SSE Direction Research Articles

The structural elements controlling the subsurface mineralization as deduced from the integration of magnetic and self-potential methods, Wadi Khosh El-Daba area, southern Sinai, Egypt

Significant copper mineralization are observed to be associated, in most cases, with some radioactive anomalies related to increased uranium and thorium contents in Southern Sinai, Egypt. These mineralizations are related to intense post-magmatic, structurally controlled hydrothermal activities in many localities. Wadi Khosh El-Daba area is one of these locations which is mainly composed of monzogranites dissected by andesite dyke and pegmatite vein. This work deals with the application of ground magnetic and self-potential methods to establish the magnetic sources governing the mineralization, to interpret the significant trends that affected the study area, and to delineate the mineralized zones. The magnetic data were processed, enhanced and interpreted using advanced techniques, such as the first-order vertical derivative (FVD), the tilt derivative (TD), Euler deconvolution (ED), and source parameter image (SPI). The main structural lineaments/contacts that control the distribution of hydrothermal alterations and mineral distributions are oriented to the NW–SE, NE–SW, and NNW–SSE directions. The self-potential (SP) data show that there are numerous mineralized zones; most of them are distributed mainly along the structural lineaments deduced from the magnetic study. The quantitative interpretation revealed that the mineralized bodies are at shallow depths ranging from 5.6 m to 12.7 m, with half-width from 5 m to 13 m. These bodies are shallow to moderate dipping towards the south and north directions. Based on this study an anomaly map is originated to locate the preferred structural elements that may be controlling the mineralization in the area for further future exploration.

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.

Paleomagnetic study of Late-Carboniferous-Permian rocks from the Cadí Basin (Eastern Pyrenees): Tectonic implications

We have carried out a detailed paleomagnetic study of volcanic rocks (18 sites) and red beds (10 sites) from the Late-Carboniferous-Permian series of the Cadí Basin (Eastern Pyrenees). The study provides reliable Late Carboniferous-Permian paleomagnetic directions, in an area where paleomagnetic studies are scarce. The main characteristic component in both rock types shows a SSE direction with a shallow inclination and a dominant reverse polarity. The magnetic carriers, both in the volcanic rocks and the red beds, are magnetite and hematite. The main component is interpreted as a primary magnetization of Permian age in the red beds; in the Late Carboniferous volcanic rocks, the main component likely represents primary magnetization or early remagnetization. These results are consistent with the poles for the Iberian plate during the Permian and indicate an absence of regional vertical axis rotations for the Orri nappe, in whose hanging wall the Cadí Basin was transported southwards during the Pyrenean orogeny.

RXCJ1111.6+4050 galaxy cluster: Observational evidence of a transitional fossil group

We present a detailed kinematical and dynamical study of the galaxy cluster RXCJ1111.6+4050 (RXCJ1111), at z = 0.0756 using 104 new spectroscopic redshifts of galaxies observed at the Telescopio Nazionale Galileo and SDSS DR16 public archive. Our analysis is performed in a multiwavelength context in order to study and compare mainly optical and X-ray properties using XMM-Newton data. We find that RXCJ1111 is a galaxy cluster showing a velocity distribution with clear deviations from Gaussianity, that we are able to explain by the presence of a substructure within the cluster. The two cluster components show velocity dispersions of 644 ± 56 km s−1 and 410 ± 123 km s−1, which yield dynamical masses of M200 = 1.9 ± 0.4 × 1014 M⊙ and 0.6 ± 0.4 × 1014 M⊙ for the main system and substructure, respectively. The 2D spatial distribution of galaxies and X-ray surface brightness of RXCJ1111 presents an elongation in the North–South direction. These observational facts, together with a gradient of 250−350 km s−1 Mpc−1 in the velocity field, following the NNE–SSE direction, suggest that the merger axis between the main system and substructure is slightly tilted with respect to the line-of-sight. The substructure is characterized by a magnitude gap Δm12 ≥ 1.8, so it fits the “fossil-like” definition of a galaxy group. From the X-ray observations, we estimate a M500, X = 1.68 ± 0.25 × 1014 M⊙, which is in good agreement with the dynamical masses when two galaxy components are considered separately. This suggests that the mass estimates obtained from X-ray and velocity dispersion are compatible even for non-relaxed clusters, at least when we are able to identify and separate galaxy clumps and derive masses by considering the virialized regions. We propose a 3D merging model and find that the fossil group is in an early phase of collision with the RXCJ1111 main cluster and placed at ∼8° ( ± 3° ) from line-of-sight. This merging model would explain the slight increase found in the TX with respect to what we would expect for relaxed clusters. Due to the presence of several brightest galaxies, after this collision, the substructure would presumably lose its fossil condition. Therefore, RXCJ1111 represents the observational evidence that the fossil stage of a system can be temporary and transitional.

