SOME RECENT ADVANCES IN OFFSHORE REGIONAL RECONNAISSANCE GEOPHYSICAL SURVEY METHODS

1967 ◽  
Vol 7 (1) ◽  
pp. 40
Author(s):  
K. R. Vale
Keyword(s):  
Phase Measurement ◽  
Survey Methods ◽  
Geophysical Methods ◽  
Low Frequency ◽  
Mineral Resources ◽  
Simultaneous Recording ◽  
Navigation Systems ◽  
Local Networks ◽  
Set Up ◽  
Geophysical Survey Methods

Traditional geophysical methods in use offshore include the airborne magnetometer, underwater gravity meter, and seismic reflection with 24-channel recording and large explosive energy source. Navigation is by range-range and hyperbolic phase-comparison radio systems set up as local networks. Other methods now being used include towed magnetometer, surface gravity meter, and automatic continuous seismic profilers, and all three methods can be used for simultaneous recording from a single recording boat. Navigation systems not requiring local networks include satellite radio doppler, very low frequency phase measurement and sonar doppler devices. These may be used word-wide and 24 hours per day. A single recording boat may thus be virtually self-sufficient. The Bureau of Mineral Resources plans a survey for 1967 that will use a number of these geophysical methods and navigation aids.

scholarly journals The Use of Combined Geophysical Survey Methods for Groundwater Investigation in a Typical Basement Complex Terrain: Case Study of Erunmu, Ibadan, Southwest Nigeria

2019 ◽  
pp. 1-16
Author(s):  
Abudulawal, Lukuman
Keyword(s):  
Water Saturation ◽  
Survey Methods ◽  
Low Frequency ◽  
Groundwater Potential ◽  
Future Research ◽  
Basement Complex ◽  
Southwest Nigeria ◽  
Subsurface Layers ◽  
Basement Layer ◽  
Geophysical Survey Methods

A combined Survey involving the very low frequency electromagnetic (VLF – EM) and Electrical resistivity surveys were carried out in order to appraise the groundwater potential, and locate appropriate positions for sighting boreholes in Erunmu Community, Egbeda local government area, Oyo State, Nigeria. VLF data were obtained along five traverses as the first step in order to locate suitable vertical electrical sounding (VES) stations. Vertical Electrical Soundings using Schlumberger array were thereafter carried out at twenty 20) locations. The integrated interpretation of both data confirms the presence of aquifers, which includes, weathered zone and basement transition/fractures beneath the area, which prior to this investigation have a history of failed boreholes and wells. The resistivity curve types obtained includes H and A which revealed the presence of 3 to 4 subsurface layers consisting of topsoil, the clay, the sandy clay, fractured zone and the highly resistive bedrock. The resulting geo-electric section from the interpretation revealed the Reflection coefficient which ranges from 0.45 – 0.98. The dominated curve type in the area investigated is the H which is typical of basement complex while the A-type is about 20% of the total curves. Hydrogeological, the topsoil is not important because the degree of water saturation in this layer is very low and cannot be utilized for groundwater. The fractured basement layer (which is present in less than 15% of the study area is very relevant in groundwater prospecting; when it is thick enough the layer could support borehole drilling. Areas identified as geological interfaces in the VLF anomaly charts were also confirmed by the interpreted VES data as poor and intermediate zones for groundwater potential in the study area. The significance of this study is such that it will serve as a useful reference for future research efforts in the aspect of basement complex groundwater studies.

Integration of Multi-geophysical Approaches to Identify Potential Pathways of Heavy Metals Contamination - A Case Study in Zeida, Morocco

2020 ◽  
Vol 25 (3) ◽  
pp. 415-423
Author(s):  
Ahmed Lachhab ◽  
El Mehdi Benyassine ◽  
Mohamed Rouai ◽  
Abdelilah Dekayir ◽  
Jean C. Parisot ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Low Frequency ◽  
Electrical Current ◽  
P Wave ◽  
Low Resistivity ◽  
Refraction Tomography ◽  
Geophysical Surveys

