SCEC Award Number 20025 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Lithologic and climatic controls on offset channel development: Implications for slip-per-event measurements
Name Organization
Karl Mueller University of Colorado, Boulder Nadine Reitman University of Colorado, Boulder
Other Participants Nadine Reitman, graduate student
SCEC Priorities 5c, 3g, 1a SCEC Groups Geology, FARM, SAFS
Report Due Date 03/15/2021 Date Report Submitted 03/15/2021
Project Abstract
Offset geomorphic piercing points, such as stream channels, are commonly used to determine fault slip rates from historic and paleoseismic earthquakes, under the assumption that they record coseismic slip. Though researchers dating back to Wallace (1968) recognized that both tectonic and geomorphic factors control the appearance and preservation of offset channels (e.g., Figure 1), few studies have explored the development of offset channels through multiple earthquake cycles or their evolution post-earthquake. In this project, we systematically investigate the formation and evolution of offset channels using numerical landscape evolution models that simulate different lithologic and climatic settings. The project includes exploration of how offsets form and evolve through 1-5 earthquake cycles depending on lithologic and climatic controls in both numerical landscape evolution models and along real strike-slip faults. Results of this work will build a fundamentally better understanding of how offset stream channels record tectonic slip under different climatic settings and evaluate how well and for how long the geomorphic paleoseismic record retains reliable information on large surface rupturing earthquakes.
Intellectual Merit The significance of the proposed research is based on developing a fundamentally better understanding of the geomorphic evolution of offset channels over a range of earthquake cycles (from 1-5 events) and different lithologic and climatic conditions through numerical landscape evolution modeling and applied to global faults. Prior results suggest that length of the open interval correlates to greater underestimation of surface offsets as geomorphic evolution occurs after each earthquake. The speed of this process may be dependent on lithology and climate of the faulted region, and thus can vary in environments that range in aridity and substrate erodibility. Our goal is to understand how climate affects channels evolution both post-earthquake and with continued progressive offset, what geomorphic conditions drive variability in measurements that may or may not be equated to moment release in large earthquakes, and how that information might be used to better interpret dense datasets of offset markers. The results of this project will be used to better define sources of uncertainty in offset markers along strike-slip faults and reduce uncertainty in slip rates. This project will translate insights gained from prior modeling to the physical world and will contribute to the SCEC objective to assess limitations of long-term earthquake rupture forecasts by evaluating how well and for how long the geomorphic paleoseismic record retains reliable information on large surface rupturing earthquakes, and how this might change in different lithologic and climatic settings.
Broader Impacts This project supported training of one PhD student and one Master’s student for one semester each. The PhD student is a woman, a group underrepresented in geoscience faculty positions. For the PhD student, the project was a chance to take the lead role in writing a proposal and following through with research, as well as mentoring a first-year Master’s student. For the Master’s student, the project served as an introduction to landscape evolution modeling, climate-tectonic interactions, and geomorphic observations of strike-slip faulting. Both students benefitted and are continuing to learn as a result of this project.
Exemplary Figure Interim/progress report. Results not final.