Subsurface Profiles Research Articles

Investigation of Soft Layer in between Hard Layer for Sedimentary Rock Formation by using Electrical Resistivity Analysis

This study aims to predict the occurrences of soft layers in between hard layers in sedimentary rock formation based on electrical resistivity analysis. ABEM Terrameter LS Box with 40 electrodes with 2.5 meters spacing in pole-dipole method was used. Standard Penetration Test (SPT) was conducted to obtain the value for the number of blows (N-value). RES2DINV was used to analyse a two-dimensional illustration of the soil layers in the pseudo section diagram. Results show that the groundwater table is located 2.0 meters below the ground surface. Based on the resistivity analysis, the subsurface profile is consists of topsoil, soft silty clay (N0-N4, 6 > Ω > 20 ohm), medium-stiff silty clay (N5-N6, 20>Ω>360 ohm), medium dense coarse sands (N13-N16, 361>Ω>550 ohm), stiff silty clay (N10-N18, 550>Ω>720 ohm), hard silty clay and gravel (N50, 720>Ω>1100 ohm), and moderate weathered and slightly fractured shale stone (N50, Ω>1100 ohm). Although the correlation between resistivity values and SPT N-values shows a very good relationship with R2 ranges from 0.83 to 0.89, electrical resistivity analysis is not suitable to determine the soft layer in between hard layer in a sedimentary rock formation due to the presence of high ground water table.

A Case Study of Building Information Modelling (BIM) for Subsurface in Malaysia

Unforeseen ground condition often leads to the occurrence of cost overrun and project delay in Malaysia’s architecture, engineering, and construction (AEC) industries. The implementation of Building Information Modelling (BIM) for subsurface was attempted to reduce uncertainties associated with the underground conditions. A pilot case study was performed to understand the 3D subsurface modelling workflow in BIM environment. A construction site in Ara Damansara, Petaling Jaya, Malaysia was selected for the pilot case study. The site investigation data of the study area were interpreted and input into AutoCAD Civil 3D with geotechnical module to perform the 3D subsurface modelling at various detail levels. The workflow of the modelling process in case study was documented for future references. Through this pilot study, it was found that the adoption of BIM for subsurface modelling could produce soil profiles for different engineering purposes such as visualisation of subsurface conditions during project initiation stage, preliminary conceptual design, and detailed analysis and design of geotechnical structures, particularly foundation. The BIM implementation for geotechnical data improves the management of site investigation data, enhances the visualisation of subsurface profile, and improves the efficiency in communicating the subsurface conditions to all stakeholders in a project team.

Microanchored borehole fiber optics allows strain profiling of the shallow subsurface

Vertical deformation profiles of subterranean geological formations are conventionally measured by borehole extensometry. Distributed strain sensing (DSS) paired with fiber-optic cables installed in the ground opens up possibilities for acquiring high-resolution static and quasistatic strain profiles of deforming strata, but it is currently limited by reduced data quality due to complicated patterns of interaction between the buried cables and their surroundings, especially in upper soil layers under low confining pressures. Extending recent DSS studies, we present an improved approach using microanchored fiber-optic cables—designed to optimize ground-to-cable coupling at the near surface—for strain determination along entire lengths of vertical boreholes. We proposed a novel criterion for soil–cable coupling evaluation based on the geotechnical bearing capacity theory. We applied this enhanced methodology to monitor groundwater-related vertical motions in both laboratory and field experiments. Corroborating extensometer recordings, acquired simultaneously, validated fiber optically determined displacements, suggesting microanchored DSS as an improved means for detecting and monitoring shallow subsurface strain profiles.

