Pomona, California June 8, 2016

CRM is a rheological description of the southern California lithosphere.

SCEC 5 theme: “Beyond Elasticity”

q1. How are faults loaded across temporal and spatial scales? q2. What is the role of off-fault inelastic deformation on strain accumulation, dynamic rupture, and radiated seismic energy?

Joins other SCEC community models: seismic velocity model (“CVM”), fault model (“CFM”), geodetic model (“CGM”), and stress model (“CSM”)

SCEC Community Rheology Model (CRM): Background and motivation

Answering these questions requires rheology: relationship between stress and strain (or strain rate)

SCEC Community Rheology Model (CRM): Background and motivation

CRM is a rheological description of the southern California lithosphere.

SCEC 5 theme: “Beyond Elasticity”

q1. How are faults loaded across temporal and spatial scales? q2. What is the role of off-fault inelastic deformation on strain accumulation, dynamic rupture, and radiated seismic energy?

Joins other SCEC community models: seismic velocity model (“CVM”), fault model (“CFM”), geodetic model (“CGM”), and stress model (“CSM”)

ƞeff σ

1-n= A eQ/RTT is from CTMA, n, Q are experimentally determined parameters depend on rock type, grain size, fluid content etc.

ϵ̇ = ση

+ σ̇Eeff

Description of the stuffrock type (3D geologic model), composition, grain size, fluid content, fabric (shear zone vs host rock)

temperature, pressure, strain rate, thermodynamic equilibrium or not?

CRM requires 3D lithosphere-scale geology

Description of the conditions

seismic imaging, surface geology, boreholes, gravity/magnetics, etc.

Gary Fuis

plastic? brittle-elastic? ductile (power-law or linear viscosity)?

whose flow laws are applicable to this stuff? mixing models for polymineralic

rocks, expert consensus…

After we know the material and its state:

Flow laws, parameters

deformation experiments, texture analyses of exhumed rock, deformation modeling

Which rheological behavior?

= 19 km depth, Peninsular Ranges mafic lower crustal rocks

submit lat, lon, elevation, shear zone or host rock?

obtain temperature (CTM) admissible rock type

and flow law(s)

Idealized CRM user experience v.0.0

first cut: assume “reasonable” strain rate etc.“live” resource - evolving over time (phased development)not just a single model - multiple admissible interpretations

http://earthquake.usgs.gov/data/3dgeologic/

Modeling deformation and stress transfer

Modeling the following is hard:

• complex 3D structure and fault geometry

• multiple earthquakes, realistic timing and locations• coupled processes

CRM and CTM provide a starting point and common

reference for modeling Southern CA deformation

• wide ranges in spatial and temporal scales

Rollins et al., 2015

• nonlinear rheologies

Jiang and Lapusta, 2015

Rupture propagation and strong motion

• background stress

• inelastic properties of upper crust and fault zone

Deviatoric stress amplitudes in the upper crust are not well constrained

Need constraints on stresses below the upper crust, and vertical stress components.

Realistic deformation models (and CRM) are needed!

SHmax

Community Stress Model

Most of the contributed models are of the upper crust and are based on focal mechanisms and

geodetic data

11 contributed stress and stress rate models, a website with tools to

compare, validate (against world stress map) and

download