Trending Faults Research Articles

Paleostress and outcrop fracture analysis along Himalayan Foothills (Eastern Salt Range), Potwar Plateau, NW Himalaya, Pakistan

The Salt Range (SR) is an ENE-WSW trending fault bend fold that form the range front of the Himalayan fold and thrust belt in Pakistan. The research is carried out in the Eastern Salt Range (ESR) with the objective to determine the paleostress inversion from reduced stress tensors by using fracture data. The surface morphology of the fold is predominantly shaped by Eocene limestone that provide best exposure of joint surfaces that can be used for kinematic and dynamic analysis. We adopted a classical circle inventory method in the field and collected orientation data (dip amount, direction, and strike) from 7 localities (outcrop stations) of the Eocene Sakesar Limestone. Three prominent fracture trends are present in the study area namely, FS-1; (E-W), FS-2; (ENE-WSW) and FS-3; (NNE-SSW). For stress analysis and data processing we used the Tensor Program of Delvaux and Sperner (2003) and calculated seven stress fields by the Right Dihedron Method. The orientations of the principal stress axes (ϭ1, ϭ2, ϭ3) and Stress Ratio (R) depicts ϭ1(Shmax) and ϭ2 are sub-horizontal while ϭ3 is vertical in all stress tensors. The paleostress results show that ϭ1(Shmax) oriented NNE-SSW belonging to a compressive regime. It is suggested that ϭ1 developed more or less perpendicular to the trend of SRT and other relevant structures in the Potwar Plateau.

Water resources exploration and management based on remote sensing and geophysical data analysis: Al-Naqab Watershed, East Central Sinai, Egypt

This study integrates remote sensing and geophysical data to identify the hydrological conditions of the Naqab reservoir watershed. The main objectives of this study are identification and the interpretation of subsurface structures and their impact on groundwater flow, the relationships between structures and groundwater and the optimum way for watershed management in this sub-basin. Geophysical data including, ground magnetic survey and 1D electrical resistivity sounding helped in identifying the lithology and delineating zones of groundwater occurrence. The magnetic data delineated the basement rock, aided in characterizing the geometry of the subsurface structures that control the land surface features and constrain groundwater flow system. The interpreted subsurface structure elements include six sets of faults trending NE-SW, NW-SE, NWW-SEE, NEE-SWW, N-S and E-W. The basement depth was estimated at zero at the southern part and about 5187 m at the northern part. Two aquifer systems were characterized, the shallow aquifer of the Wata Formation (Upper Cretaceous) and the deep aquifer of the Malha Formation (Lower Cretaceous). The probability of groundwater occurrence increases towards the central part of the study area to north direction, where the thickness of the sedimentary basin reaches its maximum at the center of the study area. Different trends of faults were interpreted from are the geo-electrical cross-sections along two transects. Three patterns of faults were characterized including step faults, graben faults and horst faults. These faults could be indicated on the geo-electrical section by a marked difference in the layers` thicknesses. The magnetic data confirmed the locations of the faults delineated by the electrical resistivity profiles. The outlined faults are trending mainly in NE-SW, NW-SE, NWW-SEE, NEE-SWW and E-W directions. Lineament structures delineation and drainage pattern analysis were evaluated and interpreted from the analysis of remote sensing (RS) data and geographic information system (GIS) technique. The SRTM-DEM (Shuttle Radar Topographic Mission-Digital Elevation Model) was also utilized to automatically identify and extract drainage network. Interpretation and analysis of the inferred lineament structures indicate the presence of a number of main lineament populations that trends: NE-SW, NW-SE, NNW-SSE, NWW-SEE, E-W and N-S. Meanwhile, the interpretation and analysis of drainage pattern network indicate the presence of three main lineament structures that trends: NW-SE, NE-SW and NWW-SEE. Azimuth distribution analysis of both the measured structures and drainage channels shows similar trends, except for very few differences in the prevailing trends. Similarity in orientation of lineament structures, drainage system, and subsurface structural trends were recognized in the area under study. In conclusion, the integration between remote sensing and geophysical data revealed a close matching between the surface structural lineaments and subsurface structural trends could be verified. The preferred conduits of surface run-off and groundwater flow, as well as, the proper locations for groundwater exploitation could be determined.

