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Earth Institute Research Projects

Collaborative Research: The North Anatolian Fault system in the Marmara Sea, Turkey - Insights from the Plio-Quaternary evolution of a multi-stranded transform

Lead PI: Dr. Michael S. Steckler , Mr. Leonardo Seeber

Unit Affiliation: Marine Geology & Geophysics, Lamont-Doherty Earth Observatory (LDEO)

October 2015 - September 2019
Inactive
Europe ; Mediterranean ; Turkey
Project Type: Research

DESCRIPTION: The North Anatolian Fault, a young continental transform fault, splits into several branches and forms a transtensional basin. Most of the strain is associated with the Northern Branch, which created three 1200-m deep basins. It has been proposed that the strain is focusing on the Northern Branch and that the Central and Southern branches are being abandoned. However, recent seafloor data demonstrate continued activity of the Central Branch. The will PI use new data collected in 2013 and 2014 in combination with a large suite of available previous data, to map the stratigraphy and faulting related to the Central Branch of the NAF and extend stratigraphic age model covering the past 0.5 Ma to greater depth and age. These data will be used to investigate two fundamental questions about transform fault systems: 1) what is the interplay between branches as a transform fault system evolves? And 2) how do cumulative slip and pre-existing structures affect the evolution of faults and strain partitioning? The Northern Branch is relatively continuous and single stranded while the Southern Branch is discontinuous and multi-stranded. By contrasting the slip history of these branches, the PIs will resolve whether different accumulated slip can fully account for these different fault properties or whether they are permanently influenced by pre-existing structure. The project will further cement international collaboration with Turkey via shared research and personnel exchanges, including Turkish graduate students. It will also support a female US postdoc and two undergraduate summer interns. Information relevant to seismogenic activity beneath the Marmara Sea is highly societally relevant considering that this seismic gap is home to 25% of Turkey's population and much of its industry.  A continental transform is expected to originate as a distributed network of small faults with complex geometries that, with continued slip, gradually coalesce and simplify into a through-going fault. The North Anatolian Fault (NAF), a young continental transform, has been proposed as a prime example of this process. In the Marmara Sea, however, the NAF splits into several branches and forms a transtensional basin. Most of the strain is associated with the Northern Branch, which spawned three 1200-m deep basins. It has been proposed that the strain is focusing on the Northern Branch and that the Central and Southern branches are being abandoned. However, recent seismic and bathymetry data demonstrate continued activity of the Central Branch. These new data collected in 2013 and 2014 image the stratigraphy and numerous individual fault strands on the southern shelf of the Marmara Sea. The PI will use these data, in combination with a large suite of available previous data, to map the stratigraphy and faulting related to the Central Branch of the NAF. The PIs propose to extend our published stratigraphic age model covering the past 0.5 Ma to greater depth and age. Earliest Pliocene fill of Messinian (~5 Ma) erosional valleys dated on land will be projected short distances to our near-shore reflection data to provide a base to the age model. Based on this stratigraphic framework, they will evaluate fault kinematics of many strands over the southern Marmara Sea during the last several million years. Basin modeling will be used to separate the effects of sediment loading, compaction and tectonic subsidence and test the extension estimates. These data will be used to investigate two fundamental questions about transform fault systems: 1) What is the interplay between branches as a transform fault system evolves? And 2) how do cumulative slip and pre-existing structures affect the evolution of faults and strain partitioning? The Northern Branch is relatively continuous and single stranded while the Southern Branch is discontinuous and multi-stranded. By contrasting the slip history of these branches, the PIs will resolve whether different accumulated slip can fully account for these different fault properties or whether they are permanently influenced by pre-existing structure. The project will further cement international collaboration with Turkey via shared research and personnel exchanges, including Turkish graduate students. It will also support a female US postdoc and two undergraduate summer interns. Information relevant to seismogenic activity beneath the Marmara Sea is highly societally relevant considering that this seismic gap is home to 25% of Turkey's population and much of its industry. The results will also be highly relevant to the southern San Andreas Fault and other similarly multi-stranded transform fault systems.