NNW Direction Research Articles

Мониторинг развития Дуплетного объекта взрыва газа С22 на полуострове Ямал по данным дистанционного зондирования Земли

The paper presents a comprehensive study of the C22 gas blowout Doublet object formed in 2023 in the central part of Yamal peninsula carried out with the use of remote sensing (RS) data and unmanned aerial vehicle (UAV). The object is situated 12.7 km south of the Bovanenkovo field. The uniqueness of the C22 crater lies in its location — 230 m from a similar, widely-known C2 object exploded in 2012, which is why the C22 object is named ‘Doublet’. Based on RS data the researchers have determined that within August 23 and September 3, 2023 the C22 permafrost heaving mound (PHM) exploded. According to ArcticDEM data for the period 2011-2023, the features of changes in the size of C22 PHM have been studied, including an abnormally high average growth rate of 44 cm/year three years before its explosion, which can serve as one of the criteria for identifying explosive PHM objects. The UAV data of May 14, 2024 has resulted in building a 3D model, which displays a partially snow-covered cavity in a ground ice massif. The depth of the cavity from the crater parapet is at least 28.5 m, the diameter of the crater neck is about 13 m. In the lower part, the cavity widens to 26 m and additionally extends by at least 8 m in the NNW direction at an azimuth of about 341°, which is consistent with the direction of the faults of the Bovanenkovo field identified by seismic exploration data. The bottom of the cavity has an elliptical shape with the size from 26×33 m to 26×41 m. The study is interdisciplinary and is included in the list of critical technologies for the prevention and reduction of risks of natural and man-made emergencies.

Simultaneous normal and reverse faulting in reactivating caldera faults: A detailed field structural analysis from Campi Flegrei (southern Italy)

Models of volcanic collapses proposed in the literature rely on combining field examples with analogue and numerical modelling to connect superficial observables to sub-surface volcano-tectonic processes. However, the behaviour of such collapses in an already faulted and fractured medium needs to be better explored.We studied a complex array of normal and reverse faults within the central sector of the active Campi Flegrei caldera, where faults with centimeters-to-meters displacements are hosted in the La Pietra tuff (∼13.5 ka) and the overlying pyroclastic succession of the last ∼5.5 kyr. We analyzed the attitude, kinematics and throw of these structures, employing a UAV-based digital outcrop model. The analysis shows that antithetic normal and reverse faults form in the hanging wall of a pre-existing WNW striking, NNE-dipping master normal fault. Moving northward, the strike of the antithetic faults rotates from WNW to NNW directions, with the latter showing a right-lateral oblique component. The simultaneity and coherence of both kinematics and attitudes are verified by the throw analysis. We associated the formation of this array with the caldera-collapse phase of the Agnano-Monte Spina eruption (∼4.55 ka), which caused off-caldera faulting beyond the main collapsed area.Based on field data, we suggest that during peak caldera-forming phases, wider areas beyond the main caldera scarps can be involved in volcano-tectonic collapses in the presence of a pre-existing fault network and complex tapped reservoirs. This highlights the role of inherited structures in weakening the crust above the magma reservoir that can potentially increase the magnitude and duration of caldera-forming eruptions, as they may induce a broader roof rock subsidence, pressurizing wider regions of the sub-caldera magma system.

Paleotectonic Stress and Present Geostress Fields and Their Implications for Coalbed Methane Exploitation: A Case Study from Dahebian Block, Liupanshui Coalfield, Guizhou, China

