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.
As part of its ongoing support for the education of students in Potential Field methods (and magnetometry), GEM and its program partners (Encom Technology, GISCO, Allied Associates Geophysical Ltd, Geostudi Astier srl, and Terraplus Canada) were pleased to support the 2nd Student Essay Awards in Magnetics.
The results of the 2nd Student Essay Awards are now in and we are pleased to report that financial and software awards have been granted to the following individuals:
Each award winner also receives a complimentary one-year subscription to Profile Analyst, an advanced geophysical application developed and distributed by Encom Technology Inc. of Australia. To access information about Profile Analyst, click here.
Aeroquest Surveys Ltd. has recently been flying a tri-directional helicopter-borne gradiometer for gold and base metal targets in British Columbia and Newfoundland. Provided by GEM, the system delivers high-resolution measured gradients in three orthogonal directions — along track, across track and vertical for geologic mapping, characterization of structure and selection of drill targets.
Industry interest in the tri-directional survey approach reflects both the advantages of “measured” gradients as well as the unique characteristics of GEM’s magnetic sensor technology. Measured gradients, for example, deliver data that is free of diurnal effects, has lower noise, can assist in performing terrain corrections of total field magnetics, and provides unique information for enhanced interpretation. GEM’s magnetic technology compliments these advantages further through the ability to detect weak magnetic features due to increased sensor sensitivity and high quality data in which heading errors are minimized.
The technology in use is based on the optically pumped Potassium sensor. Already in use by select survey groups around the world, the Potassium technology features the highest sensitivity in commercial magnetometers at 4 pt / Ã–Hz RMS at 20 Hz; minimal heading error for consistent data; sampling rates up to 20 Hz (higher speeds optional) for maximum survey density; robust sensors for maximum uptime and productivity; highest absolute accuracy for effortless work with multi-sensor gradiometers; and helicopter or fixed-wing configurations for flexibility.
The tri-directional gradiometer consists of a three-armed towed bird configured with 4 sensors for measurement of three gradients. This configuration does not require magnetic compensation and the adjustable bird skirt allows for further flight optimization and noise reduction. Additional components include a bird-mounted GPS antenna for accurate positioning of the bird during flight. Data capture is either to the GSMP-30A acquisition console or a third-party data acquisition unit.
GEM recently received an advance copy of a new book developed by several researchers from St. Petersburg, Russia. The book is entitled, “Magnetic Prospecting in Archaeology. Ten Years of Using the Overhauser GSM-19WG Gradiometer.” It is about 70 pages with many illustrations and photos (with many of them in colour). The objective is to provide a high quality, attractive volume for archaeologists planning to use magnetic prospecting for the investigation of their sites.
We are currently working on how best to distribute the book; either through the web site or possibly, on a paid basis (to cover printing costs). More information will be provided in a future issue of Quantum.
GEM invites all of its archaeological users to visit their booth at the 71st Annual Meeting, Society for American Archaeology (SAA) between April 26 and 30, 2006 in San Juan, Puerto Rico. This is a rich and diverse conference with more than 3000 attendees.
Terraplus Canada, one of GEM’s proven representatives, have kindly consented to providing us with access to their Overhauser case histories which are posted on their site. We hope you enjoy browsing the following environmental and engineering case studies:
We thank Terraplus for their consideration in making these resources available to Quantum readers.
GEM is also pleased to note that we will be attending the 19th Annual Meeting of SAGEEP — the Symposium on the Application of Geophysics to Engineering and Environmental Problems. This year, the meeting will be in Seattle, Washington, U.S.A. and will run from April 2 to 6, 2006. Please join us at our booth and catch up on the latest developments from GEM!
Quantum readers may already be aware of the SuperGradiometer — an ultra-sensitive magnetometer array that has the potential to assist in the detection and analysis of possible magnetic precursors to earthquake events. GEM has released a number of resources describing the technology and the predictive ability (hypothesized through examination of several earthquakes with precursors) for various magnitudes of earthquakes.
An interesting summary of known events is available by clicking here. This table summarizes earthquakes from a variety of locations, their magnitudes, distances to epicenters, etc.
Note that for larger earthquakes, GEM’s theoretical predictions indicate a consistency of results. These include Loma Prieta, perhaps the most famous of the precursor events. More information can be found by clicking here.
However, the results from several smaller earthquakes (i.e. Upland and Watsonville) deviate substantially … our results indicate that it is extremely unlikely to improbable that magnetic methods will be effective for a magnitude 4 earthquake at 600 km from the epicenter.