Plio–Quaternary Structural Evolution of the Outer Sector of the Marche Apennines South of the Conero Promontory, Italy

Some new results and preliminary remarks about the Plio–Quaternary structural and evolutionary characteristics of the outer Marche Apennines south in the Conero promontory are presented in this study. The present analysis is based on several subsurface seismic reflection profiles and well data, kindly provided by ENI S.p.A. and available on the VIDEPI list, together with surface geologic–stratigraphic knowledge of Plio–Quaternary evolution from the literature. Examples of negative vs. positive reactivation of inherited structures in fold and thrust belts are highlighted. Here, we present an example from the external domain of the Marche Apennines, which displays interesting reactivation examples from the subsurface geology explored. The study area shows significant evolutionary differences with respect to the northern sector of the Marche region previously investigated by the same research group. The areal distribution of the main structures changes north and south of the ENE–WSW oriented discontinuity close to the Conero promontory. Based on the old tripartite classification of the Pliocene, the results of this work suggest a strong differential subsidence with extension occurring during the Early Pliocene and principal compressive deformation starting from the Middle Pliocene and decreasing or ceasing during the Quaternary. The main structure in this area is the NNW–SSE Coastal Structure, which is composed of E-vergent shallow thrusts and high-angle deep-seated normal faults underneath. An important right-lateral strike–slip component along this feature is also suggested, which is compatible with the principal NNE–SSW shortening direction. As mentioned, the area is largely characterized by tectonic inversion. Starting from Middle Pliocene, most of the Early Pliocene normal faults became E-vergent thrusts.

Impact of updated radiative transfer scheme in snow and ice in RACMO2.3p3 on the surface mass and energy budget of the Greenland ice sheet

Abstract. Radiative transfer in snow and ice is often not modeled explicitly in regional climate models. In this study, we evaluate a new englacial radiative transfer scheme and assess the surface mass and energy budget for the Greenland ice sheet in the latest version of the regional climate model RACMO2, version 2.3p3. We also evaluate the modeled (sub)surface temperature and melt, as radiation penetration now enables internal heating. The results are compared to the previous model version and are evaluated against stake measurements and automatic weather station data of the K-transect and PROMICE projects. In addition, subsurface snow temperature profiles are compared at the K-transect, Summit, and southeast Greenland. The surface mass balance is in good agreement with observations, with a mean bias of −31 mm w.e. yr−1 (−2.67 %), and only changes considerably with respect to the previous RACMO2 version around the ice margins and near the percolation zone. Melt and refreezing, on the other hand, are changed more substantially in various regions due to the changed albedo representation, subsurface energy absorption, and meltwater percolation. Internal heating leads to higher snow temperatures in summer, in agreement with observations, and introduces a shallow layer of subsurface melt. Hence, this study shows the consequences and necessity of radiative transfer in snow and ice for regional climate modeling of the Greenland ice sheet.

Chlorophyll‐Based Model to Estimate Underwater Photosynthetically Available Radiation for Modeling, In‐Situ, and Remote‐Sensing Applications

AbstractAccurate estimation of the underwater light field associated with photosynthetically available radiation (PAR) is critical to compute phytoplankton growth rate and net primary production (NPP), and to assess photo‐physiological response of phytoplankton, such as changes in cellular pigmentation. However, methods to estimate PAR used in many previous studies lack in accuracy, likely resulting in significant bias in light‐dependent products such as NPP derived from remote sensing, model simulations, or autonomous platforms. Here we propose and validate a new model for more accurate estimation of the subsurface PAR profile which uses chlorophyll concentration as its input. Validation is performed using 1,744 BGC‐Argo profiles of chlorophyll fluorescence that are calibrated with surface satellite‐derived chlorophyll concentration over their lifetime. The independent verification with the float's PAR sensors confirms the accuracy of satellite chlorophyll estimate worldwide and in the Southern Ocean in particular.

The Application of the Seismic Method in Site Properties Assessment

Similar to the broad use of the seismic methods to identify the layers of soil and the distance strike the bedrock, initial site properties require geophysical techniques to assess them. This research was carried out to investigate the properties of the subsurface composition of a backyard area in Universiti Teknologi Malaysia, Johor campus, guided by the principles of this process. The Evaluation of seismic data analyzed using ZondST2D computer software by calculating the first arriving time of the propagated seismic wave throughout soil layers to obtain a subsurface prototype. The examined subsurface profile was composed of four layers displaying the weathering grade level of scales between 600 m/s to 4000 m/s depending on Malaysia’s rock mass categorization. Weathering concentrations were observed to be declining at higher depth, with increased density of the material and reduced seismic velocity dampness. It was found that only for shallow subsurface compositions which is far from interference and noise, can the analysis of seismic refraction be conducted progressively.