New insights into the contribution of gravity data for mapping the lithospheric architecture

Amongst all the potential field methods, gravity data constitutes the frequently measured geophysical information for deep seated lithospheric structures. The present work aims to outline the structural pattern, the main basins of Sinai and the depths to both Conrad and Moho discontinuities (CMD) by utilizing the gravity data. Several basins were depicted based on high-pass filtered gravity map and much of them are in a close agreement with the former studies. Additionally, the dominant fault trends are NE, NW, EW and ENE. An empirical equation was applied to low-pass-filtered gravity data to estimate the depth of the CMD. However, the thickness of the sedimentary basins increases northwards, reaching approximately 8 km, the minimum depths of Conrad and Moho discontinuities were attained in the northern compartments to be about 18 and 31 km respectively. Meanwhile, far a way to the south, the maximum detectable depth of Conrad and Moho discontinuities are 21 and 37 km. Eventually, 2D gravity modeling was constructed and constrained by 15 drilled wells and the calculated depth of CMD to figure out the comprehensive lithospheric geometry beneath Sinai Peninsula.

Anisotropic zoning in the upper crust of the Tianshan Tectonic Belt

The Tianshan Tectonic Belt is an intracontinental orogenic belt formed by continental convergence that has undergone long-term tectonic evolution. The reactivation that began during the Cenozoic Period has led to complex structural changes. The goals of this study are to review the seismic observational data obtained during 2009–2019 in the Xinjiang regional seismic network and analyze the anisotropy of the upper crust in the Tianshan area. Therefore, a shear-wave splitting system was adopted to collect and analyze shear-wave splitting parameters of 33 stations in the study area. The anisotropy of the upper crust of the Tianshan is spatially diverse, and the dominant polarization directions of fast shear-wave reflect the spatial variations of regional tectonic stress. In addition, the time delays of slow waves are proportional to the intensities of anisotropy in the upper crustal medium. The dominant polarization direction of the fast waves in the western segment of the North Tianshan Mountain, northwestern corner of the Tarim Basin, and northeastern edge of Pamir is consistent with the tectonic stress fields in the area. In the northern part of the Keping Block, the dominant polarization directions of the fast waves are consistent with the fault trends; however, they are at a high angle to the dominant directions of the regional tectonic stress field indicating that the anisotropy is affected by the faults in the area. The anisotropy of the eastern segment of the South Tianshan Mountains and the surrounding area of Urumqi are affected by the local stress field and fault structure. The polarization directions at some of the stations are sub-parallel to the directions of the regional principal stress. However, for other stations, the polarization directions are aligned with the neighboring faults. The polarization directions of the fast waves in most of the study area are consistent with the local tectonic stress fields. Thus, stress compression phenomena such as the Tarim Basin being thrusted and subducted between the Tianshan crust and the upper mantle due to the far field effects of the convergence between the Indian and Siberian plates are evident. Furthermore, the zoning of the time delays is distinct, and the time delays share an increasing trend from east to west in the North Tianshan and South Tianshan Mountain ranges. These results are consistent with the north-south convergence deformations across the Tianshan Mountains, where the deformation rate increased from east to west. The average values of time delays in northeastern Pamir are significantly higher than that in the other areas due to the occurrence of the most intensive tectonic movements suggesting that the anisotropy of the zone is significantly stronger than that of the other zones in the Tianshan Tectonic Belt. We successfully deciphered the seismic anisotropy in the upper crust and provided a comprehensive and systematic understanding of the dynamic mechanisms of the Tianshan Tectonic Belt.

Research on Intelligent Mining Algorithm for Distribution Network Transformer Fault Early Warning

The distribution network is the end link of the power grid. The level of management directly affects the power supply capacity and power quality. It is related to the operation level and social image of the power grid enterprise. The transformer is a very important component in the distribution network. The transformer is continuously safe and stable. Grid power supply reliability. In this context, this paper proposes an intelligent gateway intelligent fault detection algorithm for transformer operation failure, which collects data of transformers in multiple dimensions and multiple source channels, such as electrical variables and non-electrical variables. Correlation analysis and causality analysis of the data to achieve an all-round warning of transformer operation failure. The traditional method of transformer fault warning is solved by relying on the special gas concentration or transformer vibration signal generated by the fault of the transformer fault to solve the problem of fault identification and early warning singleness and low reliability, and fully exert the technical advantages of the Internet of Things and data mining. The evaluation value of the five “ancestor“ elements is 0.2, 0.25, 0.15, 0.3, 0.1. Transformer operation fault trend early warning coefficient is set to 0.80. Once the early warning coefficient is found to exceed 0.80 during data collection and mining analysis, a transformer failure early warning will be issued, which can facilitate grid operators’ intervention and control in advance. The actual calculation case also demonstrates the correctness and effectiveness of the intelligent mining algorithm. This paper provides an effective support for the development and application of big data technology in the distribution network.

