Beschreibung
Understanding which fault properties lead to seismic, aseismic or slow-slip energy release and how they affect the potential to nucleate large earthquakes is of critical importance for assessing the seismic hazard of nearby population centers. Improving our understanding of these processes and their mutual interactions requires an interdisciplinary approach integrating independent observations from different fields.
In this proposal, we aim to decipher the current seismotectonic and rheological state of the Armutlu Fault, as part of the North Anatolian Fault Zone’s (NAFZ) Marmara segment which has not ruptured in a M >7 event since 1766 and thus constitutes a seismic gap. There, the ICDP-GONAF borehole observatory is successfully operating since 2015. We will combine geological field work, microstructural, mineralogical and geochemical investigations complemented by microseismic data processing to address the following scientific questions:
- What is the role of the Armutlu Fault in the past and present tectonics of the eastern Sea of Marmara region and what does this imply for the seismic hazard of the Istanbul metropolitan area?
- Which are the dominant deformation mechanisms (e.g. seismic vs. aseismic processes) of the fault segments selected for detailed analysis?
- Which material properties control the deformation behavior of the studied fault rocks?
To address these questions, we propose to identify, map and derive (kinematic) relationships of individual fault segments and – based on these results – to sample fault rocks for subsequent analysis. Rock samples will be subjected to:
- A microstructural characterization to derive deformation mechanisms and explain the geomechanical behavior observed in past and present time.
- An investigation of the fault rocks’ mineralogical composition, especially regarding presence and amount of frictionally strong or weak phases, which will contribute to linking material properties to deformation processes.
- A geochemical analysis to quantify fluid-related alteration processes and their influence on deformation mechanisms and rock properties.
Located south of Istanbul and in the northeastern part of Armutlu Peninsula, the partially onshore Armutlu Fault is the only structure enabling direct access to fault rocks in the eastern Sea of Marmara but has only gained limited attention previously. As the goal of this proposal is to understand kinematics, deformation processes and controlling material parameters within the Sea of Marmara region, it is complementary to and of high relevance for the ICDP-GONAF observatory aiming at resolving the kinematics and deformation processes of this area mainly from a seismological / geodetic perspective. The Armutlu Fault constitutes the only onshore segment of the northern branch of the NAFZ which is overdue for a M >7 earthquake. Therefore, this proposal will provide critical information to constrain results derived from the ICDP-GONAF project.