The North Anatolian Fault within the sea of Marmara: A new interpretation based on multi-channel seismic and multi-beam bathymetry data

C. Imren, X. Le Pichon*, C. Rangin, E. Demirba, B. Ecevitolu, N. Görür

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151 Atıf (Scopus)

Özet

We analyze 2200 km of multi-channel seismic reflection profiles that have become recently available in the Sea of Marmara. This analysis benefits from the recent acquisition of multi-beam bathymetric data covering the axial portion of the northern basins. We conclude that the northern Sea of Marmara is at present cut by an active continuous strikeslip fault system, that we call the Marmara Fault. It links the 270° Izmit portion of the northern branch of the North Anatolian Fault to the east of the sea to the 245° Ganos Fault to the west. The Marmara Fault itself consists of two main parts. The western one is a single 80 km long fault. It follows a 265° direction that differs by 20° from the direction of the Ganos Fault. At its northeastern extremity, it turns toward the northern margin of the Çinarcik Basin. This western part of the fault is seismically quite active. The eastern part is more complex. It extends over 65 km in a 280° direction. There is thus a 10° clockwise rotation with respect to the 270° Izmit Fault strand that should result in a slight extensional component. Within the eastern Çinarcik Basin, this part of the Marmara Fault has two parallel branches, 10 km apart, the northern one near the foot of the northern slope, the southern one near the foot of the southern slope. A shortening zone occupies the northwestern corner of the Çinarcik Basin and much of the adjacent eastern Central High and separates the northern branch from the western one. The southern branch on the other hand may cross the eastern Central High along a narrow 280° valley. The data we have provide no definitive evidence on which of these two branches carries most of the motion. The establishment of the present trace of the fault through the Marmara Basin is contemporaneous with a recent phase of deposition of deep giant ripples, parallel to the bathymetric slope contours and adjacent to the turbidites basin deposits. The base of these deep basins sedimentary deposits is marked by a widespread erosional unconformity below which lies a gently folded sedimentary sequence that may consist of shallow Thrace Basin deposits.

Orijinal dilİngilizce
Sayfa (başlangıç-bitiş)143-158
Sayfa sayısı16
DergiEarth and Planetary Science Letters
Hacim186
Basın numarası2
DOI'lar
Yayın durumuYayınlandı - 2001

Finansman

In 1997, a program of multi-channel seismic reflection surveys was initiated by the Turkish National Marine Geology and Geophysics Program sponsored by the Turkish Scientific and Technical Research Council (TÜBİTAK) with the Mineral Research and Exploration Directorate of Turkey (MTA) Sismik-1 vessel. 200 km were shot along 11 profiles over the Western High in August 1997 during a cooperative program with German scientists. In September 1997, 1400 km were shot over the whole Sea of Marmara along 45 profiles during a second cruise made in cooperation between MTA, İstanbul Technical University (İTÜ) and Cambridge University. The latter data were first processed and interpreted in Cambridge [10] . Independently, the data were processed and interpreted in İTÜ and an interpretation was published by Okay et al. [11,12] . 600 km of multi-channel data were obtained along 16 additional profiles in September 1999 after the August 17, 1999 magnitude 7.4 Kocaeli earthquake [13] . The whole 2200 km of profiles ( Fig. 1 ) have since been reprocessed in a homogeneous fashion by the senior author and we believe that they present in coverage, quality and homogeneity, a significant improvement over previously published data sets. In addition, previous interpretations were in places misled in interpreting deep sea giant ripples that are omnipresent in the eastern Sea of Marmara as folds and some clear unconformities as detachments [12] . This paper presents a tectonic interpretation of the data set processed by the senior author.

FinansörlerFinansör numarası
Turkish Scientific and Technical Research Council
Mount Allison University
Exploration Directorate of Turkey

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