The 1500 km-long North
Anatolian fault system in Turkey accommodates 23 mm/yr. of right-horizontal
slip at the longitude of Istanbul. It splits and diverges westward in northwest
Turkey, and, south of Istanbul, it has several active strands distributed
across 100 km. The most active fault strand is the northern one, which is the
closest to Istanbul. Bends in the map trace of the fault results in segments
across which there is extension in addition to the right-horizontal slip, forming
deep, rapidly-subsiding basins. These basins are part of Marmara Sea (Figure
1). Such distributed continental fault systems are present in other parts of
the world, including the San Andreas fault system in California. In addition to
earthquake hazard, the basins can contain abundant hydrocarbon resources. We
seek to understand the past history of motion on the many fault strands of this
system, and the relations of this motion to basin formation and sedimentation.

To accomplish this study, we
continued our international collaboration between two USA Universities and two
Turkish universities. Using the Turkish ship R/V Piri Reis and the scientists
and student scientists of the SeisLab at Dokuz Eylul University, we collected
additional profiles of acoustic imaging of the sub-sea floor during 2010. These
seismic reflection profiles image stratigraphic interfaces and faults with
resolutions of a few meters and penetrations between 1 and 2 km below the sea
floor.  The profiles were critical to
stratigraphic correlations between basins.

The project has produced three
journal publications. The first presents an age model for the stratigraphy of
Marmara Sea, and used that stratigraphy to study slip on faults and formation
of basins (Fig. 2). We conclude that basin formation has been continuous at
roughly constant rates for the last half million years, and that basin
subsidence and tilting is ongoing. The vertical component of slip across the
North Branch of the North Anatolia Fault (NAF-N) has also been continuous and
at a relatively steady rate for the last half million years. Other fault
strands and basins farther south within Marmara Sea have also been active for
at least the last half million years. This activity is ongoing, but at a much
slower rate than the NAF-N and the basins along that fault branch.

The second publication
documents that folding and/or shallow-rooted faulting of the sea floor and
sub-bottom is related to downslope motion. The vertical amplitude of deformed
sedimentary layers across these folds and faults increases with depth,
indicating slow and continuous activity for several hundred thousand years
(Figure 3). Sedimentation only modifies the 3D geometry of these folds and does
not create them. Understanding these processes has implications for the
distribution of sandy petroleum reservoirs, and motion of sediment from slopes
to basins.

The third manuscript is about
a type of basin formed by both horizontal and vertical slip on faults,
comparing the basins near Istanbul to the Ridge Basin in California.

A fourth manuscript is very
close to being submitted. We document the horizontal and vertical motions
across the North Branch of the North Anatolia Fault (NAF-N) near Istanbul for
the last half million years. The results of this manuscript and the three
publications have implications to earthquake and other hazards to Istanbul and
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