Tectonic Analysis Research Articles

Tectonic Interpretation and Analysis based on Multi-source Remote Sensing Data：A Case Study of JitaiRiver in Chayi，Tibet

Tectonic Interpretation and Analysis based on Multi-source Remote Sensing Data：A Case Study of JitaiRiver in Chayi，Tibet

Post-rift anomalous thermal flux in the Songliao Basin, NE China, as revealed from fission track thermochronology and tectonic analysis

The Songliao Basin in northeastern China contains a nearly complete Cretaceous sedimentary record. It offers an unparalleled opportunity for studying the thermal behavior of a rifting basin adjacent to a subduction zone during various stages of its evolution. The post-rift thermal history of the Songliao Basin is here documented by systematic apatite and zircon fission track analyses on newly exhumed sandstone samples from the Upper Cretaceous Quantou and Qingshankou formations. The combination of thermochronology results and stratigraphic records indicates that there was an unambiguous post-rift thermal overprinting event in the Songliao Basin during the deposition of the Nenjiang Formation at ~85–80 Ma. This fossil thermal anomaly has not been previously recognized from organic maturity indicators and/or subsidence modeling. The zircon fission track results indicate an estimated maximum paleo-temperature as high as 170–220 °C near the Daqing Placanticline. Fission track analyses of sampled apatites further define a restricted thermal anomaly in the central part of the basin. Based on the context of local lithospheric structure and adjacent plate tectonic history, we conclude that the Late Cretaceous westward subduction of the Paleo-Pacific Plate not only produced vertical motions and directly controlled the topography of the Songliao Lake, but also dominated the mantle heat flow beneath East Asia. This finding has significant implications for the evolution of thermal flux in the basin.

Assemblage of strike-slip faults and tectonic extension and compression analysis: A case study of a Lower Permian commercial coal reservoir in China

The Qinshui Basin was an active residual basin in the Mesozoic and Cenozoic periods and is located inside the North China Plate. The Upper Paleozoic strata in the basin have been strongly deformed and have developed a large number of strike-slip faults. The Qinshui Basin has been influenced by compressive stress from the northeast direction since the Himalayan period, and the faults have a dextral strike-slip property. Under the action of such a stress field, the right-slip, right-order faults indicate an extension region, and the right-slip, left-order faults indicate a compression region. Based on this principle, the extension and the compression areas were divided. From northwest to southeast direction in the study area, two types of regions have interactive distribution characteristics. For the Fanzhuang block in the eastern part of the study area, the fault distribution has an ‘S-type’ trend from north to south, and the middle extension region is the ‘elbow’ or the ‘hinge zone’ of the ‘S-type’ area, which can also be called the ‘stress transition zone’. The tectonic stress field of the stress transition zone is complex, and tensile fractures are usually extremely developed with extension tectonics. Gas wells with higher capacity are mainly distributed in the extension zone, while the capacity of the gas wells in the compression area is usually lower. The study showed that the distribution of the gas well capacity is consistent with the tectonic extension and compression analysis, indicating that the tectonic analysis method in this study is reliable. The Upper Paleozoic coal measure strata in the Qinshui Basin represent a whole gas-bearing and stress-bearing system, the tectonic analysis method in this study is also applicable to other types of tight reservoirs for this set of depositional systems.

Active tectonics analysis of the Kalmard fault zone, Central Iran

Central-East Iran has numerous active Quaternary faults. This paper focuses on the analysis of geomorphic and structural characteristics of the Kalmard fault zone, including major NE–SW striking fault segments that cuts across the basement and the sedimentary cover in the Ozbak-Kuh area of Central-East Iran. Because of the absence of definite earthquakes through the Kalmard fault zone in contrast to other parts of Central Iran, we used morphotectonic methods in combination of structural studies to evaluate active tectonics of this area. Detailed structural assessment of satellite images and analysis of geomorphic indices, together with field surveys allowed us to evaluate the recent tectonic activity and support a Quaternary age for it. We used six morphometric indices including the stream-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), valley floor width–valley height ratio (Vf), drainage basin shape (Bs), and mountain-front sinuosity (Smf). We combined these indices to yield the relative active tectonics index (Iat). Based on Iat values, the study area includes class 1 (very high activity), class 2 (high), class 3 (moderate), and class 4 (low). Also the normalized steepness index (Ksn) represents a significant pattern of high values in the eastern and southeastern parts of the study area which correspond with high values of Iat index. The output is consistent with both landforms and structures observed during the field work. In particular, the high relative tectonic activity (classes 1 and 2) largely corresponds to F1 (the eastern segment of the Kalmard Fault Zone) in the Ozbak-Kuh area, while the moderate class of tectonic activity caracterizes F2 (the western segment of the Kalmarad Fault Zone). The older geological structures in the middle part of the area show the lowest relative tectonic activity. The results of this study indicate that the Kalmard fault zone is one of the major Quaternary fault zones of Central-East Iran which is potentially active.