The macroscopic structural fractures (joints) and geostress distribution characteristics of coal reservoirs are important factors affecting the exploitation of coalbed methane (CBM). In this study, the joints in the sedimentary strata of the Dahebian block in Liupanshui area, Guizhou Province were investigated. Directional coal samples were collected for observation and statistical analysis of coal microfractures, the paleotectonic stress fields of the study area were reconstructed, and the tectonic evolution was elucidated. The geostress distribution characteristics of the target coal seam (coal seam No. 11, P3l) in the study area were analyzed using the finite element numerical simulation method. The results indicate that the structural evolution of the Dahebian syncline in the study area can be divided into two stages. The Late Jurassic–Early Cretaceous stage (Early Yanshanian) is the first stage. Affected by the sinistral strike slip of the Weining–Ziyun–Luodian (WZL) fault zone, the derived stress field in the study area exhibits maximum principal stress (σ1) in the NEE–SWW direction. The Late Cretaceous stage (Late Yanshanian) is the second stage. Affected by the dextral strike slip of the WZL fault zone, the derived stress field exhibits σ1 in the NNW–SSE direction. The folds and faults formed in the first stage were modified by the structural deformation in the second stage. The dominant strikes of joints in the sedimentary strata are found to be in the NW–NNW (300°–360°) and NE (30°–60°) directions, with dip angles mostly ranging from 60° to 90°. The dominant strikes of coal microfractures are in the NW (285°–304°) and NE (43°–53°) directions. The distribution of geostress in the study area is characterized by high levels of geostress in the syncline center, decreasing towards the surrounding periphery. The overall trend of the geostress contour line is similar to the shape of the syncline and is influenced by folds and faults. The σ1 of coal seam No. 11 is vertical stress. The prediction results show that the joint density of coal seam No. 11 in the block is 36–50 joints/m, and the shape of the joint density contour line is also affected by the axial direction of the Dahebian syncline and the surrounding faults. The variation in coal seam joint density and the control effect of geostress on joints opening or closing affects the permeability of coal reservoirs. The study results provide significant guidance for the exploitation of CBM.

Evaluation of geological structures and geothermal resources in the North Tanzania Volcanic area using remote sensing and gravity data analysis

Problems Statement and Purpose. Northern Tanzania Volcanic terrain has been a subject of evaluation for geothermal potential in the last four decades. The region is characterized by Neogene to Recent volcanic and tectonic activities. This preliminary study based on remote sensing, water chemistry, gravity data, geological structures and volcanic centers distribution reports the geothermal manifestations identified and discusses the implications on geothermal fluid pathways. Oxygen-hydrogen isotope data from water samples indicate that there were involved in the hydrothermal system. Tectono-Volcanic Structures. The Northern Tanzania Divergence (NTD) area characterized by Neogene to Recent volcanic and tectonic activities. Recent volcanic and tectonic activities are ash cone and lava dome eruption at the floor of Meru crater a century ago, dyke intrusion and volcanic eruption south of Gelai volcano, and Oldoinyo-Lengai volcano, respectively. Fumarolic activities and hot springs are dominant in a relatively young volcanic area to the north-eastern and northern part of the NTD. Data and Methods. Shuttle Radar Topography Mission (SRTM), Landsat 8 Operational Land Imager (OLI) image, water isotope analysis and gravity data were used to extract and analyze the surface and subsurface geological lineaments and map the hydrothermal alteration zones in the study area. The hydrothermal alteration is used to evaluate and identify the permeable structures. Analysis and interpretation of the length and trends of extracted lineaments were used to investigate the tectonic evolution. Geological map of a study area was digitized from the existing geological maps and the age of rocks to delineate volcanic activity and associated lineaments based on the age of the lithological domain. Digital image processing was applied to enhance the visual interpretation. Gravity data were used to give insight into the subsurface structure in the study area. Results and Discussion. The higher δ 18O values and large deviation from meteoric water lines suggest that is due to the interaction of fluids with host rocks at elevated temperatures. These are consistent with open structures that act as conduits for fluid flow. The potential field gravity data reveal a basin-like structure trending in the NNW direction. The gravity data show that the basement units gradually deepen towards the central part and that it is controlled by two main fault systems that trend N-S and NW-SE respectively. The gravity data presented here provides new constraints on the tectonic evolution and geothermal resources of the study area.

The geology and geochemistry of the Rhyacian Josephine gold deposit, Northwest Ghana

ABSTRACT This paper focuses on the geology and geochemistry of the Rhyacian Josephine gold deposit in northwestern Ghana, where gold is primarily hosted in quartzites, with other lithologies observed, including granitoids, mafic intrusions, and gneisses. Four deformational events, DJO0, DJO1, DJO2, and DJO3, are observed. DJO0 is synonymous with the primary preserved sedimentary crossbedding in the quarzitic rocks. Gold mineralization within the deposit is mainly associated with the DJO1 NNW-trending dextral and steeply dipping sinusoidal shear zone. Gold occurs primarily as free gold and invisible gold within the lattices of the disseminated arsenopyrite along the shear foliation planes of the host rock. The ore body geometry is 15–40 m wide and strikes 800 m in the NNW direction. Silicification, sericitization, chloritization, and sulphidation are the main alteration assemblages associated with the gold mineralization zones within the Josephine deposit. Pathfinder elements for gold are stibnite, tellurium, sulphur, copper, silver, and Lead.