Coherent Chemical Variation Trends of the 55—25 Ma Magmatic Rocks in SE Tibet: N—S Direction Lithospheric Stretching of Eurasia during Early Stage of India—Eurasia Collision

AbstractThe progressive indentation of India into Eurasia generated an E‐W‐trending orthogonal collision belt and a N‐S‐trending oblique collision belt. Compiling available data reveals that ∼70% of the Cenozoic igneous rocks in eastern and southeastern Tibet are concentrated within an ENE‐trending, ∼550–km long and ∼250–km wide magmatic zone (CMZ) that once separated the orthogonal and oblique collision belts. The Latitude 26°N Line is now its southern boundary. The onset timing of magmatism of the CMZ varies gradually from ∼55 Ma in the westernmost part to ∼27 Ma in the easternmost. Then the magmatism successively occurred and suddenly stopped at ∼25 Ma. The segmented and coherent chemical variation trends found suggest that the CMZ magmatic rocks were formed due to partial melting of the heterogeneous upper mantle and crusts of Eurasia. Subduction of Paleo‐ and Neotethyan oceanic plates generated this compositional and mineralogical heterogeneity. Combined with available geophysical data, the CMZ was diachronously formed in response to asthenosphere upwelling induced by NNW—SSE‐direction lithosphere stretching. The difference in responses of the orthogonal and oblique collision belts to the indentation of the Indian continent has led to this lithosphere stretching.

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.

Delineation of hydrothermal alteration zones associated with mineral deposits, using remote sensing and airborne geophysics data. A case study: El-Bakriya area, Central Eastern Desert, Egypt

El-Bakriya area is situated in the Central Eastern Desert of Egypt. It includes several mineral occurrences and/or deposits. Data from remote sensing and airborne geophysics (gamma-ray and magnetic) were combined to identify the hydrothermal alteration zones and structures related to these occurrences. Various processing of ASTER satellite images revealed fifteen zones of high probability for metallic mineralizations. Airborne gamma-ray spectrometric data clarify K-enrichment zones, which are correlated geologically with the distribution of calc-alkaline, alkali feldspar granites (Younger granites), and calc-alkaline quartzdiorites to granodiorites (Older granites), as well as basement metavolcanics and metasediments. An integrated hydrothermal alteration map was constructed, based on both ASTER remote sensing and airborne gamma-ray spectrometric data. This map delineates some metallic mineral occurrences and/or deposits, which are located in the detected hydrothermal alteration zones. Besides, it displays new potential zones for mineralization, such as: Gabal (G.) El-Shalul, G. El-Bakriya, G. Siwat El-Arsha and G. Umm Bisilla. The geologic and airborne magnetic maps demonstrate five structural lineament trends of E–W, ENE–WSW, NE–SW, NW–SE, and NNW–SSE directions, which might act as pathways to transport the hydrothermal solutions in the study area.