Evaluation of bacterial strains isolated from Late Quaternary alluvial sediments spanning ~ 28 m in depth for heavy metal tolerance and Cr(VI) removal ability.

Microbial heavy metal tolerance in subsurface samples is indicative of long-term ecotoxicological impact of metals and could also reflect metal contamination of groundwater. However, the heavy metal tolerance characteristics of microbes isolated from subsurface river sediment profiles are still obscure. In the present study, determination of heavy metal tolerance of bacterial strains isolated from two Late Quaternary sediment profiles (~ 28 m and ~25 m deep) located at the Mahi river basin, Western India, was carried out. Identification of bacterial isolates by the 16S rRNA gene sequencing revealed that bacterial isolates affiliated with phyla Actinobacteria, Proteobacteria, Firmicutes, and Bacteroidetes were dominant in both sediment profiles. Heavy metal tolerance of bacterial strains as determined by plate diffusion assay revealed order of metal tolerance as follows: Hg(II)<Cd(II)< Ni(II)<Cu(II)=Cr(VI). Chromate removal study in liquid medium suggested that bacterial strains procured from subsurface possessed the ability to remove Cr(VI) with varied magnitude. A packed bed column experiment indicated that bacterial strains obtained from the subsurface have the potential for Cr(VI) removal from different particle size consistencies of the sediments.

2D Seismic Interpretation and Characterization of the Upper Qishn Clastics in Sharyoof Oil Field, Masila Basin, Yemen

The Sharyoof oil field is located off shore in Block 53 in the northeastern part of the Syaun-Masilah Basin, in the province of Hadramaut, 550 km from the city of Sana’a, the capital of Yemen. Fifteen 2D seismic lines along with six wells data are used to construct subsurface geological profile, and to identify major structural features in the study area. Synthetic seismograms have been constructed using sonic and density log for all available wells to tie horizons to seismic data and to generate time and depth subsurface maps. This research has been carried out using integrated 2D seismic and petrophysical studies in Sharyoof oilfield. Using the analysis and interpretation of seismic data, the main structural faults were identified, maps of isochrones, structural maps of depth and thickness were constructed, which subsequently will allow us to correctly determine the deep geological structures in Upper Qishn Clastics member and evaluate the oil horizons of the Sharyoof oilfield.

Characterization of a Karst Site using Electrical Resistivity Tomography and Seismic Full Waveform Inversion

Karst geology is characterized by the presence of sinkholes and voids, which may pose significant risk to existing infrastructure. Sinkhole formation is often observed near active quarries, where dewatering operations can alter regional groundwater flow patterns leading to subsidence and increased void formation. In these areas, identifying locations which may be susceptible to sinkhole formation requires an ability to map dissolution features within the rock. Traditional geotechnical explorations alone are not well-suited to this effort as they only provide subsurface information at discrete points and therefore may miss voids within the rock. Geophysical methods offer a means to produce continuous profiles of the rock surface and possible locations for voids but interpreting the results of these tests in karstic geology can be challenging. This study uses 2D electrical resistivity and seismic surveys at a site with previous sinkhole activity along an interstate in central Alabama. The site is adjacent to a limestone quarry. Resistivity data is collected using 2D dipole-dipole and strong-gradient arrays. The seismic data is processed using a full waveform inversion (FWI) technique. Subsurface profiles interpreted from the geophysical surveys are then compared to borehole data from previous site investigations. Results from the geophysical surveys are found to be consistent with borehole data regarding variation of bedrock depth and identification of possible sinkhole features. Potential limitations and sources of error pertaining to each survey type are considered.

