Investigation of induced seismicity around the Enguri reservoir

Author: Nazi Tugushi
Co-authors: Nasim karamzadeh Toularoud
Keywords: Reserviors and micro seismicity, Induced Seismicity, Template matching algorithm for detection micro earthquakes
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Induced Seismicity is typically earthquakes and tremors that are related to stress and strains changes in the reservoir and surrounding rocks that can be caused by various mechanisms ranging from pore pressure variations, most induced seismicity is of a low magnitude. Large new reservoirs can trigger earthquake and cause induced seismicity. This is due to either: 1. Change in stress because of the weight of water, or more commonly by 2. Increased groundwater pore pressure decreasing the effective strength of the rock under the reservoir. For triggered earthquakes to occur, both mechanisms require that the area is already under considerable tectonic stress. For Caucasian region the most attractive object to investigation the induced seismicity is – Enguri HPP. The Enguri HPP is a hydroelectric dam on the Enguri river in north-west part of Georgia. Currently, it is the world's second highest concrete arch dam, with a height of 271.5metres. Existence of a dam reservoir with an average volume of one billion cubic meters and annual water level variation of about 100 m in close vicinity of active faults, makes the area a very interesting case study for reservoir induced seismicity (RIS) and study of interaction between dam reservoirs and faults. Within the framework of the Georgian – German project (DAMAST) work, we should evaluate the current seismicity of Enguri HPP and study whether there is any correlation of seismicity with the natural processes that exist around the HPP (eg: seasonal water level change in the reservoir).We observed the induced micro seismicity caused by an active faults near to the dam. Also made estimation main parameters of earthquakes: kinematic (epicenter and hypocenter), energetic (local magnitude) and tensor (seismic moment). According to the research results around the Dam in 30 km radius, micro seismicity is due to a two main force: Tectonic and with water level variation in Dam.