Neogene-Quaternary response of the Novohradské hory Mts. (Czech Republic) fluvial systems to tectonics – Analyses of morphotectonics, stream-length index and structural geology

Based on comparison of morphotectonic analysis results with the SL index analysis, airborne geophysical measurements and field geological and structural data, possible Miocene to Holocene development of the landscape relief of Novohradské Mts. (southern Moldanubian Zone; Bohemian Massif) with a significant contribution of active faulting is interpreted.We suppose a polyphase reactivation of pre-existing faults under (a) the Miocene-Pliocene stress-field (regional ∼ NNW–SSE extension) as (oblique) normal faults trending ∼ SW–NE to ∼NW–SE were responsible for the subsidence of the Třeboň Basin and Kaplice Furrow and (b) the Pliocene to Holocene stress-field (Shmax = 146°) when horizontal in the ∼NNW–SSE direction with possible activity of the prevailing ∼ NNE-SSW trending faults as a sinistral strike-slips or weak reverse oblique-slip movement. The second set of subvertical ∼ WNW–ESE faults was predominantly reactivated in a dextral strike-slip regime or as gentle reverse oblique-slip faults. These Miocene to Holocene events reflect the coupling between the East-Alpine–Carpathian segment and its northern foreland, mainly due to northward motion of the African and the Arabian lithospheric plates.The core of the Novohradské hory Mts. experienced a significant uplift compared to the neighboring areas of the Kaplice Furrow and the Třeboň Basin. The most significant uplift has been found near Rychnov nad Malší, and on the tectonic border between the Kaplice Furrow and the Bukovský hřbet Ridge. This uplift took place during the late Pliocene and Pleistocene, after the sedimentation of lacustrine sediments in the Kaplice Furrow. Although the combination of GIS, morphotectonic and geophysical analyses with validation by field structural data does not provide the final proof of young tectonic activity, we conclude that there is strong indication of Neogene-Quaternary reactivation of several faults in the Novohradské Hory Mts. Based on similar morphological features, it can be supposed that many areas in the Alpine Foreland and Bohemian Massif underwent similar tectonic evolution during the Miocene to Holocene era.

Characteristics of Strong Ground Motions from Four M S ≥ 5.0 Earthquakes in the 2021 Yangbi, Southwest China, Seismic Sequence

ABSTRACT A seismic sequence has struck the Yangbi county, west part of Yunnan Province in southwest China since May 18, 2021 . This region experienced the strongest ground shakings on the night of 21 May with the successive occurrence of four earthquakes with M S ≥5.0 in a short time and more small earthquakes. Large numbers of strong-motion recordings obtained in the four earthquakes with M S ≥5.0 (i.e. the M S 5.6 foreshock, the M S 6.4 mainshock, the M S 5.0 and M S 5.2 aftershocks) were analyzed in detail to characterize the source effects, distance decay, etc. The velocity pulse-like waveform at near-source station 53YBX and the significant asymmetry of distance decay along the SSE-NNW direction (i.e. much slower toward the SSE) in the M S 6.4 mainshock seem to hint the occurrence of the asymmetrical source rupture. The source rupture directivity for the four events were investigated by fitting the azimuth-dependent residuals of the PGAs. The M S 6.4 mainshock is characterized by the significantly asymmetrical bilateral rupture propagation, predominantly in the SSE direction with a rupture velocity of about 2.24 km/s. The PGA and PSAs from the four earthquakes were further compared with the predicted medians of the ASK14 and CY14 prediction models for global shallow crustal earthquakes. The negative inter-events residuals reflect the weaker source contributions of the Yangbi events to ground motions. The source contributions to short-period ground motions approximately show the dependence on earthquake type, that is, M S 5.6 foreshock > M S 6.4 mainshock > M S 5.2 aftershock, consistent with the dependence of stress drop on earthquake type. We further noted that the inter-events values for the M S 5.0 aftershock are far below those for the M S 5.2 aftershock. This may be attributed to the differences in the spatial and temporal distance to the mainshock, that is, weak source contributions from the close aftershocks to the mainshock. The values of adjustment coefficient Δc 3 are almost positive, indicating the weaker anelastic attenuations in the study region. Finally, we also found that the distance scaling of significant duration can be well described by both empirical models (AS16 model for predicting significant duration and the BT14 model for empirically illustrating the ground-motion path duration).

