U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY PRELIMINARY MAPS OF QUATERNARY DEPOSITS AND LIQUEFACTION SUSCEPTIBILITY, NINE-COUNTY SAN FRANCISCO BAY REGION, CALIFORNIA: A DIGITAL DATABASE geology by Keith L. Knudsen(1,2), Janet M. Sowers(1), Robert C. Witter(1), Carl M. Wentworth(3) and Edward J. Helley(1) digital database by Carl M. Wentworth(3), Robert S. Nicholson(3), Heather M. Wright(3), and Katherine H. Brown(3) Open-File Report 00-444 Version 1.0 2000 Author Affiliations 1 - William Lettis & Associates, Inc. 2 - California Division of Mines and Geology 3 - U.S. Geological Survey INTRODUCTION This report presents a preliminary map and database of Quaternary deposits and liquefaction susceptibility for the nine-county San Francisco Bay region, together with a digital compendium of ground effects associated with past earthquakes in the region. The report consists of (1) a spatial database of five data layers (Quaternary deposits, quadrangle index, and three ground effects layers) and two text layers ( a labels and leaders layer for Quaternary deposits and for ground effects), (2) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility), (3) a text describing the Quaternary map, liquefaction interpretation, and the ground effects compendium, and (4) this pamphlet. All parts of the report are digital; this pamphlet describes the database and digital files and how to obtain them by downloading across the internet. The nine counties surrounding San Francisco Bay straddle the San Andreas fault system, which exposes the region to serious earthquake hazard (Working Group on California Earthquake Probabilities, 1999). Much of the land adjacent to the Bay and the major rivers and streams is underlain by unconsolidated deposits that are particularly vulnerable to earthquake shaking and liquefaction of water-saturated granular sediment. Map delineation of the different types and ages of Quaternary deposits supports evaluation of susceptibility to liquefaction, the immediate application of the work, but serves many other purposes as well. It provides a framework for interpreting the architecture and history of the Quaternary sedimentary basins, which is used in estimating earthquake shaking and modeling the groundwater system. The mapping is also useful in constraining the ages and histories of offsetting faults, in guiding geotechnical investigations, and in other engineering, geologic, and archeological applications. This new map provides a modern and regionally consistent treatment of Quaternary surficial deposits that builds on the pioneering mapping of Helley and Lajoie (Helley and others, 1979) and such intervening work as Atwater (1982), Helley and others (1994), and Helley and Graymer (1997a and b). Like these earlier studies, the current mapping uses geomorphic expression, pedogenic soils, and inferred depositional environments to define and distinguish the map units. In contrast to the twelve map units of Helley and Lajoie, however, this new map uses a complex stratigraphy of some forty units, which permits a more realistic portrayal of the Quaternary depositional system. The two colored maps provide a regional summary of the new mapping at a scale of 1:275,000, a scale that is sufficient to show the general distribution and relationships of the map units but cannot distinguish the more detailed elements that are present in the database. The report is the product of years of cooperative work by the USGS National Earthquake Hazards Reduction PROGRAM (NEHRP) and National Cooperative Geologic Mapping Programs, William Lettis and & Associates, Inc. (WLA) and, more recently, by the California Division of Mines and Geology as well. An earlier version was submitted to the Geological Survey by WLA as a final report for a NEHRP grant (Knudsen and others, 2000). The mapping has been carried out by WLA geologists under contract to the NEHRP Earthquake Program (Grants #14-08-0001-G2129, 1434-94-G-2499, 1434-HQ-97-GR-03121, and 99-HQ-GR-0095) and with other limited support from the County of Napa, and recently also by the California Division of Mines and Geology. The current map consists of this new mapping and revisions of previous USGS mapping. The report is preliminary because, although much of the mapping is at a scale of 1:24,000, for a third of the region it is at 1:100,000, including much of the core area, and another fifth meets less than 75% of the mapping criteria for the work (see part 3, Description of Mapping). Improvement of these parts of the map is the topic of ongoing work. The report consists of eight numbered parts that are represented by digital files, most of which are provided in two or three different formats. The parts and files are described in DATABASE CONTENTS (below), and their packaging for user access is described in Presentation (below). Parts 1, 2, and 3 are texts: 1. this pamphlet, including description of the Quaternary deposits, ground effects, and quadrangle index databases; 2. revision list, which lists the digital files as they are available over the Net and records version number and any revisions; 3. description of mapping, including description of mapping techniques and Quaternary units, of the liquefaction interpretation, and of the ground effects compendium (two color figures). Parts 4, 5, and 6 are digital spatial databases and associated text layers: 4. Quaternary deposits and liquefaction susceptibility database: one