEER NGA West-2 models for Idosawa fault, and 0.22 g is found as PGA value.

Thick-skinned tectonics in a Late Cretaceous-Neogene intracontinental belt (High Atlas Mountains, Morocco): The flat-ramp fault control on basement shortening and cover folding

Most of the structural studies of the intracontinental High Atlas belt of Morocco have dealt with the central part of the belt, whose basement does not crop out. Here we study the Alpine deformation of the North Subatlas Zone, which is the part of the Western High Atlas (WHA) Paleozoic Massif that involves both Paleozoic basement units and remnants of their Mesozoic-Cenozoic cover formations. Our aim is to better constrain the geometry and kinematics of the basement faults during the Alpine shortening. Based on detail mapping, satellite imagery and field observations, we describe an array of sub-equatorial, transverse and oblique faults between the WHA Axial Zone and the Haouz Neogene basin. They define a mosaic of basement blocks pushed upon one another and upon the Haouz basement along the North Atlas Fault (NAF). The Axial Zone makes up the hanging-wall of the Adassil-Medinet Fault (AMF) south of this mosaic. The faults generally presents flat-ramp-flat geometry linked to the activation of multiple décollement levels, either within the basement where its foliation is subhorizontal or within favourable cover formations (Jurassic evaporites, Lower Cretaceous silty red beds, Upper Cretaceous evaporitic marls, Neogene basal argillites). The occurrence of the North Atlas detachment (NAD) allowed folded pop-up units to develop in front of the propagating NAF. Shortening began as early as the Campanian-Maastrichtian along the AMF. The direction of the maximum horizontal stress rotated from NNE-SSW to NNW-SSE from the Maastrichtian-Paleocene to the Neogene. The amount of shortening reaches 20% in the Azegour transect. This compares with the shortening amount published for the central-eastern High Atlas, suggesting that similar structures characterize the Paleozoic basement all along the belt. The WHA thick-skinned tectonics evokes that of the frontal Sevier belt and of the external Western Alps, although with a much minor pre-inversion burial.

Structural controls on sedimentation during asymmetric extension: The case of Sorbas Basin (SE Spain)

Understanding the link between sedimentation and fault kinematics is important for reconstructing the evolution of sedimentary basins. The relationship between the mechanics of creating accommodation space and the sediment supply in asymmetric extensional basins is critical for quantifying their syn- and post-rift evolution, but is not yet well understood. One exceptional place to analyze such mechanics of normal faulting and its relationship with the evolution of depositional environments is the Sorbas Basin in the Betic Cordillera of SE Spain. We have analyzed the interplay between extension and deposition by means of a detailed sedimentological and field kinematic study. The results indicate a novel and coupled evolution, characterized by low-order tectonically induced sedimentary successions driven by the change of deformation style and high-order tectonically induced sedimentary successions driven by individual stages of fault activity. Fault mechanics and hanging-wall tilting control the formation of depositional slopes, while footwall exhumation induces enhanced sourcing of coarse sediments that may be stored in proximal areas or recycled in the basin during episodes of fault activity. Following initiation of extension, the subsequent syn-kinematic deposition was characterized by a wide spectrum of subaqueous gravity flows, whose types and transformation mechanisms were controlled by the style of normal faulting, sediment supply and basin physiography. Furthermore, the study quantifies the controls of rheological stratified sediments on normal faulting mechanics and their implications for the spatial and temporal basin evolution.

Volcanism and tectonism in the southern Central Andes: Tempo, styles, and relationships

An important objective of volcanic research is to establish a cause-and-effect relationship between the age of fault kinematics and volcanic arc evolution based on structural and stratigraphic evidence. The predominant hyperarid climate in the Central Andes since Miocene times makes it a world-class area for investigating the evolution of a volcanic arc. This region records the complete development of the late Cenozoic Andean volcanic arc. This study focuses on the interpretation of volcanism in the context of recently dated tectonic structures along the southern Central Andes Volcanic Zone between 24.5° and 27° S. This segment of the arc has had a complex evolution and consists of hundreds of volcanoes, including constructional (monogenetic and polygenetic) and caldera volcanoes. By reviewing and reevaluating the geological maps in the literature, we are able to better constrain the temporal evolution of the central Chilean volcanic arc, including timing and kinematics of regional faults. Recognition of 15 Oligocene to Pleistocene ignimbrites and their sources has allowed us to define 11 caldera systems contemporaneous with effusive constructional volcanoes. The extent of the ignimbrite deposits allows them to be correlated between isolated outcrops that preserve different stratigraphic sequences, enabling the construction of a more complete and accurate volcanic stratigraphy. Two main NE-SW– and N-S–oriented thrust systems dominate the structural architecture of this segment of the arc. The first, located in the Precordillera, was active between 25 and 14 Ma and extends over 200 km to the northeast through the Pedernales-Arizaro thrust fault. Parallel to this thrust, the east-vergent Antofalla thrust fault system developed during Oligocene–Miocene times. The second system, located within the volcanic arc, includes sinuous N-S contractional structures that developed in pulses between the middle and late Miocene. There appears to be a cause-and-effect relationship between tectonic pulses and the development of volcanism, whereby changes in the upper crustal stress field lead to the generation of extensional domains. These conditions favor magma storage at upper crustal levels, thus promoting a suction-pump effect. The coexistence of both dominantly effusive constructional volcanism and explosive caldera volcanism results from the same tectonic conditions that produced shortening, as a consequence of the maximum compressive stress and conjugated extensions. In this paper, we suggest a new model that integrates the coexistence and contemporaneity of compressive structures and the widespread development of effusive constructional volcanism and explosive caldera volcanism along the Andean Oligo-Miocene volcanic arc.

