2D discrete element method (DEM) simulations are used to investigate the properties of the dynamic rupture of a heterogeneous fault. The model consists of two rectangular blocks of fully bonded particles with a pre-existing fault between the blocks across which the particles are not bonded and interact only by frictional forces. An intrinsic small scale roughness of the fault surface is present due to the construction of the fault model from random spherical particles. Additionally, heterogeneity on a large length scale is introduced, generating asperity and non-asperity regions along the fault by varying the amount of small-scale surface roughness between these regions. Contact friction is defined using a Coulomb Law. The model evolves from a stress-free initial state into stick-slip behaviour while a constant normal stress and a constant shear velocity are applied to the edges of the model. The resulting slip events show a number of properties similar to real seismic events. We observe qualitatively realistic source-time functions, although the absolute slip velocities are too high, realistic stress drops and rupture velocities. The power spectral density (PSD) of the resulting slip distributions is consistent with a fractal distribution, as observed in nature. The results indicate that a simple friction law coupled with geometrical complexity yields many of the characteristic features seen in real rupture propagation.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 7209 Earthquake dynamics (1242);
- 7290 Computational seismology;
- 8118 Dynamics and mechanics of faulting (8004)