AIRBORNE MAGNETOMETER PROFILE FROM PORTLAND, OREGON TO ALBUQUERQUE, NEW MEXICO

Geophysics ◽  
1954 ◽  
Vol 19 (2) ◽  
pp. 270-280 ◽  
Author(s):  
W. B. Agocs ◽  
J. C. Rollins ◽  
E. Bangs
Keyword(s):  
Magnetic Field ◽  
New Mexico ◽  
Sea Level ◽  
Flight Path ◽  
Magnetic Data ◽  
Mean Sea Level ◽  
Total Magnetic Field ◽  
General Geology ◽  
Wing Tip

An airborne magnetometer profile of the variations of the earth’s anomalous total magnetic field was obtained using a wing‐tip magnetometer installation in a flight from Portland, Oregon to Albuquerque, New Mexico. The magnetic data were obtained by flying at barometric altitudes ranging from 7,000 to 10,000 feet above mean sea level. The variations in the total magnetic field are tied to the known geology along the flight path, and the possible interpretations of the magnetic data are reviewed in light of the known general geology.

A TOTAL FIELD MAGNETOMETER FOR MOBILE OPERATION

Geophysics ◽  
1948 ◽  
Vol 13 (2) ◽  
pp. 209-214 ◽  
Author(s):  
Eugene Frowe
Keyword(s):  
Magnetic Field ◽  
High Sensitivity ◽  
Ferromagnetic Material ◽  
Magnetic Data ◽  
Recording Device ◽  
Total Field ◽  
Total Magnetic Field ◽  
Inductive Type ◽  
Continuous Field ◽  
Better Than

A magnetometer which measures the earth’s total magnetic field is described. The detector or measuring element of the magnetometer contains three mutually perpendicular elements, two of which are utilized to orient the third, which in turn operates a recording device to record the total magnetic field. The detector elements are of the inductive type and do not require ferromagnetic material to give them the high sensitivity required in geophysical work. The presence of a magnetic field in the region of the detector causes alternating currents to be generated in the detector elements. These currents are amplified to actuate motors which control the orienting and neutralizing functions of the magnetometer. A tape recorder gives continuous field readings. The accuracy of the magnetic data taken is better than five gammas.

scholarly journals Interpretation of Near Surface Based on the Magnetic Data at Geothermal Area, Jaboi, Sabang

2019 ◽  
Vol 8 (3) ◽  
pp. 90-93
Author(s):  
Dinni Mahmudi ◽  
Muhammad Isa ◽  
Didik Sugiyanto
Keyword(s):  
Magnetic Field ◽  
Magnetic Anomalies ◽  
Magnetic Data ◽  
Geothermal Area ◽  
Reference Field ◽  
Subsurface Structure ◽  
International Geomagnetic Reference Field ◽  
Total Magnetic Field ◽  
International Geomagnetic Reference ◽  
Proton Precession Magnetometer

