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

北安纳托利亚断裂是一条年轻的大陆转换断裂，分成多个分支，形成一个张性盆地。大部分应变与北方分支有关，它创造了三个1200米深的盆地。有人提出，该菌株主要集中在北部分支机构，而中部和南部分支机构正在被放弃。然而，最近的海底数据表明中央分局仍在继续活动。将使用2013年和2014年收集的新数据，结合大量现有的先前数据，绘制与NAF中央分支有关的地层学和断层图，并将覆盖过去0.5 Ma的地层年龄模型扩展到更深和更早的时代。这些数据将被用来研究关于转换断层系统的两个基本问题：1)随着转换断层系统的演化，分支之间的相互作用是什么？2)累积滑动和预先存在的构造如何影响断层的演化和应变分配？北支是相对连续的单股，而南支是不连续的多股。通过对比这些分支的滑动历史，PI将确定不同的累积滑动是否能够完全解释这些不同的断层性质，或者它们是否受到预先存在的结构的永久影响。该项目将通过共享研究和人员交流，包括土耳其研究生，进一步巩固与土耳其的国际合作。它还将支持一名美国女性博士后和两名本科生暑期实习生。考虑到这个地震空隙是土耳其25%的人口和大部分工业的家园，与马尔马拉海下的地震活动相关的信息具有高度的社会意义。大陆转换预计起源于具有复杂几何形状的小断层的分布式网络，随着持续的滑动，这些小断层逐渐融合并简化为贯通断层。北安纳托利亚断层(NAF)是一种年轻的大陆转换，被认为是这一过程的一个主要例子。然而，在马尔马拉海，NAF分成了几个分支，形成了一个伸展盆地。大部分应变与北支有关，北支产生了三个1200米深的盆地。有人提出，该菌株主要集中在北部分支机构，而中部和南部分支机构正在被放弃。然而，最近的地震和水深测量数据表明中央分局仍在继续活动。2013年和2014年收集的这些新数据显示了马尔马拉海南部陆架的地层和许多单独的断层线。PI将使用这些数据，结合大量可用的先前数据，绘制与NAF中央分支相关的地层和断层图。私人调查建议将我们已公布的涵盖过去0.5 Ma的地层年龄模式扩展至更深的深度和年龄。上新世最早的上新世充填物来自梅西期(~5 Ma)侵蚀谷地，将与我们的近岸反射数据进行较短距离的投影，为年龄模型提供基础。在这个地层框架的基础上，他们将评估过去数百万年来马尔马拉海南部许多股的断层运动学。盆地模拟将被用来分离泥沙负荷、压实和构造沉降的影响，并检验扩展估计。这些数据将被用来研究关于转换断层系统的两个基本问题：1)随着转换断层系统的演化，分支之间的相互作用是什么？2)累积滑动和预先存在的构造如何影响断层的演化和应变分配？北支是相对连续的单股，而南支是不连续的多股。通过对比这些分支的滑动历史，PI将确定不同的累积滑动是否能够完全解释这些不同的断层性质，或者它们是否受到预先存在的结构的永久影响。该项目将通过共享研究和人员交流，包括土耳其研究生，进一步巩固与土耳其的国际合作。它还将支持一名美国女性博士后和两名本科生暑期实习生。考虑到这个地震空隙是土耳其25%的人口和大部分工业的家园，与马尔马拉海下的地震活动相关的信息具有高度的社会意义。这一结果也将与圣安德烈亚斯南部断层和其他类似的多股转换断层系统高度相关。

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.