Beyond Magnitudes and Catalogs: Application of Gutenberg-Richter and Omori Laws to Continuous Seismograms

Tim Clements, Elizabeth S. Cochran, Sarah E. Minson, Nicholas J. van der Elst, Clara E. Yoon, Annemarie S. Baltay, & Morgan T. Page

Published September 8, 2024, SCEC Contribution #13965, 2024 SCEC Annual Meeting Poster #206

Real-time earthquake forecasting methods have focused on forecasting the future rate of earthquakes from recent earthquake rates, while thinking of earthquakes as discrete events. In most cases, end users rely on earthquake forecasts to inform potential earthquake hazard. Here, we suggest applying earthquake forecasting techniques to forecast the spatial and temporal distribution of future earthquake ground motion from the distribution of recent ground motion recorded at a single nearby seismometer during an aftershock sequence. The highest resolution “catalog” for ground motion forecasting is a continuous seismogram, where the log10 of ground motion amplitude, A(t), is roughly equivalent to continuous local magnitude. Using continuous amplitudes, rather than just peak amplitude values, has the advantage of not needing to detect or disambiguate phase arrivals from individual earthquakes. We thus recover time-varying estimates of the Gutenberg-Richter b-value and amplitude of completeness from A(t) using a maximum likelihood approach. We apply our ground motion-based approach to the two weeks following the 2019 M7.1 Ridgecrest, CA earthquake sequence. We show that continuous seismograms recover b-values and the relaxation in ground motion early in the aftershock sequence when real-time earthquake catalogs are most incomplete. We suggest that continuous b-value measurements could be used to forecast ground motion hazard in real-time during an aftershock sequence by applying a Reasenberg and Jones, 1989-type approach to ground motion exceedance probabilities.

Key Words
b-value, Omori, Catalog, ground motion

Citation
Clements, T., Cochran, E. S., Minson, S. E., van der Elst, N. J., Yoon, C. E., Baltay, A. S., & Page, M. T. (2024, 09). Beyond Magnitudes and Catalogs: Application of Gutenberg-Richter and Omori Laws to Continuous Seismograms. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)