Upper crust anisotropy of the 2020 Jiashi MS 6.4 earthquake

The 2020 Jiashi MS 6.4 earthquake occurred north of the 1997–1998 Jiashi earthquake swarm. Because of its complex tectonic environment and frequent strong earthquake occurrence, scholars have paid extensive attention to this area. To study the upper crustal anisotropy in the source area, we applied microseismic event detection and shear-wave splitting techniques to the seismic data recorded by five stations around the epicenter. First, the earthquake catalog of the Jiashi MS 6.4 earthquake sequence was rebuilt using the “Match & Locate” method. A total of 9,695 earthquake events were obtained, and the number of newly detected earthquakes was approximately 7.3 times the number in the officially released catalog. The newly identified microseismic data greatly increased the number of effective records and improved the reliability of the results. We analyzed shear-wave splitting according to the updated catalog. The results showed that the dominant polarizations of the fast shear waves were in NW or NNW at the stations BPM, XKR, L6505, and L6513, consistent with the stress near the source area. There are also blind faults with an NNW direction in the strike distributing en echelon and parallel to the main stress direction in the Jiashi seismic area. Thus, the fast shear-wave polarization of the four stations may also reflect the strike of multiple buried NNW faults in the study area. The fast shear-wave polarization of station HLJ, located at the Halajun Basin, was E–W, with the overall trend of the Kalpin thrust nappe structure. However, this station didn’t show the same NW or NNW fast-wave direction as the four stations previously mentioned. This finding may indicate that the NW-trending buried faults in the Jiashi seismic area have a limited size in both the length and the depth, only reaching northward near the second row of the Kapingtag nappe structure. The temporal trend of the delay time at station HLJ showed that a stress-release process occurred before the MS 6.4 earthquake and that stress-release occurred again after the mainshock. At station XKR, the delay time rapidly increased and then fell in the early period after the MS 6.4 earthquake, indicating that stress accumulated rapidly after the main earthquake but was released during the aftershock sequence. This study provides novel insights into the complex structural characteristics and seismogenic environment in the Jiashi area.

Gravity inversion constrained by OBS receiver function reveals crustal structure in Ryukyu Trench

The Ryukyu Trench is located in the northern Philippine Sea. The subduction of the Philippine Sea Plate to the Eurasia Plate along the Ryukyu Trench in the NNW direction leads to extremely complex tectonic processes such as subduction, collision, accretion, and back-arc expansion. It is of great significance to obtain the crustal structure of the Ryukyu Trench for understanding the crustal deformation characteristics, subduction direction and the scale of the Philippine Sea Plate. The ocean bottom seismometer (OBS) could provide important information on the deep structure of the oceanic area, and the wide coverage of gravity anomaly can provide more constraints for the regional crustal structure. In this study, we put the time-delay term of the sedimentary layer into the H-κ stacking formula, which eliminates the influence of the sedimentary layer in traditional H-κ stacking. Based on the accurate crustal thickness at OBS locations, a gravity inversion method is proposed to solve the problem of non-uniqueness in gravity data and limited distribution of OBSs. By using this method, we obtain a crustal structure with higher resolution than Crust1.0 model in Ryukyu Trench. The results show that the crustal thickness in the Ryukyu Trench region thickens along the NNW subduction direction, revealing that the Philippine Plate’s subduction direction towards the Eurasian Plate is in the NNW direction.

