Welcome to Quantum, a periodic e-newsletter for professionals working with magnetic technologies. Quantum is designed to keep you up to speed on applications, case histories, and evolutions of quantum magnetometers in a variety of disciplines.
GEM is seeking case histories from our users regarding magnetometers and their applications to real-world earth science challenges or research projects. Submissions can be very short (two to three paragraphs), preferably with an image of data acquired in the field.
Now is your chance to contribute and inform your fellow earth science professionals about the creative work that you are conducting or interesting projects in which you have been involved.
GEM will enter you in a drawing for a GEM Golf Shirt (1 shirt per newsletter issue). Odds of winning are good, so please consider contacting us at firstname.lastname@example.org with your submission!
It has come to our attention that some users of the SM-90 magnetometer are unable to have their magnetometers serviced by the company that supplied them.
The SM-90 is originally an OEM product designed and manufactured by GEM based on its GSM-90 (EUROMAG) design. The supplying company then re-packaged them for magnetic observatories in their own consoles.
Users who require servicing may want to contact GEM directly.
GEM is pleased to offer the longest warranty in the geophysical instrumentation industry as a demonstration of its confidence in the quality of its products. All GEM products are waranteed to the original purchaser against defective parts and workmanship for two (2) years from the date of original shipping. A summary document of the precise TERMS and CONDITIONS is provided at https://www.gemsys.ca/GEM_warranty_card.htm
As part of its customer service program, GEM recently implemented an Online Maintenance capability for all customers using its magnetometers. Click the link above and you will also see a series of entry fields at the bottom of the form. Simply complete the form and submit and your warranty will be forwarded directly to us.
Then, you will be all ready for any updates that GEM prepares – a timely way to acquire new and upgraded features via the Internet.
GEM is pleased to be presenting a paper, entitled, “Development of a Potassium SuperGradiometer for Earthquake Research and Other (Exploration) Applications” at the SEG workshop on Magnetic Gradiometers on Thursday, October 15 at the SEG Annual Meeting in Denver, Colorado. The presentation will be from 11:00 am to 11:20 am. (GEM will also be exhibiting at booth 1267.)
This paper describes a new approach and what we think is a state-of-the-art methodology in (electro)magnetic measurements for earthquake research. Existing methods have met with limited success due to limited sensitivity and long-term stability of instruments, imperfect elimination of environmental noise, and in the case of induction coils, to limited low frequency features and the skin effect for their bandwidth of measurements.
We analyzed dipolar magnetic fields and their gradients generated by earthquakes with emphasis on their strongly local character. The magnetic moments of two measured precursors are calculated as well as the maximum distances at which those earthquakes can be detected with both present methods and a new proposed method (i.e. short base Potassium gradiometer).
Due to the extreme sensitivity of the Potassium SuperGradiometer, the new method is at least one order of magnitude more sensitive than presently used induction coils. SuperGrad features and installations are described.
To access your copy of the paper, click here.
HydroGEOPHYSICS, Inc. (HGI) and GEM Advanced Magnetometers have successfully integrated multi-parameter data acquisition via a special cart, called the Geophysical Operations or G.O. CART. The platform is almost entirely non-metallic, making it suitable for acquisition of high quality magnetic and other data.
Geophysical instruments are coupled with a GPS navigation system and controlled by a Pocket PC (PDA). The G.O. CART is towed by an all terrain vehicle (ATV) which is operated by a single person. These technologies provide a fundamental platform for multi-parameter mapping with high resolution magnetics and other results.
For more information and to view images of the system, click here.
Many magnetic observatories around the world are currently using GEM as their standard for total field measurements. Each observatory tends to use a mix of systems with GEM as their absolute fail-safe instrument.
For example, the Danish Meteorological Institute has several different types of magnetometers. As noted in their annual 2003 yearbook, “it was found that all proton precession magnetometers, except for the GSM-19 (Overhauser) required corrections.”
A similar result was noted by AGSO in Australia which replaced its main total field magnetometer with a GEM EUROMAG (GSM-90) in 2001. The Australian group has since standardized all instruments against the GSM-90 so that they are now consistent with the Australian Magnetic Standard held at Canberra.
In addition to the Danish and Australian examples presented here, German researchers also keep a GSM-90 on hand as a backup system in case other systems fail.
For readers interested in other yearbook results, you may want to refer to https://www.intermagnet.org/Publications_e.html
One of our customers recently reported an unknown characteristic in their data from the high Arctic. Specifically, the data showed strong linear anomalies on tie lines – indicating that there was a mismatch between line data and tie lines. This interpretation was also borne out by examination of the data which showed the occurrence of anomalies occurring between lines.
The problem started to clear up when a base station was added (i.e. at camp location approximately 21 km away). The data were still affected by magnetic diurnal effects – a result that could be lived with; however the company was determined to acquire the best data possible. This led to implementation of a base magnetometer adjacent to the grid. With this approach, it was found that the diurnal drift issue disappeared, and that tie and survey lines then matched up.
