Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, California Part 1: Introduction and Description of Database in cooperation with the California Geological Survey Geology by Robert C. Witter(1), Keith L. Knudsen(2), Janet M. Sowers(1), Carl M. Wentworth(3), Richard D. Koehler(1), and Carolyn E. Randolph(1) Digital database by Carl M. Wentworth(3), Suzanna K. Brooks(3), and Kathleen D. Gans(3) Author Affiliations (1) - William Lettis & Associates, Inc.; (2) - California Geological Survey; (3) - U.S. Geological Survey Open-File Report 2006-1037 U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey P. Patrick Leahy, Acting Director For more information on the USGS - the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Suggested Citation: Witter, R.C., Knudsen, K.L, Sowers, J.M., Wentworth, C.M., Koehler, R.D., Randolph, C. E. , Brooks, S.K., and Gans, K.D., 2006, Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, California: U.S. Geological Survey Open-File Report 2006-1037 (http://pubs.usgs.gov/of/2006/1037/) Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. This database, identified as 'Maps of Quaternary deposits and liquefaction susceptibility in the Central San Francisco Bay Region, California', has been approved for release and publication by the Director of the USGS. Although this database has been reviewed and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. This database is released on condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from its use. INTRODUCTION This report presents a map and database of Quaternary deposits and liquefaction susceptibility for the central San Francisco Bay region. It supercedes the equivalent area of U.S. Geological Survey Open-File Report 00- 444 (Knudsen and others, 2000), which covers the larger 9-county San Francisco Bay region. The report consists of (1) this text introduction the report and describing the spatial database, (2) a text describing the Quaternary map and liquefaction interpretation, (3) the spatial database, and (4) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility. 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 consistent detailed treatment of the central part of the 9-county region in which much of the mapping of Open-File Report 00-444 was either at smaller (less detailed) scale or represented only preliminary revision of earlier work. (NOTE that the San Francisco North 7.5-minute quadrangle, which includes the northern part of the city of San Francisco, is not included.) Like Open-File Report 00- 444, the current mapping uses geomorphic expression, pedogenic soils, inferred depositional environments, and geologic age to define and distinguish the map units. Further scrutiny of the factors controlling liquefaction susceptibility has led to some changes relative to Open-File Report 00-444: particularly the reclassification of San Francisco Bay mud (Qhbm) to have only MODERATE susceptibility and the rating of artificial fills according to the natural map units inferred to underlie them (other than dams - adf). The two colored maps provide a regional summary of the new mapping at a scale of 1:200,000, a scale that is sufficient to show the general distribution and relationships of the map units but not to distinguish the more detailed elements that are present in the database. The report is the product of cooperative work by the National Earthquake Hazards Reduction Program (NEHRP) and National Cooperative Geologic Mapping Program of the U.S. Geological Survey, William Lettis and & Associates, Inc. (WLA), and the California Geological Survey. An earlier version was submitted to the U.S. Geological Survey by WLA as a final report for a NEHRP grant (Witter and others, 2005). The mapping has been carried out by WLA geologists under contract to the NEHRP Earthquake Program (Grant 99-HQ-GR-0095) and by the California Geological Survey. The report consists of six 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 and liquefaction susceptibility database; 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 units and of the liquefaction interpretation. Part 4 is the digital spatial database: 4. Quaternary deposits and liquefaction susceptibility database. Parts 5 and 6 are graphic plot files for map sheets 1 and 2 at a scale of 1:200,000: 5. map sheet 1: plot file of the Quaternary deposits map, including an explanation of map units; 6. map sheet 2: plot file of the liquefaction susceptibility map. Part 7 is the database package, consisting of the spatial database (either coverage or shape file format) together with the three text files and metadata file. Part 8 is the plotfile package, with files in either postcript or PDF format. Part 9 is the metadata file, which is also included in the spatial database. The two colored maps are presented as digital plot files in PostScript and PDF format (image size 32 x 40 inches each). The PostScript map images (68.3 MB) can be used for