Assessing and mapping spatial accessibility of peri-urban and rural neighborhood of Durgapur Municipal Corporation, India: A tool for transport planning

The urban growth and its relation to transport network within the peri-urban zone were investigated in this paper. Using multi-temporal satellite imageries and road network data, the current study investigates a tool for transport planning and how it creates impact on the growth of built-up area. For the years 2001, 2011 and 2021, Landsat TM and OLI TIRS satellite images were used to create built-up area as well as the network data has been extracted from the different sources and create two 309*309 metrics table for the accessing of accessibility of peri-urban and rural neighborhood of Durgapur Municipal Corporation. From the above two metrics table alpha, beta, gamma, pi, grid tree pattern degree of connectivity, average shortest path length, shimbel index, connectivity index etc. have been calculated and mapped. Using the Open Root Service tools, the travel time from the peri-urban and rural neighborhood to city center has been also calculated. From the different above index, it has been observed that the along the NH-2, the accessibility is high. On the other hand, to show the built-up characteristics, direction and distance wise the built-up density and built-up expansion intensity index have been also analyzed. The highest expansion rate and intensity has been observed in the WNW, NNW, ESE and SSE direction. The geographical weightage regression also has been applied in this study to show the relation between built-up area and road density. The findings of this study could help regional planners assess the current state of active transportation options and pinpoint areas that need more attention to make them more accessible when allocating new urban facilities or reallocating those that are already there to lessen the negative effects that individual motorized transportation has on urban mobility.

Spatial Analysis of Structure and Metal Mineralization Based on Fractal Theory and Fry Analysis: A Case Study in Nenjiang−Heihe Metallogenic Belt

Regional tectonics can provide excellent transport channels and precipitation sites for mineralized hydrothermal fluid. Studying the spatial relationship and distribution trends of regional tectonics and metal mineralization has theoretical and practical significance for revealing regional mineralization regularities and guiding mineral exploration. This study considers the Nenjiang-Heihe metallogenic belt, through the fractal box dimension method and Fry analysis, to explore the spatial distribution characteristics and patterns of tectonics. The results were as follows. (1) NE and NW directions are the main tectonic directions in the study area, with high-density areas concentrated in the central-eastern and central-western regions, demonstrating an overall ring-like distribution pattern. (2) Fractal dimensions of the linear structures of the NE and NW directions and the entire study area are 1.543, 1.493, and 1.622, respectively, with a strong coupling relationship between the lineament fractal high-value area and rhombic-grid spatial distribution of known deposits. (3) Gold mineralization shows the NEE and NWW directions as two main mineralization trends; the intersection area is the gold-potential area. The main trend direction of the Cu-Mo metallogenic trend belt is the NNW direction; the intersection area with the NEE direction gold metallogenic trend belt is the Au-Cu-Mo potential mineralization area.

Neotectonics and Geothermal potential of the East Anatolian Tectonic Block: A case study in Diyadin (Ağrı) geothermal field, NE Turkiye

The study area is Diyadin, which is situated 71 km ESE of Ağrı very close to the Turkish-Iranian State border. It is one of several type localities of promising geothermal fields in the Eastern Anatolia. The neotectonic regime and related structures are dominated by a strike-slip tectonic regime governed by a stress field in the Eastern Anatolia where the greatest principal stress (σ1) is operating in NNW direction (N22°W) while the least principal stress (σ3) is N68°E. This stress field state was proved once more by the tensor solution of the 12 June 2022 Akçift (Muradiye-Van) earthquake of Mw = 5.1. The strike-slip neotectonic regime started at the time of latest Pliocene-early Quaternary and then triggered the first occurrence of the fissure eruption along the NNW trending Kaletepe open fracture. This event was followed by the development of both the two-peaked Tendürek strato-shild volcano and the Diyadin geothermal field (DGF). The geothermal potential of the DGF is high and its most common manifestations are the active tectonic regime and related faults (extensional horse tail strucure), active volcanoes (Tendürek and Ağrı volcanoes), fumeroles, numerous hot water springs to artesian wells, widespread iron-rich alteration zones, actively 
 growing fissure-ridge travertines and the probable presence of the unroofed hypabyssal felsic to intermediate intrusions of Quaternary age at the roots and their near environs of the isolated Quaternary volcanoes in the Eastern Anatolia. In addition, some significant similarities and contrasts are seen between the DGF and the IGF when they are compared.

