Evolving seismic and aseismic slip on a heterogeneous frictional fault with heat generation and temperature-dependent creep

Bruce Zhou, Iain W. Bailey, & Yehuda Ben-Zion

Published August 15, 2019, SCEC Contribution #9721, 2019 SCEC Annual Meeting Poster #187 (PDF)

We study the evolution of seismicity and seismic/aseismic slip partitioning on a fault using a generalized version of the Ben-Zion and Rice (1993) model for a discrete cellular fault in elastic halfspace. Previous versions of the model were shown to produce a wide variety of realistic results (e.g., frequency-size statistics, hypocenter distributions, slip distributions and temporal occurrence) using distributions of static and kinetic friction levels and creep properties that vary in space but are fixed in time. In the present study we incroporate heat generation due to slip within a 10 cm wide zone, subsequent diffusion into the surrounding halfspace, and related changes of temperature and temperature-dependent creep on the fault. We assume a power law dependency of creep on the local shear stress, with temperature-dependent parameters based on the Arrhenius equation. Temperature rises due to slip episodes lead to increased aseismic slip, which can lead to further stress concentration in a feedback loop. The partitioning of seismic/aseismic slip and the temporal distribution of seismicity are strongly affected by the activation energy in the Arrhenius equation, and frictional parameters that control the local stress drop after failure. Our initial investigations attempt to clarify changes of the fault behavior associated with variations of these two parameters. The results can be summarized as follows: (1) A constant activation energy for the whole fault produces clear depth separation of brittle and creeping parts of the fault, and leads to quasi-periodic large earthquakes in the brittle portion followed by seismic quiescence. (2) Increasing activation energy with depth in the brittle fault section from 55 to 130 kJ/mole leads to increased fault creep after seismic slip, and constant levels of background seismicity even after large earthquakes. (3) A heterogeneous distribution of activation energies can lead to further variations in the temporal distribution of seismicity, which are strongest when the fault has alternating regions of higher and lower activation energies. (4) A co-seismic activation energy drop followed by post-seismic recovery is applied to approximate rock damage evolution. The lower activation energy can lead to a further increased creeping rate, which cause the fault section to release all stored stress, with stress concentration at the edge of that fault section enhanced earthquake clustering.

Citation
Zhou, B., Bailey, I. W., & Ben-Zion, Y. (2019, 08). Evolving seismic and aseismic slip on a heterogeneous frictional fault with heat generation and temperature-dependent creep. Poster Presentation at 2019 SCEC Annual Meeting.

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