SCEC Award Number 19212 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Computing 3-D Viscoelastic Green's Functions Using SCEC Community Models and Large-Scale, High-Fidelity Finite Element Methods
Investigator(s)
Name Organization
Kaj Johnson Indiana University Thorsten Becker University of Texas at Austin
Other Participants Hori Takane is an unfunded collaborator. We request funds for a graduate student from Indiana University and a graduate student from UT Austin.
SCEC Priorities 3g, 1a, 1c SCEC Groups CXM, SDOT, SAFS
Report Due Date 04/30/2020 Date Report Submitted 11/20/2020
Project Abstract
 We developed a workflow to generate high resolution, 3-D heterogeneous viscoelastic static Green's functions (GFs) for southern California. We computed displacements and stresses in response to slip on small fault patches defined by the SCEC community fault model (CFM) using the Community Velocity Model (CVM) and Community Rheology Model (CRM) as the basis for constructing the 3-D distribution of elastic and viscous properties of the crust and uppermost mantle. To date, all GF calculations have been computed using PyLith at Indiana University.

The 2019 Ridgecrest Earthquake occurred during this project, so we directed our GF efforts to this earthquake. We construct a 3D viscosity model for Southern California based on previously published 1D viscosity models. We use this 1D model as a reference viscosity model to generate a 3D viscosity model for all of southern California using seismic velocity anomaly data available from the USArray. Temperature anomalies are computed from seismic anomalies using empirical relationships and assuming an Arrhenius flow law.

We generated a suite of forward models of the Mw 7.1 Ridgecrest earthquake incorporating afterslip and viscous mantle flow to calculate postseismic surface deformation and further explore the mantle’s rheological structure. We generated a laterally heterogeneous viscosity model and create short-term effective viscosity models incorporating both Burgers rheology and power law rheology.
Intellectual Merit We find that the 3D steady-state viscosity model for Southern California is generally consistent with observed postseismic deformation following the Ridgecrest earthquake. However short-term deformation is dominated by transient viscosity, so longer-term deformation records will be required to further assess the steady-state viscosity model.


Broader Impacts This project supported the research of a graduate student at Indiana University and another graduate student at UT-Austin.
Exemplary Figure Figure 1. Model viscosity structure. Map-view sections of 3D viscosity model at different depths