Focal Mechanism Analysis of the September 25th, 2019 Mw 6.5 Ambon Earthquake and Its Implication for Seismotectonics

On September 25th, 2019, an Mw 6.5 earthquake occurred in Ambon, Maluku Province, Indonesia, and caused casualties and infrastructures damages. The epicenter located in a tectonically active region with the potential strike-slip and thrust faulting earthquake sources, yet the responsible fault is still not well understood. Based on focal mechanism solutions from available seismological agencies, i.e. USGS, GFZ, GCMT, and BMKG, the earthquake has a similar strike-slip focal mechanism, although there are discrepancies on detailed source parameters. To provide a better understanding of the earthquake mechanism and seismotectonic, we apply the Cut-and-Paste (CAP) focal mechanism inversion method to broadband seismic waveforms from regional and teleseismic distances. The CAP inversion results on the regional data grouped in different distance ranges show a robust strike-slip solution. We then refine the earthquake focal depth by performing the CAPtele inversion and resulted in a depth of 12 km with similar fault plane solution as the regionals. The ruptured fault plane is resolved by a directivity analysis using azimuthal pattern of the apparent source durations, which indicates an obvious unilateral rupture propagation toward SSE direction. Our result suggests the NNW-SSE orientated fault is the ruptured fault plane, which is also consistent with the near N-S distributed aftershocks. This fault is located in a narrow sea between Seram, Ambon and Haruku island and was not reported yet in previous studies. The Coulomb failure stress (CFS) changes analysis of the mainshock shows that the Ambon earthquake has promoted the off-fault aftershocks which occurred to the west of the ruptured fault.

Monitoring Urban Expansion and Urban Green Spaces Change in Addis Ababa: Directional and Zonal Analysis Integrated with Landscape Expansion Index

Addis Ababa, the capital of Ethiopia, is urbanizing very fast. This study aimed to assess urban expansion and Urban Green Spaces (UGS) change in the city from 1989 to 2019. Remote Sensing and Geographical Information System (GIS) and Landscape Expansion Index (LEI) were used to extract Land Use Land Cover (LULC) data, measure urban expansion and UGS change and analyze urban growth pattern in inner zone, outer zone and eight quadrants. The results showed that urban area in the inner zone increased from 3712 ha to 3716 ha (0.1%), and from 3716 ha to 3874 ha (4.2%) and in the first (1989–1999) and second periods (1999–2009), while it decreased from 3874 ha to 3733 ha (3.6%) in the third period (2009–2019), portraying a non-unidirectional trend of change. Conversely, the UGS in the inner zone decreased from 60 ha to 54 ha (10%), and from 54 ha to 38 ha (29.6%) in the first and second periods, while it increased from 38 ha to 53 ha (39.4%) in the third period, reporting spatial tradeoff between the two land cover types. Meanwhile, urban areas in the outer zone increased from 10,729 ha to 15,112 ha (40%), from 15,112 ha to 21,377 ha (41.4%) and from 21,377 ha to 28,176 ha (31.8%) in the first, second and third periods, respectively, representing frontiers of suburbanization. On the other hand, the UGS in the outer zone decreased from 3624 ha to 3171 ha, from 3127 ha to 2555 ha and from 2555 ha to 1879 ha, with an annual rate of decline of 1.25%, 1.8% and 2.6%, respectively, showing increasing trend of UGS destruction for urban construction. Furthermore, the LEI analysis result showed that urban expansion pattern demonstrated largely an outlying growth characterized by differentiation and isolation of patches, whereas the infill and edge expansion pattern were insignificant and fluctuated over 30 years. Furthermore, the directional analysis showed that urban area predominately expanded in SEE,> SSE,> SSW,> SWW,> and NEE directions with varying magnitude in the first, second and third period, but decreased in third period in NWW, < NNW< and NNE directions. In response to such urban growth pattern, the center of gravity of urban area shifted from north to south during the study period, displaying main direction urbanization in recent years. Conclusively, zonal and directional studies are more effective in characterizing the Spatio-temporal dynamics variabilities of urban expansion and UGS change for informed urban planning towards sustainable urban development.