A certain block of oil and gas accumulation understanding

The block is located in the southern part of an oil field. A grooved area held by three structures. The blank area is 41.6 square kilometers. It accounts for about 20% of the blank area. The faults in this area are more developed, mainly in the NNW direction, Permeability 0.7~1542mD, The average is 275.1mD, the porosity is 11.1~27.8%, the average is 23.2%, the average effective thickness is 2.2m, and the river channel width is 100-300m. The three-dimensional seismic data were collected in 2004, the accuracy of the survey network was 20m×40m, the number of coverage times was 66 times, the main frequency was 39-42Hz, the surface element was 10m×10m, and the data was finely processed and explained in 2008.

Underground Water Level, Strain, and Tilt Changes Observed Around the Fault Near Tono Research Institute of Earthquake Science

Near the Tono Research Institute of Earthquake Science (TRIES), Mizunami City, Gifu, two 500 m- deep shafts with diameters of 4.5 m and 6.5 m were excavated by the Japan Atomic Energy Agency (JAEA). The 6.5 m shaft is crossed by an NNW-trending geological fault (NNW fault), which has a right-lateral strike-slip component and a dip-slip component. Since before the excavation TRIES has been performing observations by a comprehensive set of borehole crustal activity observation devices in deep boreholes and extensometers in a vault near the shafts to observe variations in, for example, strain, tilt, and groundwater level continuously. During the shaft excavation, groundwater inflow to the shafts was encountered. The water was twice pumped out. During the pumping and non-pumping periods, TRIES’s observation data such as the groundwater level, the strain, and the tilt showed anomalous variations. The analysis of them revealed relationships among the groundwater level, the fault, the strain and the tilt. Strain analysis of TGR350 borehole station showed that the direction of the maximum shear strain was parallel to strike of the NNW fault. In addition, when the water in the shafts was being pumped out, the groundwater level at TGR350 declined and the maximum shear strain showed a right-lateral strike-slip movement in the NNW direction. When pumping was paused, the groundwater level increased, and the maximum shear strain showed a left-lateral strike-slip movement in the NNW direction. On the other hand, strain analysis of TGR165 borehole station showed different behavior from that of TGR350 borehole station deeper than TGR165. Tilt analysis of TGR165 borehole station showed tilt changes nearly perpendicular to strike of the NNW fault corresponding to the pumping and the non-pumping periods. Tilt analysis of TGR350 borehole station showed tilt changes of E-W direction with much smaller amplitude than that of TGR165. Behavior of the strain and the tilt during the pumping and non-pumping periods can be attributed in part to differences in the response of the medium to groundwater fluctuations, due to differences in the number and distribution characteristics of the fractures in the medium where the observation instruments are installed. We also discussed the observation results from the viewpoint of poroelasticity.

Seismicity and Stress State in the Ryukyu Islands Subduction Zone

Based on the newly compiled and mostly complete unified earthquake catalogue for China’s seas and adjacent areas, further information was obtained about the structural shape and dip angle of the Benioff zone in the Ryukyu Islands subduction zone during the different subduction stages. In addition, using the damped regional stress tensor inversion method, we were able to investigate the complex stress field characteristics and the dynamic significance of the shallow and intermediate earthquakes in the Ryukyu Islands subduction zone. The results show that the tectonic stress field of the Ryukyu Islands subduction zone was extensional along the subduction direction in the northern area of the Tokara Strait and was compressional along the subduction direction in the southern area of the Tokara Strait. The R value of the shallow stress field of the Okinawa Trough was low, and the σ3 was stable in the NNW direction with a small dip angle (>30°). The type of stress field in the shallow part of the Okinawa Trough transitioned from strike-slip type to normal fault type from north to south, reflecting the difference in the degree of development of the trough, and the southern segment of the trough began to transform into the expansion stage. The northeastern portion of the study area and southeast Taiwan constituted the high R value (0.68–0.87) region where the σ2 had tensile components. The stress state was biaxial tension–uniaxial compression, and the principal compressive stress was determined to be in the SEE direction with a large dip angle (>30°). The σ1 in northeast Taiwan exhibited a nearly vertical (>60°) plunge, while the σ2 and σ3 were nearly horizontal. The σ2 was thrust in the ENE–WSW direction, and the σ3 was extended in the NNW direction. Through this research, a greater understanding has been gained of the seismicity characteristics and shape of the Ryukyu Islands subduction zone. Supplementary research has also been completed on the focal mechanism solution and stress field of the Ryukyu Islands subduction zone. Finally, this research is important for earthquake hazard analysis and earthquake engineering safety evaluation in this area.

