Collaborative Research: High-Resolution Structural and Source Imaging of Active Faults in Southern Turkiye

About This Grant

The 2023 earthquake sequence in southeastern Türkiye, including the devastating magnitude 7.8 and 7.5 events, occurred along and around the East Anatolian Fault Zone. Studying this sequence provides a rare opportunity to improve understanding of how large continental earthquakes happen and how their source properties are controlled by mature active fault zones. The investigators will study the aftershock sequence in detail, with the aims to uncover the physical mechanisms that drive aftershocks, and potentially foreshocks, in this complex earthquake system. The dense seismic data previously collected will be used to create detailed images of fault zone structures, helping to identify the controlling factors that determine the rupture propagation directions and damage patterns away from the active faults. The results of this research will offer new insights into the behavior of earthquake sequences and the properties of fault zones, which are crucial for assessing seismic hazards in regions prone to large earthquakes. Thus, the findings will not only advance scientific knowledge but will also benefit society by contributing to improving earthquake risk assessments in Türkiye, a region that is highly susceptible to major earthquakes. The project will strengthen scientific collaboration between the U.S. and Türkiye and provide hands-on training opportunities for students and researchers in cutting-edge methods such as machine learning for seismic event detection, promoting a more skilled future generation of geoscientists in the U.S. while contributing to global efforts in earthquake preparedness and mitigation. The proposed project focuses on analyzing seismic data collected from an extensive deployment of ~200 nodal and 16 broadband/strong-motion seismic stations in 2023 and additional ~180 nodal deployment in 2024-2025 across the rupture zone of the 2023 Kahramanmaras earthquake sequence in southeastern Türkiye. The goal is to construct a comprehensive earthquake catalog that will provide a high-resolution understanding of the physical processes driving aftershocks and foreshocks, as well as the fault zone characteristics that influence earthquake rupture behavior. The research will focus on two primary objectives: (1) individual source parameters and collective behaviors of earthquake sequences, and (2) fault zone properties and their relationship with earthquake slip behaviors. On the first objective, by applying machine-learning and template-matching techniques, the project will relocate aftershocks and determine their focal mechanisms. This approach will shed light on the underlying mechanisms that govern aftershock sequences and foreshock triggering, and it will offer insights into rupture directivity and small earthquake behaviors. On the second objective, seismic data from ultra-dense fault zone arrays will be used to visualize internal structure of faults in the region, including its damage zone and connectivity at seismogenic depths. Three-dimensional models of seismic velocity, attenuation, and anisotropy will be inverted to identify correlations between fault zone properties and earthquake rupture velocities, specifically focusing on areas where subsidiary faults, such as the Narli Fault, where the M7.8 initiated before intersecting with the main Eastern Anatolian Fault. This detailed analysis will contribute to a deeper understanding of fault zone dynamics and offer critical data for seismic hazard assessments in a region that has experienced significant seismic activity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.