Transport Influence and Potential Sources of Ozone Pollution for Nanjing During Spring and Summer in 2017

In this study, the 24-hour backward trajectories of air mass at ground level(10 m)in Nanjing were calculated by using the HYSPLIT model with the NCEP global reanalysis data from April 1st to October 31st, 2017. The backward trajectories were then combined with the hourly concentration data of O3 in Nanjing for trajectories clustering analysis and potential pollution sources analysis. The results show that in 2017, the maximum daily 8 h running average O3 level in Nanjing was around 12-261 μg·m-3 with 58 days of O3 pollution in Nanjing, mainly in the spring and summer. The monthly variation of O3 showed a single peak, with the highest O3 concentration, as well as the most days exceeding the standard, occurring in June; the diurnal variation of O3 was unimodal and reached its peak around 14:00. A total number of 5136 trajectories were obtained by simulation, among which the exceeded trajectories accounted for approximately 10%. The exceedance trajectories in May and June were significantly higher, accounting for 60% of the total exceedance trajectories. Six ground-level air mass transporting pathways were identified through clustering analysis, from the NNE, NW, SW, SSE, SE, and NE directions. The SE and SSE directions with higher O3 levels were the dominant transport routes of O3 pollution, contributing to 23.33% and 20.76% of backward trajectories, respectively. As for the potential pollution source analysis, the area with high WCWT value distribution matched the WPSCF result, indicating that the potential sources of O3 pollution were mainly distributed in Changzhou, Wuxi, Suzhou, Huzhou, and other cities around Taihu Lake. Additionally, cities located around Nanjing, such as Taizhou, Ma'anshan, Wuhu, Chuzhou, Nantong, and Lianyungang, were considered the secondary potential sources. The results indicate that O3 pollution in Nanjing is a regional issue and its control requires joint prevention and control strategies in the Yangtze River Delta.

INTEGRATION OF MAGNETIC RESIDUALS, DERIVATIVES AND LOCATED EULER DECONVOLUTION FOR STRUCTURAL AND GEOLOGIC MAPPING OF PARTS OF THE PRECAMBRIAN GNEISSES OF AGO-IWOYE, SOUTHWESTERN NIGERIA

Ground based magnetic survey conducted between longitude 06O 55I 51IIN – 06O 55I 54IIN and latitude 03O 52I 06IIE – 03O 52I 4.8IIE (Olabisi Onabanjo University) remarkably revealed a consistent subsurface NW - SE structural azimuth of localized discontinuities within the shallowly buried heterogeneous basement rocks, which at exposed locations are composed of strongly foliated granite gneiss and migmatite-gneiss with veins and veinlets principally orientated in NNW – SSE direction. Magnetic survey of the area was preceded by site inspection to avoid metallic objects interferences. Field procedure in the area involved Cartesian gridding, base station establishment, data acquisition at gridded points, and repeated bihourly diurnal checks at the base station. At the processing stage, diurnal variation effect was aptly removed before subjection to Kriging (gridding). The gridded data was then prepared as input for Forward Fourier Filter Transform (FFT), which upon definition and implementation enabled Butterworth filtering of isolated ringing effects, reduction to the equator (RTE) for geomagnetic correction, and the use of Gaussian and Upward Continuation filtering for regional magnetic intensity trend determination. Removal of the regional magnetic intensity (RMI) from the total magnetic intensity (TMI) resulted in the derivation of the residual anomaly. Enhancement filters adopted for better resolution of the residual magnetic gradient include analytical signal (AS), tilt-angle derivative (TDR), vertical derivative deconvolution (VDD), and the first vertical derivatives (FVD). TMI and RMI values range between 32925nT – 33050nT and 32935nT – 333050nT respectively, while the residual gradient ranges between 15nT/m and 10nT/m; AS ranges between 0.28nT/m and 4.1nT/m; and TDR ranges from -1.4nT/m to 1.4nT/m. Source depth calculation estimated from power spectrum analysis and Euler deconvolution ranges between 1m and 15m. Composite overlay of magnetic maps revealed jointed and faulted zones within the area; exhibiting a NW-SE principal azimuth of Liberian orogenic impress, which are in consistence with the foliation direction of the jagged foliated bedrock with an estimated maximum overburden of about 15m. The structural significance of this area as a prospective hydro-geological centre, and as an undesirable spot for high-rise building has been accurately evaluated from research findings. Application of integrated geophysical approach, complemented by detailed geological studies may furnish greater information about the subsurface structural architecture. Keywords: Gneisses; Ground Magnetic Surveying; RTE; Structural discontinuities; TDR. DOI 10.35180/gse-2020-0027