The tailings of Zeida's abandoned mine are found near the city of Midelt, in the middle of the high Moulouya watershed between the Middle and the High Atlas of Morocco. The tailings occupy an area of about 100 ha and are stored either in large mining pit lakes with clay-marl substratum or directly on a heavily fractured granite bedrock. The high contents of lead and arsenic in these tailings have transformed them into sources of pollution that disperse by wind, runoff, and seepage to the aquifer through faults and fractures. In this work, the main goal is to identify the pathways of contaminated water with heavy metals and arsenic to the local aquifers, water ponds, and Moulouya River. For this reason, geophysical surveys including electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and very low-frequency electromagnetic (VLF-EM) methods were carried out over the tailings, and directly on the substratum outside the tailings. The result obtained from combining these methods has shown that pollutants were funneled through fractures, faults, and subsurface paleochannels and contaminated the hydrological system connecting groundwater, ponds, and the river. The ERT profiles have successfully shown the location of fractures, some of which extend throughout the upper formation to depths reaching the granite. The ERT was not successful in identifying fractures directly beneath the tailings due to their low resistivity which inhibits electrical current from propagating deeper. The seismic refraction surveys have provided valuable details on the local geology, and clearly identified the thickness of the tailings and explicitly marked the boundary between the Triassic formation and the granite. It also aided in the identification of paleochannels. The tailings materials were easily identified by both their low resistivity and low P-wave velocity values. Also, both resistivity and seismic velocity values rapidly increased beneath the tailings due to the compaction of the material and lack of moisture and have proven to be effective in identifying the upper limit of the granite. Faults were found to lie along the bottom of paleochannels, which suggest that the locations of these channels were caused by these same faults. The VLF-EM surveys have shown tilt angle anomalies over fractured areas which were also evinced by low resistivity area in ERT profiles. Finally, this study showed that the three geophysical methods were complementary and in good agreement in revealing the pathways of contamination from the tailings to the local aquifer, nearby ponds and Moulouya River.

Piloting the EHR4CR Feasibility Platform across Europe

2014 ◽  
Vol 53 (04) ◽  
pp. 264-268 ◽  
Author(s):  
R. Bache ◽  
M. McGilchrist ◽  
C. Daniel ◽  
M. Dugas ◽  
F. Fritz ◽  
...  
Keyword(s):  
Electronic Health Records ◽  
Clinical Research ◽  
Test Data ◽  
Data Access ◽  
Data Warehouses ◽  
University Hospitals ◽  
Local Networks ◽  
Health Records ◽  
Electronic Health ◽  
Set Up

SummaryBackground: Pharmaceutical clinical trials are primarily conducted across many countries, yet recruitment numbers are frequently not met in time. Electronic health records store large amounts of potentially useful data that could aid in this process. The EHR4CR project aims at re-using EHR data for clinical research purposes.Objective: To evaluate whether the protocol feasibility platform produced by the Electronic Health Records for Clinical Research (EHR4CR) project can be installed and set up in accordance with local technical and governance requirements to execute protocol feasibility queries uniformly across national borders.Methods: We installed specifically engineered software and warehouses at local sites. Approvals for data access and usage of the platform were acquired and terminology mapping of local site codes to central platform codes were performed. A test data set, or real EHR data where approvals were in place, were loaded into data warehouses. Test feasibility queries were created on a central component of the platform and sent to the local components at eleven university hospitals.Results: To use real, de-identified EHR data we obtained permissions and approvals from ‘data controllers‘ and ethics committees. Through the platform we were able to create feasibility queries, distribute them to eleven university hospitals and retrieve aggregated patient counts of both test data and de-identified EHR data.Conclusion: It is possible to install a uniform piece of software in different university hospitals in five European countries and configure it to the requirements of the local networks, while complying with local data protection regulations. We were also able set up ETL processes and data warehouses, to reuse EHR data for feasibility queries distributed over the EHR4CR platform.

scholarly journals FIELD MEASUREMENTS AND MODELLING OF NEARSHORE CURRENTS AT A HIGH-ENERGY GEOLOGICALLY-CONSTRAINED BEACH

2020 ◽  
pp. 18
Author(s):  
Arthur Mouragues ◽  
Philippe Bonneton ◽  
Bruno Castelle ◽  
Vincent Marieu
Keyword(s):  
Surf Zone ◽  
Low Frequency ◽  
Field Measurements ◽  
High Energy ◽  
Oblique Wave ◽  
Wave Forcing ◽  
Circulation Patterns ◽  
Wave Conditions ◽  
Nearshore Currents ◽  
Set Up

