LOOP SOURCE TRANSIENT ELECTROMAGNETICS IN AN URBAN NOISE ENVIRONMENT: A CASE STUDY IN SANTIAGO DE CHILE

Geophysics ◽  
2021 ◽  
pp. 1-49
Author(s):  
B. Blanco-Arrué ◽  
P. Yogeshwar ◽  
B. Tezkan ◽  
D. Díaz
Keyword(s):  
Urban Environment ◽  
Low Noise ◽  
Alluvial Fan ◽  
Quality Data ◽  
Borehole Data ◽  
Urban Noise ◽  
The North ◽  
Investigation Area ◽  
Santiago De Chile ◽  
Transient Electromagnetic

We present a transient electromagnetic (TEM) study in the noisy urban environment of the megacity Santiago de Chile. Our investigation characterizes the electrical conductivity structure of the Santiago basin down to 300 m depth, providing key information about the sedimentary infill, hydrogeological aspects, and geomorphological units. Fifty-two TEM-soundings were recorded over roughly 900 km2. We identified different transient characteristics and noise patterns, both spatially correlated to the investigation area. This step allowed classification of the soundings into three groups: highly distorted data, transients severely affected by cultural electromagnetic noise sources, and good quality data with low noise levels. Conventional 1D inversion techniques were then employed to derive resistivity depth models. The models were interpreted using sedimentary units and alluvial fan information, static groundwater level observations, and verified using borehole data. Based on 1D models, different minimum sedimentary thicknesses are observed, ranging between 50 m and 300 m depth. The average derived sedimentary thickness is ∼210 m. In addition, seven soundings indicated the basement. These are mostly located towards the periphery of the Santiago basin. We found a high conductive zone towards the north and a low conductive area towards the south of the basin. The southern area is characterized by the absence of conductive layers at a depth between 100 m and 150 m depth. This is likely related to the presence of a thick gravel layer and the absence of shallow clay layers acting as aquitards. The resistivity distribution and the sedimentary thickness obtained for this noisy and urban environment are a key input for groundwater research as water supply becomes more limited, specifically in central Chile. The overall consistency of the derived subsurface models highlights the suitability of the TEM method for investigating urban noise environments.

The Oxford Handbook of Sports Economics

2012 ◽  
Keyword(s):  
Economic Analysis ◽  
College Athletics ◽  
Team Sport ◽  
Antitrust Policy ◽  
Point Of View ◽  
Quality Data ◽  
Sports Economics ◽  
Managerial Behavior ◽  
The North ◽  
Individual Productivity

This book is the second volume of the two-volume The Oxford Handbook of the Economics of Sports which includes articles by nearly all of the important authors in the quickly growing field of sports economics. The two volumes consider in depth the ways that economics and sports interact with each other. To start with, economic analysis has helped with the understanding of many of the different institutions in sports. Secondly, quality data about individual productivity, salaries, career histories, teamwork, and managerial behavior has been useful in helping economists study topics as varied as the economics of discrimination, salary dispersion, and antitrust policy. The volumes are also rich from the point of view of the sports fan. Every major team sport is covered, and many interesting comparisons can be made especially between the North American League organization and the European-style promotion and relegation leagues. Golf, NASCAR, college athletics, women's sports, the Olympics, and even bowling are represented in these pages.

Lake and inland dunes as interconnected Systems: The story of Lake Tresssee and an adjacent dune field (Schleswig-Holstein, North Germany)

The Holocene ◽  
2020 ◽  
pp. 095968362098168
Author(s):  
Christian Stolz ◽  
Magdalena Suchora ◽  
Irena A Pidek ◽  
Alexander Fülling
Keyword(s):  
Water Level ◽  
Bronze Age ◽  
Environmental Changes ◽  
High Water ◽  
Alluvial Fan ◽  
Water Levels ◽  
Lake Area ◽  
Dune Field ◽  
The North ◽  
Sand Drift

