SCEC Award Number 21108 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title A Collaborative Project: Investigating properties of small and large earthquakes on geometrically heterogeneous faults
Investigator(s)
Name Organization
Camilla Cattania Massachusetts Institute of Technology Ahmed Elbanna University of Illinois at Urbana-Champaign
Other Participants One PhD student at UIUC (Md Shumon Mia) and one PhD student at MIT.
SCEC Priorities 1d, 2d, 2e SCEC Groups FARM, Seismology, CS
Report Due Date 03/15/2022 Date Report Submitted 05/03/2022
Project Abstract
 Over the past two decades significant progress has been made in simulating long sequence of earthquakes and aseismic slip over planar faults with relatively homogeneous properties embedded in linear elastic media. Natural faults, however, are rough on multiple scales, have heterogenous stresses and strength, and interact with the surrounding bulk beyond elastic stressing by evolving damage and inelastic rheology. Synergistic feedback loops between geometry, stress, rheology, and seismicity exist over different spatial and time scales leading to the emergence of transient and persistent statistical features that could hold clues for short term earthquake predictability and reliable earthquake early warning. Numerical models for sequence of earthquakes and aseismic slip on geometrically complex fault surfaces with off-fault inelastic rheology will enable progress towards uncovering these features that might have been missed in more simplified models or are yet to be discovered in data. Building on previous work relating fault roughness to heterogeneity in normal stress, we will characterize seismicity produced by a population of asperities (defined as compressive regions induced by roughness). Our goal is twofold: first, we will determine how seismicity patterns change across the seismic cycle, as the increase in average shear stress causes increasingly strong asperities to break. Second, we will explore the relationship between stress conditions at the onset of a rupture and its subsequent evolution and verify whether the initial phases of an earthquake may be diagnostic of its final size. If successful, this work will have important implications for earthquake forecasting and predictability.
Intellectual Merit Development of novel computational tools for modeling sequence of earthquakes and aseismic slip on planar and non-planar faults with off-fault inelasticity and complex stress histories will open new opportunities for evaluating determinism in earthquakes and potential predictability relevant to earthquake early warning as well as earthquake forecasting. Testing approximated methods to represent roughness and plasticity may enable future numerical investigations at a reduced computational cost.
Broader Impacts Training of two PhD students: Md Shumon Mia (MechSe) and Mohamed Abdelmeguid (CEE) who are working on developing computational tools for modeling sequence of earthquakes and aseismic slip in complex fault geometries with off-fault inelasticity including plasticity, damage, and nucleation and propagation of off-fault cracks. Training of a Postdoc: Enrico Milanese (EAPS) who is working on implementing a more realistic approximation for plastic behavior in FDRA.
Exemplary Figure Figure 2: Example of 2D in-plane FDRA simulations using “true roughness” represented by inclined elements (left) and “pseudo-roughness”, represented by normal stresses imposed on a planar faults and evolving with slip (right). Each row is a successive mainshock.