Observations of the Temporal Evolution of Earthquake Ruptures

Men-Andrin Meier

Submitted August 16, 2016, SCEC Contribution #6720, 2016 SCEC Annual Meeting Poster #210

Source time functions (STFs) of individual earthquakes show an enormous variability. Yet, the large amount of earthquake source data available today allows extracting common features among groups of earthquakes, and to compare the "typical" behavior of different groups. We use an extensive data set of local seismic waveform data from shallow crustal earthquakes (a simple proxy for STFs) as well as a compilation of STFs from teleseismic source inversions from large subduction zone thrust earthquakes (Ye et al., 2016) to compare the behavior of events with different sizes (magnitude range M4.0-M9.1). We compare the observed source behaviors against the predictions of conceptual earthquake rupture models. We find that the STF growth rates from both local and teleseismic data are significantly lower than predicted by standard constant rupture velocity / constant stress drop models (STF~t^2). Furthermore, the observations in both data sets preclude a strongly deterministic rupture behavior: The STFs of smaller and larger earthquakes are statistically indistinguishable over roughly a third of their respective rupture durations, implying that event initiation does not dictate final rupture size. At the same time the statistically significant differences for the following two thirds of rupture imply that the preceding rupture evolution does condition the future rupture evolution to some extent. While this "limited rupture predictability" may be of limited practical use (in the sense of EEW-systems) its observation places important constraints on the factors that determine rupture propagation and termination.

Key Words
Observational seismology; rupture mechanics

Citation
Meier, M. (2016, 08). Observations of the Temporal Evolution of Earthquake Ruptures. Poster Presentation at 2016 SCEC Annual Meeting.


Related Projects & Working Groups
Seismology