The specific aim of the study was to investigate how four adjacent geomorphological systems – a lake, a dune field, a small alluvial fan and a slope system – responded to the same impacts. Lake Tresssee is a shallow lake in the North of Germany (Schleswig-Holstein). During the Holocene, the lake’s water surface declined drastically, predominately as a consequence of human impact. The adjacent inland dune field shows several traces of former sand drift events. Using 30 new radiocarbon ages and the results of 16 OSL samples, this study aims to create a new timeline tracing the interaction between lake and dunes, as well, as how both the lake and the dunes reacted to environmental changes. The water level of the lake is presumed to have peaked during the period before the Younger Dryas (YD; start at 10.73 ka BC). After the Boreal period (OSL age 8050 ± 690 BC) the level must have undergone fluctuations triggered by climatic events and the first human influences. The last demonstrable high water level was during the Late Bronze Age (1003–844 cal. BC). The first to the 9th century AD saw slightly shrinking water levels, and more significant ones thereafter. In the 19th century, the lake area was artificially reduced to a minimum by the human population. In the dunes, a total of seven different phases of sand drift were demonstrated for the last 13,000 years. It is one of the most precisely dated inland-dune chronologies of Central Europe. The small alluvial fan took shape mainly between the 13th and 17th centuries AD. After 1700 cal. BC (Middle Bronze Age), and again during the sixth and seventh centuries AD, we find enhanced slope activity with the formation of Holocene colluvia.

scholarly journals Wind Speed Retrieval from Simulated RADARSAT Constellation Mission Compact Polarimetry SAR Data for Marine Application

2019 ◽  
Vol 11 (14) ◽  
pp. 1682 ◽  
Author(s):  
Torsten Geldsetzer ◽  
Shahid K. Khurshid ◽  
Kerri Warner ◽  
Filipe Botelho ◽  
Dean Flett
Keyword(s):  
Wind Speed ◽  
Low Noise ◽  
Quality Data ◽  
Band Model ◽  
Data Set ◽  
Wind Retrieval ◽  
Wind Speeds ◽  
Geophysical Model ◽  
The Right ◽  
Quality Threshold

RADARSAT Constellation Mission (RCM) compact polarimetry (CP) data were simulated using 504 RADARSAT-2 quad-pol SAR images. These images were used to samples CP data in three RCM modes to build a data set with co-located ocean wind vector observations from in situ buoys on the West and East coasts of Canada. Wind speeds up to 18 m/s were included. CP and linear polarization parameters were related to the C-band model (CMOD) geophysical model functions CMOD-IFR2 and CMOD5n. These were evaluated for their wind retrieval potential in each RCM mode. The CP parameter Conformity was investigated to establish a data-quality threshold (>0.2), to ensure high-quality data for model validation. An accuracy analysis shows that the first Stokes vector (SV0) and the right-transmit vertical-receive backscatter (RV) parameters were as good as the VV backscatter with CMOD inversion. SV0 produced wind speed retrieval accuracies between 2.13 m/s and 2.22 m/s, depending on the RCM mode. The RCM Medium Resolution 50 m mode produced the best results. The Low Resolution 100 m and Low Noise modes provided similar results. The efficacy of SV0 and RV imparts confidence in the continuity of robust wind speed retrieval with RCM CP data. Three image-based case studies illustrate the potential for the application of CP parameters and RCM modes in operational wind retrieval systems. The results of this study provide guidance to direct research objectives once RCM is launched. The results also provide guidance for operational RCM data implementation in Canada’s National SAR winds system, which provides near-real-time wind speed estimates to operational marine forecasters and meteorologists within Environment and Climate Change Canada.

scholarly journals Hydrogeological characterisation of a glacially affected barrier island – the North Frisian Island of Föhr