Mechanism of Overlying Crack-Stress Evolution When Mining on the Dual Fault Zone

To study the fissure-stress evolution law of overburden rock in the process of working face advancing in the dual fault area. This paper took the geological occurrence condition and actual mining situation of working face 21,129 of Tucheng mine as the engineering background. The method of similarity simulation combined with field measurement was adopted. The evolution law of the stope fissure field, the stress variation trend of roof fault, and migration characteristics of overlying strata in the process of stope mining through dual faults were studied. The results showed that: Dual faults had a large effective area on the surrounding rock of the stope, the surrounding rock movement in the affected area was intense. When the working face advanced to the fault F2 area, the energy generated during the surrounding rock movement of the fault F2 was transferred to the fault F1, which intensified the activity of the rock in the fault F1 area. The activation of the fault F2 caused the fissures in the surrounding rocks of the fault F1 to expand further. The surrounding rock of the stope changed from a single-fault action mode to a double-fault joint action mode. According to the degree of development of cracks in the roof of the overlying strata, the stope’s different positions were sorted from large to small as follows: fault activated fracture zone > central dual fault zone > open-off cut zone > middle of the non-fault affected zone. The field measured data showed that the area affected by the dual fault was composed of “high-pressure area” and “low-pressure area.” The working resistance value of hydraulic support was higher than that of the non-fault affected area. The law of fracture development and distribution in overlying strata of stope in similarity simulation experiments were consistent with the law of roof pressure measured in the field.

Fluid Inclusions and H–O–C–S–Pb Isotopic Systematics of the Jinba Gold Deposit, NW China: Implications for Ore Genesis

The Jinba gold deposit is located in the Maerkakuli Shear Zone of the south Altay Orogenic Belt, NW China. Mineralization types are classified as altered rock–and quartz vein–type. Orebodies occur as veins or lenses controlled by NW–trending faults, and are hosted in phyllite (Early–Middle Devonian Ashele Formation) and plagiogranite (Early Devonian Habahe Pluton). Three paragenetic stages were identified: early quartz–pyrite–gold (Stage 1), middle quartz–chalcopyrite (Stage 2), and late calcite–quartz–galena–sphalerite (Stage 3). Fluid inclusions within the deposit are liquid–rich aqueous (LV–type), vapor–rich aqueous (VL–type), carbonic–aqueous (LC–type), and purely carbonic (C–type) FIs. Homogenization temperatures for stages 1–3 FIs were 373–406 °C, 315–345 °C, and 237–265 °C, respectively. Fluid salinities for stages 1–3 were 2.1–13.6 wt%, 3.2–6.1 wt% and 3.9–6.0 wt% NaCl equivalent, respectively. The ore–forming fluids evolved from a CO2–NaCl–H2O ± CH4 to a NaCl–H2O system from stage 1–3. Oxygen, hydrogen, and carbon isotopic data (δ18Ofluid = 1.7‰–8.1‰, δDfluid = –104.1‰ to –91.7‰, δ13Cfluid = –0.4‰–6.3‰) indicate that ore–forming fluids were metamorphic hydrothermal origin with the addition of a late meteoric fluid. Sulfur and lead isotope data for pyrite (δ34Spy = 3.3‰–5.3‰, 206Pb/204Pb = 17.912.3–18.495, 207Pb/204Pb = 15.564–15.590, 208Pb/204Pb = 37.813–38.422) show that the ore–forming materials were mainly derived from diorite and the Ashele Formation. Mineralization, FIs, and isotope studies demonstrate that the Jinba deposit is an orogenic gold deposit.