Historical and geological assessment of shoreline changes at an urbanized embayed sandy system in Garopaba, Southern Brazil

Embayed sandy beaches are dynamically complex systems that vary in time and space. The rising demand for the uses and resources associated with these environments may neglect the shoreline mobile nature and lead to imbalances in the beach sediment budget. Climate change imminence has been increasing coastal risks, with a considerable contribution of local and regional causes. This study aims to assess the influence of short to long-term processes on short spatial scales and to identify which processes control the behavior of neighboring beaches. Thereby, a case study was analyzed at Barra Beach (BB) and Ferrugem Beach (FB), a small embayment separated by an intermittent inlet located in Garopaba, Santa Catarina state, southern Brazil. The shoreline dynamic behavior of both beaches was assessed through a multi-temporal approach (historical and geological), investigating the main factors influencing their morphodynamic behavior. The historical variation was investigated through shoreline change rates along 16 years (2003–2019), calculated with Digital Shoreline Analysis System (DSAS) v5.0 – ESRI® ArcGis extension, considering past shoreline positions extracted from satellite imagery. Geological evolution was analyzed in terms of seismostratigraphy through subsurface profiles acquired with a Ground Penetrating Radar (GPR) system. Interdecadal shoreline change rates and GPR records indicated that BB has a transgressive shoreline in a retrogradational barrier, while FB is slightly progradational, with a stable shoreline from the historical scale perspective. The interannual analysis showed that the inlet surroundings are influenced by seasonality, and beach rotation was not detected between the beaches nor within themselves. The distinct morphodynamic behavior between BB and FB is a function of their shoreline geometry, architectural elements, wave energy distribution, and sediment sources/sinks, resulting in variant alongshore sediment budgets. Overall, this paper highlights the importance of local shoreline assessment, and it could enhance efficient present-day coastal management, supporting future sustainable urban planning.

Pulse-modulation eddy current imaging and evaluation of subsurface corrosion via the improved small sub-domain filtering method

Subsurface corrosion occurring in the conductive structures prone to long-term exposure to harsh and corrosive environments essentially leads to the reduction in the critical area of load carrying members, adversely aggravating the mechanical strength and structural integrity of in-service structures. This has prompted the high demand for non-invasive detection and evaluation of subsurface corrosion using non-destructive evaluation techniques. Pulse-modulation Eddy Current testing (PMEC) has been found to be superior to pulsed eddy current testing in terms of higher sensitivity to subsurface corrosion and accuracy in corrosion imaging. In this paper, a funnel-shaped PMEC probe is utilised for subsurface corrosion imaging along with the inspection sensitivity further enhanced. A novel signal feature of PMEC, namely the averaged peak value is proposed in a bid to improve the signal-to-noise ratio of the PMEC testing, based on which corrosion images are produced. In order to enhance accuracies in image-based profile identification and opening-area assessment of subsurface corrosion, an improve Small Sub-domain Filtering Method (SSFM) together with Canny algorithm is proposed and exploited in the image processing for corrosion-profile recognition. It has been indicated from the experimental results that the subsurface corrosion profile can be well identified using the proposed signal and image processing methods which could keep robust in the testing environment subject to extraneous noises. For the experimental specimens, the accuracy of the subsequent evaluation particularly regarding the corrosion-opening area reaches 94.5% at minimum.

When AI Meets DIGGS

Drilling and sampling to obtain borehole logs, together with various in-situ testing, are usually performed to determine subsurface soil and rock profiles and their associated engineering propertie...

Sectional model of a prairie buffer strip in a laboratory flume for water quality research

AbstractVegetative buffers have shown promising results in reducing runoff volume, sediment, nutrients, and manure‐borne contaminants in runoff from agricultural fields. Although these vegetative buffer systems have been extensively tested in field and plot‐scale studies that utilize either natural or simulated rainfall, studies of such systems under highly controlled conditions in the laboratory have been limited. Here, we present the development of a new system for laboratory testing of a full‐scale, sectional, physical model of a new practice under the Continuous Conservation Reserve Program (CRP) Clean Lakes, Estuaries, and Rivers (CLEAR) Initiative, CP‐43 Prairie Strips. This work includes the extraction of prairie strip sections from the field and their integration into an existing laboratory flume facility with specific auxiliary features to facilitate overland flow experimentation. As a proof of concept run, a potassium chloride (KCl) tracer study was conducted to verify system functionality and inform future work. The tracer pulse was injected under saturated conditions and the response was monitored through surface water (upstream and downstream of the prairie strip model) and subsurface water (infiltrated) sampling with continuous flow rate monitoring at the sampling locations. The tracer test provided highly resolved breakthrough curves (BTCs) with 93.5% of the injected tracer mass recovered, and provided useful information on flow partitioning, velocities, and dispersion characteristics along the surface and through the subsurface profile of the model. This model prairie strip system is expected to be useful in optimizing the performance of prairie strips under highly controlled flow and contaminant source conditions.

