Stress state of the earth’s crust and seismicity in a potassium salt mining region of Belarus

Abstract

On the basis of the experience of development of the Starobin potassium salt deposit (Belarus) the authors suggest a quantitative model of a relationship between the seismicity and stress state (SS) of the crust in the areas of mining activities. Within the Starobin deposit mining region, earthquakes arise outside the mine fields and are confined to the regional faults occurring there. The axis of the maximum horizontal compression $\text {S}_{\mathrm{H},\mathrm{max}}$ shows a NNW orientation. Within the framework of a two-dimensional elastic model the authors consider mining induced disturbances of the initial homogeneous stresses. For simplicity, the mine field is simulated as a circle within which the elastic moduli are decreased as compared to those of the environment. The rock excavation results in considerable heterogeneity of the SS outside the mine field. Horizontal compressive stresses are concentrated in areas that extend across the $\text {S}_{\mathrm{H},\mathrm{max}}$ axis giving rise to potential seismic slips of the thrust type. Conversely, the tension regime is realized in areas adjacent to the mine field along the $\text {S}_{\mathrm{H},\mathrm{max}}$ axis, which can result in the re-activation of normal faults. Strike-slip faults can be activated in directions diagonal to the principal axis of the regional stress. With an increase of the excavated rock volume the area of seismic activity can be increased.