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Statewide 3D Community Fault Model (SCFM)A statewide community-based, object-oriented, 3-D representation of active faults in California.

Presentation Outline1) Model overview2) Model components3) Fault construction4) Model updates

… for use in:• Fault systems analysis• Seismic hazard assessment...

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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 architectureTriangulated 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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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 extrapolatedPlesch et al., 2005

Generating fault surfaces

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Generating fault surfaces, from a trace and a dip estimate

A trace is digitized from a geo-referenced map or assembled from Qfaults and projected to 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).

All traces are then connected to a continuous fault surface.

View from below

filtered tracefiltered trace

Digitized traceDigitized trace

filtered trace

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Alternatives represent substantially different geometric definitions of a fault surface

Alternative 1

Alternative 2

Newport-Inglewood fault

Whittier & Chino faults

Varying degrees of detail …Different styles of fault interaction at depth …

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Each version of CFM represents a set of specific alternative representations for each fault

Unique fault name and number

Alternative 1 Alternative 2

Interpolated 1

Interpolated 2

Extrapolated 1

Interpolated 1

Interpolated 2

Extrapolated 1

Extrapolated 2

…preferred

…

Alt. 1 Alt. 2

Ext. 1

Ext. 1

Ext. 2

Ext. 3

N

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CFM Fault AttributesIn 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 strike-slip 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 relevanceSouthern San Andreas:- additional sources

Blind Palm Springs faultNorth Palm Springs faultMecca Hills - Hidden Springs fault

- modified sources that allow multiple paths for SAF rupture

BanningGarnet HillSan Gorgonio PassMission Creek

Borderlands:

- discussed in dedicated presentation

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Regional overviewSF Bay area

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Regional overviewS. Coast Ranges/S Joaquin Valley

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Regional overviewS. Coast Ranges/S Joaquin Valley

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Regional overviewSierra Nevada/Mammoth/Long Valley

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Regional overviewSierra Nevada/Mammoth/Long Valley

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Regional overviewN. Coast Ranges/Sacramento Valley

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Regional overviewN. Coast Ranges/Sacramento Valley

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Regional overviewCascadia/Klamath Mountains/Modoc

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Regional overviewCascadia/Klamath Mountains/Modoc

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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

Seismogenic thickness surface for NoCal

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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.

Hayward representationin SCFM

Qfault trace

Qfault trace

Calaveras representationin SCFM

Rogers Creek representationin SCFM

Hayward representationin Bay area model