SCEC Award Number 20104 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Modeling Sequence of Earthquakes and Aseismic Slip in Damaged Fault Zones
Name Organization
Ahmed Elbanna University of Illinois at Urbana-Champaign
Other Participants Mohamed Abdelmeguid (PhD student at UIUC)
SCEC Priorities 1d, 2d, 3d SCEC Groups FARM, CS, SDOT
Report Due Date 03/15/2021 Date Report Submitted 03/30/2021
Project Abstract
Numerous field observations indicate the existence of complex crustal structures with heterogeneous fault zones that evolve due to damage accumulation from repeated earthquakes. A realization of damaged fault zones is the so called low-velocity fault zones (LVFZs) which exist in most mature faults. Within these zones, the wave velocity is estimated to be reduced by 20 to 60% relative to the host rock [1]–[6]. The existence of damage within the fault zone may impact the long-term behavior of the earthquake cycles, resulting in complex patterns, as well as an increase in the slip due to the added compliance or slip deficit due to accommodating some deformation through off-fault inelasticity.Here we propose the extension of the hybrid method to earthquake cycle simulations of complex fault zone geometries studying the role of preexisting and evolving damage. Through the hybrid scheme numerical efficiency, we will be able to resolve the spatial scales associated with damaged fault zones, and by combining a quasi-dynamic and dynamic approaches be capable of resolving the temporal scales.
Intellectual Merit Advancing the state of the art of computational earthquake dynamics by enabling large scale simulations of sequence of earthquakes and aseismic slip with (1) off-fault bulk inelasticity, (2) full inertial effects during seismic slip, and (3) Enhanced rate weakening friction at seismic slip rates. This is a critical milestone towards understanding the non-equilibrium nature of earthquakes and fault zones that could potentially lead to development of next generation earthquake simulators and physics-informed seismic hazard models.
Broader Impacts Training of two PhD students: Md Shumon Mia (MechSe) and Mohamed Abdelmeguid (CEE) who are working on developing computational tools for modeling SEAS with high resolution fault zone physics. This work will constitute an important part of their Phd thesis.
Exemplary Figure Figure 3: Evolution of off-fault plasticity and fault slip during a sequence of earthquakes and aseismic slip using the hybrid FEBI method with alternating quasidynamic (during aseismic slip) and full inertial dynamic (during seismic slip). (a) Off-fault equivalent plastic strain after the 1st seismic event. (b) Off-fault plastic strain after the 3rd seismic event. Note that the plastic strain has grown in extension both along the fault strike-parallel direction (denoted here by the x-axis) and the fault strike-normal direction. The equivalent plastic strain has also increased in its magnitude. (c) Fault slip distribution. Blue lines represent aseismic slip drawn every 5 years. Magenta lines represent seismic slip drawn ever 1 minute. Note there is a slight dip in the slip distribution at around depth = 2.5 km, highlighted by the black arrow. This dip represents a deficit in slip accumulation on the fault plane due to an increase in the off-fault plastic strain in this region. In other words, the deformation in this zone has been partially accommodated by bulk inelasticity.