Structural and Tectonic Analysis of Bashiqa and AL-Fadhlya Anticlines- Northern Iraq

Structural and Tectonic Analysis of Bashiqa and AL-Fadhlya Anticlines- Northern Iraq

Carbonate production, accumulation and sea-level change in fault-block platform setting: a case study on the Albian sequences in Central Tunisia

The Albian series have been deposited on both sides of a major E–W paleogeographic fault, which was inherited in the early stages of the Tethyan-rifting phase. To the south of this fault, a shallow platform domain (footwall block or horst) occurred and is relayed northward by a slope-deep shelf setting (hanging wall block or graben). The platform to basin transition was analyzed northward of this fault nearby M’rhila Mountains. A detailed sedimentological study, coupled with a tectonic analysis, indicates that the Albian sedimentary deposits consist of four third-order depositional sequences. The three lower ones are only present in the deep-shelf setting and include substantial carbonate accumulations. The latter deposits are generally arranged into alternating mud-rich-bedded limestone and conglomeratic levels. Most of this material was exported from the adjacent shallow platform by mass flow and suspension transport processes. In the studied series, the maximum carbonate accumulation is recorded in the deep shelf during the moderate transgressive increasing and the late highstand decreasing rates of sea-level rise. However, the minimum carbonate sedimentation is thought to be linked to both the minimum lowstand and the maximum transgressive sea-level rise. The uppermost depositional sequence—which occurs on both sides of the major fault, is different from the three lower ones as it includes only scarce thin re-sedimented limestone beds. The youngest sequence is related to an important interplay between a pulse of tectonic subsidence and the major see level rise that happened during the upper Albian (100–98.9 Ma), resulting in a regional collapse of the substratum and the drowning of the carbonate factory situated southward. Therefore, the uppermost sequence is considered as a tectonically originated depositional sequence rather than a “pure” eustatic one. The organic-rich deposits associated to this sequence south and north of the major fault correlate well with the global anoxic events. The present study case represents a good example illustrating the role of local tectonics and global eustatic fluctuations in controlling not only the facies and thickness distribution but also the carbonate production and accumulation.

IDENTIFYING FAULT ACTIVITY IN THE CENTRAL EVOIKOS GULF (GREECE)

Geological mapping on a 1:5.000 scale and a tectonic analysis in the wider Chalkida region of the Island of Evia and the adjacent Drossia area of Central Greece, have allowed the identification of a number of active and potentially active normal faults. These faults have been formed or reactivated during the Late Quaternary, since they affect Pleistocene brackish and terrestrial deposits. Some of the faults affect the contact of the limestone bedrock with the Quaternary formations, presenting characteristic polished surfaces. The faults, in places covered by the alluvial deposits of the Chalkida plain, are also detected by geophysical research. Among the identified faults, the most important are considered the Aghios Minas- Chalkida, the Avlida and the Lefkadi active faults. The first one extends from Drossia to the Chalkida area, crossing the sea straights, and has an ENE-WSW direction and a south dip. The other two, are parallel antithetic faults oriented WNW-ESE, and bound the South Evoikos Gulf on the Greek mainland and the Evia Island respectively. The mapping and evaluation of active faults in this region of moderate seismicity, with low topographic relief and consequent absence of morphotectonic features, is especially important from a seismic hazard point of view.

