Thickness Of Sediment Layer Research Articles

Study of Crustal Structure Beneath Station Banjarnegara Indonesia (BJI) Based on Receiver Function Analysis

We applied receiver functions (RFs) analysis to estimated the crustal structures beneath Station Banjarnegara, Indonesia (BJI). We selected teleseismic earthquakes with epicentral distance 30°-90° and magnitude greater than 6 (M > 6) that recorded from 3 component broadband seismograph at the station. We determined crustal thickness, S-wave velocity profiles and ratio of ν p/νs using nonlinear Neighborhood Algorithm (NA). We migrated RFs phase to depth by AK-135 global velocity models to identify the depth of the geological structure. From the Ps conversion phase and inhomogeneity of the arrival time, we detected the near surface has a strong anisotropy. We identified delay P phase near surface that associated with thick sedimentary layer in this area at about 2.5 km. Crustal thicknesses, ‘Moho depth’, beneath the station was estimated at depth 28-32 km. The high RFs amplitude phase that might be associated with the presence of Indo-Australian Slab was identified at a depth 140-160 km according to previous studies.

Seismic interferometry ambient noise tomography—a study in the north-central part of Iran

Seismic interferometry is one of the noteworthy new subsurface imaging methods that have been used in recent years in many tomographic studies. In this study, the interstation estimated Green functions extracted from the Rayleigh and Love wave ambient noise cross-correlations are used to obtain the Love and Rayleigh wave group velocity maps in different periods across the study area in order to determine the velocity anomalies and their corresponding geological structures within the crust. In the ambient noise method, the quality of the cross-correlations increases when longer time series of data are used, so we used 22 months of continuous data from the 17 broadband seismic stations as the primary database. After performing the initial corrections of the ambient noise data and obtaining the 3-month cross-correlation time series, the longer time series were obtained by stacking the 3-month time series with acceptable quality. In the next step, by using the time-frequency analysis and the estimated Green functions, the Love and Rayleigh wave dispersion curves were determined. Then, using the 2D tomography method, the Love and Rayleigh wave group velocity maps for the periods 10–25 s were produced. In the short periods, a low-velocity zone is observed in the Love and Rayleigh wave group velocity maps from the south Caspian basin toward central Iran, which is likely due to the effect of the thick alluvial deposits and the intermountain sediments in Alborz. At the longer periods, the Rayleigh and Love wave group velocity maps show a low-velocity zone in central Alborz, while in the eastern and western parts of Alborz, they show higher velocities, which is consistent with the prior studies. The dense path coverage permits to produce images that have substantially higher lateral resolution than is currently available from global and regional group velocity studies. Tomographic maps at high frequencies are well correlated with the upper crust structure and especially with sediment layer thickness.

Subsurface Identification of Campus I Universitas PGRI Yogyakarta using The Microtremor Wave Method

Thick layers of sediment can cause Prag damage to buildings in the event of an earthquake. The subsurface identification in the Campus I area of Universitas PGRI Yogyakarta needs to be done because of the increase of new multi-story buildings in the PGRI Campus area. The identification analysis uses HVSR (Horizontal to Vertical Spectral Ratio) so that the thickness of the sedimentary layer could show in the study area. The magnitude of the dominant frequency value was measured by the microtremor method somewhere illustrates the type of soil in the study area. Based on the results of data processing, it can show that the Campus I area of PGRI Yogyakarta University is composed of thick sedimentary layers with thicknesses ranging from 26.7 m - 59.3 m. Based on the distribution map, the most adhesive sediment layer is under the area of the Rectorate building and the Faculty of Business building. These results show the similarity to the Special Region of Yogyakarta, which is an area arranged in a basin with fill material in the form of volcanic deposits.

