scec community rheology model (crm): background and …
TRANSCRIPT
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