Quantitative relationship between slow slip migration speed and frictional properties
Abstract
Owing to the development of computational capabilities, numerical simulations of multi-scale earthquake cycles on faults governed by rate- and state-dependent friction laws (RSF laws) are increasingly helpful to understand complicated processes, such as the response of faults to stress perturbations due to nearby earthquakes, involving triggered seismic and aseismic slip. To better forecast the occurrence time of earthquakes that may be triggered by aseismic slip, including aftershocks, swarms and tremors, it is necessary to know the propagation speed of postseismic slip. However, modeling this process requires many trial simulations because, despite previous numerical simulation studies, a unified theoretical relationship between frictional properties and the propagation speed is lacking. In RSF models, postseismic slip is described as weakly frictionally stable areas with slightly positive value of the frictional parameter (a-b), surrounding the earthquake source region where (a-b) is strongly negative. Here, we developed a theoretical relationship between the postseismic slip propagation speed (Vprop) and RSF parameters, applying approximations motivated by earthquake cycle simulation results. The main implications of this relationship are:
1) Lower effective normal stress "σ" increases Vprop exponentially in areas where the approach of the aseismic slip front induces large shear stresses. Otherwise, the propagation speed is independent of σ. 2) The parameter "a" has a similar effect on Vprop as σ, but in areas of small induced shear stress Vprop is roughly proportional to 1/a. 3) The parameter "b" generally has a linear effect on Vprop, whereas the parameter "dc" has a similar effect on Vprop as 1/b. 4) These results explain why Vprop depends more strongly on aσ than on (a-b)σ or on (a-b)σ/dc, as observed in previous simulations.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T33F0474A
- Keywords:
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- 1242 Seismic cycle related deformations;
- GEODESY AND GRAVITYDE: 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICSDE: 8163 Rheology and friction of fault zones;
- TECTONOPHYSICS