database layer, one text layer; 5. ground effects database: three database layers (separate polygon layers for historic and Loma Prieta effects), one text layer; 6. quadrangle index database: one database layer. Parts 7 and 8 are graphic plot files for map sheets 1 and 2 at a scale of 1:275,000: 7. map sheet 1: plot file of the Quaternary deposits map, including an index of the status of mapping and an explanation of map units; 8. map sheet 2: plot file of the liquefaction susceptibility map, including ground-effects localities. The two colored maps are presented as digital plot files in PostScript and PDF format (image size 33 x 36 inches each). The PostScript map images (28-30 MB) can be used for viewing or plotting in computer systems with sufficient capacity, and the considerably smaller PDF files (6 MB) can be viewed or plotted in full or in part from Adobe ACROBAT running on Mac, PC, or UNIX platforms. The appearance of the maps in plots (colors and line weights) will depend on file type and the particular plotter that is used. The five database layers are provided both as uncompressed ARC/INFO export files in Version 7 format and as ArcView Shape files. The database layers consist of the Quaternary deposits layer (which includes ratings for liquefaction susceptibility), the index of 7.5-minute quadrangles (which includes ratings for the status of mapping), and the three layers representing the compendium of earthquake ground effects. The label-and-leader text layers, which contain graphic elements, are provided only as uncompressed ARC/INFO export files. The full versatility of the spatial database is obtained by importing the ARC export files into ARC/INFO or an equivalent GIS package. Other GIS packages, including MapInfo and ArcView, may use either the ARC export or Shape files, although the Shape files do not retain the definition tables and do not include the text layers. The information in the definition tables is also listed in this pamphlet. The spatial database was compiled in vector form over the past several years with versions 6 through 7.2 of ARC/INFO, a commercial Geographic Information System (Environmental Systems Research Institute [ESRI], Redlands, California), using the menu interface ALACARTE (Fitzgibbon and Wentworth, 1991; Fitzgibbon, 1991; Wentworth and Fitzgibbon, 1991), and with MapInfo for part of the ground-effects database. The map plot files were assembled as graphics files in ARC/INFO from the spatial database and then converted to PostScript and PDF formats. DATABASE CONTENTS The report consists of digital files representing the eight parts of the database, most of which are presented in more than one format. The names of the files are unique designators based on the report identifier, of00-444, followed by part numbers and an extension indicating file type. Some of the files have been bundled in tape archive files (tar files: .tar extension) and the larger ones have been compressed with gzip, yielding a final .gz extension (see Presentation, below). An AML script (import.aml) is provided that will assemble the coverages and definition files in ARC/INFO from the export files. The files and their identities are as follows: 1. Open-File Pamphlet: The text of the open-file pamphlet (this text), which describes the database and how to obtain it. a. of00-444_1a.txt ASCII file, 0.06 MB. b. of00-444_1b.ps PostScript file, 0.8 MB. c. of00-444_1c.pdf PDF file, 0.08 MB 2. Revision List: A list of the parts of the report (including bundled packages of parts), indication of the current version number for the report and in which version each part was last revised (if at all), followed by a chronologic list describing any revisions (see REVISIONS, below). a. of00-444_2a.txt ASCII file 3. Description of Mapping: A 60-page text (two color figures) that describes the Quaternary deposits of the region, the 40 map units plus their subdivisions, the estimates of liquefaction susceptibility, the ground effects compendium, and the techniques and history of the work. a. of00-444_3a.txt ASCII file, 0.2 MB. (No figures are included.) b. of00-444_3b.ps PostScript file, 6.5 MB c. of00-444_3c.pdf PDF file, 1.0 MB 4. Quaternary Deposits and Liquefaction Susceptibility Database: The data files representing the lines and polygons of the Quaternary deposits layer and associated definition tables (ARC export and ArcView Shape formats), and the annotation layer containing unit labels and leaders (ARC export format only). Note that the definition tables within the ARC coverage are not retained in the Shape files. a. of00-444_4a.e00.gz - Quaternary Deposits: a compressed ARC export coverage containing lines and polygons (11 MB, uncompresses to 46 MB). Import.aml will name this coverage sf-quat. b. of00-444_4b.e00 - Annotation: ARC export coverage containing unit labels and leaders (0.4 MB) scaled for graphic display at 1:275,000. Import.aml will name this coverage sf-qanno. c. of00-444_4c.tar.gz - Quaternary Deposits: ArcView line and polygon Shape files bundled as one compressed tar file (20 MB, uncompresses to 67 MB). When opened, the tar file yields: - line files: sf-qlns.dbf, sf-qlns.shp, and sf-qlns.shx - polygon files: sf-qpys.dbf, sf-qpys.shp, and sf-qpys.shx 5. Ground Effects Database: The data files representing the points, lines, and polygons of past earthquake ground effects (ARC export and ArcView Shape formats), and the annotation layer containing station