Relative earthquake-induced landslide susceptibility of Monterey County, California

Rosenberg, Lewis I. 2001 Relative earthquake-induced landslide susceptibility of Monterey County, California version 1.0 vector digital data withheld County of Monterey 2001 21st Century General Plan Update http://www.co.monterey.ca.us/gpu Landslide Relative landslide susceptibility from earthquakes was evaluated using a simplified version of the methodology developed for San Mateo County, California by the USGS (Wieczorek and others, 1985). This approach is based on analysis of geologic and topographic data. Geologic units shown on sheets 1 and 2 were reclassified into three categories based on their assumed strength characteristics. The vector strength polygons were then converted into a raster grid with a 200-foot cell size. Slope inclination was derived from U.S. Geological Survey 30-m Digital Elevation Model files using ArcView Spatial Analyst software. The resultant values of geologic strength grid and the slope inclination were calculated for each cell and reclassified into the three categories as shown on the susceptibility matrix. Finally, the raster map was converted into a vector map. The resulting data set shows that the areas of highest susceptibility include Carmel Valley, the southern Big Sur coast, the Arroyo Seco district, and the foothills of the southern Salinas Valley. The purpose of this map is to provide a comparison of relative landslide hazards for regional planning studies in Monterey County. The focus of the map is large (hundreds to thousands of feet in length or width) deep-seated landslides caused by strong shaking. Shallow landslides such as debris flows and rock falls are strongly dependent on local site conditions and therefore are not included on this map. en 2001 publication date In work Irregular -121.988436 -120.215485 36.939328 35.758959 5688082.197000 6201151.271000 1808760.143000 2227394.194000 None earthquakes landslides mass movements slope stability geologic hazards None Aromas Arroyo Seco Big Sur Bolsa Knolls Bradley Cachagua California Carmel Highlands Carmel Valley Carmel Valley Village Carmel-By-The-Sea Castroville Del Rey Oaks Gonzales Greenfield Jamesburg Jolon King City Lockwood Lucia Marina Monterey Monterey County Moss Landing Pacific Grove Pajaro Parkfield Pebble Beach Prunedale Salinas Salinas Valley San Ardo San Lucas Sand City Seaside Soledad Spreckels Tassajara Hot Springs United States Contact the Monterey County Environmental Resource Policy Department. These data may not be distributed without the written permission of the County of Monterey. Lew Rosenberg Consulting Geologist mailing address

