Workreport 2019-3



Numerical Investigation of Earthquake Rupture and Off-Fault Fracture Response with a Coupled PFC3D/FLAC3D Environment


Darcel, C., Dedecker, F., Emam, S., Tran, M-H.



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A numerical model using a coupled approach between the distinct element software PFC3D and the finite difference software FLAC3D is setup to investigate off-fault fracture response to a controlled slip event triggered on the principal fault. The ability for PFC3D to simulate dynamic wave propagation at the desired scale is first verified, then the coupled PFC3D/FLAC3D approach is exercised on simple model scenarios and the results are sanctioned against analytical expectations, with a focus on velocity continuity and reduction of spurious, high-frequency, wave reflection at the interface between the discrete model and the finite-difference grid as well as at the outer boundaries of the finite-difference grid.

A boundary-value problem consisting of earthquake rupture and associated off-fault fracture response is constructed according to the model set up as reported by Fälth et al. (2015) for comparison of the model performance between the coupled PFC3D/FLAC3D and 3DEC tools. The coupled PFC3D/FLAC3D model approach behaves both qualitatively and quantitatively similar to the 3DEC model, with low magnitude of unrecovered slip displacement dynamically generated on the off-fault target fractures in the order of 1cm, for a controlled slip event on the order of 2m on the primary fault. This can be regarded as a conservative scenario with no internal source of energy dissipation besides frictional sliding at the fractures in the PFC3D/FLAC3D approach. Additional investigations of the role of select model parameters are conducted, and the influence of additional model features, such as the presence of background fractures and undulation of the primary fault geometry, is investigated in respect to the off-fault fracture response. While these additional features do not impact much the final results given the current limitations of the model, they provide some perspectives on the capabilities of the coupled PFC3D/FLAC3D approach to capture additional complexity in modelling of earthquake rupture process in a robust and efficient modeling environment.


PFC3D, FLAC3D, Earthquake, Rupture, Secondary Slip, Off-fault response


WR 2019-03_web (pdf) (16.7 MB)


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