Results in Earth Sciences最新文献

The magnetic method of investigation is a well-known and dependable technique for detecting underground ferro-materials. However, the application of the magnetic method to identify the exact position of underground targets such as buried explosive devices (BED), illegally buried waste (IBW), metallic storage tanks, utility pipes, and communication cables is quite challenging in both civil and environmental engineering. This article presents the results of the investigation performed at a 55 m by 55 m area within the Ahmadu Bello University Geophysical Test Site (ABUGTS) to study the signals generated by various buried targets to simulate similar situations encountered in environmental engineering. The total magnetic intensity (TMI) of the site without buried targets was obtained to identify the possible existing underground materials or faults that could generate false geophysical data. The magnetic susceptibility of the buried targets was determined in the laboratory before the burial to validate the field results. The influence of the buried materials over the magnetic signature of the site was examined, showing the TMI values vary between 34966 nT and 44510 nT before burial and 351607 nT to 49795 nT after burial. The Euler deconvolution (ED) and residual maps alongside the signal enhancement maps like analytical signal and first vertical derivative (FVD) were employed to study the magnetic anomalies due to buried targets. The results of the data interpretation confirmed the existence of cluster anomaly source bodies due to buried targets. The ED delineates the depth of the buried targets varying between 0.7 m – 3.3 m corresponding with the actual depth of burial. The analytical signal map produced a perfect behaviour of the magnetic anomalies to buried targets, capturing all the buried targets buried at the site. However, the shape of the anomaly signal is almost independent of the buried target orientation with a spherical pattern of anomalies. However, the exact size and shape of the buried targets were not achieved. Nevertheless, the FVD and analytical signal maps perform better than the residual and TMI maps due to the substantially smaller magnetic anomalies of the buried targets similar to expected. In addition, stronger magnetic anomaly signals occur maximally around buried larger ferro-materials with precise prediction of the buried target position. The magnetic method is a very powerful, convenient, cheap, and time-saving geophysical tool for investigating underground targets, which is highly applicable in engineering and environmental contexts.

Over the past two decades, significant advances in the geochemical monitoring of volcanoes have shown how crucial the observation of specific geochemical tracers is for understanding and evaluating eruptive processes. Among these, the monitoring of soil CO₂ flux is one of the most important and widely employed geochemical parameters used in volcanic monitoring. At Mt. Etna volcano (Italy) long-term soil CO₂ time series (2011–2019) are available from a network of 14 monitoring sites located around the volcano. Although variations in the exhalative regime of soil CO₂ flux are recognized as possible proxies for potential emergent eruptive activity, little has yet been explored regarding the significance of the spatial variation of soil CO₂ over time. In this paper, we look for possible dependence of CO₂ flux on the altitude of the monitoring sites, their distances from the main craters, and their azimuthal positions on the volcano flanks. While for the first two elements there seems to be no evidence of dependence, we found evidence of long-term azimuthal variations in the soil CO₂ flux that could depend on the structure of the volcano. In particular, the sites in south-eastern flank behave somehow differently from the ones located in other flanks. At yearly time scale, marked variations affect the CO₂ flux at various sites. Such variations can be ascribable to volcano dynamics during the observation period characterized by a sequence of effusive and strombolian activities. Variations within a single eruptive episode also emerge investigating the 2018–19 flank eruption with bi-monthly windows.

The influence of the changing land use land cover (LULC) pattern on the vegetation, water, and temperature parameters is ascertained in the study of the Vedavathi River basin. For the years 2005, 2010, 2015, and 2022 Landsat and MODIS satellite products (MOD11C3, MOD13Q1) along with the ground-based rainfall from IMD measurement were used to implement the methods of indices such as normalized difference vegetation index (NDVI), normalized difference water index (NDWI) along with the land surface temperature (LST), and standardized precipitation index (SPI) and analyze the situation in the basin. Since 2005 more than 2000 km² of fallow land has been transformed into cropland. 22.35% of grassland was converted to plantation in two decades while 13% of scrub forest has been reduced to wasteland. The increase in the cropland and the changing forest area has brought an increase in the mean NDVI value while at the same time an increase in the temperature value. The years 2003 and 2004 witnessed an extreme dry conditions in most of the stations while 2010 and 2020 experienced flood-like conditions. Overall majority of the drought conditions were witnessed in the 1990s and 2000s while flood conditions were prominent in the later part of the study. The study aims to provide an understanding between all these factors and what is the intensity of influence on each other.

