Upload
solomon-eaton
View
217
Download
0
Tags:
Embed Size (px)
Citation preview
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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...
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
SCEC Community Fault Model, NoCal• Version 1.5 available• > 110 faults represented• Includes alternative representations• iterated through workshop• available for review via SCEC-VDO
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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. •
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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 …
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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.
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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.
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewSF Bay area
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewS. Coast Ranges/S Joaquin Valley
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewS. Coast Ranges/S Joaquin Valley
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewSierra Nevada/Mammoth/Long Valley
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewSierra Nevada/Mammoth/Long Valley
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewN. Coast Ranges/Sacramento Valley
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewN. Coast Ranges/Sacramento Valley
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewCascadia/Klamath Mountains/Modoc
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
Regional overviewCascadia/Klamath Mountains/Modoc
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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.
EARTHQUAKE CENTERSOUTHERN CALIFORNIA
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