Neotectonic evidence for Late Quaternary reverse faulting in the northern Chile outer forearc (22.5°S-23°S): Implications for seismic hazard

In the northern Chile outer forearc (19°S to 23°S), extension is the dominant deformation style conducted by crustal faults during the Neogene-Quaternary. Most of this extension has been produced by normal faulting along submeridian branches of the Atacama Fault System (AFS). During the Late Quaternary, several of these faults have built conspicuous metric-scale normal faulting scarps in alluvial deposits; the construction of these scarps has been related, in some cases, to M~7 normal faulting paleoearthquakes. On the contrary, shortening during this time span has only been locally reported. Until now, no metric-scale reverse faulting scarps have been documented along submeridian strands of the AFS. This study presents novel evidence corresponding to reverse fault scarps produced during the Late Quaternary by three NNE and NNW trending faults in the outer forearc between 22.5°S and 23°S: the El Toro (ETF), Caliche (CF), and Sierra Valenzuela (SVF) faults. These scarps, with up to 2.5 m height, developed in basement rocks, pre-Quaternary, and/or Quaternary alluvial deposits. Based on their characteristics and the evidence suggesting that similar fault scarps in the Andean forearc have a seismogenic origin, we interpret that these neotectonic landforms were produced by single reverse faulting paleoearthquakes. Considering the maximum scarp height as a proxy for the coseismic slip and fault length as a proxy for surface rupture length, we have estimated magnitudes between M6.2 and M6.9 for the causative rupture events. To discuss how reverse crustal faulting may be related to the interseismic and/or coseismic stages of the subduction cycle, we perform elastic dislocation models to calculate the horizontal displacement fields (at 0 and 20 km depth) induced by the interplate locking distribution in the area (over a seismic cycle) and three megathrust earthquakes (Antofagasta, 1995, Tocopilla, 2007, and a synthetic rupture). Modeling results suggest that the studied faults may experience reverse slip during both stages of the subduction cycle. We propose that the ETF, CF and SVF are faults capable of producing moderate-to-large earthquakes in the future. Finally, we reinforce the need to address the earthquake potential of the studied faults, and others similar to them, to acquire a complete assessment of the seismic hazard in the northern Chile outer forearc.

Development of a hybrid framework for inventory leanness in Technical Services Organizations.

Inherent uncertainties in demand and supply make it problematic for supply chains to accomplish optimum inventory replenishment, resulting in loss of sales or keeping excessive inventories. To cope with erratic demands, organizations have to maintain excessive inventory levels, sometimes taking up to one-third of an organization’s annual budget. The two most pressing concerns to handle in inventory management are: how much to order and when to order. Therefore, an organization ought to make the correct and timely decisions based on precise demand information to avoid excessive inventory accumulation resulting in enhanced competitive advantage. Owing to the significance of inventory control and analysis, this paper reports on developing and successfully implementing a hybrid framework for optimum level inventory forecasting in Technical Services Organizations. The proposed framework is based on a case study of one of Pakistan’s leading Technical Services Organization. The paper presents a statistical analysis of historical data and a comprehensive fault trend analysis. Both these analyses set a solid foundation for the formulation of a comparative analysis matrix based upon price and quantity based analysis of inventory. Finally, a decision criterion (Forecasting Model) is proposed using three primary forecasting techniques with minimum error calculations. The study’s finding shows a forecast error of 142.5 million rupees in the last five years, resulting in the accumulation of more than 25 thousand excessive inventory stock. Application of price and quantity based analysis identifies that 65% of the annual budget is significantly dependent upon only 9% (in terms of quantity) of "High Price and Small Quantity" Items (HS). These HS items are forecasted through three different forecasting methods, i.e., Weighted Moving Average, Exponential Smoothing, and Trend Projection, with Minimum Absolute Deviation to significantly reduce the forecasting error while predicting the future required quantity. The research work aims to contribute to the inventory management literature in three ways. First, a new comparative analysis matrix concept for identifying the most critical items is introduced. Second, a Multi-Criteria Forecasting Model is developed to capture a wide range of operations. Third, the paper suggests how these forecasting criteria can be integrated into a single interactive DSS to maintain optimum inventory level stock. Even though the DSS framework is based on data from a single organization, the application is expected to manage inventory stock in a wide range of manufacturing and services industries. This study’s proposed hybrid framework is the first of its kind that encapsulates all four dimensions of inventory classification criteria, forming a multi-criteria hybrid model within a DSS framework.