2012 ◽  
Vol 9 (4) ◽  
pp. 5085-5119 ◽  
Author(s):  
T. Burschil ◽  
W. Scheer ◽  
R. Kirsch ◽  
H. Wiederhold
Keyword(s):  
North Sea ◽  
Underground Structure ◽  
Empirical Relation ◽  
Geophysical Methods ◽  
Strong Impact ◽  
Hydrogeological Model ◽  
Borehole Data ◽  
The North ◽  
The North Sea ◽  
D Model

Abstract. We present the application of geophysical investigations to characterise and improve the geological/hydrogeological model through the estimation of petrophysical parameters for groundwater modelling. Seismic reflection and airborne electromagnetic surveys in combination with borehole information enhance the 3-D geological model and allow a petrophysical interpretation of the subsurface. The North Sea Island of Föhr has a very complex underground structure what was already known from boreholes. The local waterworks use a freshwater body embedded in saline groundwater. Several glaciations disordered the Youngest Tertiary and Quaternary sediments by glaciotectonic thrust-faulting as well as incision and refill of glacial valleys. Both underground structures have a strong impact on the distribution of freshwater bearing aquifers. An initial hydrogeological model of Föhr was built from borehole data alone and was restricted to the southern part of the island where in the sandy areas of the Geest a large freshwater body was formed. We improved the geological/hydrogeological model by adding data from different geophysical methods, e.g. airborne electromagnetics (EM) for mapping the resistivity of the entire island, seismic reflections for detailed cross sections in the groundwater catchment area, and geophysical borehole logging for calibration of these measurements. An integrated evaluation of the results from the different geophysical methods yields reliable data. To determinate petrophysical parameter about 18 borehole logs, more than 75 m deep, and nearby airborne EM inversion models were analyzed concerning resistivity. We establish an empirical relation between measured resistivity and hydraulic conductivity for the specific area – the North Sea island of Föhr. Five boreholes concerning seismic interval velocities discriminate sand and till. The interpretation of these data was the basis for building the geological/hydrogeological 3-D model. We fitted the relevant model layers to all geophysical and geological data and created a consistent 3-D model. This model is the fundament for groundwater simulations considering forecasted changes in precipitation and sea level rise due to climate change.

The shape and infill of the Basadingen overdeepened glacial valley from P-wave seismic reflections

2021 ◽  
Author(s):  
Anna-Catharina Brandt ◽  
David C. Tanner ◽  
Hermann Buness ◽  
Thomas Burschil ◽  
Gerald Gabriel
Keyword(s):  
P Wave ◽  
Borehole Data ◽  
North East ◽  
The North ◽  
Glacier Valley ◽  
Sedimentary System ◽  
Climatic History ◽  
The Alps ◽  
Seismic Reflections ◽  
Seismic Images

<p><span>Overdeepened valleys in the Alps allow to probe the glacial sedimentation record, which in turn can illuminate the climatic history. In particular, seismic reflections can be used to extend punctual borehole data (for instance a number of boreholes are to be drilled into Alpine glacial overdeepened valleys as part of the DOVE ICDP project) in the second dimension or even survey a region before drilling begins. Thus, we use detailed, 2-D seismic P-wave profiles to reveal the shape and infill of an overdeepened Rhine glacier valley in the area of Basadingen, near to the German/Swiss border. We acquired two profiles nearly perpendicular to the valley strike, approximately 500 m apart. The first profile was 1246 m long, and consisted of a single spread of 624 geophones. The second profile was 1120 m long and was acquired using 200 3-component geophones using a roll-along method. For both profiles we used a vibro-source with a 12 s linear sweep of 20-240 Hz at every second geophone (two metre spacing), which produced a high fold.</span></p><p><span>Both seismic images reveal that the overdeepened basin at this location is asymmetrical and circa 260 m deep, although the deepest part (220</span><span> </span><span>m wide) covers only a small portion of the broader main valley. The infill is characterised by at least three unconformities and distinct onlap and erosive boundaries between the sedimentary units. We interpret the infill to represent a highly dynamic sedimentary system. The lower part, within the deepest part of the basin is filled with chaotic sediments and slumping. Above a major unconformity, the upper part contains strongly-dipping reflectors that probably represent a prograding point-bar in a glacio-fluviatile environment that migrated toward the north-east. Beneath the deepest part of the basin we see evidence for faults in the Tertiary Molasse basement, which correlate with known faults at the surface. The faults most likely caused the valley to be sited at this location and they were probably also the cause of the ‘valley in valley’ shape.</span></p><p><span>A new DOVE research borehole will be drilled in the centre of the valley in 2021. This will bring more light on the sedimentary history and OSL-dating of the material will bracket the timing of the infill. </span></p>

