On the Long-Range Influence of Earthquake Rupture Zones

• Published in: Journal of volcanology and seismology Vol. 12; no. 5; pp. 341 - 352
• Main Authors: Rebetsky, Yu. L., Lermontova, A. S.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.09.2018; Springer Nature B.V
• Subjects: Anomalies; Compression; Deformation; Distance; Earth; Earth and Environmental Science; Earth crust; Earth Sciences; Earthquakes; Elastic media; Elasticity; Estimation; Fault zones; Fluid pressure; Geochemistry; Geological faults; Geology; Geophysics/Geodesy; Pseudoplasticity; Reduction; Regions; Seismic activity; Strain; Stress; Stresses; Waveguides; Long-range Influence; Anomalous Inclusions; Horizontal Compression; Rebetsky; Geodynamic Types
• ISSN: 0742-0463; 1819-7108
• DOI: 10.1134/S0742046318050068

This paper proposes a new approach to estimating the long-range influence of crustal volumes that involve anomalous stress behavior. It is shown that the consideration of this problem within elasticity theory underestimates the long-range action, determining a rapid decrease in the influence of the volume involving anomalous stresses on the state of stress in the earth crust, as one goes away from the source of the anomaly. In these approaches the influence of the anomaly at great distances (100 radii of the anomalous volume) is due to a reduction of strain by a factor of 10 6 compared with the deformation in the anomalous volume. It is proposed in estimating the long-range influence of anomalous volumes to take account of the fact that there are extensive regions in a supercritical state at different crustal horizons. Such regions are fault zones in the upper crust and layers of high fluid pressure in the middle crust (waveguides). The presence of regions of supercritical deformation where the earth behaves inelastically (pseudoplastic and quasiplastic behavior) produces a different regime of long-range influence due to incipient anomalies of stress, different from the purely elastic response. We showed that in the 2-D case (a plane horizontal layer) and the classical Coulomb–Mohr criterion, the reduction in the stress disturbance due to an anomalous inclusion can be given by the law 1/ r ( r is the lateral distance relative the center of the inclusion when normalized by the size of the inclusion). The expressions derived in this study show that the level of disturbed strain at great distances is reduced by a factor of only 100 when under horizontal compression or tension. This is lower by a factor of 10 4 compared with what would be expected in an elastic medium. Consequently, the change in the level of stress due to an anomaly in a medium that is experiencing irreversible deformation occurs at a substantially lower rate in relation to increasing distance than in a purely elastic medium, where the decay of stress behaves like 1/ r  2 .