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- MakaleAçık Erişim2025Earthquake Hazard in Urban Areas of Bursa Province: Paleosismological Properties of the Ulubat, Bursa and İnegöl Active Faults
Karabacak, Volkan; Sançar, Taylan
This study provides a detailed mapping of active fault segments in Bursa and its surrounding regions, along with a comprehensive analysis of seismic behavior derived from paleoseismological data. As one of T & uuml;rkiyes' strategic economic centers with a dense population and industrial infrastructure, Bursa requires a holistic seismic risk assessment for effective disaster preparedness and mitigation. Paleoseismological analyses of the eastern segment of the Ulubat Fault indicate that it has been in a seismic quiescence period for approximately 1855 years. This prolonged period of inactivity highlights the potential for a large earthquake in the future around the Nil & uuml;fer Region of Bursa. Trench investigations conducted in Bursa city-centre reveal that the Bursa Fault has produced at least six surface ruptures over the past 12000 years, recurring approximately every 2000 years. Additionally, trench studies on the & Idot;neg & ouml;l Fault indicate that the & Idot;neg & ouml;l Fault has produced at least five surface ruptures over the last 12000 years, with the most recent major earthquake occurring more than 2500 years ago. Obtained results emphasize the potential for the Bursa and & Idot;neg & ouml;l faults to rupture simultaneously or in close succession, possibly triggering one another. Thus, the surface rupture caused by the 1855 Bursa earthquake is evaluated to have potentially triggered stress accumulation along the & Idot;neg & ouml;l Fault. This situation reveals a high probability of a surface-rupturing earthquake (M=6.2-6.9) occurring at any time on the & Idot;neg & ouml;l Fault, after 2500 years of seismic silence. Overall, these findings underscore the critical role of the faults in Bursa and its surroundings within the regional seismicity. In particular, the potential for sequential ruptures along the Bursa and & Idot;neg & ouml;l faults presents a significant earthquake hazard. This comprehensive analysis contributes to a deeper understanding of the seismotectonic dynamics of the region, providing valuable insights for seismic hazard assessment and risk mitigation efforts.
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İncele - MakaleAçık Erişim2025Scopus SJRQ2A New Ground-Motion Prediction Model for Shallow Crustal Earthquakes in Türkiye
Çeken, Ulubey; Sertçelik, Fadime; İçen, Abdullah
The recent expansion of the strong-motion observation network, along with the increase in data obtained during major earthquakes and efforts to create consistent metadata for source, path, and site effects for both old and new records, has significantly improved the quality of data and the level of modeling in Türkiye. The mainshock and aftershock records of the 6 February 2023 Kahramanmaraş earthquake doublet (MW 7.8 and 7.7), which are among the most destructive earthquakes in world history, constitute an up-to-date and important data source for this study. In this study, we present new ground-motion prediction models (GMPMs) for shallow crustal earthquakes using strong-motion data recorded in Türkiye. Our GMPMs are calibrated using 20,173 strong-motion records from 1565 shallow crustal earthquakes with depths of less than 35 km that occurred in Türkiye and its vicinity between 1976 and 2023. Our model is valid for magnitudes ranging from 4.0 to 7.8 (MW), and for the time-averaged 30 m shear wave velocity (VS30) values of 975 stations, which ranged from 131 to 1862 m/s. In the analyses performed, using the recently developed site amplification model, we calculated the model coefficients using the mixed-effects regression algorithms used by the GMPM developers. Additionally, a heteroscedastic model was created for aleatory variability as a function of MW. The closest distance to the surface projection of the fault plane (RJB) is between 0 and 350 km. Using the metadata prepared according to these criteria, we derived up-to-date ground-motion prediction models for horizontal-component peak ground velocity (PGV), peak ground acceleration (PGA), and 5% damped pseudo-spectral acceleration (PSA) response spectra, at 36 periods ranging from 0.01 to 10 s. The variability in the predictions was decomposed into within-event, between-event, and site-to-site deviations to determine the total standard deviations (σ). Compared to previous models, the proposed GMPMs were developed using a much richer database with recent major earthquakes, and the consistent estimates and lower residuals in the comparisons support the reliability of the models.
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İncele - Veri SetiYalnız künye2024Scopus SJRQ1An updated strong-motion database of Türkiye (SMD-TR)
Sandıkkaya, M Abdullah; Güryuva, Baran; Kale, Özkan; Okçu, Oğuz; İçen, Abdullah; Yenier, Emrah; Akkar, Sinan
We updated the earthquake strong-motion database of Türkiye (SMD-TR) that is initially compiled by Akkar et al. The updated data set consists of of 9244 earthquakes of magnitudes 3.0 ≤ M ≤ 7.8 that occurred between 1976 and 2023. It includes 95,890 three-component waveforms recorded at 1022 stations (55,375 records that are processed from 6710 events and 974 stations). The database is disseminated under research-oriented website DesignSafe (https://doi.org/10.17603/ds2-f21x-s189) and is compiled to provide ground-motion flatfile, which will be updated periodically until 2025. The released version includes events occurred in Türkiye until 28 February 2023, and hence, it comprises of the mainshocks and a great portion of aftershocks from the February 6th, 2023, Kahramanmaraş earthquakes. The database includes event metadata compiled from national and international seismological agencies as well as the literature. We classified events according to their tectonic environments (i.e. active crustal and subduction) and identified the aftershocks. The station information provided by AFAD1 was used to compute the major site parameters, including time-based average of shear-wave velocity of uppermost 30 m (VS30) and depth-to-rock horizon at which the shear-wave velocity (VS) attains 1 km/s (Z1). We also computed the finite-fault distance metrics and flagged the stations located on the hanging-wall side of the rupture, as well as identified pulse-like records. We developed an automatic processing algorithm to determine the waveform quality, apply appropriate filtercut-offs to remove low- and high-frequency noise, and compute ground-motion parameters. The automatic processing was applied to small-magnitude (M < 5.5) events, whereas manual processing scheme is preferred for waveforms recorded from larger events (M ≥ 5.5). The peak ground-motion values, spectral ordinates, and ground-motion duration are provided along with the key data processing parameters in the flatfile.
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