Multiphase deformation history of the Porcupine Basin, offshore west Ireland

AbstractThe Porcupine Basin is a large underexplored sedimentary basin located offshore west of Ireland within the structurally complex European North Atlantic Margin. The basin has evolved through multiple Jurassic–Recent phases of deformation and although the overall plate tectonic context of the margin is well‐documented, there are still uncertainties regarding the phases of tectonic activity, and their associated strain distribution and fault kinematics. Based on the analysis of large volumes of 2D and 3D seismic data from the Porcupine Basin, we provide an overview of the nature and origin of multiple fault systems, both tectonic and nontectonic, with links to regional tectonic events where possible. Three distinct basin‐wide phases of tectonically induced extensional faulting are recognized: (a) Late Jurassic N‐S to NE‐SW trending rift faults, (b) Late Cretaceous E‐W to ENE‐WSW trending normal faults and (c) Mid Eocene N‐S trending faults. The Jurassic faults were active over a period of 11.5 Myr between the Oxfordian and Kimmeridgian but with an intervening 4.5 Myr period of quiescence providing a two‐stage rift evolution. The Late Cretaceous faulting in the Porcupine Basin broadly correlates with extension in the Celtic Sea basins and is tentatively attributed to the rotational spreading of the Bay of Biscay in the south. The Mid Eocene phase of extension, which coincides with the onset of spreading between Europe and Greenland (Atlantic spreading), resulted in partial reactivation of the Jurassic faults. A series of non‐tectonic fault systems occur within specific stratigraphic intervals suggesting a compactional or gravitationally driven origin, including basinward dipping normal faults within a Palaeocene–early Eocene deltaic sequence, and multiple tiers of polygonal faults within Cretaceous, late Eocene and Neogene strata.

Genesis of hydrothermal gold mineralization in the Qianhe deposit, central China: Constraints from in situ sulphur isotope and trace elements of pyrite

The Qianhe gold deposit, located at Xiong'ershan in Eastern Qinling, with estimated gold reserves of 22 tons, hosts six orebodies within auriferous quartz veins and hydrothermally‐altered rocks along E–W trending faults. Here we present results from an integrated study involving field investigation, ore petrology, in situ sulphur isotopes, and trace elements analysis of gold‐bearing pyrite with a view to understanding the genesis of the hydrothermal gold mineralization. Three generations of pyrite are identified in the Qianhe Au deposit: Py1 is composed of coarse‐grained, euhedral cubic grains occurring at the margin of stage I quartz + pyrite vein; Py2 is occurs as porous grains coexisting with other sulphide minerals in stage II quartz + polymetallic sulphide veins; and Py3 is mainly composed of anhedral grains in stage III quartz + calcite + fluorite vein. Among the three generations, Py2 has the highest contents of Au (mean = 3.5 ppm), Ag (mean = 46.0 ppm), Zn (mean = 303 ppm), and Cu (mean = 346 ppm). The distribution and concentration of these trace elements are likely to be controlled by micro/nano‐inclusions in pyrite. The Co/Ni ratios range from 0.010 to 296, with most values lying between 0.1 and 10. The δ34S values of the various pyrite generations show a wide range between −17.9‰ and 4.5‰ with obviously higher values in Py3 (2.0‰ to 4.5‰) than those in Py1 (−16.7‰ to −13.5‰) and Py2 (−17.9‰ to −9.0‰). The negative δ34S values in Py1 and Py2 possibly resulted from sulphur isotope fractionation between sulphide and sulphate minerals. As sulphate minerals are absent in stage III, the slightly positive δ34S values in Py3 suggest a mixed source from mantle‐derived material and wall rocks of the Xiong'er Group. We correlate the genesis of gold mineralization in the Qianhe deposit with the extension and lithospheric thinning during Early Cretaceous, when ore‐bearing fluids channelled along fault zones induced hydrothermal alteration and Au mineralization.

Discussion of the Fault Models of the Northern Marmara Shelf and the Lagoon Küçükçekmece with New Marine Magnetic Data, Turkey

580-km length marine magnetic study was performed at the Northern Marmara Shelf and the Lagoon Kucukcekmece to provide new datasets to understand the submarine structures. The distributions of the relatively complex and differentiated low and high magnetic anomalies indicate that the study area was affected by the multiple tectonic regimes. While the magnetic highs correspond with the folding structures, magnetic low anomalies well match with the lineaments determined from the seismic profiles. Magnetic anomalies support an E-W trending fault, controlling the anticlinorium system and NNE-SSW faults related to the compressional tectonics. These magnetic structures might be associated with Thrace Eskisehir Fault Zone, an older right-lateral strike-slip fault, which was the most dominant tectonic element before the North Anatolian Fault Zone. In addition to three appx, N-S trending faults are defined beneath the Lagoon Kucukcekmece from the total and residual magnetic anomaly grids.