Occurrence of high-grade LREE allanite-pegmatites and calcite carbonatite dykes in the Ediacaran complex of Aghracha, Oulad Dlim massif (South Morocco)

High-grade REE-bearing granitic pegmatites and carbonatite dykes were recently discovered in the Aghracha area, South Morocco. They intruded the northern part of the Ediacaran complex, mainly composed of gneiss. The geochemistry of the basement samples displays compositions ranging from monzonitic to alkaline and sub-alkaline granites with prevailing positive Eu anomalies in chondrite-normalized patterns. These have been attributed to a magma mixing likely derived from the re-melting of underplated mafic rocks and a small amount of crustal rocks. The Aghracha pegmatites are rich in epidote and occur in the Awhifrit prospect in the western part of the basement. The analyzed samples display REE contents up to 17 wt%, mainly related to allanite-(Ce) (up to 13 cm in size), minor monazite-(Ce), and thorianite. The Aghracha pegmatite is referred to here as “allanite-pegmatite” because it exceeds the compositional fields of the classical LCT- or NYF-type classification. Calcite carbonatite dykes occur in the Laachariyat area in the western part of the Ediacaran complex. In addition to calcite, they also contain abundant strontianite, magnetite, barite, and apatite. The main REE-host mineral is monazite-(Ce), although minor bastnaesite and allanite also occur. Both pegmatites and carbonatite dykes strike in an NNW direction, likely associated with an extensional tectonic setting which is typical for the REE-bearing deposits and the Ediacaran complex of the Oulad Dlim massif.

Geological Characteristics of the Mesozoic Unconformities in Eastern Heilongjiang, NE China: Implications for the Mesozoic Continental Margin Evolution of Northeast Asia

Most of the significant petroleum- and coal-bearing sedimentary basins in Northeast Asia originated via rifting and thermal subsidence during the Late Jurassic-Early Cretaceous, followed by basin inversion in the Late Cretaceous. However, the tectonic background governing these basin prototype shifts has not been fully explored. The unconformities are excellent archives of plate boundary interactions and geodynamic switches in subduction zones. The Eastern Heilongjiang Province (EHLJ), Northeast China (NE China), comprises a series of Mesozoic-Cenozoic residual basins with well-preserved successions and provides significant insights into the tectonic characteristics and background of Northeast Asia. Mesozoic unconformities and large-scale contractional structures in the basins mark a series of important tectonic transitions in Northeast Asia. Based on the synthesis information of regional Mesozoic unconformities identified in the seismic reflection profiles and field outcrops of EHLJ, the tectonic characteristics and geodynamic background of the Mesozoic continental margin basins in Northeast Asia are analysed. The Middle-Upper Jurassic/basement unconformity (U1) can only be found in some areas of the Sanjiang and Hulin basins. It was a response to the continental collision of Siberia and the northern China–Mongolia tract along the Mongolia–Okhotsk suture during the Jurassic. The Paleo-Pacific Plate rapidly subducted in the NNW direction towards the eastern margin of Eurasia in the early Lower Cretaceous resulting in a mass of strike-slip faults and the widespread absence of deposits (Valanginian) (U2) in the EHLJ. Because of the subduction slab rollback of the Paleo-Pacific Plate during the late Lower Cretaceous, the local asthenospheric material upwelled, and fault and volcanic activities intensified in Northeast Asia. The Lower Cretaceous Dongshan Formation (Fm)/Muleng Fm unconformity (U3-1) reflects a specific scale of bimodal magmatism in the Songliao Basin and the EHLJ. The Pacific Plate subducted in a transformation from NNW to WNW during the early Upper Cretaceous (Cenomanian). The Houshigou Fm (Qixinhe Fm)/Lower Cretaceous angular unconformity (U3) reflects that on the basins experienced denudation after being extensively uplifted from the subduction events. With the subduction of the Kula Plate, a compression stress field during the later Upper Cretaceous Period controlled NE China. The basins underwent a widely compressive deformation, accompanied by large-scale thrusts, denudation and deplanation, resulting in Paleogene/Cretaceous unconformity (U4) was formed.

