Late quaternary seismic stratigraphy and active faults of the Gulf of İzmit (NE Marmara Sea) |
| |
Authors: | Mahmut Okyar Ali Pinar Devrim Tezcan Züheyr Kamaci |
| |
Institution: | (1) Department of Geophysical Engineering, Engineering and Architecture Faculty, Süleyman Demirel University, Cunur, Isparta, 32260, Turkey;(2) Department of Geophysics, Engineering Faculty, Istanbul University, Avcilar, Istanbul, 34850, Turkey;(3) Institute of Marine Sciences, Middle East Technical University, Erdemli, Mersin, 33731, Turkey |
| |
Abstract: | The Upper Quaternary seismic stratigraphy and active faults of the Gulf of İzmit were investigated by means of high-resolution
shallow seismic profiling data in the source region of 1999 İzmit earthquake. High-resolution seismic reflection data correlated
with borehole data indicate that the stratigraphy of İzmit Bay consists of three distinct depositional sequences formed in
response to middle Pleistocene-Holocene sea-level changes. Reflector R, separating the pre-Holocene sequences (1 and 2) from
the Holocene sequence (3), represents an erosional unconformity produced by the subaerial fluvial erosion of the continental
shelves at the time of the last glacial maximum. Occasional, anomalous reflections (acoustic turbidity) observed within the
Holocene sequence are interpreted as gas accumulations. The maximum thickness of the Holocene sediments is found to be about
25 m. The isopach map of Holocene sediment implies that the thickness of the Holocene decreases from the east towards the
central and western basins of İzmit Bay. Two distinct fault systems are interpreted in İzmit Bay. The main fault system extending
roughly in an E-W direction along the Gulf of İzmit is an active right lateral strike slip fault with a normal component.
The secondary faults are normal faults striking in different directions and these are identified as being both active and
inactive. In addition, prominent compressive features are identified in the seismic cross-sections of some profiles acquired
to the east of Hersek Peninsula where the focal mechanisms of the aftershocks of the 1999 İzmit earthquake also reveal predominantly
reverse faulting mechanisms, as identified by a local dense seismic network. |
| |
Keywords: | Holocene Late-quaternary Shallow seismic Tectonics North Anatolian Fault İ zmit Bay |
本文献已被 SpringerLink 等数据库收录! |
|