Yazar "Ergintav, Semih" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    Crustal deformation and kinematics of the Eastern Part of the North Anatolian Fault Zone (Turkey) from GPS measurements
    (Elsevier, 2012) Tatar, Orhan; Poyraz, Fatih; Gursoy, Halil; Cakir, Ziyadin; Ergintav, Semih; Akpinar, Zafer; Kocbulut, Fikret
    The North Anatolian Fault Zone (NAFZ) is a 1200 km long dextral strike-slip fault zone forming the boundary between the Eurasian and Anatolian plates. It extends from the Gulf of Saros (North Aegean) in the west to the town of Karliova in eastern Turkey. Although there have been numerous geodetic studies concerning the crustal deformation, velocity field and the slip rate of the NAFZ along its western and central segments, geodetic observations along the eastern section of the NAFZ are sparse. In order to investigate the GPS velocities and the slip rate along the eastern part of the NAFZ, a dense GPS network consisting of 36 benchmarks was installed between Tokat and Erzincan on both sides of the fault zone and measured from 2006 to 2008. Measurement results indicate that the slip rate of the NAFZ increases westwards within about 400 km from 16.3 +/- 2.3 mm/year to 24.0 +/- 2.9 mm/year, in consistence with the observation that the Anatolian block is being pulled by the Hellenic trench rather than being pushed by the Arabian plate as a result of continental collision between the Arabian and Eurasian plates in eastern Turkey since late Miocene. Modelling the GPS velocities shows that fault locking depth increases also in the same direction from 8.1 +/- 3.3 km to 12.8 +/- 3.9 km. Slip rate decreases as moving off the Hellenic trench. An average slip rate of 20.1 +/- 2.4 mm/year and a locking depth of 12.5 +/- 3.5 km are also estimated for the entire study area by using all of the GPS measurements obtained in this study. The GPS velocities are in good agreement with the kinematic models created by paleomagnetic studies in the region and complete the overall picture. (C) 2011 Elsevier B.V. All rights reserved.
  • Küçük Resim
    Öğe
    The neglected Istanbul earthquakes in the North Anatolian Shear Zone: tectonic implications and broad-band ground motion simulations for a future moderate event
    (Oxford University Press, 2023) Tan, Onur; Karagöz, Özlem; Ergintav, Semih; Duran, Kemal
    Istanbul (Marmara Region, NW Turkey) is one of the megacities in the world and suffered from destructive earthquakes on the North Anatolian Fault, a member of the North Anatolian Shear Zone, throughout history. The 1999 Kocaeli and Duzce earthquakes emphasize the earthquake potential of the fault, crossing the Sea of Marmara, and the importance of seismic hazards in the region. The studies in the last 20 yr have concentrated on the main fault and its future destructive earthquake potential. In this study, unlike the previous ones, we focus on the two main topics about the earthquakes not interested previously in Istanbul: (1) Investigating recent earthquake activity masked by the blasts in the metropolitan area and its tectonic implications, (2) revealing their effects in Istanbul utilizing numerical ground motion simulations for a future moderate event (M-w 5). First, the 386 earthquakes from 2006 to 2016 are relocated with the double-difference method using the dense seismic network operated in the same period. The source mechanisms of the events (M-L >= 3), including the most recent 2021 Kartal-Istanbul earthquake (M-L 4.1), are determined. In addition to the analysis of the recent seismic activity, the location of the two moderate and pre-instrumental-period Istanbul earthquakes, which occurred in 1923 (M-w 5.5) and 1929 (M-w 5.1), are revised. Using the relocated epicentres outside of the principal deformation zone and the fault plane solutions, the roles of the earthquakes in the stress regime of the Marmara region are explained. The epicentres on the Cenozoic or Palaeozoic formation in the Istanbul-Zonguldak Zone are interpreted as the re-activation of the palaeo-structures under the recent tectonic stresses, and their fault plane solutions agree with the synthetic/antithetic shears of a transtensional regime corresponding to the right lateral strike-slip system with mainly N-S extension in the Marmara Region. In the second part, we investigate the effects of moderate scenario events (M-w 5) considering the current earthquake epicentres in the Istanbul metropolitan area, using characterized earthquake source model and 1-D velocity structure verified with the broad-band (0.1-10 Hz) numerical ground motion simulation of the 2021 Kartal-Istanbul earthquake. The simulated PGAs agree with the ground-motion prediction equations for short epicentral distances (<30 km). Furthermore, according to the empirical relation for Turkish earthquakes, the maximum PGA value of the synthetic models (similar to 0.3 g) corresponds to the felt intensity of MMI IX. The simulated spectral accelerations for the M-w 5 earthquake scenarios may exceed the design spectrum between 0.2 and 0.6 s given in the Turkish Building Earthquake Code (2018). In addition, certain models also generate spectral accelerations close to the design-level spectrum between 0.4 and 1 s, leading to resonance phenomena. The results indicate that a moderate event (M-w 5) in the Istanbul metropolitan area is capable of damage potential for the mid-rise buildings (4-10 stories) because of the site condition with resonance phenomena and poor construction quality.