scholarly journals Late Holocene temperature variability in Tasmania inferred from borehole temperature data

2017 ◽  
Vol 13 (6) ◽  
pp. 559-572 ◽  
Author(s):  
Asadusjjaman Suman ◽  
Fiona Dyer ◽  
Duanne White
Keyword(s):  
East Coast ◽  
Past Century ◽  
Borehole Data ◽  
Depth Profiles ◽  
The Past ◽  
North East ◽  
The North ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. Thirty-six borehole temperature–depth profiles were analysed to reconstruct the ground surface temperature history (GSTH) of eastern Tasmania for the past 5 centuries. We used the singular value decomposition method to invert borehole temperatures to produce temperature histories. The quality of borehole data was classified as high or low based on model misfit. The quality of the borehole data was not dependent on topography or land use. Analysis reveals that three to five high-quality borehole temperature–depth profiles were adequate to reconstruct robust paleotemperature records from any area. Average GSTH reconstructed from Tasmanian boreholes shows temperature increases about 1.2 ± 0.2 °C during the past 5 centuries. Reconstructed temperatures were consistent with meteorological records and other proxy records from Tasmania during their period of overlap. Temperature changes were greatest around the north-east coast and decreased towards the centre of Tasmania. The extension of the East Australian Current (EAC) further south and its strengthening around the north-east coast of Tasmania over the past century was considered a prime driver of warmer temperatures observed in north-east Tasmania.

Early history of the Midcontinent Rift inferred from geochemistry and sedimentology of the Mesoproterozoic Osler Group, northwestern Ontario

2007 ◽  
Vol 44 (3) ◽  
pp. 389-412 ◽  
Author(s):  
Pete Hollings ◽  
Philip Fralick ◽  
Brian Cousens
Keyword(s):  
Alluvial Fan ◽  
Midcontinent Rift ◽  
Fluvial Systems ◽  
The North ◽  
Northwestern Ontario ◽  
History Of ◽  
Group A ◽  
South Axis ◽  
Island Basalt ◽  
East West

The Mesoproterozoic 1108–1105 Ma Osler Group, a 3 km thick succession of basaltic flows and sedimentary units on the north shore of Lake Superior, is among the oldest expressions of the Midcontinent Rift. Basal sediments of the Simpson Island Formation (new name) deposited by braided fluvial systems record westward transport of debris eroded from local Archean and Proterozoic rock units. Strata deposited by this fluvial system are intercalated with, and overlain by, ocean-island basalt (OIB)-like basalts, which become increasingly contaminated up section (εNd(1100Ma) = +0.3 to –5.3). The light rare-earth element (LREE) enriched (La/Smn = 1.5–3.9) and heavy REE (HREE) fractionated (Gd/Ybn = 1.5–3.7) subaerial flows are divisible into two units that correlate with other sections of the Osler Group to the east, but simple correlations with more distant sequences are difficult. The volcanic rock dominated portion of the succession is overlain by a thin (25 m thick) conglomerate–sandstone assemblage representing southeast progradation of an alluvial fan in a semi-arid climatic setting. Clast lithologies and geochemistry indicate no extra-rift detritus was delivered from the hinterland of the fan. Various lines of evidence in both volcanic and sedimentary rocks support a scenario where early, pre-1108 Ma, subsidence along a north–south axis from the western arm of the rift to the Nipigon Embayment was replaced by subsidence along the east–west rift axis between 1108 and 1105 Ma.