Evidences of neotectonic activity along Goriganga River, Higher Central Kumaun Himalaya, India

This paper focuses on the analysis of geomorphic landform development, particularly between the Trans Himadri Fault and the Main Central Thrust including Berinag Thrust and other major NNE–SSW and NW–SE striking faults/thrusts in the Higher Central Kumaun Himalaya. Digital analysis of remote sensing data, field investigations including drainage analysis, and development of landforms have been carried out to understand the morphotectonic evolution and, thereby, the neotectonics in this region. A number of morphometric indices [(stream length‐gradient index (SL), steepness index (ks), Chi (χ)] were computed together with knick point analysis. Offsetting of the major river and tributaries was observed along a NNW–SSE direction. Other tectonic landforms, including truncated saddles and disturbed terrace patterns, show that the area is presently undergoing active deformation. The valley floor morphology in the vicinity of the major thrusts provides evidence for aggradation of recent fluvial activity. Developments of various neotectonic features, such as starth terraces, off‐streams, truncated saddles, disrupted terraces, and palaeolake deposits, are evidences for recent tectonic activities associated with the major thrusts/faults. Cut‐and‐fill terraces with thick alluvial cover, debris‐flow terraces, and alluvial fan terraces are significant aggradational landforms observed within the valley that provide signatures of past climatic records. Our study reveals that the fluvially modified debris‐flow terraces were formed between 5 and 20 ka. We infer that the major phase of valley‐fill happened between 5 and 12 ka, whereas the youngest phase of aggradation may have responded to the Holocene tectonic activity that took place around 5–6 ka. The study is significant to understand the recent geomorphic development and tectonic deformation in the study area and may be helpful for future infrastructural development in the region.

Detailed volcanic and tectonic morphology of Nakadomari Hill in the southern Okinawa Trough

Nakadomari Hill is an unexplored edifice in the southern Okinawa Trough back-arc basin where crustal extension by continental rifting occurs and few submarine eruptions associated with back-arc volcanism have been mapped in detail. High-resolution bathymetric mapping with an autonomous underwater vehicle (AUV) reveals that Nakadomari Hill is a submarine volcanic complex with recent lava flow eruptions. The high-resolution (2 m) bathymetry shows striking contrast between rugged terrain in the central area and the adjacent smooth terrain. The cone-shaped features in the rugged terrain are covered by ropey fabric with high acoustic reflectivity and are devoid of tectonic deformation, thus they are interpreted to be relatively younger lava domes. The cone-shaped features in the smooth terrain show low reflectivity and are dissected by ENE–WSW trending tectonic lineaments, suggesting they were formed during older volcanism. Nakadomari Hill developed through multi-stage eruptions before and after back-arc rifting and faulting. The ropey and curtain-folded morphology with high acoustic reflectivity are interpreted to be a field of lava flows and they are relatively young. The area considered to be lava flows is estimated to be over 13 km2, showing that eruptions in the southern Okinawa Trough have been extensive. An active volcanic system is supported by indicators of high-temperature hydrothermal venting. Hydrothermal plumes with concurrent sharp temperature increases of up to 0.17 °C were present even at the vehicle altitude of ~100 m above the bottom. The alignment of volcanic cone-shaped features at Nakadomari Hill is in the NNW–SSE direction which is clearly different from the orientation of local rifting (ENE–WSW). At a larger scale, the volcanic edifices west of Kume Island from the arc to back-arc are also aligned roughly in the NNW–SSE direction and they are sub-parallel to a major tectonic structure in the arc, the Kerama Gap. The agreement of the local volcanic and tectonic trends implies that magmatic focusing may have taken place along the tectonic structures of the Kerama gap and in turn caused the extensive back-arc volcanism in this area.

