Characterization of earthquake source properties for weak events using broadband dynamic rupture models

Frantisek Gallovic, Lubica Valentova K., Lav Joshi, & Sara A. Sgobba

Submitted August 30, 2026, SCEC Contribution #15108, 2026 SCEC Annual Meeting Poster #TBD

Standard characterization of weak earthquakes based on observed source spectra relies on corner frequency (stress drop) and radiated energy estimates only as general source characteristics. However, the standard seismological analysis cannot provide physical details, including the heterogeneity of the rupture process. These can be inferred from dynamic rupture modeling that combines elastodynamics and a friction law; however, this approach is used almost exclusively for large events. In Gallovič et al. (2026, Nature Comm.), we have developed a novel Bayesian dynamic inversion of apparent (station-specific) source spectra up to 25 Hz (corrected for path and site effects) for slip-weakening friction parameters heterogeneous along a finite-extent planar fault. The approach is demonstrated through two real-world applications with distinct source radiation: a directive and a nondirective Mw~4 event in Central Italy. We find that, despite the events’ small sizes, heterogeneity in rupture propagation down to the smallest scales (~100 m) is required to accurately model the high-frequency radiation of the observed apparent spectra. We characterize the inferred heterogeneity statistically using a von Kármán correlation function. We then analyze apparent source spectra up to 25 Hz of 49 weak earthquakes (Mw~3-4.5) from Central Italy, inferring various station-averaged spectral decays, directivity effects, and positive correlations between corner frequency and spectral fall-off rates. We generate an ensemble of ~2000 spontaneous dynamic rupture scenarios with spatial heterogeneity in dynamic rupture parameters, characterized by the von Kármán correlation function, and show that they can explain the observed azimuthal characteristics of the apparent source spectra across the full frequency range (Joshi et al., 2026, CommEE). The study bridges observational seismology with dynamic rupture modeling at broadband scales, improving understanding of earthquake physics.

Citation
Gallovic, F., Valentova K., L., Joshi, L., & Sgobba, S. A. (2026, 08). Characterization of earthquake source properties for weak events using broadband dynamic rupture models. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)