Detailed Analysis of Near Tectonic Features Along the East Pacific Rise at 16°N, Near the Mathematician Hot Spot

AbstractSpreading processes at the axes of fast spreading ridges are mainly controlled by magmatic activity, whereas tectonic activity dominates further away from the axis. High‐resolution near‐bottom bathymetry data, photographs, videos, and human observations from submersible surveys are used to develop a detailed tectonic analysis of the 16°N segment of the East Pacific Rise (EPR). These data are used to evaluate how a highly magmatic segment, close to a hot spot, affects the nucleation and evolution of faulting patterns and impacts the evaluation of tectonic strain within 2 km of the spreading axis. Our study shows that (1) the growth of tectonic features differs in response to dike intrusion and tectonic extension, (2) the initiation of brittle extension is strongly controlled by the location of the axial magma lens and the development of layer 2A, and (3) the high magmatic budget and the off‐axis magma lens in the west part of the plateau do not significantly impact the initiation of brittle extension along the central portion of the 16°N segment. Within the axial summit region, more than 2% of plate separation at 16°N on the EPR is accommodated by brittle extension, as is observed at other EPR segments. The interaction of the Mathematician hot spot with this EPR segment has no significant influence on the initiation of the tectonic deformation, but it does reduce the development of the brittle deformation.

Discovery of Precambrian thick black mudstones and its implication for hydrocarbon exploration in the southwest Tarim Basin

Due to deep burial of Precambrian in Tarim Basin, no breakthrough in the hydrocarbon exploration has been achieved from these strata, and development of high-quality source rocks is also uncertain. More than 30 exploratory wells have been drilled in the southwest Tarim Basin and the pediment region of Kunlun Mountains with a total area of more than 100 × 103 km2. Though some marine oil/gas fields such as Hetianhe, Bashituopu, Yubei and Luosi 2 have been discovered, the Cambrian or Ordovician source rocks have not been drilled, and hydrocarbon source still remain controversial. Recently, a set of thick black shales and mudstones has been found in the southwest Tarim Basin. The total thickness of mudstones is more than 140 m, and the total organic carbon mainly ranges from 0.6% to 1.9% with an average of 1.0%. Tmax is from 490 °C to 520 °C, equivalent to Ro from 1.99% to 2.99%. Pyrites are very rich in mudstone. According to stratigraphic contact relationship and isotopic chronology, this mudstone may have the age of more than 517 Ma, and is tentatively named as the “Western Kunlun black rock series”. Through the plate tectonic analysis, this set of thick black mudstones is possibly distributed widely in the southwest Tarim Basin, and its formation may be controlled by the aulacogen. This set of black mudstones may be an important source rocks in the southwest Tarim Basin, which suggest that the Precambrian-Cambrian strata in Tarim Basin has geological conditions for hydrocarbon accumulations. This discovery of the black thick mudstones in the southwest Tarim Basin will promote hydrocarbon exploration in the deep and ultra-deep strata of the Tarim Basin.

Tectonic analysis of fracturing associated with occator crater

Occator crater, a Ceres crater that hosts multiple bright spots on its floor, has several sets of fractures associated with it. A tectonic analysis of each of these fracture sets suggests that the concentric and radial fractures around the central pit and the concentric fractures high on the crater wall (near the rim) most likely formed due to well known impact cratering processes. Uplift of the crater floor due to magmatic injection is suggested to have resulted in the concentric floor fractures at the base of the crater wall, as well as the cross-cutting fractures in the lower part of the southwestern wall. A mathematical analysis shows that a cryomagmatic plume (diapir) could have both reached the height necessary to cause fracturing within Occator, and that the stresses required are reasonable. Expansion a lobate flow from beneath is proposed to have formed those linear fractures associated with the Vinalia Faculae. Circumferential fractures surrounding Occator appear to have formed due to the volumetric compaction of the ejecta blanket over the buried pre-existing topography.

Influence of Fault Geometry on the Spatial Distribution of Long‐Term Slip with Implications for Determining Representative Fault‐Slip Rates

Determining representative slip rates of active faults is essential to seismic hazard assessment and tectonic analysis. Here, we take a two-pronged approach to determine how spatially variable slip over many earthquake cycles impacts the sliprate record at potential sites of geologic investigation near releasing stepovers. First, we use 2D parametric models to estimate the probability that a point measurement is representative of the average slip-rate for continuous strike-slip faults and those with a range of releasing stepover geometries and friction values. All models result in skewed distributions for which a randomly selected site has a higher probability of sampling a slip rate that exceeds the mean. For most configurations, individual point measurements are unlikely (p < 0.5) to yield a slip rate within +/- 1 mm/yr of the mean. The probability can be notably improved (15%-300%) by summing slip rates of overlapping segments. Second, we use 3D mechanical models of a well-studied releasing stepover along the San Jacinto fault to investigate the impact of specific fault geometries on slip-rate distribution and the implications for existing slip-rate estimates. The model-calculated dextral-slip rates are consistent with the abundant geologic slip-rate data available for this system. Although summing the slip rates at geologic sites across the stepover may produce a nonrepresentative slip rate, the summed slip rates from the model are compatible with the representative slip rate. Thus, the complete along-trace slip-rate distribution produced from the geologically consistent models provides a way to select sites for determining slip rates or interpreting isolated geologic slip-rate data. The site-specific models also illustrate how to assess the uncertainty of slip-rate data due to the spatial variability of slip rates in geometrically complex fault systems.