numbers and leaders (ARC export format only). a. of00-444_5a.e00.tar.gz - Ground Effects: four ARC export coverages containing point, line, and polygon localities and station-number annotation and leaders for the historic and Loma Prieta datasets, bundled as one compressed tar file (0.07 MB, uncompresses to 0.6 MB). When opened, the tar file yields: - of00-444_5a1.e00: ARC export file containing point and line localities for both the historic and Loma Prieta datasets. Import.aml will name this coverage sf-effects. - of00-444_5a2.e00: ARC export file containing polygon localities for the historic dataset. Import.aml will name this coverage sf-efhspys. - of00-444_5a3.e00: ARC export file containing polygon localities for the Loma Prieta dataset. Import.aml will name this coverage sf-eflppys. - of00-444_5a4.e00: ARC export file containing station-number annotation and leaders for the whole effects database scaled for graphic display at 1:275,000 (1:100,000 for San Francisco). Import.aml will name this coverage sf-eanno. b. of00-444_5b.tar.gz - Ground Effects: ArcView point, line, and polygon Shape files bundled as one compressed tar file (0.03 MB, uncompresses to 0.2 MB). When opened, the tar file yields: - point files: sf-epts.dbf, sf-epts.shp, sf-epts.shx (the points of sf-effects) - line files: sf-elns.dbf, sf-elns.shp, and sf-elns.shx (the lines of sf-effects) - polygon files: sf-hpys.dbf, sf-hpys.shp, and sf-hpys.shx (the polygons of sf-efhspys) - polygon files: sf-lpys.dbf, sf-lpys.shp, and sf-lpys.shx (the polygons of sf-eflppys) 6. Quadrangle Index Database: The data files representing the lines and polygons of the 7.5-minute quadrangle and status-of-mapping index. a. of00-444_6a.e00.gz - Compressed ARC export coverage (0.2 MB). Import.aml will name this sf-qdgrid b. of00-444_6b.tar.gz - ArcView line and polygon Shape files bundled as one compressed tar file (0.2 MB, uncompresses to 0.9 MB). When opened, the tar file yields: - line files: sf-ilns.dbf, sf-ilns.shp, and sf-ilns.shx - polygon files: sf-ipys.dbf, sf-ipys.shp, and sf-ipys.shx 7. Plot File of Quaternary Deposits Map: image size 33 x 36 inches. a. of00-444_7a.ps.gz PostScript file, 5.9 MB, uncompresses to 27 MB b. of00-444_7b.pdf PDF file, 5.9 MB 8. Plot File of Liquefaction Susceptibility Map: image size 33 x 36 inches. a. of00-444_8a.ps.gz PostScript file, 6.2 MB, uncompresses to 30 MB b. of00-444_8b.pdf PDF file, 5.9 MB Presentation The database files are provided individually (including Shape files packaged in tar files by equivalent ARC coverages) and some of the files are also packaged together in larger tape archive files (.tar). Most of the larger files have been compressed with gzip (.gz). Separate Text Files: The revision list (of00-444_2a.txt) and the three formats of the open-file text (of00-444_1) and the Description of Mapping (of00-444_3) are provided separately, together with an abbreviated version of the ASCII text version of part 2 as a README. These text files in all three formats are also bundled in the database package. Separate Database Files: The Quaternary deposits and liquefaction susceptibility database (of00-444_4), the ground effects database (of00-444_5) and the quadrangle-index database (of00-444_6) are provided separately in both ARC export (.e00) and ArcView shape (.tar) formats, as well as being bundled in the database package. Separate Plot Files: The plot files for the Quaternary deposits map and liquefaction susceptibility map are provided separately in both PostScript and PDF format, as well as being bundled together in the plotfile package. Database Package: The Quaternary deposits and liquefaction susceptibility layers (of00-444_4), the ground effects layers (of00-444_5), and the quadrangle index (of00-444_6) are packaged together in a single gzip-compressed tar file in both ARC (a) and ArcView shape (b) format. This package also includes text file of00-444_2a.txt and text files of00-444_1 and of00-444_3 in all three formats. of00-444_9a.tar.gz 13 MB, uncompresses to 58 MB of00-444_9b.tar.gz 23 MB, uncompresses to 77 MB Plotfile Package: Plotfiles of the Quaternary deposits map and the liquefaction susceptibility map are packaged together in a single gzip-compressed tar file in both PostScript (a) and PDF (b) format. of00-444_10a.tar.gz 12 MB, uncompresses to 57 MB of00-444_10b.tar 12 MB OBTAINING THE DIGITAL FILES The database and image files can be downloaded from the Western Region Geologic Information Web Server or by anonymous ftp over the Internet. 1. Anonymous ftp over the Internet The files for this report are stored on the Western Region publication server of the U.S. Geological Survey. The Internet address of this server is: geopubs.wr.usgs.gov Connect to this address directly using ftp or through a browser, log in with the user name `anonymous', and enter your e-mail address as the password. This will give you access to all the publications available from the server. The files for this report are stored in the subdirectory: pub/open-file/of00-444 2. From the Western Region Geologic Publications Web Server The U.S. Geological Survey supports a set of graphical pages on the World Wide Web from which digital publications such as this one can be obtained. The Web server for digital publications from the Western Region is: http://geopubs.wr.usgs.gov This report can be reached by number (of00-444) through either the California or Open-File Reports 2000 options.