P.O. Box 183

Templeton CA 93465-0183 (805) 434-1750 (805) 434-1750 Lrosenberg@thegrid.net Monday to Friday, 8 AM to 5 PM, Pacific Time ESRI ArcCatalog 9.3.1.3000 Feature Class All attributes created during the creation process were verified by displaying the lines in both the database and the spatial coverage, but no formal tests were performed. These data are believed to be logically consistent, although no tests were performed. Several assumptions were made in creating this map. The geologic strength data and slope inclinations were evaluated using a simplified version of the methodology developed by Wieczorek and others (1985) for their analysis of earthquake-induced landsliding in San Mateo County, California. Wieczorek and others (1985) used the Newmark method to estimate the amount of ground displacement of a landslide caused by an earthquake. Because of the lack of engineering data such as cohesion and shear strength for most of Monterey County and the lack of near-field strong motion records (with the exception of the sparsely settled Parkfield district) it was not possible to calibrate the San Mateo County methodology for Monterey County. However, because many of the same geologic units and faults are present in both San Mateo and Monterey Counties, these simplifying assumptions are appropriate. In summary, the Monterey County map is intended for regional planning purposes, but the relative susceptibilityboundaries may change slightly with the availability of sufficient quality and quantity engineering data for Monterey County. The landslide data are based on information compiled from geologic maps ranging from 1:2,400 to 1:125,000 scale, with the majority at 1:62,500 scale. Using the "map resolution" concept outined by R.R. Wahl (USGS Open-File Report 99-386, p. 96: where (Map scale denominator) / 2/ 1000 = map scale, in meters), the estimated horizontal error ranges from 1.2 m (1:2,400 scale) to 62.5 m (1:125,000 scale), with a typical error of 31.3 m (1:62,500) scale. This error level reflects the accuracy of the conversion from hard copy to digital maps; however, the overall accuracy may differ if the uncertainty in each individual map used in the compilation is included. Because the source authors do not quantitatively specify the estimate error in their mapping, it is not possible toinclude this in the overall horizontal positional accuracy report. The slope inclinations were derived from the USGS National Elevation Database file which is based on 7.5-minute quadrangles (30-m resolution). According to the USGS: "The accuracy of DEM data depends on the source and resolution of the data samples. DEM data accuracy is derived by comparing linear interpolation elevations in the DEM with corresponding map location elevations and computing the statistical standard deviation or root-mean-square error (RMSE). The RMSE is used to describe the DEM accuracy. For 7.5-minute DEM's derived from a photogrammetric source, 90 percent have a vertical accuracy of 7-meter RMSE or better and 10 percent are in the 8- to 15-meter range. For 7.5- and 15-minute DEM's derived from vector or DLG hypsographic and hydrographic source data, an RMSE of one-half of a contour interval or better is required. The 1-degree DEM data have an absolute accuracy of 130 meters horizontally and 30 meters vertically." U.S. GeoData Digital Elevation Models Fact Sheet 040-00 (April 2000) online at: http://mac.usgs.gov/mac/isb/pubs/factsheets/fs04000.html. In addition, the conversion from raster to vector format involved generalization of landslide susceptibility boundaries. The maximum amount of distortion is unknown, but is probably on the order of a few cells or about 600 feet. Therefore, this data set should only be used for regional planning and not for site-specific investigations. Rosenberg, Lewis I. 2001 Digital geologic map of Monterey County, California version 1.0 vector digital data County of Monterey 2001 21st Century General Plan Update http://www.co.monterey.ca.us/gpu CD-ROM 2001 publication date Rosenberg (2001) Lithologic units U.S. Geological Survey, EROS Data Center 1999 National Elevation Database 1 raster digital data Sioux Falls, SD USGS http://edcnts12.cr.usgs.gov/ned/ned.html 24000 CD-ROM 19990201 unknown publication date USGS (1999) Digital elevation model used to derived slope inclination Wieczorek, G.F. Wilson, R.C. Harp, E.L. 1985 Map showing slope stability during earthquakes in San Mateo County, California map Miscellaneous Investigations Series 1257-E U.S. Geological Survey 62500 paper 1985 publication date Wieczorek and others (1985) Methodology used in landslide susceptibility analysis 1. Lithologic units on the digital geologic map (Rosenberg, 2001) were classified into three groups based on their assumed strength properties following the methodology of Wieczorek and others (1985). Using ArcView software, the units were dissolved into the three groups. 2. A slope percentage map was derived from a digital elevation model of Monterey County (USGS, 1999) using ArcView Spatial Analyst software. The slope percentages were combined into six classes. Numeric values were assigned to each slope class (0-5 degrees = 1; 5-15 degrees = 2; 15-30 degrees = 3; 30-50 degrees = 4; 50-70 degrees = 7; >70 degrees = 16). 3. The strength class map developed in step 1 was converted from digital vector to digital raster (grid) format using Spatial Analyst. Numeric values were assigned to each strength class (A =1; B =3; C = 4). 4. The strength class map and the slope map were digitally overlain in Spatial Analyst and the values of each cell were added together in an algebraic matix. The resultant values were assigned to high, moderate, and low categories following a simplified version of the matrix used by Wieczorek and others (1985). 5. The raster digital data boundaries were generalized using four passes of the "majority filter" and "boundary clean" scripts with the Spatial Tools ArcView extension (USGS, 1998; http://www.absc.usgs.gov/glba/gistools/SpatialTools_doc.htm) 6. The cleaned raster digital data were converted to raster vector data (ESRI Shapefiles) using ArcView. withheld withheld withheld 20010405 Lew Rosenberg Consulting Geologist mailing address

