U.S. Geological Survey 20040929 171207 GMT Version 3.0 Map http://earthquake.usgs.gov/shakemap ShakeMap is designed as a rapid response tool to portray the extent and variation of ground shaking throughout the affected region immediately following significant earthquakes. Ground motion and intensity maps are derived from peak ground motion amplitudes recorded on seismic sensors (accelerometers), with interpolation based on both estimated amplitudes where data are lacking, and site amplification corrections. Color-coded instrumental intensity maps are derived from empirical relations between peak ground motions and Modified Mercalli intensity. This ShakeMap describes the event: 51148806, 8 km NW of Parkfield, CA As a rapid response tool, the ShakeMap ground motion values are used for emergency response, loss estimation, assessment of damage to the lifeline and utility networks, and for providing information to the general public. 20040929 171207 GMT ground condition Complete As needed -121.742 -119.242 36.785 35.119 None ShakeMap peak ground motions shaking intensity instrumental intensity earthquake damage Advanced National Seismic Systems (ANSS) California Integrated Seismic Network (CISN) None California none none USGS Advanced National Seismic System (ANSS) David J. Wald Geophysicist mailing

U.S. Geological Survey P.O. Box 25046, Mail Stop 966

Denver CO 80225-0046 USA (303) 273-8441 (303) 273-8600 wald@usgs.gov http://earthquake.usgs.gov/shakemap/nc/shake/51148806/intensity.html Instrumental Intensity ShakeMap within a web page; all other ShakeMap maps and products can be accessed from this site. Typically the image itself is 600x400 pixels and about 100k bytes in size. JPEG Wald, D.J. Quitoriano, V. Heaton, T.H. Kanamori, H. Scrivner, C.W. Worden, C.B. 1999 Earthquake Spectra Vol. 15, No. 3 pp 537-556 http://earthquake.usgs.gov/shakemap/nc/shake/about.html#references Wald, D.J. Quitoriano, V. Heaton, T.H. Kanamori, H. 1999 Earthquake Spectra Vol. 15, No. 3 pp 557-564 http://earthquake.usgs.gov/shakemap/nc/shake/about.html#references Wald, D.J. Worden, C.B. Quitoriano, V. Pankow, K. 2003 U.S. Geological Survey [Open File Report] [ZZZ-03] [160 pp] Slight variations in peak ground motions and spectral values may depend on processing. Corrections or changes in station and amplitude information are reflected by the authoritative seismic network. In addition, changes in magnitude may result in changes to estimated ground motions in areas with sparse seismic station coverage. Ground motion data are direct measurements only at the location of seismic stations; all other data are interpolated (as described in the citations). Seismic station coverage varies in density as well as instrumentation across the region in question. Uncertainty in the reported ground motions generally increases with distance from seismic stations, and in areas of very low station density may be largely the product of empirical relationships. Uncertainties in ground motions may also arise from inaccurate ground motion amplitudes from seismic stations, or inaccurate information regarding earthquake epicenter or magnitude, as reported by the generating network. Included in this version are data available up to the time processed. Additional data (seismic stations) may be added at a later time. Shaking maps are prepared by contouring shaking information interpolated onto a square grid uniformly sampled at a spacing of 1 minute (about 1.6 km) throughout California. If there were stations at each of the tens of thousands of grid points, then the creation of shaking maps would be relatively simple. Of course stations are not available for all of these grid points, and in many cases grid points may be tens of kilometers from the nearest reporting station. The overall mapping philosophy is to combine information from individual stations, geology (representing site amplification), and the distance to the epicenter or causative fault to create the best composite map. The procedure produces reasonable estimates at grid points located far from available data, while preserving the detailed shaking information available for regions where there are