SCEC Community Fault Model (CFM)

Introduction

The SCEC Community Fault Model (CFM) is an object-oriented, three-dimensional representation of active faults in southern California and adjacent offshore basins. For each fault object, the CFM provides triangulated surface representations (t-surfs) in several resolutions, fault traces in several different file formats (shape files, GMT plain text, and GoogleEarth kml), and complete metadata including references used to constrain the surfaces. The CFM faults are defined based on all available data including surface traces, seismicity, seismic reflection profiles, well data, geologic cross sections, and various other types of data and models. The CFM serves the Southern California Earthquake Center (SCEC) as a unified resource for physics-based fault systems modeling, strong ground-motion prediction, and probabilistic seismic hazards assessment (e.g., UCERF3). Together with the Community Velocity Model (CVM-H 15.1.0), the CFM comprises SCEC's Unified Structural Representation of the Southern California crust and upper mantle (Shaw et al., 2015).

Current Model Version: CFM6.1

The current version of the SCEC Community Fault Model version 6.1 (CFM6.1) and is partially the result of a community evaluation of CFM5.3. CFM6.1 serves as the latest update to Plesch et al. (2007) and builds on previous CFM releases. New to CFM6.1 are two additional separate and fully-documented sub models: the ruptures and alternatives model. In total, CFM6.1 comprises the following components:

1. The CFM6.1 Preferred Model: a set of 443 fault objects that constitute the preferred set of active faults in southern California.
2. The CFM6.1 Rupture Model: a set of 13 fault objects assembled from the CFM6.1 preferred model that ruptured during selected significant historic events. These are not earthquake source models, but are representations of the entire fault surfaces where a significant historic rupture occurred. This model is intended to indicate which CFM fault objects were involved with selected significant historic ruptures.
3. The CFM6.1 Alternatives: a set of 38 alternative representations where structural differences have been proposed that could potentially significantly impact fault mechanics and associated seismic hazards. These alternative representations were selected based on community rankings following a comprehensive evaluation of the CFM that took place in May of 2022.

Including all sub models, the CFM6.1 incorporates 494 fully-documented objects. If you use the CFM, we would appreciate you citing the DOI where the archive is stored.

CFM6.1 Change Log

CFM6.1 differs from CFM6.0 in several ways, as described below.

1. The Southern San Andreas fault was updated to the dipping model based on Fuis et al., (2012) which also contains a portion of the Banning fault.

   • SAFS-SAFZ-MULT-Southern_San_Andreas_fault_and_Banning-CFM6 is now the preferred representation. Naming of this object is challenging because this object contains both what is typically referred to as the Southern San Andreas fault and a portion of the Banning fault. This is included in the metadata comments.

   • SAFS-SAFZ-COAV-Southern_San_Andreas_fault-CFM4 (Steeply dipping) is now an alternative representation, SAFS-SAFZ-COAV-Southern_San_Andreas_fault-ALT6.

2. The East Shoreline fault has been shortened to not extend north of Mecca Hills. 

   • SAFS-SAFZ-COAV-East_Shoreline_fault-CFM6 is the preferred version (same name in CFM6.0) and now no longer extends north of Mecca Hills. This is consistent with Janecke et al. (2019) where north of Mecca Hills the fault presence and location is mapped as speculative.

   • The longer SAFS-SAFZ-COAV-East_Shoreline_fault-CFM5 is now provided as an alternative, SAFS-SAFZ-COAV-East_Shoreline_fault-ALT6.

3. The Malibu Coast fault (east segment) has been truncated and merges with the Malibu Coast fault (west segment) and no longer extends farther to the west. The object name, WTRA-SFFS-SMMT-Malibu_Coast_fault_east-CFM6, remains the same.

Directory Structure and Contents of the CFM6 Archive

The archive directory structure is as follows:

doc/
Documentation and metadata, which include an MS Excel spreadsheet with detailed metadata about each fault surface. Metadata for the preferred, rupture, and alternative models are provided in separate but otherwise identically formatted sheets within the file. All faults contain references to the works that helped to define the 3D fault surface geometry. More information about the metadata columns is provided in doc/README.txt

obj/preferred/
obj/ruptures/
obj/alternatives/
These directories contain the model components for the preferred, rupture, and alternative models, respectively. Each model contains an identical directory structure, which is described below using the preferred model as an example.

obj/preferred/native/
The CFM6.1 preferred fault surfaces in gocad tsurf format using the native mesh. The native mesh uses a variable mesh resolution. Smaller triangles generally indicate where a fault is well-constrained by data. All tsurf files are provided in UTM zone 11 using the NAD27 datum (EPSG:26711).

obj/preferred/500m/
The CFM6.1 preferred fault surfaces with a semi-regularized mesh of ~500m resolution in gocad tsurf format. All tsurf files are provided in UTM zone 11 using the NAD27 datum (EPSG:26711).

obj/preferred/1000m/
The CFM6.1 preferred fault surfaces with a semi-regularized mesh of ~1000m resolution in gocad tsurf format. All tsurf files are provided in UTM zone 11 using the NAD27 datum (EPSG:26711).

obj/preferred/2000m/
The CFM6.1 preferred fault surfaces with a semi-regularized mesh of ~2000m resolution in gocad tsurf format. All tsurf files are provided in UTM zone 11 using the NAD27 datum (EPSG:26711).

obj/preferred/traces/
Fault traces and upper tip lines (for blind faults) of the CFM6.1 preferred faults. While the CFM6.1 is a 3D model, it is often useful to make map-based visualizations of the model. The traces and blind faults are provided in several different formats described below.

obj/preferred/traces/gmt/
Fault traces and blind faults in Generic Mapping Tools multisegment ASCII format (i.e., plain text).