Coseismic and postseismic deformation of the 2016 Mw 6.0 Petermann ranges earthquake from satellite radar observations

Continental earthquakes, especially shallow earthquakes, can cause disasters in populated areas. On 20 May 2016, a moderate magnitude earthquake (Mw 6.0) ruptured on Northern Territory of Australia. With the aim of seismic hazard assessment, coseismic and postsesmic deformation of the Petermann earthquake has been determined using ALOS-2 ascending and Sentinel-1A descending images. The coseismic deformation field suggests that the earthquake ruptured in the NNW direction with a length of about 20 km, a rake angle of 57.1° and a moment magnitude of Mw 6.06. The maximum slip of 1.31 m can be observed at the depth of 1.25 km. The small baseline subset (SBAS) InSAR was utilized to obtain the postseismic deformation from 69 Sentinel-1A images in a descending orbit. The spatiotemporal evolution of the postseismic deformation presents a gradually decaying trend, with a maximum displacement of 5.4 cm within 858 days after the mainshock. Our afterslip model suggests that the maximum slip of 0.28 m occurred at the depth of 0.25 km with a slight shift to the northwest compared to the coseismic slip. The static Coulomb failure stress (CFS) changes at various depths were calculated, indicating the consistency between high loaded stress zones and aftershock distribution.

Investigating the Characteristics and Predictability of Measured Wind Speed Data Over Rio de Janeiro, Brazil

This study aims to characterize the wind regime in the state of Rio de Janeiro (SRJ), Brazil, and relate it to the physiographic aspects and influence of meteorological systems, based on 12 Brazilian National Institute of Meteorology (INMET) automatic meteorological stations, for the period from 2008 to 2019. Box plots are used for the assessment of monthly and hourly patterns. Similarity was found among the stations at a monthly and daily scale. On the monthly scale, there were two well-defined cycles, a minimum (between February and July) and a maximum (between August and November), both greatly influenced by frontal systems (FS). On the hourly scale, there was a decrease in the intensity of the wind during the night and early morning, followed by an intensification in wind patterns between 11 h to 20 h, except for the Arraial do Cabo and Petropolis stations. The stations that are located near the Serra do Mar ridge and Sepetiba Bay presented prevailing N, SW, W, ENE and NE winds, respectively. Arraial do Cabo station is located near the state’s shoreline and in the resurgence region, with predominant NE and E wind directions. Petropolis station is located in the Mountainous region, with NNW and NW wind directions. The logistic regression model identified that the rainfall, temperature (air, maximum and wet bulb) and relative humidity contributed to the probability of wind velocity above the 70 percentile (WS70) occurring in the SRJ. The South American Convergence Zone (SACZ) and FS acted as triggers of the WS70 in different areas of the state, where the influence of the SACZ was stronger than that of the FS.

Structural Interpretation and Attribute Evaluation for Characterization of Oil Field: A Case Study of “Sowari” Field, Niger Delta, Nigeria

Effective structural interpretation and attribute analysis using well logs, high-resolution 3D seismic data and surface attributes maps of the Sowari field Niger Delta, Nigeria have been successfully investigated. The approach includes correlation of wells using GR and SP logs to establish the lithology of the Formation, identification of reservoirs from the resistivity logs, horizon and fault mapping, generation of depth structure map and surface attribute analysis. Two horizons, H1 and H2 were mapped, and structure contour maps produced for each of the horizons. The study of faults showed a complex pattern of subsurface structures. The formation has extensive simple rollover structures bounded by growth faults trending in the NNW direction. Faulted rollover anticlines exist in the middle zone while the southern area is featured by collapsed crest structures. Structural closures considered as good hydrocarbon prospects were identified and delineated. Horizon (H1) lies at a depth of 2758m, and Horizon (H2) is at a depth 3190m across the reservoir. Average energy, Maximum Amplitude and RMS Amplitude surface attribute maps were extracted to reveal bright spot and high amplitude zones. Thus, seismic attribute analysis is a good complement to conventional structural interpretation, identification and correlation of geological structures.