stations nearby. Estimation of shaking over the regional extent for an earthquake in California is obtained by the spatial interpolation of the measured ground motions with geologically based frequency and amplitude-dependent site corrections. We use the California Site Condition Map (California Geological Survey, CGS) maps of National Earthquake Hazard Reduction Program (NEHRP) classification site conditions as the basis for our site corrections. These site condition maps have coverage throughout the state at 1:250,000 scale (Wills et al., 2000). We use the amplification factors of Borcherdt et al. (1994). In addition, ShakeMap ground motions in regions of sparse station spacing are estimated using ground motion regression, initially from a point location at the epicenter. Later, as information about fault dimensions became available (in the form of aftershocks, source rupture models, and observed surface slip), the fault location and rupture dimensions are used as the basis for ground motion estimation. First, peak ground motion parameters are recovered for each station and associated with a particular earthquake origin time and epicenter. We then create a coarse, uniformly spaced grid of 30-km spaced "phantom" stations. Peak ground motions and spectral acceleration values are assigned to each coarse grid point using the attenuation relationship of Boore et al. (1997) distance attenuation relationship for rock sites and the magnitude of the earthquake and distance to each grid point. In practice, we apply a static correction to the amplitudes of the regression by using the network-determined magnitude, predicting the observed amplitudes, and correcting for an amplitude bias term between the predictions and the data. Site corrections are then used to interpolate from ground motions recorded on a fairly sparse, non-uniformly spaced network of stations to maps showing spatially continuous functions (i.e., contours). Prior to interpolation, we reduce the ground motion amplitudes to a common reference, in this case bedrock motions. Peak ground motion amplitudes from the seismic stations are corrected to rock site conditions; and the observations (corrected to rock) and the coarse phantom stations (computed for rock) are then interpolated to a fine rock site grid (roughly 1.6-km spacing). We scale the peak acceleration (PGA) amplitude with the Borcherdt et al. (1994) short-period amplification factors while the peak ground velocity (PGV) values are corrected with the mid-period factors. Response spectral values are scaled by the short-period factors at 0.3 sec, and by the mid-period response at 1.0 and 3.0 seconds. The site correction procedure is applied so that the original data values are returned at each station; hence, the actual recorded motions are preserved in the process and the final contours reflect the observations wherever they exist. Next, the interpolated rock grid is corrected at each point for local site amplification and instrumental intensity map is generated by relating the peak ground acceleration or velocity at each grid point to intensity as described by Wald et al. (1999). This fine grid is saved and exported to the file "grid.xyz". A continuous surface is also fit to the fine grid to produce the contour maps and GIS formatted maps. 20040929 171207 GMT 0.017 0.017 Decimal degrees World Geodetic System 1984 WGS 84 6378137 298.257 mmi.dbf (shapefile from "shape.zip" download file) Polygons of estimated instrumental intensity ESRI Shapefile Technical Description GRID_CODE Estimated instrumental intensity (double) Wald, et al., Relationship between Peak Ground Acceleration, Peak Ground Velocity, and Modified Mercalli Intensity for Earthquakes in California, Earthquake Spectra, Vol. 15, No. 3, 1999, pp 557-564. 0.0 10.0 Intensity 0.1 VALUE Estimated instrumental intensity (double) Wald, et al., Relationship between Peak Ground Acceleration, Peak Ground Velocity, and Modified Mercalli Intensity for Earthquakes in California, Earthquake Spectra, Vol. 15, No. 3, 1999, pp 557-564. 