Abstract
We relocated the seismicity in SE Aegean that was recorded by both permanent and temporary seismic networks during 2004–2018 in order to investigate its correlation with the active faults in this area. P and S-phase travel times of best quality events were used to estimate a minimum 1D velocity model with station delays by utilizing VELEST. This velocity model and station delays were then used to obtain absolute locations of 3055 events, utilizing the probabilistic nonlinear algorithm NLLOC. The double-difference algorithm was used along with catalog and cross-correlation differential times to relocate all the events, resulting in 2200 precise relative locations with horizontal and vertical uncertainties of less than 1.0 km. The precise locations delineated faults along the Gulf of Gökova, SW of Nisyros, and Karpathos area. Based on the comparison of the resulting seismicity distribution with the regional stress field, it can be concluded that seismicity only occurred along faults with ENE-WSW strike in the area north of Tilos and N-S strike in the area south of Tilos. Seismogenic layer thickness estimated from the hypocentral depth distribution was found to vary between 12.1 and 15.4 km. Expected moment magnitudes of faults in this area were calculated by using their geometrical properties and the seismogenic layer thickness, yielding magnitudes in the range of 5.9–6.9. The fact that most of the seismically active faults in SE Aegean lie offshore increases the probability that a major earthquake will be followed by a tsunami and calls for the close monitoring of seismicity in this area.
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Acknowledgments
The waveforms recorded by EGELADOS network can be downloaded from GFZ, Postdam, European Integrated Data Archive (EIDA) website (http://eida.gfz-postdam.de/webdc3) with the network code Z3. The waveforms recorded by HUSN can be downloaded from the National Observatory of Athens, EIDA archives with the network code HUSN (http://eida.gein.noa.gr/webdc3). The waveforms recorded by KOERI can be downloaded from Boğaziçi University website (http://koeri.boun.edu.tr/sismo/2/data-request/). The moment tensor solutions used in this study can be found in the RCMT database (http://rcmt2.bo.ingv.it) and the database of National Observatory of Athens, Institute of Geodynamics (http://bbnet.gein.noa.gr). We would like to thank Frederik Tilmann for allowing us to use his waveform cross-correlation code as well as the editor A. Kiratzi and two anonymous reviewers for their constructive comments.
Funding
This research has been funded by a scholarship from the National Central University (NCU) School of Earth Sciences (R. Andinisari), a Ministry of Science and Technology of Taiwan (MOST) grant (K.I. Konstantinou), and also a Taiwan International Graduate Program (TIGP) scholarship (P. Ranjan).
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Article Highlights
• As many as 2200 crustal earthquakes in South East Aegean have been precisely relocated.
• The estimated seismogenic layer thickness in the area is 12.1–15.4 km.
• Expected magnitudes of future earthquakes in South East Aegean vary between 5.9 and 6.9.
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Andinisari, R., Konstantinou, K.I. & Ranjan, P. Seismotectonics of SE Aegean inferred from precise relative locations of shallow crustal earthquakes. J Seismol 24, 1–22 (2020). https://doi.org/10.1007/s10950-019-09881-8
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DOI: https://doi.org/10.1007/s10950-019-09881-8