Earthquake Rupture in Fault Zones With Along‐Strike Material Heterogeneity

Abstract

Geological and geophysical observations reveal along‐strike fault zone heterogeneity on major strike‐slip faults, which can play a significant role in earthquake rupture propagation and termination. I present 2‐D dynamic rupture simulations to demonstrate rupture characteristics in such heterogeneous fault zone structure. The modeled rupture is nucleated in a damaged fault zone and propagates on a preexisting fault toward the zone of intact rocks. There is an intermediate range of nucleation lengths that only allow rupture to spontaneously propagate in the damaged fault zone but not in a homogeneous medium given the same stresses and frictional parameters. Rupture with an intermediate nucleation length tends to stop when it reaches the zone of intact rocks for uniform fault stress conditions, especially when the rupture propagation distance in the damaged fault zone is relatively short and when the damaged fault zone is relatively narrow or smooth in the fault‐normal direction. Pronounced small‐scale heterogeneity within the damaged fault zone also contributes to such early rupture termination. In asymmetric fault zones bisected by a bimaterial fault, rupture moving in the direction of slip of faster rocks tends to terminate under the same conditions as in symmetric fault zones, whereas rupture moving in the direction of slip of slower rocks can penetrate into the zone of intact rocks. A sufficiently large asperity located at the edge of the zone of intact rocks also allows break‐through rupture. The results suggest that the along‐strike fault zone heterogeneity can play a critical role in seismicity distribution.

Spatiotemporal Variations in Crustal Seismic Anisotropy Surrounding Induced Earthquakes Near Fox Creek, Alberta

“…We suggest that, at the moment of rupture, a surrounding fault damage zone (Kim et al, 2004) is expected to be around the main slip zone with numerous juxtaposed fractures or small-scale faults in the cataclastic shale formation (Billi et al, 2003;Huang, 2018). The width of the damage zone is influenced by fault strength, lithology, diagenesis, and fluids (Childs et al, 2009), and such a damage zone could potentially disrupt the hydraulic fractures in the immediate surrounding the HF well.…”

Detailed Investigation of the Foreshock Sequence of the 2010 Mw7.2 El Mayor‐Cucapah Earthquake

“…The starting catalog contains earthquakes listed in the Waveform Relocated Earthquake Catalog for Southern California (Hauksson et al, 2012) (the updated 1981-2018. We selected events located within the following spatial grid: 115.40 W to 115.20 W, 32.2 N to 32.4 N ( Figure 1c and Figure S1).…”

Effect of fault damage zones on long-term earthquake behavior on mature strike-slip faults

“…Using L = 8 mm leads to a nucleation size of 3.9 km in a homogeneous medium. As the nucleation size is proportional to the rigidity of the near-source medium (Rubin & Ampuero, 2005;Kaneko et al, 2011), it is reduced by a factor of ∼ 3 in a damaged medium with a shear wave velocity reduction of 40% (Huang, 2018). The theoretical estimate of the nucleation size in a layered medium for a mode III rupture is derived by Kaneko et al (2011) using linear stability analysis : where µ and µ D are the rigidity of the host rock and the layer respectively, γ (= π/4) is an empirical parameter dependent on the geometry, and H is the thickness of the layered medium.…”

“…The damage zones, exhibiting sharp contrast of seismic velocities with respect to the host rocck, are capable of trapping seismic waves. The fault damage zone can potentially promote complex stress distribution along faults due to its pronounced dynamic effect on earthquake rupture nucleation and propagation (e.g., Harris and Day (1997); Huang and Ampuero (2011); Huang et al (2014); Ma and Elbanna (2015); Albertini and Kammer (2017); Weng et al (2016); Huang (2018)).…”