Hakan Alp

Evidence for active faults in Küçükçekmece Lagoon (Marmara Sea, Turkey), inferred from high-resolution seismic data

A total of 42 km of high-resolution seismic reflection and bathymetric data were collected for the first time to document stratigraphic and structural features of the uppermost 5 m of the Holocene sedimentary infill of Küçükçekmece Lagoon along the Marmara Sea coast of Turkey. The lagoon gradually deepens from 1 m off the northern coast to a maximum of 20 m in the southern basin. Stratigraphically, the uppermost seismic unit is characterized by a generally parallel reflection configuration, indicating deposition under low-energy conditions. In the southern basin of the lagoon, the sub-bottom is locally characterized by frequency attenuated and chaotic reflections interpreted as gas-charged sediments. Structurally, the soft sediment of the first 5 m below the lagoon floor is locally deformed by active strike-slip fault zones, here named FZ1, FZ2, and FZ3. These fault zones are NW–SE oriented and follow the long axis of the lagoon, compatible with the geographic alignment of the lagoon, the onland drainage pattern, and the scarps of the surrounding terrain. Moreover, the fault zones in Küçükçekmece Lagoon are well correlated with active offshore faults mapped during previous studies. This suggests that the FZ1, FZ2, and FZ3 fault zones are not merely local fault systems deforming the Küçükçekmece Lagoon bottom, but that they may be part of a regional fault zone extending both north and southward to merge with the northern branch of the North Anatolian Fault Zone (NAFZ) in the Çınarcık Basin. This, however, needs to be confirmed by further structural and seismological studies around Küçükçekmece Lagoon in order to more firmly establish its link with the NAFZ in the Marmara Sea, and to highlight potential seismic risks for the densely populated Istanbul metropolitan area.

Seismic stratigraphy and depositional history of the Büyükçekmece Bay since Latest Pleistocene, Marmara Sea, Turkey

High-resolution seismic data shed light on latest Pleistocene and Holocene sedimentation beneath the Büyükçekmece Bay, northern shelf area of the Marmara Sea, Turkey. Discontinuous fluvio-marine and marine deposits overlying the erosional truncation surface of Oligocene–Lower Miocene deposits are as thick as 30 m and preserved preferentially within the incised valleys that were controlled by some old faults. A series of prograding shoreline, laterally passing to the latest Pleistocene–Holocene valley-fill deposits, are thought to have accumulated mainly during times of shoreline transgression and sea-level rise. The overall morphology and stratigraphic setting observed in the Büyükçekmece Bay and at the southern outlet of the Bosphorus Strait have nearly same characteristics, implying that similar hydrodynamic conditions, erosional and depositional processes were mainly under the control of strong northerly flows during the Late Quaternary. These flows were less powerful in the Büyükçekmece region with decreased sediment input and smaller accommodation space.

Active tectonics and deformation patterns evidenced from new Chirp seismic data from Marmara Sea, Turkey

Summary The northern branch of the North Anatolian Fault (NAF) zone is the most active tectonic element in the Marmara Sea and responsible for most of the seafloor and subsurface deformations observed along the northern shelf. Various of these deformations are determined by using Chirp data. In this context, Chirp seismic data were conducted in 2015. A total of 500 km Chirp data have been interpreted to reveal the structural features of the basement rocks covered with late Quaternary sediments along the northern shelf. The sediment thickness of the thin overlying seismic unit (U2) increases close the coastline and beyond the shelf break. The lower unit (U1) gradually thins in the middle of the shelf and towards the shelf break in the study area; mostly under the control of the terraces observed on top of the U1. All faults and tectonic deformation have only been observed under this Holocene unit. It is merely observed tectonic features (folding, undulation, faults) in the U1. The Holocene unit covered not only the tectonic structures and faults below the truncational erosion surface but also the older lithology, mainly folded and sometimes tightly folded.. The faults in the lower unit actually have low seismic activity.

A view of lineaments on East Anatolian Fault Zone using by wavelet analysis method

In this study, Wavelet analysis is applied to gravity anomaly data in which geophysical data. Study area is chosen by East Anatolian region. Lineaments and neotectonic information is detected using by wavelet analysis carry out Bouger digital data. The vertical, horizontal and diagonal components of wavelet output are evaluated simultaneously and an underground model is obtained by suitable cross-sections. Thus tectonic properties of East Anatolian Fault Zone (EAFZ) are extracted. EAFZ forms a 400 km boundary along to observed lengthiness. The various views and proposed relations between this area. A renewed tectonic map is prepared by EAFZ is traced and some buried faults are elicited by Bouger gravity data.