Andaman–Nicobar–Sumatra Margin Revisited: Analysis of the Lithospheric Structure and Deformation Based on Gravity Modeling and Distribution of Seismicity

The Andaman–Nicobar–Sumatra subduction margin, with a well-developed Benioff zone down to ~ 200 km depth, extends over 1300 km along strike and has a lateral extent of ~ 200 km. Two-dimensional (2D) profiles based on generalized inversion of free-air gravity anomaly data across different segments of the Andaman–Nicobar sector of the margin were analyzed by reconstructing the geometry of the converging India–Eurasia lithospheric plates. Detailed 2D structures of the Ninetyeast Ridge (NER), fore-arc basin, volcanic arc, back-arc basin, spreading ridge, Sewell Rise, Mergui Ridge and Mergui Basin, and depths of Moho and the lithosphere–asthenosphere boundary were delineated. The volcanic arc is located at a distance of ~ 150–200 km from the trench and is marked by a zone of positive gravity anomaly separated from the trench by the fore-arc basin with a zone of gravity low. The topographic and gravity anomaly patterns show complex geometrical patterns over the volcanic arc due to the presence of a number of regional faults striking parallel to the trench axis developing a series of pull-apart (transtensional) basins as well as the interaction of the spreading ridges on the overriding plate. A narrow zone of negative gravity anomaly (~ − 185 to − 110 mGal) observed in the gravity model of the margin is interpreted to be associated with fore-arc shear fault above a zone of fractured oceanic crust with a thick sedimentary layer, located above a zone of sharp bending of the eastward converging Indian lithosphere in the fore-arc basin. A high concentration of seismicity and a trench-parallel band of moderate moment energy release along this fault might have been caused by concentrated deformation within the zone of flexing of the descending plate. A wide fore-arc (> 200 km) and the enhanced deformation of the subducting Indian oceanic plate in central sectors possibly resulted from increased interaction between the NER and the Andaman trench and extension in the Andaman back-arc. Appearance of a second moderate energy band and shifting of seismicity toward the trench axis following the 2004 MW 9.2 mega-event are apparently caused by the migration of the stress field from deeper to shallower part of the Indian lithosphere. A similar type of seismicity migration toward shallower part of the descending plate has been recorded along other subduction margins around the globe.

Sediment and Crustal Structure Beneath East Kalimantan and East Java, Indonesia From Receiver Function

We investigate the sediment and Earth’s crustal structure beneath the East Kalimantan and East Java by modelling the stacked receiver function from six seismic broadband stations belong to the Meteorology, Climatology and Geophysics Agency of Indonesia (BMKG). The calculation of receiver functions from 60 teleseismic earthquake events using iterative time-domain deconvolution method. Inversion result shows a significant variation in the sediment layer thickness from 1 km to 4 km beneath East Java. It is correlated with the South East Java basinal area (station KRK) and the North East Java Basin (station GRJI and BWJI). The sediment layer of about 5 to 10 km beneath East Kalimantan is associated with the Kutai Basin (station SGKI, SMKI, and BKB). Average Sediment layer shear velocity (Vs) beneath all station is observed to be less than 2.31 km/s. Crustal thickness beneath East Java varies between 20 to 40 km and 34 to 50 km beneath East Kalimantan, with average crustal shear wave velocity, Vs 4.60 km/s.

Relation between H/V Spectrum Ratio of Microtremor and Thickness of Sedimentary Layer with Different Landform Evolution: A Study for Applying Microtremor to Hazard Maps

Relation between H/V Spectrum Ratio of Microtremor and Thickness of Sedimentary Layer with Different Landform Evolution: A Study for Applying Microtremor to Hazard Maps

Sediment thickness mapping and soil classification using ellipticity inversion of Rayleigh wave in the eastern part of Mataram City, Indonesia

A soil’s dynamic characteristics greatly influence earthquake potential damage inland. Subsurface investigations to determine the dynamic characteristics of the soil can minimize the risk of such damage. The sediment layer thickness is one of the parameters to assess the local geological character in response to an earthquake. Another parameter is Vs30 value, which is used to classify soil types as an indicator of soil response, which generally dominates ground motion amplification. In this study, the two parameters are analyzed to determine the potential for local damage in the event of an earthquake in the eastern area of Mataram City using the rayleigh wave inversion from microtremor data. The research area covers 3 districts, including Selaparang, Cakranegara, and Sandubaya Districts. The results showed that the value of the sediment thickness in the entire study area ranged from 12.78 m to 57.20 m. The value of Vs30 varies between 286 m/s to 866 m/s with the classification of rigid soils, very dense soils, and soft rocks and rocks. These results indicate that the study area in general experiences a large potential for damage if an earthquake occurs. This research is expected to be a reference for the spatial plan of Mataram City.

