Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Investigation of Reservoir Induced Earthquakes in Oymapınar and Altınkaya Dams

The earthquakes referred as reservoir-associated earthquakes in dams are induced activities. In our country, there are 617 constructed dams and 68 under-construction dams and hydroelectric power plants, which are administered by The General Directorate of State Hydrolicworks (DSI). Within the scope of the study, the earthquakes of Oymapinar Dam (Antalya) and Altinkaya Dam (Samsun), which are two samples of the constructed ones, are investigated. The earthquake and water level data of the dams, are obtained from DSI Geotechnical Services and Ground Water Department (YAS) and Department of Operation and Maintenance, respectively.

In the thesis, the seismic activity before water loading (STO) and after water loading (STS) of Oymapinar and Altinkaya Dams, and characteristics of the earthquakes are deduced, using the data for different periods that are determined by considering the number of occurrences and magnitudes. For the determination of earthquake characteristics, the b-value of Gutenberg and Richter (1954), and the M0-M1 and M1/M0 values where M0 and M1 are the main shock magnitude and the largest aftershock magnitude respectively, are calculated. In addition, the p-values that indicate the decay rate of foreshocks and aftershocks by the time are obtained using the modified Omori Law.

The earthquakes in the Oymapinar Dam area are investigated for three different states in the STS period. In particular, in the second and third states, the b-values are low for the foreshocks and high for the aftershocks. This result is coherent with the findings of Berg (1968) and Rastogi and et al. (1997). However, since overall deduced b- values are lower than the value of 1.0, they are not in coherence with the findings of Gupta and Rastogi (1976). In respect to the inverse proportion between M0-M1 and M1/M0 values in II and III states, it is consistent with the proposals of Papazachos et al. (1967), Chaudhury and Srivastava (1973), Rastogi and et al. (1995; 1997). The p-values are generally low and seismicity characteristics in the region do not obey the Modified Omori Law. In general, the foreshock-aftershock patterns are similar and correspond to Type 2 of Mogi’s Model.

The earthquake characteristics for STS period in Altinkaya Dam could not be investigated due to the insufficient data.