SCEC Award Number 19067 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Effects of fault zone damage on rupture patterns throughout multiple earthquake cycles
Name Organization
Jean-Paul Ampuero California Institute of Technology
Other Participants Benjamin Idini, Graduate Student
SCEC Priorities 3d, 1d, 2e SCEC Groups FARM, SDOT, CS
Report Due Date 04/30/2020 Date Report Submitted 05/03/2020
Project Abstract
The overarching goal of this continuing project is to understand the interactions between dynamic rupture processes and the structural evolution of damaged fault zones over long time scales. This year’s work extended our previous findings, which were based on quasi-dynamic modeling, by developing fully dynamic models that include wave propagation effects. Our new results confirm that pre-existing damaged fault zones affect earthquake rupture persistently over multiple earthquake cycles. In particular, they lead to multiple pulse-like ruptures and back-propagating fronts. With dynamic modeling we can now determine how these complex rupture patterns can be identified in observational and laboratory studies.
Intellectual Merit This project contributes directly to the SCEC goal “to achieve a multicycle simulation capability that can account for slip history, inertial effects, fault zone complexity”, to the FARM research objective to develop “physics-based fault models applicable to various spatial and temporal scales, such as nucleation, propagation and arrest of dynamic rupture or long-term earthquake sequence simulations”, to the FARM research strategy for the “characterization of fault damage zones and their evolution over both seismic and interseismic periods using […] numerical experiments”. It also complements the SCEC5 theme “beyond elasticity”: it goes even beyond plasticity by making progress towards accounting for dynamic changes of elastic moduli throughout multiple earthquake cycles.
Damage zones are ubiquitous in active faults, yet their effects on dynamic rupture and earthquake cycles are incompletely understood. Previous single-rupture models and quasi-dynamic cycle models by our team have shown effects of fault damage zones on key source properties, such as rupture speed, but the robustness of those results remained to be confirmed in fully-dynamic cycle models. This project is aimed at filling that gap.
Broader Impacts The project provided research opportunities for an undergraduate student, a graduate student and a postdoctoral researcher. Two are Hispanic and one is a woman. The project involved two international visits between Caltech and Geoazur (France). The code developed for this project is open-source.
Exemplary Figure Figure 2.
Left: Space-time distribution of slip velocity of characteristic earthquakes in 3 fully-dynamic earthquake cycle simulations with fault damage zones of different damage levels (60%, 80% and 90%). The fault zone thickness (2h) is 1/40 the size of the fault (Lvw). The ripples observed in the three cases are the result of rupture complexity involving multiple simultaneous pulses and back-propagating pulses. The ratio of rise time (average among all pulses) to rupture duration is reported at the bottom.
Right: The parameter values of these fully-dynamic simulations are reported in a figure summarizing the ratio of rise time to rupture duration in the quasi-dynamic simulations by Idini and Ampuero (2019). Compared to quasi-dynamic models, short rise time and complex slip patterns occur in fully-dynamic at lower and more realistic levels of damage.