Influence of fault zone on the respect distance and margin for excavation: a case study of the F4 fault in the Jijicao rock block, China

A high-level radioactive waste repository requires a rock mass to have good retardation properties. However, because a fault zone can be a potential seepage conduit for nuclides, its influence on the hydraulic conductivity of that fault zone must be assessed. Key sets of fractures were found based on an assessment of the statistical characteristics of fracture orientations and the tectonic analysis of a representative north–east fault in the Jijicao rock block in the Beishan region of Gansu Province, China. The trace midpoint density of each set was calculated using ArcGIS, a geographic information system, and a model of the hydraulic conductivity in the fault zone was developed based on a water pressure test and calculations, such that the respect distance and margin for excavation of this fault could also be determined. The calculated results show that the fault core and host rock are less conductive when the damage zone is 10- to 100-fold more conductive due to its greater density of fractures. The density is stable at 100 m, while the key set is stable until 65 m, and the calculated hydraulic conductivity is stable until 25 m; these results are consistent with the results of water pressure analysis.

Improving Tectonic Geomorphology Analysis and Interpretation of River Mobility Utilizing LiDAR-derived DEMs

Improving Tectonic Geomorphology Analysis and Interpretation of River Mobility Utilizing LiDAR-derived DEMs

Rupture processes of the 2013–2014 Minab earthquake sequence, Iran

We constrain epicentroid locations, magnitudes and depths of moderate-magnitude earthquakes in the 2013-2014 Minab sequence using surface-wave cross-correlations, surfacewave spectra and teleseismic body-wave modelling. We estimate precise relative locations of 54 Mw ≥ 3.8 earthquakes using 48 409 teleseismic, intermediate-period Rayleigh and Lovewave cross-correlation measurements. To reduce significant regional biases in our relative locations, we shift the relative locations to align the Mw 6.2 main-shock centroid to a location derived from an independent InSAR fault model. Our relocations suggest that the events lie along a roughly east-west trend that is consistent with the faulting geometry in the GCMT catalogue. The results support previous studies that suggest the sequence consists of leftlateral strain release, but better defines the main-shock fault length and shows that most of the Mw ≥ 5.0 aftershocks occurred on one or two similarly oriented structures. We also show that aftershock activity migrated westwards along strike, away from the main shock, suggesting that Coulomb stress transfer played a role in the fault failure. We estimate the magnitudes of the relocated events using surface-wave cross-correlation amplitudes and find good agreement with the GCMT moment magnitudes for the larger events and underestimation of small-event size by catalogue MS. In addition to clarifying details of the Minab sequence, the results demonstrate that even in tectonically complex regions, relative relocation using teleseismic surface waves greatly improves the precision of relative earthquake epicentroid locations and can facilitate detailed tectonic analyses of remote earthquake sequences.

Tectonic Analysis of the Pennsylvanian Ely‐Bird Spring Basin: Late Paleozoic Tectonism on the Southwestern Laurentia Margin and the Distal Limit of the Ancestral Rocky Mountains

AbstractDuring Pennsylvanian to Early Permian time, much of southwestern Laurentia experienced broad deformation far from the nearest plate boundaries. The bulk of this deformation is known as the Ancestral Rocky Mountains orogeny, which consists of several basement uplifts and proximal basins north and northwest of the Ouachita‐Marathon suture. The Ely‐Bird Spring basin formed during this time, located between the classic Ancestral Rocky Mountains and the complex and poorly constrained western Laurentian margin. In this study, we used tectonic subsidence curve analyses to evaluate the tectonic style of basin subsidence in this basin and several northern Ancestral Rocky Mountains basins. The Ely‐Bird Spring and Wood River basins have convex upward and stair‐stepped tectonic subsidence curves similar to curves from migrating foreland basins. These curves, combined with sedimentological and structural data, are consistent with these basins forming due to loading from the west and northwest as part of the complex western Laurentian plate boundary, not due to classic Ancestral Rocky Mountains tectonics. The other northern Ancestral Rocky Mountains basins have much steeper and more linear subsidence curves, similar to foreland basins with fixed loads. However, the Oquirrh basin, in particular, displays a large amount of subsidence far from hypothesized tectonic drivers of deformation. A combination of transmitted stress from both the western Laurentia margin and traditional Ancestral Rocky Mountains tectonism explains the anomalously large subsidence in the Oquirrh basin. Therefore, transmitted stresses from more than one side of western and southern Laurentia are required to explain the observed pattern of deformation.

