Powell Center Working Group on Paleoseismometry Constraints for Seismic Hazard Models
Devin McPhillips, Drake M. Singleton, Thomas L. Pratt, Edward H. Field, Ramon Arrowsmith, Daniel S. Brothers, Zhiang Chen, Audrey Dunham, Christopher B. DuRoss, Fernando E. Garcia, Alex Grant, Anne Hulsey, Albert R. Kottke, Sean Lahusen, Christopher M. Madugo, Xiaofeng Meng, Anna H. Rood, Brian Sherrod, Mark Stirling, Katleen Wils, & Robert C. WitterSubmitted August 30, 2026, SCEC Contribution #15264, 2026 SCEC Annual Meeting Poster #TBD
The U.S. National Seismic Hazard Model (NSHM) quantifies the probability of damaging earthquake shaking to guide engineering, planning and preparedness. Both the NSHM and ground-motion simulations are difficult to test because the return times of damaging earthquakes are long (10^2 to 10^4+ yr). Geologic data may provide the only data on past shaking intensity from earthquakes prior to written records. Precariously balanced rocks and other fragile geologic features have been studied for decades as upper-bound constraints on past shaking intensity. Complementary constraints from landslide scars, liquefaction, and lake deposits have been developed more recently. We term any measurement of past shaking intensity as paleoseismometry. The Powell Center Working Group with the short title ‘New Data for Hazard Models’ convenes in 2026 and 2027 to compile paleoseismometry data and begin to operationalize them in the U.S. NSHM.
Paleoseismometry data are complex and discipline-specific, but a few themes provide the basis for compilation. A geologic observation suitable for compilation must have a quantitative description of the probability of failure as a function of shaking intensity. For example, these fragility functions may be developed from shake table experiments, for some precariously balanced rocks, or empirical calibrations, for some lake deposits. Candidates must also have a time interval to associate with the fragility function. These intervals may derive from the age of a precariously balanced rock or perhaps the length of lake-bottom stratigraphy. Finally, candidates must define the uncertainties for both fragility and age. Fragility functions inherently incorporate aleatory variability, but multiple functions, ideally derived from multiple methods, should be compiled to quantify epistemic uncertainty. Using these data, we are building a public OpenSHA tool to perform simple hazard curve validations with these data.
A sufficiently large paleoseismometry database has many potential applications, such as development of non-ergodic ground motion models, improvement of 3D ground-motion simulations, and NSHM logic-tree weighting. The initial database and validation tool developed by the Working Group will ideally serve as a foundation for future paleoseismometry research.
Key Words
Paleoseismometry, ground motions, hazard model, fragile geologic features,
Citation
McPhillips, D., Singleton, D. M., Pratt, T. L., Field, E. H., Arrowsmith, R., Brothers, D. S., Chen, Z., Dunham, A., DuRoss, C. B., Garcia, F. E., Grant, A., Hulsey, A., Kottke, A. R., Lahusen, S., Madugo, C. M., Meng, X., Rood, A. H., Sherrod, B., Stirling, M., Wils, K., & Witter, R. (2026, 08). Powell Center Working Group on Paleoseismometry Constraints for Seismic Hazard Models. Poster Presentation at 2026 SCEC Annual Meeting.
Related Projects & Working Groups
Earthquake Geology