This discrepancy highlights one of the main obstacles in implementing magnetometer / gradiometer methods (i.e. improbable results increase skepticism of the method). However, work from GEM and others is continuing … using reasonable assumptions … to continue to validate the method and hasten its introduction as a general tool for the earthquake prediction practitioner.
GEM’s optically pumped Potassium ground magnetometer / gradiometer has, until now, only been available in a configuration with extended sensor poles … primarily with Environmental & Engineering, and Archaeology applications in mind.
Now, users working with mineral exploration projects can also take advantage of GEM’s high sensitivity, high gradient tolerance Potassium option. This system is ideal for sensitive prospecting around suspected kimberlite deposits, for example. It also has applicability for prospecting for iron deposits where high gradients often render magnetic readings difficult to acquire. Other deposit types can also benefit from the new system.
The Potassium Mineral Magnetometer has been designed with hands-free, backpack-mounted operation in mind for ease-of-use in the bush and difficult terrain. Another feature is in data acquisition; the system uses a ruggedized Personal Digital Assistant (PDA) for key acquisition tasks, including system setup, data recording, and most uniquely, navigation. This gives the operator additional safety as the PDA is compact and can be easily stored during difficult traverses.
More details will follow in future issues of Quantum.
GEM would also like to invite its users to visit with its booth staff in booth 510, Prospectors and Developers Association of Canada (PDAC), Toronto, Canada. The convention runs from March 5 to 8, 2006.
The dIdD Vector Magnetometer (delta Inclination delta Declination) is an advanced system developed specially for the Observatory sector in conjunction with the Eotvos Lorand Institute of Hungary.
Setting up the magnetometer correctly is essential to acquire high quality total field and inclination data. To assist our users in getting up and running quickly, we recently developed a new tutorial.
For your copy, send an email to email@example.com with the subject, dIdD Tutorial Request, and we will promptly make one available to you.
Visit to Tihany Observatory, Hungary: Note that scientists interested in seeing a working observatory are welcome to visit as described here. This is the 50th anniversary of the observatory and the trip is timed to coordinate with the IAGA meeting in Belsk, Poland so that professionals can take part in both events.
One of the interesting projects we recently worked on was a training workshop for a Hong Kong construction firm that is building a new golf course on a former range area on Kau Sai Chau island near Hong Kong. The project involved training five non-geophysical technical personnel to acquire high resolution data using GEM’s Overhauser gradiometer system.
Due to the sensitive nature of surveying on UXO ground, training was quite rigorous and was based on the following learning modules:
At the end of the workshop, attendees were granted certificates in application of the Overhauser magnetometer.
The ultimate role of the systems will be to follow up over the proposed golf course over ground that has been cleared to a shallow depth by earth moving machines. After interpretation of anomalies using specialist software, the group will generate maps to assist in final clearance and certification of the former range for civilian uses.
The world-renowned Istituto Nazionale di Geofisica e Vulcanologia in Italy has established one of the most comprehensive networks for acquiring and analysing magnetic data related to volcanic activity. As shown at https://maglab.ct.ingv.it/en/index.html, the objective is to develop almost completely automated systems for working with volcano-related magnetometer data.
For groups interested in setting up similar networks, GEM provides a comprehensive series of commands for controlling the magnetometer data acquisition process. These are available as an option to GSM-19 and GSM-90 series magnetometers. To learn more about the commands that are supported, please click here.
Very low frequency EM (VLF-EM) is an inductive technique which measures very low frequency horizontal EM signals from remote military transmitters. A VLF instrument is used to detect perturbations / anomalies in this EM field. The method is best used to detect linear, steeply dipping electrically charged conductors. Detection depth depends mainly upon ground conductivity, but is commonly over 35 metres.
Typical applications include locating fractures, imaging subsurface voids, mapping landfill boundaries, locating buried conductive utilities, locating mineralization … which is a full range of applications for a relatively simple electromagnetic method.
In groundwater applications, fractures are key since they tend to increase permeability in the bedrock, hence increasing the likelihood of finding water.
GEM is a leading commercial provider of VLF systems and has supplied systems for both mineral and water exploration. The VLF option is built in to a GEM console. It comprises a small white box that can be attached to the backpack assembly. VLF data can be plotted on the graphic display in real time. In addition, the Walking mode option allows magnetic and VLF surveys to be conducted simultaneously and with very little user intervention.
Data values acquired include:
For more information on VLF systems, please click here.
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. To see a summary document of the precise TERMS and CONDITIONS, click here.
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.
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 2005. 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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