β Scribed by A. Uribe-carvajal; E. Nyland
No coin nor oath required. For personal study only.
Consolidation theory and concepts of rock failure can be used to evaluate the probable risk of induced seismicity as a result of filling of reservoirs. This evaluation indicates the safest way to fill a reservoir, and depends only on the geometry of the load, the rate of filling and the geological structures in the area. The stability function is actually a measure of the risk of having failure, with time, for a particular loading history in respect to a plane of weakness.
The stability function is applied to the area of the Itzantun reservoir, which will be in southern Mexico. Drawdowns can increase the risk of triggering earthquakes in this area, which is prone to thrust faulting. It is possible to estimate the stresses after a period during which the water level is maintained and a decrease in stresses with the depth of the observation point.
The estimates of the probable induced seismicity are limited as the residual stress in the area prior to the impounding is unknown. With a measure of the residual tectonic stress it will be possible to determine an optimal filling rate to reduce the probability of induced seismicity.
During the last twenty years, it has been observed that large engineering projects may change the characteristics of the seismic events in the surrounding region. These changes are induced by changes in stress that are a result of man's activities. Among the activities and events that cause induced seismicity are fluid injection, fluid extraction, mining, underground detonations, flooding, and reservoir impoundment . Here we will deal only with reservoir impoundment.
There are many examples of where the filling of reservoirs has changed the characteristics of events in an area. These changes range from the induction of large magnitude events to changes in the micro-earthquake activity. The filling of large reservoirs, however, has not always resulted in induced seismicity. Attempts to relate induced seismicity to size or depth of a reservoir have had little success. The changes in seismic activity do not follow
π SIMILAR VOLUMES