An example of secondary fault activity along the North Anatolian Fault on the NE Marmara Sea Shelf, NW Turkey

Seismic data on the NE Marmara Sea Shelf indicate that a NNE-SSW-oriented buried basin and ridge system exist on the sub-marine extension of the Paleozoic Rocks delimited by the northern segment of the North Anatolian Fault (NS-NAF), while seismic and multi-beam bathymetric data imply that four NW-SE-oriented strike-slip faults also exist on the shelf area. Seismic data indicate that NW-SE-oriented strike-slip faults are the youngest structures that dissect the basin-ridge system. One of the NW-SE-oriented faults (F1) is aligned with a rupture of the North Anatolian Fault (NAF) cutting the northern slope of the Cinarcik Basin. This observation indicates that these faults have similar characteristics with the NS-NAF along the Marmara Sea. Therefore, they may have a secondary relation to the NAF since the principle deformation zone of the NAF follows the Marmara Trough in that region. The seismic energy recorded on these secondary faults is much less than that on the NAF in the Marmara Sea. These faults may, however, produce a large earthquake in the long term

Hydrology in the Sea of Marmara during the last 23 ka : implications for timing of Black Sea connections and sapropel deposition

Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 25 (2010): PA1205, doi:10.1029/2009PA001735.Sediments deposited under lacustrine and marine conditions in the Sea of Marmara hold a Late Quaternary record for water exchange between the Black Sea and the Mediterranean Sea. Here we report a multiproxy data set based on oxygen and strontium isotope results obtained from carbonate shells, major and trace elements, and specific organic biomarker measurements, as well as a micropaleontological study from a 14C-dated sediment core retrieved from the Sea of Marmara. Pronounced changes occurred in δ18O and 87Sr/86Sr values at the fresh and marine water transition, providing additional information in relation to micropaleontological data. Organic biomarker concentrations documented the marine origin of the sapropelic layer while changes in n-alkane concentrations clearly indicated an enhanced contribution for organic matter of terrestrial origin before and after the event. When compared with the Black Sea record, the results suggest that the Black Sea was outflowing to the Sea of Marmara from the Last Glacial Maximum until the warmer Bølling-Allerød. The first marine incursion in the Sea of Marmara occurred at 14.7 cal ka B.P. However, salinification of the basin was gradual, indicating that Black Sea freshwaters were still contributing to the Marmara seawater budget. After the Younger Dryas (which is associated with a high input of organic matter of terrestrial origin) both basins were disconnected, resulting in a salinity increase in the Sea of Marmara. The deposition of organic-rich sapropel that followed was mainly related to enhanced primary productivity characterized by a reorganization of the phytoplankton population.We acknowledge support from INSU and the French Polar Institute IPEV

Reply: "Characteristic features of the North Anatolian Fault in the Eastern Marmara Region and its tectonic evolution"

Shallow seismic profiles are used to image the tectonic and stratigraphic setting in Izmit Bay, eastern Marmara Sea. Four seismic units were detected in the sediments of Izmit Bay, which carry the effects of the tectonic uplift and global sea-level variations. The area appears to be a negative flower structure controlled by the northern branch of the North Anatolian Fault. In the late Pliocene the North Anatolian Fault reached Marmara Sea as a master fault. Smallscale faults were evolved around the master fault under a regime of dextral shear. The northward bending of the master fault gave rise to en-echelon faults, opening the sub-basins in Izmit Bay as releasing bends. The secondary faults which developed as low-angle oblique to the master fault are also the products of dextral shear. To the south, short dextral ENE-WSW trending faults are interpreted as "P"-shears, while to the north, dextral WNW-ESE trending faults represents 'R'-shears. These faults absorbed the deformation at the western end of the ruptured zone during the Izmit Earthquake (August 17, 1999), causing the migration of failure stress westward. (C) 2002 Elsevier Science B.V. All rights reserved

The effects of the North Anatolian Fault zone on the latest connection between Black Sea and Sea of Marmara

