Browsing by Author "Ozturk, Serkan"

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An Evaluation of the Earthquake Potential With Seismic and Tectonic Variables for the West Anatolian Region of Turkiye
(inst Geology & Geography, 2024) Ozturk, Serkan; Alkan, Hamdi
In the present study, an evaluation of the region-time-magnitude behaviours of the earthquake occurrences in the West Anatolian Region (WAR), Turkiye, is carried out using the statistical and seismotectonic parameters such as the b-value of Gutenberg-Richter relation, occurrence probabilities, and return periods of earthquakes. We also have mapped the Coulomb stress changes to observe the current and future earthquake hazard. In recent years, several large earthquakes such as the 1919 Soma (Mw = 6.7) and the 2022 and 2024 Aegean Sea (Mw = 5.3 and Mw = 5.1) revealed earthquake potential in the WAR. Coulomb stress analyses of 41 local events with mostly normal fault mechanisms have shown that positive lobes (> 0.0 in bars) are mainly confined in the crust and uppermost mantle depths around Samos, Kos, and south of Lesvos. The smaller b-values (< 1.0) are observed in the same regions. On the contrary, we have observed a higher b-value from the offshore to onshore, south to north-trending direction, and negative scattered stress lobes (< 0.0 in bars) in slightly NW-SE oriented. The relationship between an increased b-value and negative stress change may indicate a similar seismicity for the region. In addition, we have analyzed the occurrence probabilities and return periods of the earthquakes, which showed us that Mw = 6.0 may occur at 75% in the intermediate term with an estimation of similar to 7 years. Our results reflect that these types of multiple-parameter assessments are important to define regional seismicity, seismic, tectonic, and statistical behaviours. Consequently, the areas with reductions in b-values and increments in stress imply the possible seismic hazard in the intermediate/long term.
Seismic Hazard Implications in and Around the Yedisu Seismic Gap (Eastern Türkiye) Based on Coulomb Stress Changes, B-Values, and S-Wave Velocity
(Springer Basel Ag, 2023) Alkan, Hamdi; Ozturk, Serkan; Akkaya, Ismail
The Yedisu Seismic Gap is one of the most important seismic gaps throughout the North Anatolian Fault Zone since it has not produced destructive earthquakes for a long time. To analyze the characteristics of future seismic hazards, the interrelationships between seismotectonic b-values, Coulomb stress changes, and S-wave velocity models of crust are presented in and around the Yedisu Seismic Gap located northwest of the Karliova Triple Junction. For this purpose, the most up-to-date earthquake catalog and the focal mechanism solutions of recent earthquakes are used to image the different depth intervals. Results show that the relatively positive stresses are accumulating along the Varto Fault Zone and Kargapazari and Yedisu Segments between 5 and 15 km depth intervals. At the same time, the lower b-values between 0.6 and 1.0 are found in the same segments. However, in the volcanic regions around the Karliova Triple Junction, the low S-wave velocity zones may be related to high b-values, negative stress changes, and volcanic structures. The region between the Turnadag? volcano and the Varto caldera shows scattered stress and b-value changes in the upper crust. Moreover, the probability of earthquakes for Mw = 6.0, 7.0, and 7.7 in the intermediate term (10 years) is estimated as -65%, -17%, and -5%, respectively. Recurrence of earthquakes with Mw = 6.0, 7.0, and 7.7 are calculated as -10, -55, and -187 years, respectively. Con-sequently, the regions characterized by low strong b-values and positive stress loading reveal high earthquake hazard potential on the whole in the next decade.
Statistical and Seismotectonic Analyses of the Marmara Region Under Existing Stress Regime in the West of the Nafz
(Springer int Publ Ag, 2025) Alkan, Hamdi; Ozturk, Serkan; Bektas, Ozcan; Buyuksarac, Aydin
The Marmara Region is an active tectonic region in northwestern T & uuml;rkiye, which comprises some important strike-slip active fault mechanisms and important tectonic units, located near the western part of the North Anatolian Fault Zone. In the historical and instrumental period, the Marmara Region experienced large/devastating earthquakes. Considering this continuous activity, in this study, we investigate the tectonic structure and performed future seismic hazard estimation of the region based on some seismotectonic parameters. For this evaluation, we plot the Coulomb stress change maps of 1912 M & uuml;refte-& Scedil;ark & ouml;y, 1953 Yenice-G & ouml;nen and 1999 & Idot;zmit mainshocks with the earthquakes (MW >= 4.5) that occurred in the study region after 2003. For the estimation of b-value, occurrence probabilities and return periods of earthquakes, we used a homogenous local seismicity catalogue consisting of 119.029 events for the period between 1912 and 2023. In the findings of this study, the lower b-values and increasing Coulomb stress changes which are trigger stress failure compatible are observed in the west and northwest of the Marmara Sea. In contrast, the higher/moderate b-values and decreasing Coulomb stress values are observed in the east and southeast of the Marmara Sea. The results of probability assessments show that an earthquake with Mw = 6.5 may occur with a probability of 98% in the west of the Marmara Sea after 2025. As a remarkable fact, a comprehensive assessment of these types of variables will supply important findings for earthquake hazard and potential in the study region.