Underground Measurements of Electromagnetic Radiation Related to Stress-induced Fractures in the Odenwald Mountains (Germany) |
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| Authors: | Marco Lichtenberger |
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| Institution: | (1) Geological-Palaeontological Institute, University of Heidelberg, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany |
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| Abstract: | The regional stress field at Wald-Michelbach (Odenwald Mountains, Germany) induces a secondary stress field around the space
of the local railway tunnel. Resulting maximum shear stresses produce microfractures, which emit electromagnetic radiation
(EMR). From EMR measured along the cross section and the long axis of the tunnel, the regional stress field is determined
by a correlation of detected impulses per time with stresses calculated from the orientation of the tunnel, its diameter,
and topographic load. The major horizontal principal stress has an azimuth of 103°. At times, strongly alternating EMR values
are observed, which indicate electromagnetic disturbances of unknown origin. Such disturbances are identified by repeated
measurements and are not evaluated. The repeated measurements, which are not disturbed, differ with median 112 impulses per
100 ms. This difference corresponds to 0.037 MPa and indicates a good reproducibility of the results. Regional stress magnitudes
and the WNW-ESE orientation of the major horizontal principal stress indicate a minor N – S directed tensional force at the
western shoulder of the Upper Rhine Graben. |
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| Keywords: | Electromagnetic radiation stress tunnel Odenwald Upper Rhine Graben Cerescope |
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