Integration of ASTER and geophysical data for delineating potential mineralization zones in Dungash-Atud area, Central Eastern Desert, Egypt

Dungash-Atud area, located in the southeastern Egyptian Desert, is intensively distinguished by gold mineralization and associated mineral deposits. This area was studied using the integrated analysis and interpretation of ASTER, aeromagnetic, and gamma-ray spectrometric data. For ASTER, different approaches of image processing, such as false color composite (FCC), ASTER-TIR indices, principal component analysis (PCA), and spectral mapping, have been used to determine the desired information on the geology, lithology reclassification, and the existing minerals, particularly older and younger granites, basic, and ultrabasic rocks. Also, the alteration imagery maps of different minerals, sericite, chlorite, illite, kaolinite, calcite, epidote, and quartz, are obtained and classified, in addition to Mafic and Quartz Index. The processed and interpreted aeromagnetic data helped effectively for the detection of the deep subsurface and near-surface structural elements affecting the area and inspection favorable sites of mineralization that give strong magnetization of which chromite bodies associated with serpentinite rocks. In addition, the aerospectrometric data, equivalent uranium eU, equivalent thorium eTh, potassium K%, and total count (TC), were analyzed and hence the ratio maps (eTh/K, eU/K, and eU/eTh) and ternary radioelement composite images were produced to infer the enriched sites of U and Th mineralization. The integration of these results was guided and tied with previous geological information, especially ancient and present gold mines and associated mineral deposits. Such results gave clear clue about the existing number of basic to ultrabasic parallel wide dikes injected within fault zones trending mainly parallel to the Red Sea rift tectonics (NW and NNW directions) and other faults/dikes, trending in the NE direction. The long-extended NW trending wide dykes are cutting across the whole investigated area reflecting its deeper extension. Other faults show lateral displacements representing major shear zones, trending mainly in the NE direction. The produced potentiality map using GIS technique showed that most of the ancient gold mines and/or associated mineral deposits are related and controlled greatly with the detected structural elements, dykes, and rock affinity. Hence, it is easy to follow other sites that could have a high potential for mineral deposits including a gold through further field investigation in coordination with the detailed ground geophysical survey.

Study on System of Faults in the Gulf of Mexico and Adjacent Region based on Gravity Data

AbstractIn the Gulf of Mexico and adjacent landmasses, faults are very complex, and their distribution is closely related to plate tectonics, ocean–land boundary, and former structure. The plane position of the faults can be identified by the maximum characteristic of the vertical derivative of the normalized vertical derivative of the total horizontal derivative (NVDR‐THDR) of the Bouguer gravity anomaly. The apparent depth of the faults is inverted by the Bouguer gravity anomaly curvature property. Based on tectonic evolutionary processes and the plane distribution and apparent depth characteristics of the faults, a complete fault system for the Gulf of Mexico and adjacent areas has been established, including 102 faults. The apparent depths of 33 first‐class faults are 16–20 km and for 69 second‐class faults are 12–16 km. The F1‐2 and F1‐3 subduction fault zones are two caused by the subduction of the Cocos Plate into the old Yucatan and Chorti landmasses; F1‐11 and F1‐12 fault zones extend westward to the coast of Guatemala and do not extend into the continent; F1‐17 and F1‐20 faults, which control the boundary of the oceanic crust, do not extend southward into the continent. The fault system, which radiates in a “fan‐shaped” structure as a whole, unfolds to the northeast. Faults of different nature and sizes are distributed in the Cocos Plate subduction zone, Continental, Gulf of Mexico, Yucatan old landmass and Caribbean Plate in NW, NNW, NS, NE and NEE directions. In the Gulf of Mexico region, the fault system is a comprehensive reflection of former tectonic movements, such as plate movement, drift of old landmasses and expansion of oceanic crusts. The first‐class faults control the plate and ocean–continental boundaries. The second‐class faults are subordinate to the first‐class faults or related to the distribution of different sedimentary layers.