Structural Complexity and Mineral Potential of Central Benue Trough, Using High Resolution Aeromagnetic Dataset

Mineral mining is an important resource for economic development, and its mineralization is controlled by geology, structures and hydrothermal alteration within rock formations. For this reason, high resolution magnetic dataset covering parts of the Central Benue Trough was processed and filtered/enhanced using analytic signal, first vertical derivative and tilt derivative algorithms. Qualitative interpretation of the total magnetic intensity maps reveals numerous magnetic depletion zones defined as hydrothermal active areas within Dampar, Wuro Jam, Kishr, Yamere, Shnye, Jibu, Adi, Amafan, Akwana, Akahana, Ayere, Awe and Tunga. There is a major NE-SW trending low magnetic amplitude stretching from Ugba to Kwarata, which is interpreted as active zones at the contact between the Central Benue Trough and Eastern Nigerian Basement Complex, the zone is interpreted as a major area of interest, especially around intense structurally active areas at Wukari, Chonku, Ngbebe, Bayawai, Gidan Idi, Wamgbe, Gusawa, Anzwa and Gada Mayo. Derivative filters revealed majorly NE-SW trending structures within the Central Benue Trough, with minor NW-SE trends observed at the contact between the Central Benue Trough and Eastern Nigerian Basement Complex with the longest fault having a length of about 42 km, stretching from Sankara to Apar, Hundu area. Major folds are mapped at Dampar, Wuro Jam and Kishr area. Long stretched fault systems within the Central Benue trough is observed at Bangalala, Gwinwan, Amar, Yamere and Rufai, Uzam, Sojo area. The dominating series of high angle NE-SW trending faults and folds structure was defined to have resulted from two major regional series of deformation stages. Integration of geological information and geophysical interpretation defined Wukari, Chonku, Bayawai, Wamgbe, Gusawa, Anzwa, Dampar, Yamere, Akwana, Akahana, Bangalala, Gwinwan,and Tunga as area of highest potential of mineral deposits occurrences based on the geology, extensive alteration and structural complexity.

3-D isotropic and anisotropic tomography of P-wave travel times from the Anhui airgun experiment in the Yangtze River

The Middle-Lower Yangtze River is a typical transition region between the nearly NW-oriented Tethys and NE-trending Pacific tectonic regimes. Structures of different periods and directions overlap strongly during these processes. The NE-trending Yangtze River compound structural belt and NW-trending Tongling-Hangzhou structural belt both control the magmatic activities and distributions of the metallogenic belts in the area. Here, we obtain 3-D high-resolution isotropic and azimuthally anisotropic velocity structures at depths of 1–10 km using the first arrivals from airgun sources. The velocity maps correspond well with the tectonic structures, with high-velocity anomalies distributed in ore-concentrated districts and low-velocity anomalies distributed along the Yangtze River. The fast directions are generally consistent with the fault strike, indicating that the azimuthal anisotropy is mainly dominated by the fault and fracture trends in the upper crust. The complicated fast directions near the Luzong and Tongling ore deposits reveal complex deformations in the upper crust, which are mainly caused by the intersection of the Yangtze River compound and Tongling-Hangzhou structural belts. The magma intrusion beneath the two ore deposits (Luzong and Tongling) are connected at depths of 5–10 km.

High resolution tomography of the Tanlu fault zone near Hefei with passive seismic and magnetotelluric linear array data

As the largest fault trending NNE-SSW to NE-SW in the eastern Eurasia Continent, the Tanlu fault zone (TLFZ) extends over 2,400 km within China, roughly from Wuxue, Hubei Province, to Russia. Since the Quaternary period, the TLFZ has been an earthquake-prone area in eastern China where several major earthquakes resulted by tectonic compression occurred, causing tremendous casualties and significant economic losses. Many studies on different segments of the TLFZ have been carried out in the past few decades. However, numerous key questions regarding the fault zone remain unanswered due to a lack of clear subsurface characterization and fault delineation. In this study, we present high-resolution tomographic results across the TLFZ to the east of Hefei, where one 22-km-long passive seismic array with densely spaced short-period nodes, and a 24-km-long magnetotelluric array were deployed adjacent to each other. We find the velocity and resistivity variations are highly consistent with known surface geology. Sharp property contrasts in both the seismic shear wave velocity and electrical resistivity profiles clearly delineate the Tanlu F1 fault (TLF-1) near Hefei. More interestingly, an upwelling with distinct high velocity is imaged within the Hefei Basin to the west of the TLF-1, whereas a slanted block with low-velocity and low-resistivity seems to cut into or thrust upon the high-grade to low-grade middle-pressure rocks in the Zhangbaling uplift right below the Tanlu F2 ductile shear fault (TLF-2). The presented results show a new approach to characterize deep subsurface structure of the TLFZ beyond 2-km depths using passive data, which it is often difficult for active seismic surveys with refracted and reflected waves to image.