    .lonLat - Longitude/Latitude coordinates (WGS84 datum)
    .utm    - UTM zone 11 NAD27 datum (EPSG:26711)

obj/preferred/traces/kml/
Fault traces and blind faults in Google Earth .kml format (WGS84 datum). The kml files also contain selected metadata, which pops up if a fault is clicked on in the Google Earth interface.

obj/preferred/traces/shp/
Fault traces and blind faults in GIS shapefile format. Longitude/Latitude coordinates (WGS84 datum).

CFM Contributors

The current and past versions of the CFM would not be possible without contributions from numerous SCEC community members. We would like to thank the following CFM contributors:

Christine Benson, William Bryant, Sara Carena, Michele Cooke, James Dolan, Jessica Don, Gary Fuis, Eldon Gath, Judith Hubbard, Susanne Janecke, Yuval Levy, Lisa Grant Ludwig, Egill Hauksson, Thomas Jordan, Marc Kamerling, Mark Legg, Scott Lindvall, Harold Magistrale, Scott Marshall, Jonathan Matti, Craig Nicholson, Nathan Niemi, Michael Oskin, Sue Perry, George Planansky, Andreas Plesch, Thomas Rockwell, John Shaw, Peter Shearer, Christopher Sorlien, M. Peter Süss, John Suppe, Jerry Treiman, Franklin Wolfe, Robert Yeats, and every colleague that has participated in a CFM community evaluation. We could not make the CFM without this community effort.

CFM Evaluators

Before assembling CFM6.1, a team of SCEC colleagues participated in a rigorous evaluation of CFM5.3 in April-May of 2022. This evaluation was open to the SCEC community and focused on 23 critical fault representations where different proposed interpretations have the potential to significantly affect seismic hazards. This evaluation resulted in 14 new fault representations in the CFM6.1 preferred model. The lower ranked representations are now provided in the CFM6.1 alternative model. We would like to thank the following CFM evaluators for volunteering their time and expertise to this process:

Sinan Akçiz, Sara Carena, Michele Cooke, Tim Dawson, Jessica Don, Austin Elliot, Erik Frost, Gary Fuis, Athanassios Ganas, Eldon Gath, Alex Hatem, Susanne Janecke, Marc Kamerling, Christodoulos Kyriakopoulos, Mark Legg, Karen Luttrell, Chris Madugo, Scott Marshall, Andrew Meigs, Craig Nicholson, Nate Onderdonk, Alba Rodríguez Padilla, Andreas Plesch, Kate Scharer, John Shaw, Chris Sorlien, Franklin Wolfe, Doug Yule, Judy Zachariasen.

References

●      Evans, W. S., Plesch, A., Shaw, J. H., Pillai, N. L., Yu, E., Meier, M., & Hauksson, E. (2020). A Statistical Method for Associating Earthquakes with Their Source Faults in Southern California. Bulletin of the Seismological Society of America, 110(1), 213-225. doi: 10.1785/0120190115. SCEC Contribution 9057

●      Hauksson, E., Yang, W., and Shearer, P. M., "Waveform Relocated Earthquake Catalog for Southern California (1981 to 2011)"; Bull. Seismol. Soc. Am., Vol. 102, No. 5, pp.2239-2244, October 2012, doi: 10.1785/0120120010 SCEC Contribution 1528

●      Plesch, A., et al. (2007). "Community Fault Model (CFM) for Southern California." Bulletin of the Seismological Society of America 97: 1793-1802. SCEC Contribution 1134

●      Plesch, A., Marshall, S. T., Nicholson, C., Shaw, J. H., Maechling, P. J., & Su, M. (2020, 08). The Community Fault Model version 5.3 and new web-based tools. Poster Presentation at 2020 SCEC Annual Meeting. SCEC Contribution 10547

●      Shaw, J. H., Plesch, A., Tape, C., Suess, M., Jordan, T. H., Ely, G., Hauksson, E., Tromp, J., Tanimoto, T., Graves, R., Olsen, K., Nicholson, C., Maechling, P. J., Rivero, C., Lovely, P., Brankman, C. M., & Munster, J. (2015). Unified Structural Representation of the southern California crust and upper mantle. Earth and Planetary Science Letters, 415, 1-15. doi: 10.1016/j.epsl.2015.01.016. SCEC Contribution 2068