Mechanical Interaction between Neighboring Active Faults : Static and Dynamic Stress Field Induced by Faulting
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概要
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The seismic disturbances that a potentially active fault receives from a slip on a neighboring fault might be considered as nature's mechanical stability. The problem of static and dynamic stress fields induced by faulting is analysed as a way to estimate the stability of nearby active faults. The source fault is modelled by a Volterra dislocation of a strike-slip type along a vertical surface embedded in an elastic homogeneous infinite medium for both dynamic and static models. In order to represent quantitatively a resultant effect of stress caused by the source fault, a new scalar quantity is introduced in reference to the results of laboratory studies on fault friction. This quantity, which is called the resultant stress, is the linear combination of shear and normal components of the induced stress vector acting on the potential fault which is assumed to be parallel to the source fault. The spatial distribution of the static resultant stress in the seismogenic layer, which was calculated in the semiinfinite medium, indicates four regions around the source where the resultant stress takes positive values. These regions extend from the fault surface and in the direction close to the strike of the fault. The probability of further fracture in these regions increases as a result of stress redistribution in the medium due to faulting. The dominant characteristics of the dynamic stress field is the strong directivity effect, which is especially apparent in the case of a unilateral rupture. The correlation between the static and the dynamic field is also notable. The maximum values of the dynamic resultant stress are of the order of 10 bars at distances comparable to fault dimensions, if we assume a fault model which is equivalent to a M7.0 earthquake. The ratio of maximum dynamic stress to the corresponding static stress takes the values ranging from a few to 50 bars or more, depending on the location of an observer and the character of rupture propagation. This means that if a potentially active fault is located in the vicinity of a seismic source, then it could be loaded with high dynamic stress whose peak value would be equivalent to tens of years of stress accumulation at a normal tectonic rate. Such interpretation, however, must be checked carefully with respect to the time-dependence effect of applied stress on material strength.
- 東京大学地震研究所,Earthquake Research Institute, University of Tokyo,東京大学地震研究所の論文
- 1985-09-05
東京大学地震研究所,Earthquake Research Institute, University of Tokyo,東京大学地震研究所 | 論文
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