NSF Award
2420543
Large earthquakes have the potential to have catastrophic impacts on humans and infrastructure when risks are not mitigated. Earthquakes nucleate at depth, but it is the upper ~1 km of a fault zone where seismic waves, rocks and sediments, fluids, humans, and their built environment intersect to drive earthquake hazard. This is the critical zone for earthquakes. This Frontier Research in Earth Sciences (FRES) project investigates how material properties that vary in space and time in the earthquake critical zone impact earthquake rupture propagation, radiation of seismic waves, ground shaking intensity, and surface deformation in between earthquakes. This research targets two similar faults, each with significant human impact, that are at different points in their earthquake cycle: the southern San Andreas fault, CA, in a quiet period between earthquakes, and the Çardak-Çığlık fault, Turkey, in the immediate aftermath of the 6 February 2023 Mw 7.6 Elbistan earthquake, part of the devastating Kahramanmaraş earthquake sequence. The research team will bridge geoscience and engineering concepts, approaches, data, and models, as well as leverage shared-use equipment and cyber-infrastructure, to deliver publicly available products on the NSF-funded Natural Hazards Engineering Research Infrastructure DesignSafe Data Depot that can improve earthquake hazard models and seismic site response analyses near seismogenic faults, which are needed for increased resilience of communities to earthquakes. Research and broader impacts are anchored in intellectual, educational, and cultural reciprocity to broaden STEM knowledge, perspectives, and participation. Research pathways will meaningfully intersect by training the next generation of Earth scientists at the nexus of geosciences and engineering, strengthening international partnerships with Turkish colleagues, and expanding the Utah State University (USU) Native American Student Mentoring Program through geoscience-engineering research experiences to increase the transition rate of Native American students from a 2-year campus at USU Blanding, UT, to the 4-year campus in Logan, UT.<br/><br/>This FRES project investigates how the earthquake critical zone accumulates, redistributes, and releases earthquake energy on major strike-slip faults. Models of earthquake rupture, seismic wave propagation, and local surface ground shaking are commonly decoupled and limited because the detailed properties of the earthquake critical zone are generalized. This FRES research will overcome these limitations by characterizing the earthquake critical zone of two major continental strike-slip faults with five intersecting research pathways that will yield geologic, geophysical, geochemical, mechanical, and engineering data. The pathways are: (1) a field-based geologic framework, (2) time-series CO2 flux data, a proxy for fault permeability and healing, (3) in-situ earthquake engineering geophysics to characterize material moduli, attenuation, and fault architecture, (4) deformation experiments to quantify fault healing, permeability, and attenuation at conditions designed to inform different stages of a seismic cycle, and (5) geochemical, microstructural, and fault rock chronology analyses to bridge natural and experimental earthquake cycle processes. These datasets will be integrated in a sixth pathway to produce stacked quasi-static, dynamic, and seismic site response numerical models. Research and broader impact activities bring together six PIs with diverse but overlapping geoscience and engineering expertise to train the next generation of Earth scientists at the intersection of these fields (three postdoctoral fellows, four PhD students, one MSc student, and undergraduate researchers). Undergraduate researchers will be recruited through the USU Honors Program, a Brown REU, and California State University Fullerton (CSUF) Project RAISE, which all focus on recruiting students underrepresented in the geosciences. International partnerships will be strengthened by having two Turkish colleagues participate in field work along the SSAF and lead Turkey-based research and by having US-based researchers connect with Turkish counterparts at public seminars at Istanbul Technical University. PIs and mentees will create and offer a new multi-year program to expand the USU-based Native American Student Mentoring Program with a goal to improve recruitment and retention of Native American students. These students will be hosted at PI labs at USU Logan, with help from Brown and CSUF researchers, where they will be taught earthquake and engineering concepts, and subsequently be taken to the south San Andreas fault for field work. Their progress will be tracked and assessed by evaluating learning outcomes and STEM engagement through these experiences. This project is funded by the Frontier Research in Earth Science (FRES) program as well as Education and Human Resources (EHR) in support of Research Experiences for Undergraduates and Postdoctoral Scholars.<br/><br/>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.