Due to the lack of rainfall potential in Central Iran, the water scarcity is still the main problem of production in the country. Accordingly, the use of unconventional waters will be inevitable. This study presents the amount of water required by the Chadormalu mine from the water wells of the Sepidan Plain, as well as the deficit or excess for exploiting the complex and the water treatment plant by reverse osmosis (RO) method. These studies were carried out to manage the groundwater resources of the Sepidan and Saghand basins and include the water level variations of piezometers, the water consumption of exploitive wells, aqueducts, and the Sepidan River every month. Furthermore, a sample of complete chemical analysis of the aqueducts' Saghand basin and the water entering the RO and leaving it for environmental evaluations have been carried out each season. The average discharges of water wells in the Sepidan Plain were 86.45 and 82.28 l/s in 2221 and 2023, respectively. Moreover, the amount of water exploitation has been lower than the renewable (dynamic) reserves, which in the heart of the water intake has a uniform increase in the monthly hydrograph's water level. At the same time, the reduction of total dissolved solids (TDS) entering from exploitation water intakes to the amount of 580 mg/l indicates the principled exploitation of dynamic reserves. The RO unit's output had no effect on the quality of the Saghand Playa's water but improved it qualitatively.

In this study, we have investigated four glaciers, namely Zemu, Talung, Alukthang and Rathong within Kanchenjunga national park. This study evaluates physical and morphometric parameters (area, length, perimeter, area of accumulation zone, ablation zone length, snout position, thickness and specific mass balance) of multiple glaciers and to ascertain the poorly understood glaciers of western Sikkim region under Kanchenjunga national park. The principal objective of this research is to find out the changes of glacial mass and other physical parameters of the selected glaciers using multi sources digital elevation model data.Various techniques of statistics, including Mann-Kendall and Sen’s slope tests have been applied at different confidence interval. We have identified that climate change is responsible for the alterations of the physical characteristics of the glaciers. Result shows that during the study period, Zemu glacier has faced highest amount of deglaciation in terms of area (20.79 sq.km) along with maximum 30 m elevation reduction, 24 m increase of snout elevation and 200 m retreat of terminus. Furthermore, it is observed that terminus of the each selected glaciers retreated during the study period. Rathong experienced maximum retreat rate, approximately 550 m, and is accompanied by a notable 163% increase in the ablation zone. Alukthang and Talung reduced their areas 0.56 and 4.06 sq.km respectively, along with 2.75 m and 9.10 m thickness respectively. Maximum 36.39 m/y^-1 flow rate has been observed over Zemu glacier. The flow rate of Talung, Rathong and Alukthang glacier is 26.4 m/y^-1, 34.1 m/y^-1, and 23.7 m/y^-1 respectively.

Statistical analysis of detected ionospheric anomalies with earthquake magnitudes was carried out on two seismic events of March 4, 2021, (M7.3 Gisborne and M8.1 Kermadec Earthquakes) to ascertain a possible link between observed perturbations and event size. GPS-TEC data were downloaded 20 days pre and 5 days post the events from stations within the epicenter of respective earthquakes. The data were statistically analyzed to detect unusual variations within the investigative window. The investigation revealed that the M7.3 Gisborne EQ shown two variations on –19 and –4 days; both being positive perturbations. However, five anomalies were detected for the M8.1 Kermadec EQ on –15, –11, –5, –3 and –2 days. With exception of the irregularities on –3 days, all others were positive anomalies. The observed anomalies were subjected to further scrutiny using the geomagnetic indices of Kernnifzer digit (kp) and disturbance storm time (Dst.) for geomagnetically induced perturbations while sunspot number and F 10.7 cm were used to monitor solar activities within this same period. The study suggested an increased in detected anomalies with earthquake magnitudes.

The Kutch Rift Basin (KRB) is of great attention for its possible hydrocarbon reserve. In this context, geomorphologic and structural geologic studies of the onland basin area are crucial. Application of geomorphic indicators viz., compactness coefficient (Cc), lemniscate coefficient (k), form ratio (Rf), basin shape index (Bs), basin asymmetry factor (AF), hypsometric integral (HI), elongation ratio (Re) and circularity ratio (Rc) have been utilized to calculate the Index of Active Tectonics (IAT) for a part of KRB. Watersheds 5 (the Bhuj area), 9, 10, 11, 17, 18 and 20 belong to class 1 as per the IAT. This indicates that these watersheds are very highly tectonically active at present. Calculated valley floor width height ratio (V_f) and mountain front sinuosity (Smf) quantify the active valley incision in the Quaternary that uplifted the Bhuj area. This uplift was accompanied by a high-degree of drainage rejuvenation due to neotectonics and formation of a canyon in the Khari river. Paleostress analyses revealed NNE and NW-oriented extensions around Bhuj that can correspond to NW and NNE-trending normal fault planes, respectively.

