Spatial variation of aftershock activity across the rupture zone of the 17 August 1999 Izmit earthquake, Turkey

Aktar, Mustafa; Özalaybey, Serdar; Ergin, M.; Karabulut, Hayrullah; Bouin, Marie‐Paule; Tapirdamaz, C.; Biçmen, Faruk; Yörük, Ahmet; Bouchon, Micheĺ

doi:10.1016/j.tecto.2004.07.020

Cited by 26 publications

(22 citation statements)

References 25 publications

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“…Their seismic findings were in line with the gravity and magnetic anomaly profiles previously described by Ates et al (2003). Aktar et al (2004) found high b-values at asperity, indicating that the crustal material had been severely crushed due to high slip during the main shock rupture of the Izmit earthquake on 17 August 1999. High b-values also indicate reactivation of highly fractured zones due to this major earthquake.…”

Section: Introductionsupporting

confidence: 86%

A tectonic interpretation of the Marmara Sea, NW Turkey from geophysical data

et al. 2008

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Recent scientific investigations have revealed the deep structure and fault mechanisms in the Marmara Sea and surroundings. However, magnetic and gravity anomalies display interesting features which were not resolved in detail. In this paper, simple two-dimensional magnetic and gravity models are constructed utilizing parameters such as the density contrast and susceptibilities obtained from a borehole, seismic sections and field susceptibility measurements, respectively. The gravity model shows the existence of horst-like structures, as suggested previously. The top of the magnetic bodies in the Marmara Sea is close to the sea bottom. In general, these magnetic bodies are fault-related. The gravity model complies with the seismic base map, which was constructed previously. The magnetic anomalies of anomalous regions of the Cinarcik and Western Basins demonstrate slight anticlockwise block rotations, while large anticlockwise block rotation is observed in the eastern extremity of the Marmara Sea. Geophysical data and modeling results suggest that the origin and evaluation of the Marmara Sea began with the possibility of emplacement of horst-like structures in the Central Ridge during the Palaeozoic or earlier followed by block rotations and intrusion of the magnetic material into the upper crust with sediment deposition and faulting. It can also be suggested that the horst-like structures in the central Marmara act to diffuse the propagation of the Northern Boundary Fault (NBF). This aspect is correlated with the focal mechanisms of the major earthquakes.

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Section: Introductionsupporting

confidence: 86%

A tectonic interpretation of the Marmara Sea, NW Turkey from geophysical data

et al. 2008

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“…Nakamura et al (2002) obtained mainly reverse faulting mechanisms, while the results of Karabulut et al (2002) show reverse, strikeslip, and normal faulting mechanisms. The aftershock activity on this segment yields low b-values (Aktar et al, 2004). The 3-D crustal structure studies of Barış et al (2005) and Nakamura et al (2002) reveal somewhat contradictory images for the Yalova segment; the former shows stronger upper and weaker lower crust and the latter weaker upper crust.…”

Section: Yalova Cluster (B)mentioning

confidence: 82%

“…1 and 4) where the highest b-values were obtained (Aktar et al, 2004). The co-seismic surface ruptures on the 26-km-long Sakarya segment started from 0.5 m at the eastern margin of Lake Sapanca and increased to a maximum of 5.1 m just 3 km away from the lake.…”

Section: Sakarya-akyazı Cluster (F)mentioning

confidence: 83%

“…Moreover, the fault plane solutions of the aftershocks on this segment determined by Nakamura et al (2002) show a thrusting mechanism, while different types of mechanisms are estimated byÖzalaybey et al (2002). Also, the central portion of the segment shows relatively higher b-values than the tips of the segment (Aktar et al, 2004). The higher b-values on the segment correlate with the relatively higher seismic velocities Barış et al, 2005).…”

Section: Gölcük Cluster (C)mentioning

confidence: 94%

“…The remarkable features of this cluster are: (1) no co-seismic failures were found associated with the August 17 mainshock; (2) the aftershock activity commenced 2 days after the mainshock, probably triggered by Coulomb failure stress increase (P nar et al, 2001), post-seismic slip , or increased pore pressure (Karabulut et al, 2003); (3) the aftershock activity yields a relatively higher b-value (Aktar et al, 2004).…”

Section: ç ıNarcık Cluster (A)mentioning

confidence: 97%

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Spatial variation of the stress field along the fault rupture zone of the 1999 Izmit earthquake

et al. 2010

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We have investigated the spatial variation of the stress eld along the fault rupture zone of the 1999 Izmit earthquake (M w 7.4) using rst-motion polarity data at seven distinct aftershock clusters. In our approach, the rst-motion polarities of all the aftershocks in a cluster are simultaneously inverted to determine the stress tensor parameters and fault plane solutions of individual events, in accordance with the method of Horiuchi et al. (1995). Where post-seismic slip was signi cant (e.g., Sapanca, Sakarya-Akyaz , and Karadere segments), we obtained stress tensors with the fault parallel or fault normal maximum (σ 1 ) and minimum (σ 3 ) principal compressive stress axes, which may imply either low frictional coef cients or fault weakness. A stress tensor with similar features was derived from the Ç narc k cluster, where the aftershocks lie in a low-velocity zone beneath the geothermal area. The maximum principal stress axis tends to remain parallel to the trend of the pre-mainshock σ 1 around the Yalova segment; this segment experienced little to no co-seismic displacements. The stress tensor around the Gölcük segment, where the largest surface displacement of 5.5 m was observed, was determined to be 20-25• counterclockwise rotated, but the aftershock alignment remained fault parallel. We interpret these results in terms of the strong crust. On the other hand, both the aftershock alignment and the stress tensor were found to be rotated in the Izmit earthquake epicentral region despite the lower co-seismic displacements. We attribute this feature to the weak crust.

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Fault Structures in Marmara Sea (Turkey) and Their Connection to Earthquake Generation Processes

Aktar

2017

Active Global Seismology

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Spatial variation of aftershock activity across the rupture zone of the 17 August 1999 Izmit earthquake, Turkey

Cited by 26 publications

References 25 publications

A tectonic interpretation of the Marmara Sea, NW Turkey from geophysical data

A tectonic interpretation of the Marmara Sea, NW Turkey from geophysical data

Spatial variation of the stress field along the fault rupture zone of the 1999 Izmit earthquake

Fault Structures in Marmara Sea (Turkey) and Their Connection to Earthquake Generation Processes

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