Increasingly, researchers are looking in to the applications of magnetics alone or in combination with seismic or radon measurements for earthquake research. GEM’s new SuperGrad technology is the highest sensitivity gradiometer ever developed for these types of applications.
Below is a set of commonly asked system-related questions about SuperGrad.
The GEM Systems GSMP-20GS3 is the highest sensitivity total magnetic field measuring device ever developed. The GSMP-20GS has a 0.05 pT root-mean-square (rms) sensitivity at a sampling rate of 20 Hz (averaged over a 1 second interval) – making it well over an order-of-magnitude more sensitive than any other gradiometer in existence.
The GSMP-20GS3 was developed in response to the United State Geological Survey’s (USGS) requirement for an ultra-high sensitivity magnetic gradiometer. Key technologies include the implementation of optically pumped Potassium methods combined with large sensors for ultra-high sensitivities, suitable for resolving very subtle anomalies.
Depending on the strength of total field anomaly generated by a subsurface object or source, the range of influence of SuperGrad is estimated to lie between 10’s to several 100’s of kilometers of the surface. This range makes it ideal for investigation of earthquake sources which generally lie well within these extents.
According to earthquake researchers, “There is convincing evidence that changes in ground resistivity and low frequency (dc to 10Hz) electric and magnetic fields precede earthquakes.”
The SuperGrad’s role is to look at low frequency magnetic phenomena with a greater sensitivity than ever before possible. This is the objective of current research in Israel which is progressing with the establishment of a second observatory station, in the central sector of the Dead Sea Rift, to complement the existing station established in 2001.
Specifically, the SuperGrad is targeted to sense extremely minute variations in gradiometric fields that may be associated with the precursor movement and/or strain loading prior to an upcoming earthquake event.
The main limitation of SuperGrad reflects the key strength of the method (i.e. sensitivity). The system is very sensitive and must be totally immobilized in order to maintain precise measurement. This can be mitigated through careful design and thermal shielding of the instrument sensors in a wind-proof enclosure.
During an earthquake, the sensors will necessarily move as the ground encounters strong motion. Therefore, readings will be disrupted during the earthquake and may be shifted after the event.
However, as the purpose of the system is to detect precursor events, this sensitivity is not a significant issue; the system is able to detect the events for which it is designed provided installation guidelines are followed.
For more information on Potassium technologies, please refer to the technical papers on this site. Specifications on the SuperGrad are provided in the GSMP-20S3 brochure. In addition, you may want to refer to:
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