Vol. 55, n.3, September pp. 589-616
Multidisciplinary analyses to understand the tectonic
activity and the evolution of the North Anatolian Fault
in the Hersek Peninsula (Izmit Gulf, Turkey)
E. Forte, M. Sugan, A. Del Ben, M. Pipan, L. Gasperini and H. Kurt
received: December 11, 2013; accepted: March 7, 2014
Abstract
Despite several offshore data are available, a general model of the central part of the
İzmit Gulf is still a challenge and only few measurements have been done on the
Hersek peninsula. This area is a key point not only because represents the only onshore
segment of the North Anatolian Fault (NAF) within the central part of the İzmit Gulf,
but also because the new Istanbul-İzmit highway will cross such gulf in this zone,
with a suspension bridge, which will be the second longest bridge of such type in
the world. This paper, integrating different analyses and data sets aims verifying at
some of the present hypotheses. In particular, we propose the joint interpretation of
new seismic reflection profiles from the Hersek Peninsula, as well as geophysical,
remote sensing and geological data from the İzmit Gulf (Sea of Marmara, Turkey),
close to the epicenter of the 1999, Mw 7.4 İzmit earthquake, to identify shallow-crustal
deformations associated with the NAF. Our seismic reflection profiles, which are
the first onshore two-components records within the İzmit Gulf, image compressive
features that form a structural high cut by the principal deformation zone of the NAF.
The observed transpressive stress pattern appears to be the main factor contributing
to the physiography of the peninsula, together with the growth northwards of the
Yalakdere River deposits. We demonstrate that this pattern is compatible with an 8o
bending of the NAF strand. Based on these new data, we propose a kinematic model
for the evolution of this structure around the Hersek Peninsula during Holocene, and
we test our reconstruction using a finite-elements numerical simulation model of the
stress/strain distribution.
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