Electronic Supplement to
Location of the Focus and Tectonics of the Focal Region of the California Earthquake of 18 April 1906

by A. Lomax

3D visualization and data files for NonLinLoc (NLL) relocations and FPFIT mechanism determinations presented in the printed paper

3D Java visualization

The Java visualization using the Java Seismicity Viewer (http://alomax.net/seismicity) shows the NLL (http://alomax.net/nlloc) relocations of recent (1971-2007) micro-earthquakes in the study region. The pdf for the preferred mainshock location of Lomax (2005) is represented by the red cloud of points. The likely focal volume is indicated by a 3-D polygon (orange lines). Approximate extent of NWSAF, WSF, SFP and DEEP cluster structures indicated by dashed lines. Thin magenta lines show simplified California faults; thick magenta lines show selected major faults from Bruns et al. (2002). PL, Point Lobos; LM, Lake Merced; DC, Daly City; PSP, Point San Pedro; SAFZ, San Andreas fault zone; GGF, Golden Gate fault; SGFZ, San Gregorio fault zone; SCF, Seal Cove fault. (see Figures 1 and 3 in the printed paper for details).

NLL maximum likelihood hypocenters are shown by color in depth: above -1km, brown; -1 to 2km, orange; 2 to 5km, yellow; 5 to 10km, green; 10 to 16km, blue; below 16km, magenta. In the printed paper events shallow than 2km depth are not shown.

Important: Due to the large size of the data files, and depending on the speed of your Internet connection, the 3D Java visualizations may take some time to initialize. The Java visualizations require the Java plug-in (v1.4 or higher) in your browser and that your network and browser security allow Java applets and active content. To download the Java plug-in visit: http://www.java.com

Relocations, 1906 pdf, Faulting Structures - All relocated hypocenters, 1906 pdf and likely focal volume, faulting structures and basic map elements.

Relocations - All relocated hypocenters and basic map elements only.

Focal mechanism P and T axes - Focal mechanism P and T axes and basic map elements only. Select Show Horiz P/T axes for: Thrust/Normal/Strike-slip to display axis closest to horizontal for Thrust/Normal/Strike-slip events defined as described in the printed paper. Select MaxLikelihood to display relocated hypocenters.

Viewing tips:

Results files

Results files from NLL relocations and FPFIT mechainism determinations presented in the printed paper.

locsum_cencal_X.hyp.zip - [1.7 Mb] NLL final relocation results with mechanism and phase data for 887 selected locations (see printed paper for details). In NLLoc Hypocenter-Phase format (see NLL documentation: http://alomax.net/nlloc -> Formats -> Location Files -> NLLoc Hypocenter-Phase file)

cencal_velmod2_CUT_EDT_LOCGAU2.sum.grid0.loc.stat_totcorr - [19kb] NLL final station corrections. In NLLoc Phase Statistics format (see NLL documentation: http://alomax.net/nlloc -> Formats -> Location Files -> Phase Statistics file)

fpfit_cencal.zip - [11 Mb] FPFIT input, data and output files for all NLL locations before selection (see printed paper for details). In HypoInverse Archive format and standard FPFIT formats (see Reasenberg and Oppenheimer, 1985) .

Files required to run NLL relocations

Input and data files for NLL relocation results presented in the printed paper. See NLL documentation: http://alomax.net/nlloc for more information on installing and running NLL.

cencal_velmod2_CUT_EDT_LOCGAU2.in - [17kb] NLL control file (see NLL documentation: http://alomax.net/nlloc -> Control File)

model/ - Files required to run the NLL program Grid2Time to calculate and store travel times: 3-D, P velocity model (USGS, 2005; Brocher, 2005) in NLL 3D Grid File format and station locations in GRSRCE format (see NLL documentation: http://alomax.net/nlloc -> Grid2Time)

usgs_cat_poly_20070614_ALL.txt.zip - [2.2Mb] USGS NCSN Catalog + Phase in Hypoinverse format for all events in study region. In NCEDC Y2K Hypoinverse catalog and phase format (see: >Northern California Earthquake Data Center (NCEDC; http://www.ncedc.org))

locsum_CUT_STEPOVER_NEW.hyp.zip - [740kb] NLL initial locations and phase data for events only within the sub-region used to develop stations corrections (see printed paper for details). In NLLoc Hypocenter-Phase format (see NLL documentation: http://alomax.net/nlloc -> Formats -> Location Files -> NLLoc Hypocenter-Phase file)


Brocher, T.M. (2005). Compressional and Shear Wave Velocity Versus Depth in the San Francisco Bay Area, California: Rules for USGS Bay Area Velocity Model 05.0.0, U.S. Geol. Surv. Open-File Rept., 2005-1317.

Bruns, T.R., A.K. Cooper, P.R. Carlson, and D. S. McCulloch (2002). Structure of the Submerged San Andreas and San Gregorio Fault Zones in the Gulf of the Farallones off San Francisco, California, from High-Resolution Seismic-Reflection Data, in Crustal Structure of the Coastal and Marine, San Francisco Bay Region, California, T. Parsons (ed.), U.S. Geol. Surv. Prof. Paper 1658. Available online: http://geopubs.wr.usgs.gov/prof-paper/pp1658/

Lomax, A. (2005). A Reanalysis of the Hypocentral Location and Related Observations for the Great 1906 California Earthquake, Bull. Seism. Soc. Am., 95, 861?877.

Reasenberg, P. & Oppenheimer, D. (1985). FPFIT, FPPLOT and FPPAGE: FORTRAN computer programs for calculating and plotting earthquake fault-plane solutions, U.S. Geol. Surv. Open-File Rep., 85739.

USGS (2005). 3D Geologic and Seismic Velocity Model of the San Francisco Bay Region, http://quake.wr.usgs.gov/research/3Dgeologic/.

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