Analysis of gravity and aeromagnetic data to determine structural trend and basement depth beneath the Ajdabiya Trough in northeastern Libya

In this study, we analyse both ground gravity and aeromagnetic data in order to delineate structural trends, fault systems and deduce sedimentary thicknesses within the Ajdabiya Trough in Libya’s northeast. A high-pass filter and a reduced-to-the-pole (RTP) transformation are applied to the gravity and aeromagnetic data respectively. Different filters are used to enhance the structural signatures and fault trends within the study area. The Werner deconvolution and source parameter imaging (SPI) techniques are applied to the RTP magnetic data for source depth estimation. Four well-data within the area are used as constraints in the two-dimensional forward modelling process. The results show that the Ajdabiya Trough is characterised by gravity anomaly highs and magnetic anomaly lows. The analysis of gravity data shows predominant Northeast–Southwest structural trends, whereas the analysis of magnetic data shows predominant North–South magnetic lineaments within the Ajdabiya Trough. The Euler deconvolution depth estimates of faults depths range between 1500 and 9500 m. The SPI estimates of the magnetic basement range between 2500 and 11,500 m beneath the study area (deepest beneath the Ajdabiya Trough). Constrained by the well-data, six major layers characterize the four profiles that are taken within the area. One of the profiles shows a high-density intrusion (about 4 km from the surface) within the sedimentary sequence. The intrusion may be the result of the rifting Sirt Basin which caused a weakening of the crust to allow for mantle intrusion.

Geomorphological Evidence of Active Faulting in Low Seismicity Regions—Examples From the Valley of Gobi Lakes, Southern Mongolia

Active intraplate deformation as a far-field effect of the India-Eurasia convergence has led to four Mw∼8 earthquakes in western and southern Mongolia in the past century. Palaeoseismological and morphotectonic studies have shown that these earthquakes are characteristic events along transpressive fault systems with cumulative offsets. The tectonically active Gobi Altai and Hangay mountains are separated by the seismically quiescent Valley of Gobi Lakes, which consists of major perennial rivers draining into endorheic lakes. Despite the scarcity of recorded earthquakes, Quaternary deposits in the Valley of Gobi Lakes are crosscut by multiple fault scarps with significant, landscape-altering displacements. To assess past earthquakes and the potential seismic hazard of this area, we apply remote sensing, tectono-morphometric techniques and cosmogenic nuclide dating to estimate the amount of deformation the faults in the Valley of Gobi Lakes are accommodating, and to determine the effect of these faults on local landscape evolution. The Tuyn Gol (gol = Mongolian for river) is crosscut by four E-W to NE-SW trending fault scarps that display variable fault kinematics due to scarp orientation differences relative to a stable NE-SW principle stress direction. Mapping of the >40–90 km long Valley of Gobi Lake faults shows that they can accommodate M ∼ 7 earthquakes. Offset measurements of the Tuyn Gol deposits allow Middle Pleistocene to modern vertical slip rate estimates and M ∼ 7 earthquake recurrence intervals of 0.012 ± 0.007–0.13 ± 0.07 mm/yr and 5.24 ± 2.61–81.57 ± 46.05 kyr, respectively. Cumulative vertical displacement amounts to 0.27 ± 0.08 mm/yr, which is similar to that of major tectonic structures such as the Bogd fault in the Gobi Altai. This implies that the total active deformation accommodated by southern Mongolian faults may be larger than previously expected and distributed across more faults between the Hangay and the (Gobi) Altai mountain ranges. Geomorphological observations and surface exposure dating indicate that the Tuyn Gol drainage system developed over four to five 100 kyr climate cycles, during which active deformation played an important role in drainage reorganization. Our results demonstrate the dominant role of tectonics on local landscape dynamics, indicating the importance of studying regional geomorphology to adequately estimate the earthquake potential of faults that were considered inactive.