SHALLOW REFLECTION METHOD FOR PAVEMENT THICKNESS MEASUREMENT

The seismic reflection technique utilizes the concept of the reflected wave when the media changes its stiffness. Previous studies utilized this technique for deep subsurface profiling in the oil field exploration. The objective of this study is to assess the seismic reflection technique for measuring the shallow profile of the pavement layer and thus able to identify the layer of asphalt thickness. Via applying the non-destructive seismic reflection technique, an early sign of abnormal pavement can be detected, and thus only minimum points for destructive tests can be suggested. The analysis of reflection waves in the time domain can calculate the thickness of the asphalt pavement layer directly on site. An attempt is made to model concrete slabs with different thicknesses. The result shows the sensors arrangement twice of the thickness able to give a lower error of 0.4 % and 15% of the thickness and p-wave velocity, respectively.

LANDSLIDE HAZARD IDENTIFICATION (LHI) BASED ON GEOELECTRICAL MAPPING ANALYSIS (GEM): CASE STUDY FROM LUYANG, KOTA KINABALU, SABAH, MALAYSIA

Landslides are amongst the most damaging natural hazards in Malaysia. The study of landslides has drawn nationwide attention mainly due to increasing awareness of the socio-economic impact of landslides, as well as the increasing pressure of urbanization. Landslide Hazard Identification (LHI) is part of the process used to evaluate if any particular situation, item, thing, etc. may have the potential to cause harm. The description of LHI should include the location, volume (or area), classification and velocity of the potential landslides and any resultant detached material, and the probability of their occurrence within a given period of time. In this paper, we present the results of the measurement for the subsurface resistivity within by using the pole-dipole electrode array and present the 2D view of each resistivity profile. The result presented successfully detect the dominant layer consists of interbedded sandstone and shale of the Crocker Formation with highly weathered. This both layers have high porosity and potential to contain high water content which can trigger landslide to occur. Besides that, there are several boulders zone (weathered to fresh rock) that can be found at the top of the subsurface profile at about 1.5m to 15m in depth. The bedrock layer was estimated to be found at 4m to 32.5m in depth from the original ground and one possible fault line that had been identified. This fault line believed plays a role in the occurrence of landslide in which rock materials have lower strength compared to surrounding rocks. High density of fault means lower stability. Therefore the faut line have been regarded as a critical factor in triggering landslide in the study area. The results of these study findings are expected to be used as uniform guidelines and principles are very useful and have integrity in providing coordination of standards or policies for each planning activities for new development in the future. As a result of the lack of concern for the developer of the concept of Sustainable Development Goals (SDG) or balancing and control of environmental health, the results of this study can also be used as a yardstick to party developers who intend to develop a high ground and hillside in deciding whether to continuing development planning or not.

Surface and subsurface characterisation of salt pans expressing polygonal patterns

Abstract. The data set described here contains information about the surface, subsurface, and environmental conditions of salt pans that express polygonal patterns in their surface salt crust (Lasser et al., 2020b; https://doi.org/10.5880/fidgeo.2020.037). Information stems from 5 field sites at Badwater Basin and 21 field sites at Owens Lake – both in central California. All data were recorded during two field campaigns from between November and December 2016 and in January 2018. Crust surfaces, including the mean diameter and fluctuations in the height of the polygonal patterns, were characterised by a terrestrial laser scanner (TLS). The data contain the resulting three-dimensional point clouds that describe these surfaces. The subsurface is characterised by grain size distributions of samples taken from depths between 5 and 100 cm below the salt crust and measured with a laser particle size analyser. Subsurface salinity profiles were recorded, and the groundwater density was also measured. Additionally, the salts present in the crust and pore water were analysed to determine their composition. To characterise the environmental conditions at Owens Lake, including the differences between nearby crust features, records were made of the temperature and relative humidity during 1 week in November 2016. The field sites are characterised by images showing the general context of each site, such as pictures of selected salt polygons, including any which were sampled, a typical core from each site at which core samples were taken, and close-ups of the salt crust morphology. Finally, two videos of salt crust growth over the course of spring 2018 and reconstructed from time lapse images are included.

