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Statewide 3D Community Fault Model (SCFM)
A statewide community-based, object-oriented, 3-D
representation of active faults in California.
… for use in:
• Fault systems analysis
• Seismic hazard assessment
...
Presentation Outline
1) Model overview
2) Model components
3) Fault construction
4) Model updates
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SCFM Overview
• consists of SoCal and NoCal CFMs
• community models
• Includes alternative representations
• > 270 faults represented
• variable detail
• consistent base of model (base of
seismicity)
• Distributed through website:
http://structure.harvard.edu/cfm/
• derived models: CFM-R, trace maps
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SCEC Community Fault Model, NoCal
• Version 1.5 available
• > 110 faults represented
• Includes alternative representations
• iterated through workshop
• available for review via SCEC-VDO
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SCEC Community Fault Model, SoCal
• Version 4.0 preview available
• > 150 faults represented
• Includes alternative representations
• Virtual Workshop evaluated model &
ranked alternative fault
representations (via LA3D)
• Widely used in fault system, strong
ground motion, & seismic hazards
studies in SCEC. •
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CFM components and architecture
Triangulated surface fault representations
• flexible representation
• simple ASCII format
Regional topographic surface
• USGS DEM (1:250,000 – 60m) SoCal
• SRTM DEM (90m) NoCal
Seismogenic thickness surface
• Nazareth & Hauksson (2004) SoCal
• based on Waldhauser (2009) DD catalog NoCal
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Generating fault surfaces
Seismic profiles (1), wells (2),
geologic data (3), and cross
sections (4) are assembled and
geo-referenced, as well as
hypocenters (5) and focal
mechanism (5).
Fault surfaces are interpolated
(a) and extrapolated (b) to
define CFM representations.
Extrapolated extents can be
classified as connectors.
Fault surfaces are extrapolated
Plesch et al., 2005
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Generating fault surfaces, from a trace and a dip estimate
A trace is digitized from a georeferenced map or assembled
from Qfaults and projected to
Digitized trace
the topographic/bathymetric
level.
A length (eg. 2000m) filtered
trace is shifted along the dip to
a first depth level (eg. 3km),
and a coarser trace to a deep
level (eg. 10km).
filtered trace
All traces are then connected to
a continuous fault surface.
filtered trace
View from below
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Alternatives represent substantially different
geometric definitions of a fault surface
Varying degrees of detail …
Different styles of fault
interaction at depth …
Whittier & Chino faults
Alternative 1
Alternative 2
Newport-Inglewood fault
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Each version of CFM represents a set of specific
alternative representations for each fault
Unique fault name and number
preferred
Alternative 1
Alternative 2
Interpolated 1
Interpolated 1
Interpolated 2
Interpolated 2
…
Alt. 1
Ext. 1
Ext. 1
Extrapolated 1
Extrapolated 1
Extrapolated 2
…
Alt. 2
Ext. 2
Ext. 3
N
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CFM Fault Attributes
In the database, each alternative representation will have a unique set
of attributes assigned to it, including:
• fault type (rl or ll strike-slip, thrust, normal, oblique …)
• surface or blind designation, connector
• average spatial uncertainty
• qualitative assessment of representation (1-5)
• slip rate range (CGS/SCFAD)
• primary reference list
• date generated
The database can be queried using these attributes.
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Model updates
Southern San Andreas:
- seismicity based updates
- compliance with Qfaults
improved
Borderlands:
- alternative representations of
thrusts which allow for all
modes of interaction with strikeslip faults.
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Model updates in progress
Revision of naming and numbering system:
- hierarchical: Peninsular Ranges – San Jacinto fault – San Bernardino section –
San Jacinto-Claremont fault – vertical
- meaningful numbers: two digits for each level
- reflects system behaviour
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Model updates, UCERF3 relevance
Southern San Andreas:
- additional sources
Blind Palm Springs fault
North Palm Springs fault
Mecca Hills - Hidden Springs
fault
- modified sources that allow
multiple paths for SAF rupture
Banning
Garnet Hill
San Gorgonio Pass
Mission Creek
Borderlands:
- discussed in dedicated
presentation
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Regional overview
SF Bay area
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Regional overview
S. Coast Ranges/S Joaquin Valley
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Regional overview
S. Coast Ranges/S Joaquin Valley
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Regional overview
Sierra Nevada/Mammoth/Long Valley
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Regional overview
Sierra Nevada/Mammoth/Long Valley
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Regional overview
N. Coast Ranges/Sacramento Valley
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Regional overview
N. Coast Ranges/Sacramento Valley
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Regional overview
Cascadia/Klamath Mountains/Modoc
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Regional overview
Cascadia/Klamath Mountains/Modoc
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Seismogenic thickness surface for NoCal


Nazareth & Hauksson
(2004) use the depth where
99.9% of the total moment
in a vertical column was
released
Steps:




Selection of events
Gridding and
computation
Filtering of low quality
cells
Smooth interpolation
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Seismogenic thickness surface for NoCal


Central Valley has little
seismicity in some
places.
Mask nodes in depth
surface which are more
than 30 km away from
closest grid point used
in interpolation.
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Generating fault surfaces, from the USGS Bay area
model and Qfaults
Bay area model fault is
extracted and compared to
Qfault representation.
The top of the fault is adjusted
to conform to topography, and
its length adjusted to conform to
Qfaults.
Qfault trace
Hayward representation
in Bay area model
Rogers Creek representation
in SCFM
Qfault trace
Calaveras representation
in SCFM
Hayward representation
in SCFM