Большепанюшево-1 — новое поселение позднебронзового века в Алейской степи (подъемные сборы керамики 2020 года)

The article publishes materials of the settlement, opened in the vicinity of the village of Bolshepanyushevo in 2020. The archaeological monument is located on the floodplain of the river. Alei, overlapping with a thick layer of river sediments. The most representative collection of finds from collections of fragments of vessels, which were divided into several groups: ceramics of the Irmen and Sargarin-Alekseevsk culture (including the hybrid Irmen-Sargarin), as well as ceramics of the Early Iron Age and uncertain cultural affiliation. The bulk of the material is dated to the final period of the Bronze Age (end of the 2nd millennium BC). Currently, it is an immune organism to the Alei River.

Distribution of Present Heat Flow in the Phu Khanh Basin, Offshore Vietnam

This study aims to determine the distribution of present heat flow in the Phu Khanh basin from shallow water to deep water throughout the basin. The results from 42 present heat flow data points extracted from the global heat flow database by Goutorbe et al. (2011) indicated that there is an uneven distribution of the present heat flow in the research area. Heat flow accumulation in uplift structures in the north-west direction (78 - 86 mW/m2) of the Phu Khanh basin is usually higher than in trenches or deep depressions in the south-east direction of the basin (58 - 72 mW/m2). This is due to the sediment layer up to more than 10,000m thick in the deep water of the Phu Khanh basin. As a result, heat flow values in deep water are significantly lower than in shallow water of the Phu Khanh basin. The thick sediment layer acts as an insulator that prevents heat flow from escaping to the surface. The mean values of present heat flow calculated from wells TH - 1X and CMT - 1X are 85.60 mW/m2 and 83.20 mW/m2 respectively. These values are relatively consistent with the predicted results from Kriging 42 data points extracted from the global heat flow data set in the study of Goutorbe et al. (2011). The high present heat flow values can be explained by the fact that the Phu Khanh basin is still experiencing thermal subsidence because of its relatively young age (approximately 35 million years). This basin has not yet regained its thermal equilibrium value after the Early Oligocene - Miocene extension stage, so the present heat flow value is still high in this basin.

Peculiarities of Using 2D Electrical Resistivity Tomography in Caves

The efficiency of archaeological studies inside caves could be greatly enhanced by geophysical methods because of their potential for examining deposit structure and features. Application of those methods in caves entails a number of problems caused by limited space for measurements and the complexity of the surrounding medium s structure as compared to above-ground measurements. In 2017, Selungur Cave in the Fergana Valley, Kyrgyzstan, was examined using electrical resistivity tomography. Because of the above concerns, in the course of the work the question of the reliability of the results arose. To clarify the issue, a numerical experiment was performed to assess the effect of the three-dimensional cave geometry on the results of a two-dimensional inversion. It was found that variations of cave geometry parameters result in unexpected false anomalies, and considerable errors in bedrock location and resistivity can occur. In the case of downward diverging cave walls, an accurate resistivity section can be obtained by using the inversion based on a two-dimensional model. Therefore, electrical resistivity tomography in caves with similar geometry can yield reliable results concerning the shape of bedrock surface, the thickness of sedimentary layers, and size and position of inclusions such as fallen fragments of roof therein.

Sedimentary structure of the Sichuan Basin derived from seismic ambient noise tomography

SUMMARY Determining a detailed 3-D velocity model with high resolution for the sedimentary layer in the Sichuan Basin is potentially beneficial both to the industrial oil/gas exploration and earthquake hazards’ mitigation. In this study, we apply the ambient noise tomography method to construct a 3-D S-wave velocity model. This model focuses on the sedimentary layer of the Sichuan Basin, with a 0.3° × 0.3° grid precision. Dispersion curves of both group and phase velocities of Rayleigh wave at 4 to 40 s periods are utilized, which are extracted from 87 broad-band stations in the Sichuan Basin and the surrounding areas. The 3-D model reveals a thick sedimentary layer of the Sichuan Basin with S-wave velocity ranging from ∼2.0 to 3.4 km s−1. The sediment thickness in the margins of the Sichuan Basin is generally greater than the typical values of 6–10 km in the central areas due to surrounding orogenic activities, with a maximum depth of ∼13 km in the northwestern margin. Moreover, a prominent low S-wave velocity anomaly in the margins may be caused by the sediment accumulations from large-scale landslides and pronounced denudation of the surrounding orogenic belts. Major geologic units in the sedimentary layer are delineated in this study. The S-wave velocity values within each geologic unit and their bottom interfaces are obtained. Based on our model, we calculate synthetic ground motions for the 2013 Lushan earthquake and obtain the distribution of the peak ground acceleration from the earthquake epicentre to the western Sichuan Basin. The result clearly illustrates the basin amplification effect on the seismic waves.

