Seismic investigations of Lake Iznik (Turkey)

Description:

Lake Iznik is the largest lake in the southern Marmara region covering about 313 km2. It is situated at an active branch of the North Anatolian fault zone, the plate boundary between the European plate in the north and the Anatolian block in the south. The lake sediments are of fluvio-lacustrine and marine origin and were accumulated during Pliocene and Quaternary times. The lake offers the unique opportunity of investigating the interplay of sedimentary and tectonic processes (paleoseismology).

Studies on the lacustrine sediments allow

• reconstructions on the tectonic evolution of the North Anatolian fault zone in this area,
• paleoclimate reconstructions of the southern Marmara region, and
• reconstructions of human impact in the lake region.

Within the framework of a geological pilot study (sampling of short cores) of the Universities of Bonn and Cologne, the Technical University of Istanbul and the GFZ Potsdam, the AWI carried out a seismic survey on Lake Iznik to better understand the lake geometry. Furthermore, the seismic survey allows studying tectonic movements within the lake sediments that were active in the Quaternary and/or Pliocene.

First results of the seismic data show three basins (two main basins at the northern and southern rim of the lake with high sedimentation rates, and a third basin located in the western part of the lake). Lower sedimentation rates occur on the ridge in the lake center. Refraction in combination with reflection seismic data show a cyclic sediment reservoir of about 700 m thickness, making the lake a potential target for continental deep drilling (ICDP). Processing and interpretation of the seismic data (single-channel and multi-channel reflection seismics, refraction seismics with sonobuoys, and high-frequency sediment echosounding profiles) is presently going on.

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