P.O. Box 183

Templeton CA 93465-0183 (805) 434-1750 (805) 434-1750 Lrosenberg@thegrid.net Monday to Friday, 8 AM to 5 PM, Pacific Tim Dataset copied. withheld Dataset copied. withheld Metadata imported. withheld 20041227 14411100 Dataset copied. withheld 20080806 12462900 Vector Simple FALSE 6010 TRUE FALSE coordinate pair 0.000250 0.000250 survey feet North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 GCS_North_American_1983 NAD_1983_StatePlane_California_IV_FIPS_0404_Feet 1.000000 Explicit elevation coordinate included with horizontal coordinates Landslide Relative landslide susceptibility rating author Feature Class 6010 Shape Feature geometry. ESRI Coordinates defining the features. OBJECTID OID 4 10 0 OBJECTID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Geometry 4 0 0 SHAPE SUSCEPT String 8 0 0 Feature geometry. ESRI Coordinates defining the features. SHAPE.STLength() GlobalID GlobalID 38 0 0 SUSCEPT Relative landslide susceptibility rating author high area of relatively high susceptibility to earthquake-induced landslides author moderate area of relatively moderate susceptibility to earthquake-induced landslides author low area of relatively low susceptibility to earthquake-induced landslides author SHAPE.STArea() Double 0 0 0 SHAPE.STArea() SHAPE.STLength() Double 0 0 0 Monterey County Environmental Resource Policy Department Database Coordinator mailing address

P.O. Box 180

Salinas CA 93902 (831) 755-5353 (831) 796-3062 Monday to Friday, 8 AM to 5 PM, Pacific Time Downloadable Data This database is intended for regional planning purposes and not for site-specific evaluation. Information in this data set is preliminary in nature. This information is provided with understanding that it is not guaranteed to be correct or and conclusions drawn from such information, whether from individual use or aggregate use with other data, are the responsibility of the user. 2.238 Contact the Monterey County Environmental Resource Policy Department for a printed copy of the map or for an ESRI shapefile of the data set. For those users that do not have ArcView or ARC/INFO, ESRI provides a free GIS data viewer, ArcExplorer, that can be downloaded from their website at: http://www.esri.com/software/arcexplorer/index.html. ArcExplorer is currently only supported on the Windows 95/98 or Windows NT platforms. 20100317 20010507 Lew Rosenberg Consulting Geologist mailing address

P.O. Box 183

Templeton CA 93465-0183 (805) 434-1750 (805) 434-1750 Lrosenberg@thegrid.net Monday to Friday, 8 AM to 5 PM, Pacific Time FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time http://www.esri.com/metadata/esriprof80.html ESRI Metadata Profile http://www.esri.com/metadata/esriprof80.html ESRI Metadata Profile en 20190219 14014400 FALSE 20210817 13474000 20210817 13474000 Landslide 002 5688082.197000 6201151.271000 1808760.143000 2227394.194000 1 Projected GCS_North_American_1983 Linear Unit: Foot_US (0.304801) NAD_1983_StatePlane_California_IV_FIPS_0404_Feet <ProjectedCoordinateSystem xsi:type='typens:ProjectedCoordinateSystem' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:typens='http://www.esri.com/schemas/ArcGIS/10.6'><WKT>PROJCS["NAD_1983_StatePlane_California_IV_FIPS_0404_Feet",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",6561666.666666666],PARAMETER["False_Northing",1640416.666666667],PARAMETER["Central_Meridian",-119.0],PARAMETER["Standard_Parallel_1",36.0],PARAMETER["Standard_Parallel_2",37.25],PARAMETER["Latitude_Of_Origin",35.33333333333334],UNIT["Foot_US",0.3048006096012192],AUTHORITY["EPSG",2228]]</WKT><XOrigin>-116466200</XOrigin><YOrigin>-92735300</YOrigin><XYScale>4000</XYScale><ZOrigin>0</ZOrigin><ZScale>1</ZScale><MOrigin>0</MOrigin><MScale>1</MScale><XYTolerance>0.002</XYTolerance><ZTolerance>0.002</ZTolerance><MTolerance>1.9999999999999998e-05</MTolerance><HighPrecision>true</HighPrecision><WKID>102644</WKID><LatestWKID>2228</LatestWKID></ProjectedCoordinateSystem> 1.0 Version 6.2 (Build 9200) ; Esri ArcGIS 10.6.1.9273 Landslide 5688082.197 6201151.271 2227394.194 1808760.143 1 -121.988436 -120.215485 36.939328 35.758959 1 1 -121.988436 -120.215485 36.939328 35.758959 ISO 19115 Geographic Information - Metadata DIS_ESRI1.0 dataset 002 withheld Feature Class Feature Class NAD_1983_StatePlane_California_IV_FIPS_0404_Feet EPSG 5.3(9.0.0) 6010 20210817