Numerical Modelling to Evaluate Sedimentation Effects on Heat Flow and Subsidence during Continental Rifting

Sedimentation impacts thermal and subsidence evolution in continental rifting. Estimating the blanketing effect of sediments is crucial to reconstructing the heat flow during rifting. The sedimentary load affects the basin subsidence rate. Numerical investigation of these effects requires active and complex simulations of the thermal structure, lithospheric stretching, and sedimentation. In this paper, we introduce a numerical model to quantify these effects, which was developed using the COMSOL Multiphysics® simulation software. Our numerical setting for the analytical and numerical solutions of thermal structure and subsidence is based on previous continental rifting studies. In our model, we accumulate a column of 5 m thick sediment layers with varied stretching factors and sedimentation rates, spanning the syn-rift to early post-rift phases over a period of 12 myr. Our results provide intuitive models to understand these sedimentation effects. The models show that an increase in sedimentation thickness significantly decreases surface heat flow, leading to lower geothermal temperature, and amplifies the subsidence magnitude. The findings also demonstrate that increases in the stretching factor and sedimentation rate enhance the blanketing effect and subsidence rate. Based on these results, we discuss key outcomes for geological applications and the possible limitations of our approach.

Applying Automatic Mapping Processing By GMT to Bathymetric and Geophysical Data: Cascadia Subduction Zone, Pacific Ocean

AbstractThe Cascadia Trench is stretching along the convergent plate boundaries of Pacific Plate, North America Plate and Juan De Fuca Plate. It is an important geomorphological structural feature in the north-east Pacific Ocean. The aim of the paper is to analyse the geomorphology of the Cascadia Trench west of Vancouver Island (Canada and USA) using the GMT cartographic scripting toolset. The unique geomorphological feature of the Cascadia Trench is that the thick sediment layer completely obscures the subduction zone and abyssal hills. This results in the asymmetric profile in the cross-section of the trench. Bathymetric data were extracted from the GEBCO 2019 dataset (15 arc-second grid), sediment thickness by the GlobSed dataset. Due to the dominance of high sedimentary rate and complexity of the tectonic processes and geologic settings, Cascadia Trench develops very specific asymmetric geomorphic shape comparing to the typical V-form. The results of the geomorphic modelling show that eastern side of the trench has a gentle curvature (slope: 35.12°), partially stepped, due to the tectonic movements and faults. The opposite, oceanward side is almost completely leveled. The trench is narrow with maximal depth at the selected segment -3489 m and for the whole dataset -6201 m. The most repetitive depth is in a range -2500 to -2400 m (267 samples) and -2500 to -2600 m (261 samples). The bottom is mostly flat due to the high sedimentation rates indicating the accumulative leveling processes. Marine free-air gravity anomalies along the Cascadia Subduction Zone are characterized by weakly positive values (20 mGal) increasing rapidly in the zone of the continental slope (>200 mGal), which is associated with a decrease in thickness of the Earth’s crust.

The influence of sediment blanketing on subduction-zone seismicity

Subduction of oceanic lithosphere is now occurring beneath the Aegean and central Caspian Seas, and beneath the Indo-Burman Ranges in NE India, generating zones of earthquakes that reach depths of more than 150 km. Their existence is surprising. In general, where the temperature of the mantle part of the oceanic lithosphere can be estimated, earthquakes are confined to material whose temperature is below 600C∘. In these three regions the oceanic lithosphere is overlain by sediments with low thermal conductivity whose thickness is probably 10–25 km. The temperature of the oceanic crust and upper half of the lithosphere should be considerably increased by such a thick sedimentary cover, yet there is no obvious difference between these subduction zones and those where there is little sediment on the subducting plate. Detailed thermal modelling of the temperature shows that, for the first 40 Ma, the deposition of even a thick sedimentary layer has little effect on the thickness of the region of lithosphere whose temperature is below 600C∘, principally because little heat is conducted across the Moho. The modest effect of sediment blanketing over a period as long as 40 Ma was quite unexpected. Over the next 200 Ma the lithospheric temperature increases, until the Moho temperature reaches ∼600C∘. This behaviour has important implications for oil and gas generation in the sediments, and for the existence of large earthquakes at depths of 150 km or more beneath the Hindu Kush, Pamirs and Romania.