The development of the Strait of Istanbul is also one of the principal results of the tectonics which led to the evolution of the North Anatolian Fault Zone (NAFZ) in the Marmara Region 3.7 Ma ago. High resolution seismic profiles from the Marmara entrance of the Strait of Istanbul show a folding which occurred after the deposition of the parallel reflected Tyrrhenian sediments. Over the Tyrrhenian strata, a fondoform zone of a deltaic sequence and marine sediments of the latest sea level rising are present. These sediments also display syn-depositional folding. This situation implies that a local compressional stress field was created over the area probably since the Wurm Glacial age. This recent variation of the tectonic regime in the northern shelf of the Sea of Marmara may indicate a significant change in the development of the NAFZ through the Sea of Marmara. This variation of evolution of the NAFZ affected the latest development of the Strait of Istanbul via clockwise rotation of the Istanbul and Kocaeli peninsulas by right-lateral shearing between two zone bounding faults. This rotation has led to the development of NNE-SSW left-lateral faults in the Strait of Istanbul and local compressional and tensional areas explaining the compressional structures seen in the southern entrance of the Strait of Istanbul. Therefore, the latest Mediterranean-Black Sea connection was established by means of the sufficient deepening of the Bosphorus channel by a variation in the evolution of NAFZ through the Sea of Marmara. (C) 2002 Elsevier Science B.V. All rights reserved

Monitoring of earthquake precursors by multi-parameter stations in Eskisehir region (Turkey)

The objective of this study was to investigate the geochemical and hydrogeological effects of earthquakes on fluids in aquifers, particularly in a seismically active area such as Eskisehir (Turkey) where the Thrace–Eskisehir Fault Zone stretches over the region. The study area is also close to the North Anatolian Fault Zone generating devastating earthquakes such as the ones experienced in 1999, reactivating the Thrace–Eskisehir Fault. In the studied area, Rn and CO2 gas concentrations, redox potential, electrical conductivity, pH, water level, water temperature, and the climatic parameters were continuously measured in five stations for about a year. Based on the gathered data from the stations, some ambiguous anomalies in geochemical parameters and Rn concentration of groundwater were observed as precursors several days prior to an earthquake. According to the mid-term observations of this study, well-water level changes were found to be a good indicator for seismic estimations in the area, as it comprises naturally filtered anomalies reflecting only the changes due to earthquakes. Also, the results obtained from this study suggest that both the changes in well-water level and gas–water chemistry need to be interpretated together for more accurate estimations. Valid for the studied area, it can be said that shallow earthquakes with epicentral distances of <30 km from the observation stations have more influence on hydrochemical parameters of groundwater and well-water level changes. Although some hydrochemical anomalies were observed in the area, it requires further observations in order to be able to identify them as precursors

Surface runoff and carbonates-based definition of protection zones for Egirdir Lake in western Turkey

Freshwater of Isparta and Egirdir is supplied from the Egirdir Lake, which is the second largest freshwater lake of the Lakes District in Western Turkey. The Egirdir Lake has been studied within the framework of the Basin Protection Plan Special Provisions of the Egirdir Lake. The impact of runoff is taken into account in determining protection zones of the surface water reservoirs in Turkey. An approach that emphasizes the impact of groundwater flow in addition to the surface runoff has been adopted in this study. Water in Lake Egirdir is often classified as the Class II water according to terrestrial water resources quality criteria in Water Pollution Control Regulation of Turkey. The geological and hydrogeological studies reveal a significant amount of groundwater recharge into the Egirdir Lake through carbonate rocks and alluvial deposits outcropping in the basin, which is why Egirdir Lake still has a less contaminated water quality in spite of heavy pollutants. For this purpose, groundwater flow is prominently used in defining protection zones and surface runoff as well. The inner protection zone, which is defined as the 50-day travel time, and the outer protection zone, defined as the 400-day travel time, were estimated by infiltrometer and pumping tests in alluvium. Pumping tests results were used for the determination of hydraulic conductivities and groundwater levels for the determination of hydraulic gradients. Protection zones in karstic areas are based on the vulnerability map and large karstic springs