Telah dilakukan penelitian geofisika menggunakan metode magnetik untuk mendapatkan struktur bawah permukaan di daerah prospek panas bumi Jaboi, Sukajaya, Kota Sabang. Pengukuran medan magnetik total dilakukan pada 40 titik menggunakan Proton Precession Magnetometer (PPM). Daerah Jaboi memiliki sudut inkinasi -4.416 dan deklinasi -0.875 dengan nilai medan magnetik total berkisar antara 41550 hingga 42600 nT. Untuk mendapatkan nilai anomali magnetik dilakukan koreksi diurnal dan koreksi IGRF (International Geomagnetic Reference Field). Setelah koreksi dilakukan diperoleh nilai anomali magnetik daerah panas bumi Jaboi antara -200 nT sampai dengan -950 nT. Selanjutnya hasil anomali magnetik ini digunakan dalam memodelkan struktur bawah permukaan dengan panjang lintasan 1800 m dari Tenggara-Barat Laut. Berdasarkan interpretasi data anomali magnetik menunjukkan daerah penelitian didominasi oleh anomali rendah yang berarti daerah manifestasi panas bumi. Interpretasi anomali tinggi dan rendah menunjukkan adanya patahan yang diduga sebagai patahan Ceuneuhot. Dari hasil pemodelan 2D menggunakan software Mag2DC, menunjukkan bahwa terdapat 5 lapisan dengan kedalaman 0 - 1000 m. Lapisan-lapisan ini adalah soil ( = 0,00 x 10-6 SI), andesit terubah (  = 13,408 x 10-6 SI), breksi tufa terubah (  = 12,686 x 10-6 SI), andesit terubah (  = 13,423 x 10-6 SI) dan breksi andesit (  = 13,535 x 10-6 SI). Melalui pemodelan ini diyakini zona patahan adalah patahan Ceuneuhot. Geophysical reasearch by using magnetic method was done in order to obtain subsurface structure of geothermal prospect area Jaboi, Sukajaya, Sabang City. The measurement of total magnetic field was taken at 40 points using Proton Precession Magnetometer (PPM). Jaboi area has an inklination angle -4.416 and declination angle -0.875 which has total magnetic field range between 41550 to 42600 nT. Diurnal Correction and IGRF (International Geomagnetic Reference Field) correction was used to obtain magnetic anomalies. The values of magnetic anomalies in Jaboi Geothermal Area is -200 to -950 nT. The result of magnetic anomalies was used to modelled the subsurface structure with profile distance is about 1800 m from Southeast to Northwest. Based on the magnetic anomalies data, the reaserch area dominated by low anomalies that indicated geothermal manifestation area. High and low magnetic anomalies indicated a fault that estimated as Ceuneuhot fault. From the result of 2D modelling using software Mag2DC, showed that the research area consist of 5 subsurface structure from 0 – 1000 m depth. The layers are soil (  = 0.00 × 10-6 SI), altered andesite (  = 13.408 × 10-6 SI), altered breccia-tuff (  = 12.686 × 10-6 SI), altered andesite (  = 13.423 × 10-6 SI), and breccia-andesite (  = 13.535 × 10-6 SI). Also from the model was  obtained the Ceuneuhot fault zone.  Keywords: Magnetik, Anomali Magnetik, Struktur Bawah Permukaan, Panas Bumi

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

An Augmented Iteratively Re-weighted and Refined Least Squares Method for lp Minimization Problem in Inverse Modeling of Potential Field Magnetic Data

2020 ◽  
Vol 1 (3) ◽  
Author(s):  
Maysam Abedi
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Least Squares ◽  
Minimization Problem ◽  
Potential Field ◽  
Field Data ◽  
Least Squares Method ◽  
Porphyry Copper ◽  
Magnetic Data ◽  
Magnetic Field Data

The presented work examines application of an Augmented Iteratively Re-weighted and Refined Least Squares method (AIRRLS) to construct a 3D magnetic susceptibility property from potential field magnetic anomalies. This algorithm replaces an lp minimization problem by a sequence of weighted linear systems in which the retrieved magnetic susceptibility model is successively converged to an optimum solution, while the regularization parameter is the stopping iteration numbers. To avoid the natural tendency of causative magnetic sources to concentrate at shallow depth, a prior depth weighting function is incorporated in the original formulation of the objective function. The speed of lp minimization problem is increased by inserting a pre-conditioner conjugate gradient method (PCCG) to solve the central system of equation in cases of large scale magnetic field data. It is assumed that there is no remanent magnetization since this study focuses on inversion of a geological structure with low magnetic susceptibility property. The method is applied on a multi-source noise-corrupted synthetic magnetic field data to demonstrate its suitability for 3D inversion, and then is applied to a real data pertaining to a geologically plausible porphyry copper unit.  The real case study located in  Semnan province of  Iran  consists  of  an arc-shaped  porphyry  andesite  covered  by  sedimentary  units  which  may  have  potential  of  mineral  occurrences, especially  porphyry copper. It is demonstrated that such structure extends down at depth, and consequently exploratory drilling is highly recommended for acquiring more pieces of information about its potential for ore-bearing mineralization.

