Recent Advances in AMT/MT Hardware (SSMT-Satellite Synchronized MT) and Applications (High density 3-D MT Survey and 3-D AMT for deep mining exploration)
Mitsuru Yamashita, Leo Fox, Gary McNeice and Gerald Graham
Phoenix Geophysics Limited (Toronto, Canada),
Unit 3,3781 Victoria Park Avenue, Scarborough, Ontario, CANADA M1W 3K5.
Tel: OO1-416-491-7340 / Fax: OO1-491-7378 E-mail: Phxgeo@netcom.ca
Abstract
Previous MT (2000 sec- 384 Hz) survey was non-optimal because "...under sampled telluric sites and over sampled magnetic sites". Equipment was relatively complex, costly, heavy requiring skilled operators, cable links and repeated long journeys to mate and re-synchronize clocks. The high survey cost with previous MT equipment prevented 3-D interpretation.
The new, optimized "distributed" system architecture (SSMT) solves these problems. SSMT uses three different types of data acquisition units (DAU), measuring 2 telluric (Ex,Ey) channels 3 magnetic (Hx,Hy,Hz) channels or both combined (5 channels)
The benefits include :
- permanent +/- 1 microsec GPS synchronization accuracy among all units (no phase error) without mating DAU for re-synchronization
- no cable links
- unlimited number of channels (economy of scale)
- simpler construction and higher reliability of DAU : fewer channels per unit, no keyboard or display simpler analog circuitry because of 24 bit ADC, VHDL and DSP (Digital Signal Processor)
- much lighter weight, smaller batteries
- simpler operation with fewer, less skilled Personnel
- lower price per channel
- reduced survey cost
- greater site density for better (3-D) interpretation
- less line cutting
Since delivery of SSMT in late 1997, more than 1500 MT sites were measured for oil and geothermal exploration in Japan, China, Canada and Hungary.
GPS synchronization now permits remote-referenced AMT (1 Hz to 10kHz) survey acquiring time-series data, increasing data quality in noisy mining areas. In Canada during 1998, a large (400+ site) 3-D Tensor AMT survey was successfully performed for deep (ca. 2000m) ore deposits . Investigation deeper than 500m is difficult for CSAMT due to the near-field problem.
raeg98@tansa.kumst.kyoto-u.ac.jp
Last modified: Mon Oct 19 17:33:05 1998