Lithofacies architecture, composition, and age of the Carboniferous Teplice Rhyolite (German–Czech border): Insights into the evolution of the Altenberg-Teplice Caldera

The Teplice Rhyolite (TR) intra-caldera deposits of the Altenberg-Teplice Caldera (ATC, Central Europe) were investigated by lithofacies analysis, stratigraphy, and whole-rock chemistry as well as laser ablation U–Pb zircon dating. The aim was to demonstrate that the joint application of these methods can discern complex stratigraphy of ancient volcanic successions, susceptible to erosion and alteration, taking the TR as case study. The TR was regarded as a formation and divided into nine members that represent three main eruptions, each one separated by periods of volcanic quiescence. The first two eruptions mainly portrayed opening and clearing of vents, which were dominated by lithic-rich ignimbrites with lateral lithofacies changes (fiamme-rich to crystal-rich) covered by lava flows/domes. Eruption style was low pyroclastic fountaining alternated with effusive lava outpour. A sustained buoyant eruption column was exclusively interpreted at the outset of the second eruption based on the presence of a basal fallout deposit. The third eruption recorded three different phases: further vent opening, a waxing phase, and final lava extrusion. The vent opening phase was similar to those occurred in previous eruptions. The waxing phase produced voluminous, massive, poorly-sorted, very crystal-rich (>50vol.%) ignimbrites, exhibiting progressive increase in crystal contents with height and chemical composition variations that indicate deposition by progressive aggradation. Low pyroclastic fountaining formed these high-particle concentration currents that waxed and reached quasi-steady conditions. Eruption ended with extrusion of a lava flow. The TR ignimbrites were emplaced hot and were partially to densely welded, as evidenced by eutaxitic texture, deformed glass shards, spherulites, perlitic cracks, and microcrystalline to granophyric textures. Horizontal and vertical lithofacies variations in pyroclastic deposits, together with progressive infill and association between TR feeding systems and faulting, demonstrate that eruptions developed through several fissure vents or faults. A volcanic explosivity index of 7 was estimated according to a minimum ejecta volume of ∼320km3 (DRE). Volcanic architecture of the TR can be linked to sequential caldera subsidence that occurred synchronously with progressive deposition. Regional faulting (NE–SW-trending rhyolitic dykes) related to ATC feeding conduits suggests that progressive subsidence and final trap-door caldera collapse, possibly with a piece-meal component (faulted caldera floor), originated from post-Variscan tensional stress regime (∼NNW–SSE direction). The TR Formation has a general rhyolitic composition with A-type granite affinities and a normal chemical zoning. U–Pb zircon dating yielded ages from 323 to 312Ma, which, compared to age data from other ATC rocks, indicate that the TR was generated within a time span of ∼325–317Ma.

The Effects of Structural Elements on Groundwater of Wadi Yalamlam, Saudi Arabia Using Integration of Remote Sensing and Airborne Magnetic Survey

The present study aimed to develop an integrated approach that utilized field geology, remote sensing and airborne magnetic data to identify the Quaternary aquifers impounded by dykes and explain the dykes/lineaments relationship and their effects on the storage and flow of the groundwater of Sadiyah sub-basin, lower part of Wadi Yalamlam basin, Western Arabian Shield, Saudi Arabia. Field visits supported by Landsat ETM + ratio images (5/7, 5/4 and 5/1) revealed the presence of three main dyke types that can be chronologically arranged from older to younger as: Sheared mafic and acidic dykes (D1); Damm dyke complex (D2); and Ghumayqah dykes (D3). Two dykes referred to the first type (D1) were traced with depth using airborne magnetic survey crosscutting the main course of Wadi Yalamlam around Sadiyah village at high angle. According to water table elevation measurements, the aquifer of lower Wadi Yalamlam area is divided into three parts namely I, II and III. The water table elevations decreased from 158 m in the first part (I) to reach 66 m in the third part (III) of the aquifer. This drop is attributed to the effect of dykes which act as natural barriers. The study area was affected by three major fault systems as confirmed by field study and total magnetic map. Two of these systems have NE–SW to ENE–WSW and N–S to NNW–SSE directions, whereas the third one represents the Najd fault system trends in NW–SE direction. The present study identifies two locations valid for agricultural expansion lie just to the north of Sheikh Said and Abu Helal Farms.