scholarly journals Deterministic approach for multiple-source tsunami hazard assessment for Sines, Portugal

2015 ◽  
Vol 15 (11) ◽  
pp. 2557-2568 ◽  
Author(s):  
M. Wronna ◽  
R. Omira ◽  
M. A. Baptista
Keyword(s):  
Sea Level ◽  
Wave Height ◽  
Hazard Assessment ◽  
Test Site ◽  
Tsunami Hazard ◽  
Deterministic Approach ◽  
Flow Depth ◽  
Mean Sea Level ◽  
Tsunami Hazard Assessment ◽  
The Impact

Abstract. In this paper, we present a deterministic approach to tsunami hazard assessment for the city and harbour of Sines, Portugal, one of the test sites of project ASTARTE (Assessment, STrategy And Risk Reduction for Tsunamis in Europe). Sines has one of the most important deep-water ports, which has oil-bearing, petrochemical, liquid-bulk, coal, and container terminals. The port and its industrial infrastructures face the ocean southwest towards the main seismogenic sources. This work considers two different seismic zones: the Southwest Iberian Margin and the Gloria Fault. Within these two regions, we selected a total of six scenarios to assess the tsunami impact at the test site. The tsunami simulations are computed using NSWING, a Non-linear Shallow Water model wIth Nested Grids. In this study, the static effect of tides is analysed for three different tidal stages: MLLW (mean lower low water), MSL (mean sea level), and MHHW (mean higher high water). For each scenario, the tsunami hazard is described by maximum values of wave height, flow depth, drawback, maximum inundation area and run-up. Synthetic waveforms are computed at virtual tide gauges at specific locations outside and inside the harbour. The final results describe the impact at the Sines test site considering the single scenarios at mean sea level, the aggregate scenario, and the influence of the tide on the aggregate scenario. The results confirm the composite source of Horseshoe and Marques de Pombal faults as the worst-case scenario, with wave heights of over 10 m, which reach the coast approximately 22 min after the rupture. It dominates the aggregate scenario by about 60 % of the impact area at the test site, considering maximum wave height and maximum flow depth. The HSMPF scenario inundates a total area of 3.5 km2.

scholarly journals Tropical cyclone simulations over Bangladesh at convection permitting 4.4 km & 1.5 km resolution

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hamish Steptoe ◽  
Nicholas Henry Savage ◽  
Saeed Sadri ◽  
Kate Salmon ◽  
Zubair Maalick ◽  
...  
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Sea Level ◽  
Tropical Cyclones ◽  
Weather Forecasting ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Medium Range ◽  
Gust Speed

AbstractHigh resolution simulations at 4.4 km and 1.5 km resolution have been performed for 12 historical tropical cyclones impacting Bangladesh. We use the European Centre for Medium-Range Weather Forecasting 5th generation Re-Analysis (ERA5) to provide a 9-member ensemble of initial and boundary conditions for the regional configuration of the Met Office Unified Model. The simulations are compared to the original ERA5 data and the International Best Track Archive for Climate Stewardship (IBTrACS) tropical cyclone database for wind speed, gust speed and mean sea-level pressure. The 4.4 km simulations show a typical increase in peak gust speed of 41 to 118 knots relative to ERA5, and a deepening of minimum mean sea-level pressure of up to −27 hPa, relative to ERA5 and IBTrACS data. The downscaled simulations compare more favourably with IBTrACS data than the ERA5 data suggesting tropical cyclone hazards in the ERA5 deterministic output may be underestimated. The dataset is freely available from 10.5281/zenodo.3600201.

scholarly journals Flooding Conditions at Aveiro Port (Portugal) within the Framework of Projected Climate Change