ANÁLISIS NEOTECTÓNICO EN EL PIEDEMONTE ORIENTAL DE CORDILLERA FRONTAL, ANDES CENTRALES. SAN JUAN, ARGENTINA

El presente trabajo tiene por objetivo dar a conocer evidencias de actividad neotectónica sobre el Piedemonte Oriental de Cordillera Frontal, Andes Centrales, Argentina. La geomorfología de la región es compleja, producto de la interacción entre procesos sedimentarios, climáticos y tectónicos, predominando en los piedemontes de los principales cordones montañosos, sistemas de abanicos aluviales de edad pleistocena. La morfología de los sistemas aluviales ha sido modificada por la actividad tectónica vinculada al Sistema de Falla Colangüil (SFC); el cual generó durante el Cuaternario, anomalías en la red de drenaje y un conjunto de escarpas a contra pendiente que afectan distintos niveles aluviales. Se diferenciaron 4 niveles aluviales; siendo Q1 el más reciente y coincidente con los actuales cauces y Q4 el más antiguo, el más elevado topográficamente y el menos preservado. En el tramo sur de este sistema se identificaron dos exposiciones naturales, denominadas Trinchera I y Trinchera II que permitieron conocer la cinemática de las fallas y los depósitos afectados. El análisis paleosismológico de las mismas indicaría la ocurrencia en el sector de al menos dos eventos sísmicos, el último de ellos con una edad inferior a ~ 37.000 años. Finalmente no se descarta un tercer evento durante el Holoceno.

Fault kinematics and localised inversion within the Troms-Finnmark Fault Complex, SW Barents Sea

The areas bounding the Troms-Finnmark Fault Complex are affected by complex tectonic evolution. In this work, the history of fault growth, reactivation, and inversion of major faults in the Troms-Finnmark Fault Complex and the Ringvassøy Loppa Fault Complex is interpreted from three-dimensional seismic data, structural maps and fault displacement plots. Our results reveal eight normal faults bounding rotated fault blocks in the Troms-Finnmark Fault Complex. Both the throw-depth and displacement-distance plots show that the faults exhibit complex configurations of lateral and vertical segmentation with varied profiles. Some of the faults were reactivated by dip-linkages during the Late Jurassic and exhibit polycyclic fault growth, including radial, syn-sedimentary, and hybrid propagation. Localised positive inversion is the main mechanism of fault reactivation occurring at the Troms-Finnmark Fault Complex. The observed structural styles include folds associated with extensional faults, folded growth wedges and inverted depocentres. Localised inversion was intermittent with rifting during the Middle Jurassic–Early Cretaceous at the boundaries of the Troms-Finnmark Fault Complex to the Finnmark Platform. Additionally, tectonic inversion was more intense at the boundaries of the two fault complexes, affecting Middle Triassic to Early Cretaceous strata. Our study shows that localised folding is either a product of compressional forces or of lateral movements in the Troms-Finnmark Fault Complex. Regional stresses due to the uplift in the Loppa High and halokinesis in the Tromsø Basin are likely additional causes of inversion in the Troms-Finnmark Fault Complex.

Earthquake damage orientation to infer seismic parameters in archaeological sites and historical earthquakes