The structure of the sedimentary cover and crystalline crust in the Sichuan Basin and its tectonic implications

SUMMARY The Sichuan Basin, located to the east of the Tibetan Plateau, experienced successive marine and continental depositions since the Sinian. Structures of the sedimentary cover and crystalline crust, for example, thickness and Vp/Vs ratio, are of great significance to study the basin's properties and evolution, which have not been investigated simultaneously. In this paper, we extended the traditional single-layer H–k stacking method of receiver functions to a multilayer H–k stacking approach and applied it to invert for thickness and Vp/Vs ratio of the sedimentary cover and crystalline crust beneath 14 seismic stations in the Sichuan Basin. The observed thickness and Vp/Vs ratio of the sedimentary cover range from 4.2 to 7.5 km and from 1.86 to 2.55, respectively, suggesting unconsolidated sediments containing water or other fluids. Two-layer sedimentary cover was observed beneath eight stations, probably corresponding to the sediment in the Phanerozoic and Precambrian. The observed thickness and Vp/Vs ratio of the crystalline crust range from 33.4 to 41.8 km and from 1.61 to 1.78, respectively, suggesting typical cratonic crust in the Sichuan Basin. Theoretical analyses of H–k stacking were further performed for different types of sedimentary basins, and the results suggest that the multilayer H–k stacking is more effective to study basin's structure with a thick sedimentary layer and thin subsediment crust.

Recycling lake sediment to agriculture: Effects on plant growth, nutrient availability, and leaching

Sediment removal from eutrophicated shallow lakes may not only be an effective method for lake restoration but also provides the potential for recycling nutrients from sediments to crop production. However, finding a suitable strategy for sustainably reusing the sediment remains a challenge. Therefore, current study focused on the best practices in applying the sediment from a shallow eutrophicated lake to the soil in terms of grass yield, nutrient uptake, and nutrient leaching. During a nine-month lysimeter experiment, 100-cm high columns were filled with six combinations of soil, sediment, and biochar, with or without meat bone meal organic fertilizer. Aboveground biomass, root mass distribution in soil, nutrient concentration, phosphorus (P) uptake of perennial ryegrass (Lolium perenne L.) along with easily soluble nutrients in the growing medium, and leached mineral nitrogen (N) and P levels were measured. Plant growth conditions were improved by sediment additions, as the yield and P uptake of ryegrass nearly doubled in treatments containing sediment compared to the control soil. While the sediment was richer in macro and micronutrients (e.g. P and N) compared to the soil, the leached N and P levels from both treatments were almost equivalent (N < 830 mg m−2 and P < 3 mg m−2). In addition, applying a 2-cm layer of biochar between the sediment and soil reduced P and N leaching by 50%. According to the results, applying a 75-cm thick layer of sediments on agricultural sandy loam soils surrounding the lake seems a promising practice for improving plant yield and soil nutrient status without increasing of P and N leaching from soil.

Microtremor HVSR analysis of heterogeneous shallow sedimentary structures at Pohang, South Korea

AbstractWe apply the single-station microtremor horizontal-to-vertical spectral ratio (HVSR) method to image the geometry of Pohang Basin, South Korea, which experienced the greatest earthquake damage in Korea during a series of anthropogenic earthquakes between November 2017 and February 2018. We collected and analysed the ambient seismic noise at 124 temporary stations. The resonance frequencies, which vary significantly across the area (0.35–19.86 Hz), were inverted to constrain the depth of the major impedance contrast, which is interpreted to be the sediment–bedrock interface beneath each station. The sedimentary layer thickness is generally thin in the north and thickens to the southern and central parts of the basin, where the depth to bedrock is up to 340 m. We compare the HVSR results with six borehole observations in the area, whose depth to bedrock ranges from 189 to 359 m. The sediment thicknesses obtained via the direct borehole measurements and HVSR method are comparable with each other. The resultant three-dimensional shape of the sedimentary basin provides crucial information for the microzonation of the Pohang area for seismic risk mitigation. It also provides a realistic initial velocity model for three-dimensional tomographic inversions to elucidate the detailed subsurface structure of the region.