0.0 10.0 Intensity 0.1 pga.dbf (shapefile from "shape.zip" download file) Polygons of peak ground motion (acceleration) ESRI Shapefile Technical Description GRID_CODE Peak ground motion (acceleration, as integer percent of g) self-evident -200.0 200.0 percent of g 4 VALUE Peak ground motion (acceleration, as fraction of g) self-evident -200.0 200.0 fraction of g 0.04 pgv.dbf (shapefile from "shape.zip" download file) Polygons of peak ground motion (velocity) ESRI Shapefile Technical Description GRID_CODE Peak ground motion (velocity in cm/s, integer) self-evident -500.0 500.0 cm/s 4 VALUE Peak ground motion (velocity in cm/s, double) self-evident -500.0 500.0 cm/s 4 psa03.dbf (shapefile (from "shape.zip" download file) Polygons of spectral acceleration at 0.3 s period, 5% damping ESRI Shapefile Technical Description GRID_CODE Spectral acceleration at 0.3 s period, 5% damping (integer percent of g) self-evident -400.0 400.0 percent of g 4 VALUE Spectral acceleration at 0.3 s period, 5% damping (fraction of g) self-evident -400.0 400.0 fraction of g 0.04 psa10.dbf (shapefile from "shape.zip" download file) Polygons of spectral acceleration at 1.0 s period, 5% damping ESRI Shapefile Technical Description GRID_CODE Spectral acceleration at 1.0 s period, 5% damping (integer percent of g) self-evident -400.0 400.0 percent of g 4 VALUE Spectral acceleration at 1.0 s period, 5% damping (fraction of g) self-evident -400.0 400.0 fraction of g 0.04 psa30.dbf (shapefile from "shape.zip" download file) Polygons of spectral acceleration at 3.0 s period, 5% damping ESRI Shapefile Technical Description GRID_CODE Spectral acceleration at 3.0 s period, 5% damping (integer percent of g) self-evident 2 34 percent of g 4 VALUE Spectral acceleration at 3.0 s period, 5% damping (fraction of g) self-evident -400.0 400.0 fraction of g 0.04 pga.dbf (shapefile from "hazus.zip" download file) Polygons of "mean" ground motion (acceleration), scaled from recorded peak values by 15% (empirical correction from peak to mean) to conform to HAZUS input requirements. ESRI Shapefile Technical Description GRID_CODE Mean ground motion (acceleration, as integer percent of g) self-evident -200.0 200.0 percent of g 4 VALUE Mean ground motion (acceleration, as fraction of g) self-evident -200.0 200.0 fraction of g 0.04 pgv.dbf (shapefile (from "hazus.zip" download file) Polygons of "mean" ground motion (velocity), scaled from recorded peak values by 15% (empirical correction from peak to mean) to conform to HAZUS input requirements. ESRI Shapefile Technical Description GRID_CODE Mean ground motion (velocity in inches/sec, integer) self-evident -200.0 200.0 cm/s 2 VALUE Mean ground motion (velocity in inches/s, double) self-evident -500.0 500.0 cm/s 2.0 psa03.dbf (shapefile from "hazus.zip" download file) Polygons of "mean" spectral acceleration at 0.3 s period, 5% damping, scaled from recorded peak values by 15% (empirical correction from peak to mean) to conform to HAZUS input requirements. ESRI Shapefile Technical Description GRID_CODE Mean Spectral acceleration at 0.3 s period, 5% damping (integer percent of g) self-evident -400.0 400.0 percent of g 4 VALUE Mean spectral acceleration at 0.3 s period, 5% damping (fraction of g), scaled from recorded peak values by 15% (empirical correction from peak to mean) to conform to HAZUS input requirements. self-evident -400.0 400.0 fraction of g 0.04 psa10.dbf (shapefile from "hazus.zip" download file) Polygons of mean spectral acceleration at 1.0 s period, 5% damping, scaled from recorded peak values by 15% (empirical correction from peak to mean) to conform to HAZUS input requirements. ESRI Shapefile Technical Description GRID_CODE Mean spectral acceleration at 1.0 s period, 5% damping (integer percent of g) self-evident -400.0 400.0 percent of g 4 VALUE Mean spectral acceleration at 1.0 s period, 5% damping (fraction of g), scaled from recorded peak values by 15% (empirical correction from peak to mean) to conform to HAZUS input requirements. self-evident -400.0 400.0 fraction of g 0.04 File grid.xyz Values of the peak amplitudes at the ShakeMap map grid nodes. File is ASCII text in the following format: First line is a header, space-delimited, with all of the following: ><name/CUSPID of event> <mag> <epicentral lat> <epicentral lon> ><MMM DD YYYY> <HH:MM:SS timezone> ><W bound> <S bound> <E bound> <N bound> >(Process time: <time>) <Location String> The first 'time' field is the time of the event. 