Using a local base station may eliminate the need for tie lines; although it was recommended that the practice be continued at least for the initial period of surveying on the grid until gaining confidence in the data. This has the advantage of enabling the operator to eliminate tie line corrections (which are often difficult to match) and save significant processing time. This savings in processing time more than offsets the minimal amount of work required to run the base magnetometer near the grid on a daily basis.
One of the northern states in the US has a unique and very aggressive environmental protection program, especially with regard to water well management. Specifically, every property transaction that occurs in the state requires a disclosure of wells on the property. For properties with no well, then that is disclosed. For properties with a well, the well status (in use, not in use, or sealed by a licensed well contractor) and a rough sketch of the well location is required.
Not in use wells are considered abandoned so the government contacts the buyers and requires the well to be either put back into use, sealed by a licensed well contractor (who certifies this work with a form that details the work done to properly seal the well) or apply for an annual $125 maintenance permit (which is rarely allowed).
While GEM’s customer represents the only state doing this at this time, several others are interested in similar approaches. For the past 10 years, the state has had 10,000 – 12,000 wells contractor sealed every year. Almost very county has cost assistance grant programs the assist with 50%-75% of the costs.
The application for using magnetometers is to locate lost water wells in order to get them sealed to [government] code. Usually yellow stick variety fluxgate magnetic locators work well in finding the wells but they are more of a pinpointing tool because they are directional (the type in use also has a polarity meter which tells us if the magnetic object is vertically or horizontally oriented in the ground) and operators usually need to be pretty much over the the well to detect it.
Operators can sweep with the locators but that really doesn’t help much. You can’t wave a locator around horizontally and expect it to find a well for you.
Proton magnetometers don’t pinpont well but they do an impressive job leading the operator to the lost wells especially in open fields. They also work in towns with magnetic clutter nearby. Because the state is in a high lattitude and the wells are vertical and made of steel casing, the anomalies are quite large, 300 to 1300 nT, and can easily be detected from 40 to 50 feet away (a conservative estimate). “The mapping features are not necessary but they are a very good idea,” according to the client.
The problem is quite widespread as there are over 1.5 million wells in the state and there is the potential for significant contamination as the wells can facilitate groundwater conduction from contaminated sources. Currently, the group responsible for wells notes that the state has, “sealed 12,000 wells per year for 10 years but 12,000 new wells are added each year so the problem is static”.
The challenge in this environment is assisting overloaded inspectors who have other responsibilities other than finding wells. Also, there are 700 disclosures a month from sellers. Their process means that the inspectors have to contact each one to get buyers to get wells located and sealed.
To date, well drillers and geophysicists have not been very interested in finding abandoned wells although it does represent another service that could save time on the site – hence reducing overall downtime and loss of productivity. The stakes are also large for home owners. If there is a lost well on the property, the potential liability can be huge.
GEM’s recommendation for the client was the GSM-19T proton precession magnetometer. This type of approach has huge potential savings – reducing the amount of time the inspector (operator) spends on site considerably. Ultimately, if inspectors spend less time looking for wells, they can spend more time on their main task which is monitoring the implementation of new wells.
The Nechako basin is one of several interior basins within British Columbia. Although the potential for economic quantities of hydrocarbons exists within the basin only limited exploration has been carried out. Quaternary surficial sediments and Tertiary volcanic outcrop cover large areas of the basin, limiting surface geological mapping and potentially creating seismic acquisition problems. In addition volcanic rocks within the sedimentary section can cause seismic acquisition and processing problems. The presence of these volcanic rocks also complicates the interpretation of seismic and magnetic data.
As part of the BC government’s initiative for economic development within British Columbia, Bemex Consulting International was awarded a contract to carry out ground gravity and magnetic surveys in the southern Nechako basin. The purpose of the survey was to promote the basin’s potential and to illustrate how integrated potential field data can provide constraints on basin structure, sediment thickness and volcanic structures within the sedimentary section. An approximate east-west profile was selected for this survey based on the regional gravity data collected by Canadian Hunter. Data collected along this profile included gravity, total field magnetic and the vertical gradient of the total field. Elevations and UTM coordinates were acquired along the profile as well.
The total magnetic field data and vertical gradient are also shown in Fig. 3 in the attached PDF document. The average value of the total magnetic field is approximately 57,500 nT between stations 0 and 36 (0 and 6 km). There are large variations within the magnetic field (from 52,000 to 60,000 nT) along this same segment of the profile. These large magnetic field values are associated with higher elevation and are likely related to shallow basalt flows. This may explain, at least in part, the tendency towards higher gravity values in that region.
The rest of the profile has an average total field value closer to 56,500 nT, with less variation in the magnetic field magnitude. The magnetic features from station 36 to the end of the line at station 200 are therefore likely deeper than the magnetic features between station 0 and station 36. The deeper magnetic features are coincident with the gravity low which perhaps indicate that sediments may exist above the magnetic basement in this area.
