Assessing the potential for reservoir induced seismicity from the Bisri dam project in Lebanon

Abstract

Reservoir induced seismicity has been observed in multiple cases around the world. The Bisri dam project, planned to be constructed in the Bisri Valley in Lebanon, has overlooked the concerns for safety raised by experts, which puts thousands of people and various structures at risk. In this paper, we study the potential for reservoir induced seismicity from this project. We use a two-dimensional poroelastic model where fluid flow and solid deformation are coupled to estimate the change in Coulomb Failure Stress (CFS) and the rate of seismicity (R). The high permeability damage zone of the Bisri fault lies directly beneath the proposed reservoir, which allows the pore pressure to diffuse into deeper levels, decreasing the effective normal stress, destabilizing the fault, and increasing the seismicity rate. Our results show that the increase in the rate of seismicity remains decades after the initial impoundment indicating a high risk for protracted seismicity. Moreover, the activation of the Bisri fault can cause the reactivation of the Roum fault, which is a major and active branch of the Dead Sea Transform Fault that hosted the epicenters of recent and major seismic events in the region. Hence, the risk for induced seismicity from the Bisri project should be taken into consideration very seriously by the authorities.