'Process time' is the time this file was last updated. For large or historic earthquakes the "Location String" will usually be the name of the earthquake, otherwise it will be something of the form "12.1 mi. SSW of Carpinteria, CA" The remaining lines are of the form: ><lon> <lat> <pga> <pgv> <mmi> <psa03> <psa10> <psa30> >pga = peak ground motion (acceleration, as percent of g) >pgv = peak ground motion (velocity in cm/s) >mmi = estimated instrumental intensity >psa03 = spectral acceleration at 0.3 s period, 5% damping (percent of g) >psa10 = spectral acceleration at 1.0 s period, 5% damping (percent of g) >psa30 = spectral acceleration at 3.0 s period, 5% damping (percent of g) http://earthquake.usgs.gov/shakemap/nc/shake/51148806/about_formats.html David J Wald U.S. Geological Survey, GEO-CR-GHT Geophysicist mailing address

P.O. Box 25046

Lakewood CO 80225 USA 303-273-8441 626-583-7827 wald@usgs.gov Shakemap data for 51148806 Some USGS information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete, and conclusions drawn from such information are the sole responsibility of the user. These are automatic computer generated maps and have not necessarily been checked by human oversight, so they may contain errors. Further, the input data is raw and unchecked, and may contain errors. Contours can be misleading since data gaps may exist. Caution should be used in deciding which features in the contour patterns are required by the data. Ground motions and intensities can vary greatly over small distances, so these maps are only approximate; when maps are enlarged beyond the limits of the original data in an effort to show small areas, the maps are unreliable. These maps are preliminary in nature and will be updated as data arrives from distributed sources. The estimated intensity map is derived from ground motions recorded by seismographs and represents Modified Mercalli Intensities (MMI's) that are likely to have been associated with the ground motions. Unlike conventional Modified Mercalli Intensities, the estimated intensities are not based on observations of the earthquake effects on people or structures. Locations within the same intensity area will not necessarily experience the same level of damage since damage depends heavily on the type of structure, the nature of the construction, and the details of the ground motion at that site. For this reason more or less damage than described in the MMI scale may occur. Large earthquakes can generate very long-period ground motions that can cause damage at great distances from the epicenter; although the intensity estimated from the ground motions may be small, significant effects to large structures (bridges, tall buildings, storage tanks) may be notable. The ground motion levels and descriptions associated with each intensity value are based on recent damaging earthquakes. There may be revisions in these parameters as more data become available or from further improvements in methodology. ESRI shapefile Ground shaking intensity, acceleration, and velocity contours unzip 2 megabytes http://earthquake.usgs.gov/shakemap/nc/shake/51148806/download/shape.zip http://earthquake.usgs.gov/shakemap/nc/shake/51148806/download/hazus.zip Text 1.0 Within lines, values are delimited by spaces. First line is a header containing <name/CUSPID of event> <mag> <epicentral lat> <epicentral lon> <MMM DD YYYY> <HH:MM:SS timezone> <W bound> <S bound> <E bound> <N bound> (Process time: <time>) <Location String> The remaining lines contain <lon> <lat> <pga> <pgv> <mmi> <psa03> <psa10> <psa30> Ground-shaking intensity and acceleration data unzip 0.5 megabytes http://earthquake.usgs.gov/shakemap/nc/shake/51148806/download/grid.xyz.zip none 20040929 USGS Advanced National Seismic System (ANSS) David J. Wald Geophysicist mailing

U.S. Geological Survey P.O. Box 25046, Mail Stop 966

Denver CO 80225-0046 USA (303) 273-8441 (303) 273-8600 wald@usgs.gov Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998