United States Geological Survey Open File Report 2004-1437 Digital database of faulting accompanying the 1966 Parkfield, California, earthquake Digital database prepared by: Christopher J. Crosby, 2004 Geology by: Lienkaemper, J. J. and R. D. Brown, Map of faulting accompanying the 1966 Parkfield, California, earthquake, U.S. Geol. Surv. Open File Rep., 85-661, 1985. Digital database preparation completed as part of NSF grant EAR-0310357 "Kilometer- scale fault zone structure and Kinematics along the San Andreas Fault near Parkfield, California" supervised by Dr. Ramon Arrowsmith at Arizona State University, Tempe, AZ. INTRODUCTION This digital map database is prepared from a previously published map by Lienkaemper and Brown (1985). The fault database delineates tectonic ground rupture associated with the 1966 Parkfield, California earthquake and observation localities along the surface rupture where geologic data were gathered. Our goal is to provide earthquake scientists working along the San Andreas fault near Parkfield with a digital version of the Lienkaemper and Brown (1985) map that may be used for field work, input to geophysical models, and for comparison to the next Parkfield earthquake. METHODS The database was compiled using ArcGIS versions 8.3 and 9.0, a commercially available Geographic Information System (GIS) produced by the Environmental Systems Research Institute (ESRI). The three 1:12,000 scale paper maps comprising the plates from Lienkaemper and Brown (1985) were scanned on a high-resolution, large format drum scanner at a resolution of 500 dpi. These scans were then georeferenced to U.S. Geological Survey Digital Raster Graphics (DRGs) of the Parkfield region using the "Georeferencing" tool available in ArcGIS. The projection of the georeferenced maps was set to UTM North American Datum 1983, zone 10N. The rupture trace and observation localities, as mapped by Lienkaemper and Brown (1985), were then "heads up" digitized into shapefiles at a constant scale of 1:2500. Observation data for the localities noted by Lienkaemper and Brown (1985) in Table 1 were manually entered into the attribute table of the shapefiles to include these important field observations in the digital database. FILES: Files have been grouped and compressed as zip files to ease downloading. The file OFR_2004-1437.zip contains the following files: 1. rupture_trace.shp – This file contains all tectonic ground rupture mapping as depicted in Lienkaemper and Brown (1985). Where Lienkaemper and Brown chose to depict en echelon steps in the rupture trace (when mapped from 1:6,000 scale aerial photography), we simplified by depicting the rupture with a through- going, best fitting line. En echelon rupture depiction when mapped at 1:24,000 was preserved in the digital database. The following attribute information is included in this shapefile: certainty – an indication of confidence in mapped fault trace. Values of "certain" were entered where Lienkaemper and Brown mapped a solid fault trace. "Uncertain" was used where the fault trace was inferred and "queried" was entered where the map showed a queried fault trace. map_depict – notes whether Lienkaemper and Brown (1985) were mapping on 1:6000 aerial photography or 1:24000 topographic maps. 2. obs_loc.shp – This file contains all observation point locality information as presented on map plates 1-3 and in Table 1 in Lienkaemper and Brown (1985). The following attribute information is included in the shapefile: loc_num - Locality number used on Lienkaemper and Brown (1985) map. frac_azim - Fracture azimuth. 360 is true north. 0 indicates no value reported, not a north azimuth. frcazim_er - +/- value representing error range for azimuth as reported by Lienkaemper and Brown. 0 indicates no value reported. frac_lengt - Maximum length of fractures (ft). frac_space - Spacing between fractures (ft). frac_rlsep - Right-lateral separation on fractures (in). 0 indicates no value reported. frcrlsp_er - +/- value representing error range for right-lateral separation measurements (in). 0 indicates no value reported. frac_exten - Extensional component of separation on fractures (in). zone_azim - Fault zone azimuth. 360 is true north. 0 indicates no value reported. znazim_err - +/- value representing error range for azimuth as reported by Lienkaemper and Brown. 0 indicates no value reported. zone_width - Width of fracture zone (ft). observer - Field observer. obs_date - Date of observation. codes - Codes used in Lienkaemper and Brown (1985), Table 1: "F12" - locality # used in Brown and Vedder (1967). "B-8" - pinhole in air photo and notebook number of R.D. Brown notes used to supplement table. "K-5" - pinhole in air photo and notebook number of R. Kachadoorian; notes missing. "V-3" - pinhole in air photo and notebook number of J.G. Vedder; notes missing. "R-4" - pinhole in air photo; benchmark installed in 1966 fractures; R-1 and R-2 not pin-holed. QH - quadrilateral for measuring after slip; see Wallace and Roth (1966). 3. obs_area.shp - This file contains all observation area locality information as presented on map plates 1-3 and in Table 1 in Lienkaemper and Brown (1985). Information in this file differs from the obs_loc.shp in that it applies to a section of the ground rupture as opposed to a single point observation. Attribute information and format are identical to that of the obs_loc.shp file. 4. rupture_trace_6k.csv – Comma-delimited text file of the coordinates for all fault traces mapped at 1:6000 scale. Coordinates are referenced to the WGS84 datum (lat./long.) for each point. Fault traces are grouped (separated by two blank lines) to denote discrete fault segments, with initial and final points of each file corresponding to segment end points and intermediate points corresponding to segment vertices. 5. rupture_trace_24k.csv - Comma-delimited text file of the coordinates for all fault traces mapped at 1:24000 scale. Coordinates are referenced to the WGS84 datum (lat./long.) for each point. Fault traces are grouped (separated by two blank lines) to denote discrete fault segments, with initial and final points of each file corresponding to segment end points and intermediate points corresponding to segment vertices. 6. 66_rupturemap_DEM.pdf – 30x36 inch Adobe Acrobat file of rupture map and observation locality information overlain on hillshade of 10 meter USGS digital elevation model (DEM) data. File has been generated at 300 dpi. 7. 66_rupturemap_DOQ.pdf – 30x36 inch Adobe Acrobat file of rupture map and observation locality information overlain on USGS digital orthophoto quarter quadrangles (DOQQs). File has been generated at 300 dpi. 8. OF99_661PKFD.pdf – Adobe Acrobat file of original informational pamphlet accompanying Lienkaemper and Brown (1985) Open File Report. PROJECTION INFORMATION (not applicable to comma-delimited lat./long. files) Horizontal coordinate system Projected coordinate system name: NAD_1983_UTM_Zone_10N Geographic coordinate system name: GCS_North_American_1983 Details Grid Coordinate System Name: Universal Transverse Mercator UTM Zone Number: 10 Transverse Mercator Projection Scale Factor at Central Meridian: 0.999600 Longitude of Central Meridian: -123.000000 Latitude of Projection Origin: 0.000000 False Easting: 500000.000000 False Northing: 0.000000 Planar Coordinate Information Planar Distance Units: meters Coordinate Encoding Method: coordinate pair Coordinate Representation Abscissa Resolution: 0.000064 Ordinate Resolution: 0.000064 Geodetic Model Horizontal Datum Name: North American Datum of 1983 Ellipsoid Name: Geodetic Reference System 80 Semi-major Axis: 6378137.000000 Denominator of Flattening Ratio: 298.257222