We present field measurements of nearshore currents at a high-energy mesotidal beach with the presence of a 500-m headland and a submerged reef. Small changes in wave forcing and tide elevation were found to largely impact circulation patterns. In particular, under 4-m oblique wave conditions, our measurements indicate the presence of an intense low-frequency fluctuating deflection rip flowing against the headland and extending well beyond the surf zone. An XBeach model is further set up to hindcast such flow patterns.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/EiqnjBIkWJE

scholarly journals Detection and Identification of Sediment Layer to Discover the Marine Mineral Resources Potential in Aruah Islands

2021 ◽  
Vol 9 (1) ◽  
pp. 70
Author(s):  
Pareng Rengi ◽  
Ulil Amri ◽  
Tomi Ramadona ◽  
Ediar Usman ◽  
Bustari Bustari
Keyword(s):  
Sediment Sample ◽  
Single Channel ◽  
Low Frequency ◽  
Mineral Resources ◽  
Coarse Sand ◽  
Sediment Layer ◽  
Sediment Thickness ◽  
Seismic Profiles ◽  
Detection And Identification ◽  
Sediment Layers

<p>Aruah Islands is located on an international shipping line adjacent to Malaysia. The important aspect in borderline management is the maritime resource potential, one of which is sea minerals. In order to dig the information about marine mineral resources in Aruah Islands, a high-resolution seismic reflection with low frequency was applied, which capable to detect the depth and identify the sedimentary layers clearly and accurately. The depth of water and sediment layers were detected using an echosounder, reason Navi sound type 210 with a tow fish 100 kHz and shallow seismic boomer with a single channel type and wave energy 200 Joules. Gravity core and grab sampler were used to collect the sediment sample. There were three stages on seismic interpretation: sequence analysis, facies analysis, and reflection character identification. Furthermore, sediments containing coarse sand-sized minerals were observed using a microscope. The measurement result of Aruah Islands water depth was ranging from 0-80 m, the deepest part is on the Northern of Batu Mandi island which was 80 m depth. Seismic profiles indicated that the upper layer of tertiary sedimentary as the youngest rocks. Based on sediment thickness, the thickest area was found on the Western (approx. 50 m) and the Northern (approx. 32 m). In line with the island’s Southern part condition, which was plain or shallow sea exposure, the Southeastern island sediment thickness ranged only about 10-18 m. Generally, based on the analyzed sediment sample, quartz was the main mineral found, which was 60-80% of the composition. Other minerals were zircon, tin, hematite, magnetite, limonite, biotite, and dolomite.</p>

Squeezing-enhanced fiber Mach-Zehnder interferometer for low-frequency phase measurement

2017 ◽  
Vol 110 (2) ◽  
pp. 021106 ◽  
Author(s):  
Fang Liu ◽  
Yaoyao Zhou ◽  
Juan Yu ◽  
Jiale Guo ◽  
Yang Wu ◽  
...  
Keyword(s):  
Phase Measurement ◽  
Low Frequency ◽  
Zehnder Interferometer ◽  
Frequency Phase ◽  
Mach Zehnder Interferometer

scholarly journals Formation, breaching and flood consequences of a landslide dam near Bujumbura, Burundi

2018 ◽  
Vol 18 (7) ◽  
pp. 1867-1890 ◽  
Author(s):  
Léonidas Nibigira ◽  
Hans-Balder Havenith ◽  
Pierre Archambeau ◽  
Benjamin Dewals
Keyword(s):  
Distinct Element ◽  
Mass Movement ◽  
Geophysical Methods ◽  
Landslide Dam ◽  
Propagation Time ◽  
Universal Distinct Element Code ◽  
Landslide Process ◽  
Distinct Element Code ◽  
Set Up ◽  
Flood Intensity

Abstract. This paper investigates the possible formation of a landslide dam on the Kanyosha River near Bujumbura, the capital of Burundi, as well as the interplay between the breaching of this landslide dam and the flooding along the river. We present an end-to-end analysis, ranging from the origin of the landslide up to the computation of flood waves induced by the dam breaching. The study includes three main steps. First, the mass movement site was investigated with various geophysical methods that allowed us to build a general 3-D model and detailed 2-D sections of the landslide. Second, this model was used for dynamic landslide process modelling with the Universal Distinct Element Code. The results showed that a 15 m high landslide dam may form on the river. Finally, a 2-D hydraulic model was set up to find out the consequences of the breaching of the landslide dam on flooding along the river, especially in an urban area located downstream. Based on 2-D maps of maximum water depth, flow velocity and wave propagation time, the results highlight that neglecting the influence of such landslide dams leads to substantial underestimation of flood intensity in the downstream area.

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