Akademik Veri Yönetim Sistemi
Turkish Journal of Earth Sciences, cilt.34, sa.1, ss.68-77, 2025 (SCI-Expanded, Scopus, TRDizin)
The Germencik geothermal field with 240 °C fluid temperature is one of the most important energy production areas located at the westernmost end of the Büyük Menderes Graben in western Türkiye. The northern boundary faults of the graben have dip angles greater than 50° and listric characteristics. In this brief study, knowledge of the earthquake activity between 2007 and 2024 in the Germencik geothermal field is improved with the double-difference inversion method to image the deep normal fault planes down to 20 km of crust. Considering the steeply southward dipping boundary faults in the graben, probable listric normal faults in the upper crust are demonstrated with earthquake hypocenters for the first time. Deep imaging of the listric faults indicates that they are the main carriers for the upwelling hot geothermal fluid, schematically shown in the conceptual geothermal models of Germencik. Furthermore, significant microearthquake activity was observed in 2009, when the energy production of Germencik was starting. The slope of the Gutenberg–Richter relation of the activity between 2007 and 2011 (b-value = 1.55) is higher than the tectonically normal value of 1.0 and may be related to the initiation of geothermal operations. However, the seismological data of the national network after 2011 do not show any evident relationship between moderate/large earthquake occurrence and geothermal operation activity in Germencik.