The main objective of this research is to investigate the distribution, concentration, and surface micro-textures of heavy minerals in beach sediments from four micro-environments: dune, backshore, berm, and foreshore. A total of forty-eight samples (twenty-four samples in each season) were collected along the Govindampalli (GP) to Durgarajupatnam (DP) Coast on the east coast of India, covering the pre-monsoon and post-monsoon periods from June 2016 to December 2016. The study revealed significant heterogeneity in beach sediment properties, heavy mineral distribution, and concentrations. Heavy mineral analysis was conducted on the coarse (+60), medium (+120), and fine (+230) fractions of the beach sediment. The analysis of weight percentage (wt%) demonstrated that a higher proportion of heavy minerals was associated with the fine fraction (+230) compared to the coarse and medium fractions at all stations. Opaque minerals, garnets, zircons, and monazites were found in promising quantities along the coast. The total concentrations of heavy minerals were higher during the pre-monsoon season compared to the post-monsoon season. The surface micro-textures of heavy mineral grains from various stations in the study area were primarily influenced by mechanical and chemical processes occurring on the grain surfaces. These micro-textures indicated significant mechanical influences at the estuary point and moderate to high wave energy in the beach deposits.

Several different geochemical signatures, i.e., mid-oceanic ridge (MOR) and supra subduction zone (SSZ), are frequently reported from ophiolite belts. Such bi-modal geochemical signatures are generally interpreted in terms of formation in two contrasting tectonic settings: divergent and convergent settings with associated petrogenetic processes. Whilst MOR-like and SSZ-like geochemical signatures are well understood in general terms, their combined occurrence in the peridotite component of ophiolite belts is not fully understood. Here, we describe the geochemically comparable Nagaland and Manipur ophiolites which are part of a same belt located in the Indo-Burma Range, India, and represent part of the eastern Tethys regime. In this study we explore the mechanisms which are responsible for this dual geochemical signature in a contiguous ophiolite belt formed during the closure of eastern Neo-Tethys. The existing and new whole-rock Nd isotopic signatures in the serpentinized peridotites from the Manipur ophiolite reveal that the dual geochemical signatures observed in the peridotites are due to patchy metasomatism of the mantle wedge. Thus, the entire mantle section peridotite in the Nagaland and Manipur ophiolites represents a relic of that Neo-Tethyan mantle wedge and this is also supported by the occurrence of high Cs/Th and low U/Th in the serpentinised peridotites. Further, variation of La_N/Yb_N, Sm_N/Hf_N, Ti/Eu, Zr/Hf, Ca/Al and Mg# observed in the secondary and primary clinopyroxenes of the studied peridotites can be explained by an influx of carbonate-rich fluid derived from subducted pelagic limestone. Elemental zoning and associated modeling of clinopyroxenes also clarify that the mantle metasomatism and different degrees of partial melting in the mantle wedge were responsible for the heterogeneity of the Neo-Tethyan mantle preserved in the Nagaland and Manipur ophiolites of the Indo-Burma Range.

The rapid growth of population in the sub-Sahara Africa, coupled with increasing industrial activities leads to greater demand for safe water for domestic use. Thus, aquifer system and vulnerability studies is of paramount important and a responsibilities of current researchers. This study intends to delineate aquifer systems and aquifer vulnerability using geoelectrical parameters around Ashaka cement industry. The Ashaka area is part of the Gongola Sub-basin of the Upper Benue Trough that include sandstone, shale, and limestone. The oldest stratigraphic units is Bima Formation which occurs on the floor and is overlain by Pindiga Formation. To delineate the aquifer systems and evaluate the vulnerability of aquifers around the research location, 35 Vertical Electrical soundings were undertaken. The Vertical Electrical Soundings measurements results suggests a maximum of five geo electrical layers which indicates that the aquiferours layer lies between fourth to fifth layers. The transmissivity values ranges from moderate (110.137 m2/day) to high (893.57 m2/day) potentials and the hydraulic conductivity ranges between 4.551 m/day and 29.789 m/day with an average of 17.650 m/day. Correlation of borehole lithology with the interpreted lithologies from the VES revealed that the aquifer systems are unconfined to semi-confined, consisting of sandstone and weathered limestone of various thicknesses. Longitudinal conductance was computed to evaluate the aquifer vulnerability which shows values ranging from between 0.20701 and 1.43308 with an average of 0.75298, and thus indicates that the area is free from surface contamination having moderate to good aquifer protective capacity.