Geodetic and seismological investigation of crustal deformation near Izmir (Western Anatolia) |
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| Institution: | 1. China Earthquake Networks Center, Beijing 100045, China;2. Institute of Geology, China Earthquake Administrator, Beijing 100029, China;1. Department of Applied and Environmental Geophysics, Faculty of Natural Sciences, Comenius University, Ilkovi?ova 6, 842 15 Bratislava, Slovak Republic;2. GEOPS, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France;3. Earth Science Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava, Slovak Republic |
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| Abstract: | The Aegean region including western Turkey, mainland Greece, and the Hellenic Arc is the most seismological and geodynamical active domain in the Alpine Himalayan Belt. In this study, we processed 3 years of survey-mode GPS data and present the analysis of a combination of geodetic and seismological data around Izmir, which is the third most populated city in Turkey. The velocities obtained from 15 sites vary between 25 mm/yr and 28 mm/yr relative to the Eurasian plate. The power law exponent of earthquake size distribution (b-value) ranges from 0.8 to 2.8 in the Izmir region between 26.2°E and 27.2°E. The lowest b-value zones are found along Karaburun Fault (b = 0.8) and, between Seferihisar and Tuzla Faults (b = 0.8). A localized stress concentration is expected from numerical models of seismicity along geometrical locked fault patches. Therefore, areas with lowest b-values are considered to be the most likely location for a strong earthquake, a prediction that is confirmed by the 2005 Mw = 5.9 Seferihisar earthquake sequences, with epicentres located to the south of the Karaburun Fault. The north–south extension of the Izmir area is corroborated by extension rates up to 140 nanostrain/yr as obtained from our GPS data. We combined the 3-year GPS velocity field with the published velocity field to determine the strain rate pattern in the area. The spatial distribution of b-value reflects the normal background due to the tectonic framework and is corroborated by the geodetic data. b-Values correlate with strain pattern. This relationship suggests that decrease of b-values signifies accumulating strain. |
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| Keywords: | Aegean region GPS Crustal deformation Seismicity |
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