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A-24 (274) K.P. Teisseyre, Modelling of Crack Induced Resistivity Changes - Applications to Earthquake Studies

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Abstract, 3

1. Introduction, 4

1.1 Apparent electric resistivity in monitoring of earthquakes, mine shocks and rupture of rock samples, 4

1.2 Mechanisms of preseismic electric resistivity changes, 8

1.3 Oriented crack structures in the future focal zone, 9

1.4 Material containing inclusions of different resisitivities, 11

2. Model of the anisotropic rock resistivity, 12

2.1 Principal features of the modelled medium, 12

2.2 Analogies of electrical circuit laws for continuous anisotropic media, 13

2.3 Contrast distribution functions, 16

2.3.1 High resistivity cracks - the electric current deviation, 16

2.3.2 The influence of low resistivity cracks size, 17

2.4 Geometrical coefficients - general case, 18

2.5 Numerical simulations, 20

2.5.1 Essential characteristics, 20

2.5.2 Apparent resistivity simulation, 34

2.5.3 Medium resistivity variations when all cracks are either wet or dry, 34

2.5.4 Concurrent wet and dry sub-systems, 36

2.5.5 The influence of primary anisotropy on resistivity, 37

2.5.6 Effect of unsynchronous variations in dry and wet crack concentrations - simulation of tectonic-origin resistivity changes, 37

2.5.7 Simulated resistivity variations due to drying or rainfall, 38

2.6 Geometry of cracks with complicated shape, 38

2.7 The problem of connections between cracks, 39

3. Experiments with artificial samples, 39

3.1 Resistivity anisotropy - laboratory results, 39

3.2 Methodology of the authorĀ“s experiments, 41

3.3 Influence of current frequency and sample moisture on electric resistivity, 42

3.4 Influence of anisotropic inclusions system, 42

4. Anisotropic resistivity changes - field results, 48

4.1 Resistivity anisotropy in seismic zones, 48

4.2 Anisotropy revealed in monitoring in the mines, 52

5. Discussion, 55

5.1 Remarks on the main results of the authorĀ“s experiments, 55

5.2 Different resistivity models, 56

5.3 Practical inferences from the present modelling, 59

6. Conclusions, 60

References, 61


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