2021 ◽  
Vol 9 (6) ◽  
pp. 595
Author(s):  
Américo Soares Ribeiro ◽  
Carina Lurdes Lopes ◽  
Magda Catarina Sousa ◽  
Moncho Gomez-Gesteira ◽  
João Miguel Dias
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Climate Change Impacts ◽  
Storm Surges ◽  
Historical Period ◽  
Return Periods ◽  
Wave Regime ◽  
Mean Sea Level ◽  
Sea Levels ◽  
Far Future

Ports constitute a significant influence in the economic activity in coastal areas through operations and infrastructures to facilitate land and maritime transport of cargo. Ports are located in a multi-dimensional environment facing ocean and river hazards. Higher warming scenarios indicate Europe’s ports will be exposed to higher risk due to the increase in extreme sea levels (ESL), a combination of the mean sea level, tide, and storm surge. Located on the west Iberia Peninsula, the Aveiro Port is located in a coastal lagoon exposed to ocean and river flows, contributing to higher flood risk. This study aims to assess the flood extent for Aveiro Port for historical (1979–2005), near future (2026–2045), and far future (2081–2099) periods scenarios considering different return periods (10, 25, and 100-year) for the flood drivers, through numerical simulations of the ESL, wave regime, and riverine flows simultaneously. Spatial maps considering the flood extent and calculated area show that most of the port infrastructures' resilience to flooding is found under the historical period, with some marginal floods. Under climate change impacts, the port flood extent gradually increases for higher return periods, where most of the terminals are at high risk of being flooded for the far-future period, whose contribution is primarily due to mean sea-level rise and storm surges.

scholarly journals Approaching Sea-Level Rise (SLR) Change: Strengthening Local Responses to Sea-Level Rise and Coping with Climate Change in Northern Mozambique

2021 ◽  
Vol 9 (2) ◽  
pp. 205
Author(s):  
Serafino Afonso Rui Mucova ◽  
Ulisses Miranda Azeiteiro ◽  
Walter Leal Filho ◽  
Carina Lurdes Lopes ◽  
João Miguel Dias ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Sea Level Rise ◽  
Sea Level ◽  
North Coast ◽  
Coastal Regions ◽  
Mean Sea Level ◽  
Representative Concentration Pathways ◽  
Local Responses ◽  
Ipcc Report ◽  
Global Estimates

Mean sea-level is expected to rise significantly by 2100 in all scenarios, including those compatible with the objectives of the Paris Climate Agreement. Global sea level rise projections indicate devastating implications for populations, ecosystem services and biodiversity. The implications of the sea-level rise (SLR) on low-lying islands and coastal regions and communities are substantial and require deep-rooted coping measures. In the absence of adequate responses for coping, Mozambique is expected to record huge losses, with an impact on the economy and development in many sectors of its coastal regions mainly in northern Mozambique. This research aimed to perform projections on SLR in Mozambique, and to understand its role and implications on the north coast of the country. SLR was estimated through the analysis of model outputs that support the global estimates of the fifth IPCC report near the Mozambican coast, for each of the four representative concentration pathways (RCPs) scenarios. Regional coastline retreat and coastal erosion were estimated through the results of global sandy coastlines projections developed by Vousdoukas. Mean sea-level rise projections indicate that regional estimates for the Mozambican coast are relative higher than global estimates (~0.05 m) for all representative concentration pathways (RCPs). Yet, we highlight significant differences in sea-level rises of 0.5 m, 0.7 m or 1.0 m by 2100 compared to the global mean. It is expected that with the increase in the mean sea level in the northern part of the Mozambican coast, erosive effects will increase, as well as the retreat of the coastline until 2100. With this, the tourism sector, settlements, ecosystem services and local populations are expected to be significantly affected by 2050, with increased threats in 2100 (RCP4.5, RCP8.5). Local responses for coping are proposed and properly discussed for the RCP4.5 and RCP8.5 scenarios through 2100.

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