Assessment of near-surface mapping capabilities by airborne transient electromagnetic data — An extensive comparison to conventional borehole data

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. B187-B199 ◽  
Author(s):  
Cyril Schamper ◽  
Flemming Jørgensen ◽  
Esben Auken ◽  
Flemming Effersø
Keyword(s):  
Raw Materials ◽  
Sedimentary Environment ◽  
Poor Quality ◽  
Aquifer Vulnerability ◽  
Data Types ◽  
Borehole Data ◽  
Surface Mapping ◽  
Near Surface ◽  
Transient Electromagnetic

A newly developed helicopter transient electromagnetic (TEM) system has the ability to measure very early times within just a few μs after the turn off of the primary current. For such a system, careful calibration and accurate modeling of the electromagnetic (EM) response is critical to get true resistivities of the very shallow geologic layers. We discovered that this leads to resolution of the same level or in some cases even better than what can be obtained from airborne frequency EM systems. This allowed a range of important applications where high and accurate resolution is mandatory, e.g., geotechnical applications such as urban planning, railroad and road investigations, landslides or distribution of raw materials, and assessing aquifer vulnerability. We evaluated the results of a pilot survey covering the Norsminde catchment south of Aarhus, Denmark, where we found that near-surface layers (top 30 m) can be mapped with an accuracy of a few meters in a complicated glacial sedimentary environment. The mapping of the geologic layers was assessed by a detailed analysis in which we developed a general methodology for crosschecking the EM and borehole data. This methodology is general and can easily be adapted to other data types and surveys. After rating the quality of the boreholes based on a list of predefined criteria, we concluded that the EM data matched with about three-quarters of the boreholes located within less than 15 m from the closest EM soundings. The remaining quarter of the boreholes fell into two groups in which half of the boreholes were of very poor quality or had inaccurate coordinates. Only eight of all the boreholes could not be reproduced by the data, and we attributed this to be caused by very strong lateral or vertical geologic variations not resolvable by the TEM technique.

Results of geoelectrical soundings for mapping of a marine clay along the Tangkak-Pagoh highway Johor, Malaysia

1989 ◽  
Vol 20 (2) ◽  
pp. 117
Author(s):  
A.G. Rafek ◽  
A.R. Samsudin
Keyword(s):  
Apparent Resistivity ◽  
Fine Sand ◽  
Convex Curve ◽  
Marine Clay ◽  
Borehole Data ◽  
Individual Layer ◽  
The North ◽  
Geoelectrical Resistivity ◽  
Good Agreement ◽  
Clay Horizon

Geoelectrical resistivity soundings conducted along the north-south expressway in the Tangkak-Pagoh area during its construction enabled the mapping of a marine clay which was present in alluvium. The apparent resistivity curves of the marine clay area, were characterised by low apparent resistivity values falling to almost zero, and a characteristic shape which was different from areas of weathered metasediments and weathered granite adjacent to this area. Apparent resistivities for both metasediments and granite were intermediate to high, with a distinct upward convex curve for metasediments and a flat upward convex curve for granite. Quantitative interpretation was able to distinguish between an upper and a lower clay horizon, which have differentconsistency and fine sand content. The thickness of the upper clay horizon, which varies between 8.0 m to 9.0 m according to borehole data showed good agreement with that obtained by resistivity soundings. The base of the lower clay horizon remained undetected by the resistivity soundings because of its very low specific resistivity. Using the thickness of weathered layers as observed along the road cuttings as a guide, good agreement between field data and calculated values was obtained in determining the specific resistivities and individual layer thicknesses for the granite and metasediment weathering profiles.

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