Studies to provide information concerning seismic parameters and seismic sources of historical and archaeological seismic events are used to better evaluate the seismic hazard of a region. This is of especial interest when no surface rupture is recorded or the seismogenic fault cannot be identified. The orientation pattern of the earthquake damage (ED) (e.g., fallen columns, dropped key stones) that affected architectonic elements of cities after earthquakes has been traditionally used in historical and archaeoseismological studies to infer seismic parameters. However, in the literature depending on the authors, the parameters that can be obtained are contradictory (it has been proposed: the epicenter location, the orientation of the P-waves, the orientation of the compressional strain and the fault kinematics) and authors even question these relations with the earthquake damage. The earthquakes of Lorca in 2011, Christchurch in 2011 and Emilia Romagna in 2012 present an opportunity to measure systematically a large number and wide variety of earthquake damage in historical buildings (the same structures that are used in historical and archaeological studies). The damage pattern orientation has been compared with modern instrumental data, which is not possible in historical and archaeoseismological studies. From measurements and quantification of the orientation patterns in the studied earthquakes, it is observed that there is a systematic pattern of the earthquake damage orientation (EDO) in the proximity of the seismic source (fault trace) (<10 km). The EDO in these earthquakes is normal to the fault trend (±15°). This orientation can be generated by a pulse of motion that in the near fault region has a distinguishable acceleration normal to the fault due to the polarization of the S-waves. Therefore, the earthquake damage orientation could be used to estimate the seismogenic fault trend of historical earthquakes studies where no instrumental data are available.

МОРФОСТРУКТУРА ЗОНЫ СОЧЛЕНЕНИЯ СЕВЕРО-ЗАПАДНОГО КАВКАЗА И КЕРЧЕНСКО-ТАМАНСКОЙ ОБЛАСТИ, "Геоморфология"

Морфоструктурный анализ, основанный на интерпретации цифровых моделей рельефа и полевых исследованиях, а также новейшие геолого-геофизические данные подтвердили, что складчато-разрывные морфоструктуры Северо-Западного Кавказа продолжаются структурами Керченско-Таманской области и развиваются в единой обстановке сжатия. Направление сжатия при этом меняет вектор с северо-восточного на меридиональное, что выражается в переориентировке осей складчатых морфоструктур и геофизических аномалий с северо-западного на широтное. Уточнены положение и кинематические характеристики разрывных структур, играющих роль западного ограничения орогена Северо-Западного Кавказа. Широко описанная в литературе поперечная Анапско-Джигинская зона сбросового типа имеет диффузный характер и слабо выражена в рельефе. В свете новых данных роль границы горного сооружения приобретает расположенная к востоку от нее Абрауская поперечная зона сбросо-раздвиговой кинематики с вертикальной амплитудой деформаций минимум в 600 м за четвертичный этап. Она выделяется нами в качестве разрывного нарушения регионального значения с функцией ограничения орогена.

Geological and seismological evidence for NW-SE crustal extension at the southern margin of Heraklion basin, Crete.

In this paper we present new geological and seismological data on the orientation of crustal extension in central Crete (SE Heraklion basin) following the occurrence of two shallow seismic sequences: a) the May 2005 Assimi M=4.1 earthquake sequence and b) the 2013 Houdetsi-Tefeli sequence (3.2≤Mw≤3.6). Emphasis is given to the results of the geological field work, stress analysis, source inversion, aftershock relocations and mapping of earthquake-induced environmental effects. For the first time we find seismological evidence for N-S strike-slip motions along shallow fault planes in central Crete (Amourgeles fault). Our results indicate that while crustal extension dominates there is a combination of active fault kinematics, ranging from normal faulting along the northern edge of Messara basin (south-dipping Plakiotissa fault) to strike-slip faulting inside the SE part Heraklion basin (Houdetsi-Tefeli). The combination of active fault motions accommodates a NW-SE extension of the upper crust.

A Comparison of Geodetic and Geologic Rates Prior to Large Strike‐Slip Earthquakes: A Diversity of Earthquake‐Cycle Behaviors?

AbstractComparison of preevent geodetic and geologic rates in three large‐magnitude (Mw = 7.6–7.9) strike‐slip earthquakes reveals a wide range of behaviors. Specifically, geodetic rates of 26–28 mm/yr for the North Anatolian fault along the 1999 MW = 7.6 Izmit rupture are ∼40% faster than Holocene geologic rates. In contrast, geodetic rates of ∼6–8 mm/yr along the Denali fault prior to the 2002 MW = 7.9 Denali earthquake are only approximately half as fast as the latest Pleistocene‐Holocene geologic rate of ∼12 mm/yr. In the third example where a sufficiently long pre‐earthquake geodetic time series exists, the geodetic and geologic rates along the 2001 MW = 7.8 Kokoxili rupture on the Kunlun fault are approximately equal at ∼11 mm/yr. These results are not readily explicable with extant earthquake‐cycle modeling, suggesting that they may instead be due to some combination of regional kinematic fault interactions, temporal variations in the strength of lithospheric‐scale shear zones, and/or variations in local relative plate motion rate. Whatever the exact causes of these variable behaviors, these observations indicate that either the ratio of geodetic to geologic rates before an earthquake may not be diagnostic of the time to the next earthquake, as predicted by many rheologically based geodynamic models of earthquake‐cycle behavior, or different behaviors characterize different fault systems in a manner that is not yet understood or predictable.