Spectral Analysis of Magnetic data in the Ajmer-Sambar Sector, North-Central Rajasthan

Ajmer-Sambar sector of Delhi fold belt, North-Central Rajasthan has got importance due to its litho characters, structure, metamorphism, magmatism, migmatisation, metallogeny and rich potential of base metal mineralization. This sector is comprised of Delhi sequence of rocks hosted by the Banded Gneisses Complex (BGC). In view of the significance of this region, ground magnetic survey was conducted along six regional profiles to understand the structural features, magnetic nature of the basement and depth to the basement. Analysis of the magnetic data has clearly identified two magnetic lineaments (a) L1 in WNW-ESE direction that appears to represent litho-contact between Kalyanpura sequences in the south to Anasagar migmatite in the north and (b) L2 in NNW to SSE direction south of Parvatsar which is inferred to be a structural control about which the quartzite rocks of Taragarh Formation culminate. An average depth to basement of 3.7 km is estimated through spectral analysis of magnetic data. The maximum depth of the basin 4.5 km is estimated in central part of the study area. The obtained depth results are in good agreement with the Cummulative Total Intensity Magnetic Anomaly field (CTIMAF) and Deep seismic stuides.

Complex Rupture of the 2014 Ms 6.6 Jinggu Earthquake Sequence in Yunnan Province Inferred from Double-Difference Relocation

To study the seismogenic structure of the 7 October 2014 Ms 6.6 Jinggu earthquake, we use the cut-and-paste (CAP) method to obtain the focal mechanisms and depths of the mainshock and the two largest aftershocks with Ms > 5. Then, we take advantage of waveform cross-correlations to obtain precise time difference data and apply the double-difference method to relocate the aftershocks between October 7 and December 31. We relocate 2076 earthquakes (approximately 73.6% of the total) with an average horizontal accuracy of approximately 150 m and a depth uncertainty of approximately 700 m. The Ms 6.6 mainshock epicenter originated at 23.378°N, 100.475°E at a depth of 15.38 km. The Jinggu earthquake sequence exhibited a linearly concentrated distribution in the northwest–southeast direction with obvious segmentation features and, thus, it can be divided into four branches spatially and two stages temporally. The aftershocks first appeared around the Ms 6.6 mainshock and then extended on either side of the mainshock along the NW–SE direction (the NW branch). The earthquake rupture direction experienced a slight clockwise deflection at the NW end and rotated clockwise by approximately 90° toward the SW (the NE branch) at the SE end. Then, the rupture propagated a short distance along the SW direction and rotated counterclockwise by approximately 90° into an SSE direction (the NNW branch). There is a small angle between the NW and NNW branches. The depths of the whole sequence with vertical dip angles were shallower toward the NW and deeper with two seismogenic layers toward the SE. According to the distributions of the earthquakes and nearby fractures, it is highly possible that the Jinggu earthquake sequence occurred along a hidden fracture section of the Wuliangshan fault in the NW direction. Moreover, we can confirm that the three large earthquakes all occurred along right-lateral strike-slip faults.

Land Use Change in Hongta District in Yuxi City, China Based on Archived Landsat Data of the Past 30 Years

Urban expansion, which has affected ecosystem functioning and services at local to global scale, is projected to have aggravating impacts on landscape in the future. A detailed study on spatiotemporal patterns of Hongta District in Yuxi City over a relatively long timeframe was conducted using multi-temporal Landsat TM, ETM+ and OLI data of 1987-2017 associated with Geographic Information System techniques and landscape analysis approaches. Results showed that sealed surfaces (urban area) have expanded from 1.4% to 11.8%, with an annually increasing rate of 7.63%. Trees, farm areas and barren lands all underwent a slight reduction during this time period, whereby 23.8% of farms and 9.8% of bare lands transferred into sealed surfaces. Focusing on the urban expansion pattern, it presents a uninuclear polarizing polygon mode illustrating the urbanization sprawl over time to all directions. The greatest expansions are seen in NNE and SSE direction, mainly because of the topographic constraints. A trade-off between urbanization and sustainable development is under investigation by reclaiming barren soil at the mountain range to transfer farming areas from low altitude plains to make way for urban growth.