Resurgent uplift at large calderas and relationship to caldera-forming faults and the magma reservoir: New insights from the Neapolitan Yellow Tuff caldera (Italy)

Resurgence uplift is the rising of the caldera floor, mainly due to pressure or volume changes in the magma reservoir. Identifying resurgence structures and understanding their relationship to the magmatic reservoir is challenging. We investigate the resurgence structures of the Neapolitan Yellow Tuff caldera (Italy) by integrating bathymetric data, high-resolution seismic profiles and Differential Synthetic-Aperture Radar Interferometry data. Our results show that the resurgent area is manifested as 1) a central dome constituted by two main blocks bounded by NNE-SSW trending faults, 2) an apical graben developed on top of the most uplifted block, 3) a peripheral zone including several uplifted and tilted blocks, bounded by inward-dipping faults. The onset of the uplift of the central dome occurred through re-activation, in reverse motion, of normal faults formed during the caldera collapse, and located in the peripheral zone. During periods of unrests, the blocks of the central dome move independently at different velocities, and the peripheral zone accommodates the deformation. The restless behaviour of the caldera is the result of a shallow magmatic reservoir located at 3.5 ± 0.7 km and characterised by a width that roughly corresponds to the extension of the overlaying resurgent area. Defining the caldera-forming fault system and identifying the area involved by the resurgence is crucial for estimating depth and width of the magma reservoir, and predicting the caldera behaviour during periods of unrest by localising possible vents and sectors that will deform. This knowledge contributes to the evaluation of the volcanic hazard.

Visual high dimensional industrial process monitoring based on deep discriminant features and t-SNE

Visual process monitoring allows operators to identify and diagnose faults intuitively and quickly. The performance of visual process monitoring depends on the quality of extracted features and the performance of the visual model to visualize these features. In this study, we propose a deep model for feature extraction. First, a stacked auto-encoder is used to obtain the feature representation of the input data. Second, the feature representation is fed into a multi-layer perceptron (MLP) with the Fisher criterion as the objective function. The outputs of the MLP are the extracted discriminant features. We combine the proposed feature extraction method with the visual model consisting of t-distributed stochastic neighbor embedding (t-SNE) and a back-propagation (BP) neural network (t-SNE-BP) for visual process monitoring. In this method, an industrial data set is reorganized into a dynamic sample set containing fault trend. Subsequently, the proposed feature extraction method is used to extract discriminant features from the dynamic sample set. Finally, the t-SNE-BP model maps these discriminant features into a two-dimensional space in which the normal and fault states are represented by different regions. Visual process monitoring is performed on this two-dimensional space. The Tennessee Eastman process is used to demonstrate the performance of the proposed feature extraction and visual process monitoring methods.

Genesis of Gold Deposit in Um Trambishi Area, NE Atbara, Sudan.

Um Trambishi area consists of volcano-sedimentary sequence intruded by syntectonic pluton of granitoids composition with marginal fissures injected by aplite, had been subjected to dynamic metamorphism and obliterated by recrystallization forming different rock units varying in composition, forming greenschist terrains. These are an assemblage of recrystalline schists, meta-acid, cataclastic tonalite, granodiorites, meta-andesite, chlorite schists, quartzite, marble, metabanded chert, together with two generations of unmineralized deformed and undeformed white quartz, which are oriented mainly in E-W and N-S direction following faults trend. The area is subjected to four deformational phases of brittle-ductile transition. The metamorphic grade is Green Schist Facies. The alteration around the endo-contact zone is characterized by minerals: albite, chlorite, epidote, sericite, carbonate and kaolin with anomalous Au=0.91ppm, Ag=1.75ppm, As=44.6XRF, Co=15.70XRF, V=65XRF, Ti=4796XRF, Cr=23XRF, Sr=269XRF, and base metals Pb=1.51ppm, Zn=22.02ppm and Cu=13.59ppm. The first phase of hydrothermal solution carrying gold is related to the magmatic high temperature associated with granitoidal intrusions, deposited into the planar fabric S1 and has a characteristic signature of hypothermal processes .The second mode of occurrence is the regeneration of auriferous quartz stringers filling into the tectonic fissures trending 340⁰ and oblique to S1 as a result of D3 (Keraf Shear Zone) and has a characteristic signature of mesothermal processes.