The qualitative description of the gravity and magnetic profiles is quite limited. However if the gravity and magnetic profiles are studied in conjunction with regional potential field data a more detailed interpretation can be provided.
Consequently we recommend integrating the above profiles with regional potential field data (GSC regional aeromagnetic data and the Canadian Hunter regional gravity data) to carry out a preliminary interpretation of the southern portion of the Neshkoro basin, particularly in the vicinity of the regional gravity low.
In addition to the regional potential field data the interpretation should incorporate geological information as well as all available well and seismic data. One or more of the Canadian Hunter seismic lines that cross or are close to the regional gravity low should be incorporated into the interpretation (they should be reprocessed first, if the digital data is available). The seismic and well data can be used to provide depth constraints for the quantitative interpretation of the gravity and magnetic data. For the article, access M_Best_potential_field_paper_2004_1.pdf
Note: The article was written by Melvyn Best (BEMIX) and published as a CD in the “Summary of Activities, 2004, BC Ministry of Energy and Mines, p. 73-77”. The work was compiled by Filipo Ferri.
As part of our service to our customers, GEM regularly performs searches on the Internet to familiarize our clients with the latest developments in magnetics (regardless of Magnetometer supplier). Here are some of our recent results:
GEM’s R&D team has been busy enhancing the GSMP series of K-Mags – GEM’s unique optically pumped Potassium offerings. Recent advances have focused on maximizing the upper limit of magnetic fields and gradient tolerance.
Working on a custom basis for several clients, GEM has recently delivered to a German client a magnetometer capable of reading up to 2.2 Gauss (220,000 nT). Another project involved development of a magnetometer with 3.5 Gauss capability.
Gradient tolerance for the GSMP-40 (standard portable system) was also increased to more than 35,000 nT / m. Moreover, sampling rates were enhanced from 20 to 40 times per second.
These capabilities are ideal for working in magnetically noisy areas, such as over outcrops or near human structures … traditionally challenging environments for magnetometers and gradiometers.
Increased sampling rates permit high efficiency surveying using various ground and airborne platforms, such as towed carts; and / or Unmanned Airborne Vehicles (UAVs), fixed-wing aircraft and helicopters.
Magnetometer purchasers are fortunate to have a good selection of total field instruments geared to different earth science needs with GEM providing the most complete line of total field magnetometers on the market. These offerings include Overhauser, Potassium and Proton magnetometers and gradiometers.
Each system has different sensitivities, sampling rates, and ultimately, applications.
Overhauser and the K-Mag offer many advantages over Cesium devices. These can be as straight-forward as attractive pricing, low power consumption and high quality data (Overhauser) to reduced maintenance costs, minimal heading errors, and very high quality data (Potassium).
To assist our clients in understanding the differences, GEM has created two white papers:
For your copy, access www.gemsys.ca. You will see several buttons on the right side of the screen with email links. Send the form and you will automatically receive the white papers. Happy reading! And we hope that you find the white papers to provide useful information for now and in future.
The American Geophysical Union has recently published a collection of articles in a volume entitled, “Mt. Etna: Vocano Laboratory”. This topic is of particular interest as GEM has a variety of magnetic instruments (EUROMAG, Walking Mag) currently active on the site; evaluating magnetic phenomena related to various processes.
Researchers interested in volcanology should find the Etna edition useful, judging from the table of contents and introduction. In addition to scientific topics, the volume also traces the development of research activities on and near the site.
After the Second World War, with its frequent but non life-threatening eruptions Mt Etna represented an ideal location for volcanological research for the national and international scientific community. Numerous scientists from Belgium, Germany, France, the United Kingdom and the United States of America have taken part in volcanological research aimed at understanding the volcano.
Early observations were sporadic and tended to be descriptive before the availability of modern quantitative tools. Volcano observations and studies began in a more permanent and continuous fashion when, at the end of the 1960’s, the International Institute of Volcanology (IIV) was set up within the National Research Council (C.N.R.) under the patronage of UNESCO with its scientific center at Catania.
The primary goal was to establish Etna as a “volcano-laboratory” and IIV as research center of reference for volcanologists worldwide. The IIV became the primary research body in the region and gradually assumed the role of co-ordination and meeting point for the various national and international research teams that carried out research on Etna.
More information is available at https://www.agu.org/cgi-bin/agubookstore?memb=agu&cart=95609&preface=SEGM1434084&order=&book=SEGM1434084&topic=..GM&search=
As usual, we leave the last word to our customers – our key focus in ensuring that we continue to serve the market effectively and to our customers’ satisfaction.
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Copyright 2004. GEM Systems, Inc. Advanced Magnetometers. All rights reserved with the exception of organizations that have contributed links to this issue. Our thanks to the contributors who have made this edition possible, and who are identified in the text of related articles or through their company websites. Note that some quotes relating to industry-specific trends may have been obtained from public-domain sources, and are not intended to promote GEM Systems, Inc. Other examples may not necessarily reflect GEM products; rather these examples are intended to illustrate the use of magnetics and magnetometry for selected applications.BACK
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