An earthquake gap south of Istanbul

Bohnhoff, Marco; Bulut, Fatih; Dresen, Georg; Malin, Péter; Eken, Tuna; Aktar, Mustafa

doi:10.1038/ncomms2999

Cited by 132 publications

(148 citation statements)

References 34 publications

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“…Together with seismological and seismotectonic studies (Gürbüz et al 2000;Oncel and Wyss 2001;Oncel and Wilson 2006;Kalafat et al 2011), recent GPS and kinematic studies (Meade et al 2002;Flerit et al 2003) have indicated that the northern branch of the NAFZ is more active and also creates much larger motion than the southern branch. This hypothesis has also been verified by historical period (Ambraseys and Jackson 2000;Ambraseys 2001aAmbraseys , b, 2002a, instrumental period (Kalafat et al 2011), and recent detailed microearthquake seismicity studies (Sato et al 2004;Bohnhoof et al 2013). The northern branch of the NAFZ in the Sea of Marmara, extending for more than 150 km, has been identified as a seismic gap because it has not generated a strong earthquake during the earthquake series of the last century (Bohnhoof et al 2013).…”

Section: Introductionmentioning

confidence: 64%

“…This hypothesis has also been verified by historical period (Ambraseys and Jackson 2000;Ambraseys 2001aAmbraseys , b, 2002a, instrumental period (Kalafat et al 2011), and recent detailed microearthquake seismicity studies (Sato et al 2004;Bohnhoof et al 2013). The northern branch of the NAFZ in the Sea of Marmara, extending for more than 150 km, has been identified as a seismic gap because it has not generated a strong earthquake during the earthquake series of the last century (Bohnhoof et al 2013). If we consider that the annual dextral motion across the Marmara Sea is 23-24 mm/year and that the last significant earthquake occurred in 1766, this seismic gap may have accumulated a slip deficit of more than 5 m (Bohnhoof et al 2013).…”

Section: Introductionmentioning

confidence: 64%

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Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

et al. 2016

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The main motivation for this study was the impending occurrence of a catastrophic earthquake along the Prince Island Fault (PIF) in the Marmara Sea and the disaster risk around the Marmara region, especially in Istanbul. This study provides the results of a physically based probabilistic seismic hazard analysis (PSHA) methodology, using broadband strong ground motion simulations, for sites within the Marmara region, Turkey, that may be vulnerable to possible large earthquakes throughout the PIF segments in the Marmara Sea. The methodology is called physically based because it depends on the physical processes of earthquake rupture and wave propagation to simulate earthquake ground motion time histories. We included the effects of all considerable-magnitude earthquakes. To generate the high-frequency (0.5-20 Hz) part of the broadband earthquake simulation, real, small-magnitude earthquakes recorded by a local seismic array were used as empirical Green's functions. For the frequencies below 0.5 Hz, the simulations were obtained by using synthetic Green's functions, which are synthetic seismograms calculated by an explicit 2D/3D elastic finite difference wave propagation routine. By using a range of rupture scenarios for all considerablemagnitude earthquakes throughout the PIF segments, we produced a hazard calculation for frequencies of 0.1-20 Hz. The physically based PSHA used here followed the same procedure as conventional PSHA, except that conventional PSHA utilizes point sources or a series of point sources to represent earthquakes, and this approach utilizes the full rupture of earthquakes along faults. Furthermore, conventional PSHA predicts ground motion parameters by using empirical attenuation relationships, whereas this approach calculates synthetic seismograms for all magnitudes of earthquakes to obtain ground motion parameters. PSHA results were produced for 2, 10, and 50 % hazards for all sites studied in the Marmara region.

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Section: Introductionmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 64%

Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

et al. 2016

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“…Following the suggestions of [26], the Princes Islands and Marmara segments of the North Anatolian Fault beneath the Marmara Sea were considered as the major source of seismicity for Istanbul ( figure 10). Within the scope of this study, seismic hazard for the Fatih and Kadikoy districts of Istanbul was assessed (figure 10).…”

Section: Effect Of Single Source Single Station Standard Deviation (σmentioning

confidence: 99%

Single Station Sigma for Turkish Strong Motion Stations

Cagnan¹,

Akkar²

2017

Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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“…For example, Bohnhoff et al (2013) studied microearthquakes recorded by a near-fault seismic network on the Princes Islands, the PIRES network (Bulut et al, 2009(Bulut et al, , 2011. Based on a 4 yr hypocenter catalog, these authors identified a ≥ 30-km-long aseismic fault patch extending down to 10 km depth south of the Princes Islands.…”

Section: Tectonic Setting and The Gonaf Projectmentioning

confidence: 99%

Seismic‐Wave Propagation in Shallow Layers at the GONAF‐Tuzla Site, Istanbul, Turkey

Raub

Bohnhoff

Petrović

et al. 2016

Bulletin of the Seismological Society of America

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Using the first dataset available from the downhole Geophysical Observatory of the North Anatolian Fault, we investigated near-surface seismic-wave propagation on the Tuzla Peninsula, Istanbul, Turkey. We selected a dataset of 26 seismograms recorded at Tuzla at sensor depths of 0, 71, 144, 215, and 288 m. To determine near-surface velocities and attenuation structures, the waveforms from all sensors were pairwise deconvolved and stacked. This produced low-noise empirical Green's functions for each borehole depth interval. From the Green's functions, we identified reflections from the free surface and a low-velocity layer between ∼90 and ∼140 m depth. The presence of a low-velocity zone was also confirmed by a sonic log run in the borehole. This structure, plus high near-surface P-and S-wave velocities of ∼3600-4100 and ∼1800 m=s, lead to complex interference effects between upgoing and downgoing waves. As a result, the determination of quality factors (Q) with standard spectral ratio techniques was not possible. Instead, we forward modeled the Green's functions in the time domain to determine effective Q values and to refine our velocity estimates. The effective Q P values for the depth intervals of 0-71, 0-144, 0-215, and 0-288 m were found to be 19, 35, 39, and 42, respectively. For the S waves, we obtained an effective Q S of 20 in the depth interval of 0-288 m. Considering the assumptions made in our modeling approach, it is evident that these effective quality factors are biased by impedance contrasts between our observation points. Our results show that, even after correcting for a free-surface factor of 2, the motion at the surface was found to be 1.7 times greater than that at 71 m depth. Our efforts also illustrate some of the difficulties of dealing with site effects in a strongly heterogeneous subsurface.Online Material: Plots of resistivity and caliper logs and the spectra of all 26 events.

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An earthquake gap south of Istanbul

Cited by 132 publications

References 34 publications

Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

Single Station Sigma for Turkish Strong Motion Stations

Seismic‐Wave Propagation in Shallow Layers at the GONAF‐Tuzla Site, Istanbul, Turkey

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