Integration and Interpretation of Aeromagnetic, 3D Seismic and Well Logs Data in Hydrocarbon Exploration in Niger Delta Basin

As the challenges associated with hydrocarbon exploration rises with upsurge in energy demand, the need to minimize risk associated with hydrocarbon exploration if supply is to keep up with demand.&#x0D; In this work, high resolution aeromagnetic, 3D seismic and well-logs data were adopted and integrated to aid in exploration and characterization of reservoirs in ''XYZ'' field in offshore Niger Delta. Fast Fourier Transform Filter using Oasis Montaj software was applied to the Total Magnetic Intensity grid in horizon and fault interpretation also used to produce subsurface structural maps for sedimentary layer thickness estimation. Direct hydrocarbon indicators (bright spots) on the seismic section was shown using seismic signal. Petrel software and wireline log signatures were used to identify hydrocarbon-bearing sands and determine petrophysical parameters such as porosity, hydrocarbon saturation and net thickness.&#x0D; The structural maps generated showed: Three major (synthetic) faults dips south and one minor (antithetic) fault dips north in the field; three identified prospective sands (A, B, C) were delineated. Possible presence of oil accumulation was indicated by the combined Neutron-Density log response. The range of values of effective porosity, hydrocarbon saturation and net thickness were 18-22%, 34-58% and 19.1-28.1 m, respectively. &#x0D; This study established that integration of magnetic, 3D seismic and well-log data are desirable innovative techniques to better understand and analyze subsurface for hydrocarbon potential and exploration.

Benthic Communities on the Mohn’s Treasure Mound: Implications for Management of Seabed Mining in the Arctic Mid-Ocean Ridge

The Mohn’s Treasure, described as an inactive sulphide mound, was discovered at 2600 m depth on the Arctic Mid-Ocean Ridge in 2002. In 2015, we conducted the first biological survey of Mohn’s Treasure using ROV photo transects and sampling. This site is covered by a thick layer of fine sediments, where hard substratum is only visible as rocky outcrops on ridges. The observed benthic community was typical of Arctic bathyal systems. A total of 46 species (identified as morphospecies) were recorded, with densities varying from 12.2 to 31.6 ind.m-2. The two most abundant phyla were Porifera and Echinodermata. The sediment is dominated by fields of the stalked crinoid Bathycrinus carpenterii, while areas of hard substratum were characterised by high abundances of several sponge species and associated fauna. Interest in commercial exploration and exploitation of minerals from massive sulphide deposits is rising globally, and the Arctic Mid-Ocean Ridge is being targeted for mineral exploration within Norwegian waters. Gathering baseline ecological data from these poorly known sites is thus urgent and essential if robust resource management measures are to be developed and implemented. The results of this ecological survey are discussed in relation to the designation of deep-sea Vulnerable Marine Ecosystems and their implication in management and conservation of areas targeted by the emerging deep-sea mining industry.

Characteristics of particles in groundwater and their prospecting significance for the Shijiangshan Pb-Zn-Ag deposit, Inner Mongolia, China

The Shijiangshan concealed deposit in Inner Mongolia, China is located in a semi-arid region with a thick sediment layer on the surface. Samples of particles from deep and shallow groundwater in the deposit were analyzed by transmission electron microscopy (TEM). Corresponding fault gouge and oxide ore powder were collected and analyzed at the same time. These particles had sizes ranging from 5 to 400 nm and contained metallogenic elements, such as Pb, Zn, As, Cu, and Ag. Groundwater particles can reflect the properties of the deep concealed ores because the metal-bearing particles in the groundwater are similar in composition to the deep ores. In this study, particles with a carbon film covering their surface were discovered in groundwater. The carbon coating helped particles to remain in their primitive state, and thus, retain the more direct metallogenic information. Shallow groundwater particles can be used to predict the composition of deep concealed ore deposits. In thick overburdened areas, where local geochemical information on abnormal elemental levels is not obvious and geophysical prospecting methods may have multiple solutions, the accuracy of prospecting can be improved by using particles in groundwater that provide concealed orebody information, making such particles very important for prospecting.