The stretching amplitude and thermal regime of the lithosphere in the nonvolcanic passive margin of Antarctica in the Mawson Sea region

The burial history and thermal evolution of the lithosphere within the passive nonvolcanic Antarctic margin in the region of the Mawson Sea are numerically reconstructed for the margin areas along the seismic profile 5909 with the use of the GALO basin modeling system. The amplitudes of the lithosphere stretching at the different stages of continental rifting which took place from 160 to 90 Ma ago are calculated from the geophysical estimates of the thickness of the consolidated crust and the tectonic analysis of the variations in the thickness of the sedimentary cover and sea depths during the evolution of the basin. It is hypothesized that the formation of the recent sedimentary section sequence in the studied region of the Antarctic margin began ~140 Ma ago on a basement that was thinned by a factor of 1.6 to 4.5 during the first episode of margin stretching (160–140 Ma) under a fairly high heat flux. The reconstruction of the thermal regime of the lithosphere has shown that the mantle rocks could occur within the temperature interval of serpentinization and simultaneously within the time interval of lithospheric stretching (–160 < t <–90 Ma) only within separate segments of profile 5909 in the Mawson Sea. The calculations of the rock strength distribution with depth by the example of the section of pseudowell 4 have shown that a significant part of the crust and uppermost mantle fall here in the region of brittle deformations in the most recent period of lithosphere stretching (–104 to–90 Ma ago). The younger basin segments of profile 5909 in the region of pseudowells 5 and 6 are characterized by a high heat flux, and the formation of through-thickness brittle fractures in these zones is less probable. However, serpentinization could take place in these areas as in the other margin segments at the stage of presedimentation ultra slow basement stretching.

Tectonic Analysis of a Perseverant Disfigurement of a Zuma II Entry Route

Tectonic Analysis of a Perseverant Disfigurement of a Zuma II Entry Route

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

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.

Analysis of the lithospheric magnetic anomalies and tectonics in continental China and the adjacent regions using CHAMP satellite data

In this paper, the CHAMP satellite data from the last decade are used to map the lithospheric magnetic field in continental China at altitudes of 300 and 400 km using the spline function model technique. The results show that our model has higher amplitude than the spherical harmonic magnetic field model MF7. The resulting lithospheric anomaly distribution of continental China agrees with the geotectonic structure and crustal thermal structure. The magnetic anomaly distribution clearly indicates extrusion of the Tibetan Plateau towards the northeast and northwest directions. Northward movement is impeded by the relative rigid Tarim Basin featured with positive magnetic anomalies. The positive magnetic anomalies in Tarim basin extend to the northern Tibetan Plateau, suggesting that the southern part of Tarim Basin underthrusted the northern Tibetan Plateau.

Oil reservoirs of the crystalline basement of the White Tiger field

Analysis of tectonics and rock petrotypes of The White Tiger oil field (the Southern Vietnamese shelf), and logs data of 165 wells revealed tectonic and petrological factors of formation and intensity of the secondary cavitation in the basement reservoirs. Studying of the pore space of rock reservoirs by the wells logging method is primarily based on acoustic and electric characteristics of the matrix porosity, fractures and caverns. The consistent pattern of variability (reduction) of porosity with depth was revealed. This pattern occurs in all selected geological blocks. The major factor causing the formation of the secondary cavitation in basement rocks is the tectonic factor, which reduces its influence with depth. The tectonic factor has the greatest influence on rocks of the Central and Northern blocks. An important factor causing the pattern of the porosity allocation is the allocation of rock petrotypes related with the direction and intensity of the secondary cavitation of rock reservoirs. Significant specific yield dependencies on the secondary cavitation determined by logs data were found for rock reservoirs of the basement in the Central and Northern blocks.