SEISMIC REFRACTION METHOD IN THE DETERMINATION OF SITE CHARACTERISTICS

Preliminary site properties need geophysical methods to determine it, the same as the large use of the seismic refraction method to detect the layers of soil and the depth reaching the bedrock. This study was conducted to find out the subsurface profile characteristics of a backyard field in UTM, Skudai following the principles of this method. The analysis of seismic data processed using ZondST2D software by determining the first arrival time until we get a block model of 2D shape based on the primary propagation of seismic velocity wave’s in soil layers. It was found that the investigated subsurface profile consists of four layers showing the level of weathering grade ranges from 600–4000 m/s based on the classification of rock mass in Malaysia. It was found that weathering rates decreased at higher depth, with the increase of density for the material and dampness reduction of seismic velocity. It was concluded that the survey of seismic refraction in development can be used only for shallow subsurface profiles and far from noise and disturbance.

The focus thermal study around the spreading center of southwestern Okinawa trough

Voluminous hydrothermal systems are corresponding to the heat flow anomaly discovered from previous geophysical surveys in the Southern Okinawa Trough (SOT), which is an area with a high sedimentation rate supplied by the East China Sea shelf and the island of Taiwan. Our latest fifteen field measurements around the Geolin Mound (GLM) (24° 36.6 ‘N, 122° 53’E) are located at a sedimentary basin west of the Yonaguni Rift, which is nearby the southwestern tip of a NE-SW trending volcano trail in the SOT. The heat flow results illustrate a concentric decrease from 31,477 to 180 mW/m2 in a 1-km radius around the GLM, evidently proving the focus fluid migration along the major fluid conduit. The ultrahigh temperature observations revealed the existence of magmatic components in shallow sediments. Combining the subsurface profiles with the temperature fields around the GLM, a 0.16-km2 acoustic blanking area of the G1 fluid conduit was recognized from the chirp sonar image and numerous interpreted igneous reflections with fluids related features from seismic profiles. As a result, we proposed a conceptual model, which simultaneously illustrates the hydrothermal circulation pattern from the previous general surveys and the enormous thermal anomaly from current detailed measurements. The sill-to-sill feeding sedimentary basin of the GLM is capable of demonstrating the enormous thermal anomaly around the spreading center of the SOT and appropriately represents the potential hydrothermal discharge and recharge by heat flow distribution around the GLM.

Improving the ocean and atmosphere in a coupled ocean–atmosphere model by assimilating satellite sea‐surface temperature and subsurface profile data

AbstractAn ensemble‐based data assimilation framework for a coupled ocean–atmosphere model is applied to investigate the influence of assimilating different types of ocean observations on the ocean and atmosphere simulation. The data assimilation is performed with the parallel data assimilation framework (PDAF) for the climate model AWI‐CM. Observations of the ocean, namely satellite sea‐surface temperature (SST) and temperature and salinity profiles, are assimilated into the ocean component. The atmospheric state is only influenced by the model dynamics. Different assimilation scenarios were carried out with different combinations of observations to investigate to what extent the assimilation into the coupled model leads to a better estimation of the state of the ocean as well as the atmosphere. The influence of the data assimilation is assessed by comparing the ocean prediction with dependent and independent ocean observations. For the atmosphere, the assimilation result is compared with the ERA‐Interim atmospheric reanalysis data. The ocean temperature and salinity are improved by all the assimilation scenarios in the coupled system. The assimilation leads to a response of the atmosphere throughout the troposphere and impacts the global atmospheric circulation. Globally the temperature and wind speed are improved in the atmosphere on average.