viewing or plotting in computer systems with sufficient capacity, and the considerably smaller PDF files (30.4 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 map database is provided both as an uncompressed ARC/INFO export file and as ArcView Shape files. The spatial database was compiled in vector form over the past several years using workstation ArcInfo, a commercial Geographic Information System (Environmental Systems Research Institute [ESRI], Redlands, California), and the menu interface ALACARTE (Fitzgibbon and Wentworth, 1991; Fitzgibbon, 1991; Wentworth and Fitzgibbon, 1991). The map plot files were assembled as graphics files in ARC/INFO from the spatial database, modified in Adobe Illustrator, and then converted to PostScript and PDF formats. DIGITAL FILES AND PACKAGING The report consists of digital files representing the nine 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, of06- 1037, followed by part numbers and an extension indicating the 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). The files and their identities are as follows: 1. Introduction and Description of Database: This text, which describes the database and how to obtain it. a. of06-1037_1a.txt ASCII file, 0.03 MB. b. of06-1037_1b.ps PostScript file, 0.1 MB. c. of06-1037_1c.pdf PDF file, 0.06 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. of06-1037_2a.txt ASCII file 3. Description of Mapping and Liquefaction Interpretation: A 44-page text (2 color figures) that describes the Quaternary deposits of the region, the 60 map units, the estimates of liquefaction susceptibility, and the techniques and history of the work. a. of06-1037_3a.txt ASCII file, 0.12 MB. (No figures included.) b. of06-1037_3b.eps PostScript file, 0.3 MB c. of06-1037_3c.pdf PDF file, 3.1 MB 4. Quaternary Deposits and Liquefaction Susceptibility Database: The data files representing the lines and polygons of the Quaternary deposits database (ARC export and ArcView Shape formats). a. of06-1037_4a.e00.zip - Quaternary Deposits: a compressed ArcInfo export coverage containing lines and polygons (9.6 MB, uncompresses to 42.9 MB). b. of06-1037_4b.shp.zip - Quaternary Deposits: ArcMap line and polygon shape files bundled as one compressed zip file (16.5 MB, uncompresses to 8 files totaling 57.3 MB). When opened, the zip file yields: - line files: sfq2lns.dbf, sfq2lns.shp, sfq2lns.shp.xml, and sfq2lns.shx - polygon files: sfq2pys.dbf, sfq2pys.shp, sfq2pys.shp.xml,and sfq2pys.shx 5. Plot File of Quaternary Deposits Map: image size 33 x 36 inches. a. of06-1037_5a.eps.zip PostScript file, 11.9 MB, uncompresses to 68.3 MB b. of06-1037_5b.pdf.zip PDF file, 12.1 MB, uncompresses to 30.0 MB 6. Plot File of Liquefaction Susceptibility Map: image size 33 x 36 inches. a. of06-1037_6a.eps.zip PostScript file, 11.7 MB, uncompresses to 68.3 MB b. of06-1037_6b.pdf.zip PDF file, 12.1 MB, uncompresses to 30.4 MB 7. Database Package a. of06-1037_7a.zip ArcInfo coverage version: Assembled text (parts 1, 2, 3, 9), ArcInfo-export database (part 4), bundled as one compressed zip file, 12.4 MB b. of06-1037_7b.zip ArcMap shape file version: Assembled text (parts 1, 2, 3, 9) and ArcMap shape files (part 4), bundled as one compressed zip file, 19.3 MB 8. Plotfile Package a. of06-1037_8a.tar.zip Postscript version: plot files for the Quaternary deposits map (part 5) and the liquefaction susceptibility map (part 6) bundled as one compressed zip file, 23.6 MB b. of06-1037_8b.zip PDF version: plot files for the Quaternary deposits map (part 5) and the liquefaction susceptibility map (part 6) bundled as one compressed zip file, 24.2 MB 9. Metadata file a. of06-1037_9.meta ASCI file. OBTAINING THE DIGITAL FILES The report, including text, database, and image files, can be obtained from the US. Geological Survey publications server at: http://pubs.usgs.gov/of/2006/1037/ PROCESSING THE FILES Some of the files require initial processing before they are usable, both to open bundled and/or compressed files and to import the Arc export file. Opening Tar and Gzip Files Some of the files are assembled as tape archive files (tar files), and the larger files containing the databases and images have been compressed with gzip. Thus, gzip or equivalent is required to uncompress the files, and a tar utility is required to open the tar files. Once extracted from the compressed tar files, the Arc export file of06-10374a.e00 can be imported into workstation ArcInfo using the ARC import command. To match the descriptions herein, it should be named SF-QUAT2. REVISIONS Changes to any part of this report (parts are the numbered items described above in 'Database Contents' and listed in the revision list (of06-1037_2a.txt) may be made in the future if needed. This could involve, for example, fixing files that don't work properly, revising geologic details, adding new file formats, or adding other components to the report. The report begins at version 1.0. Any revisions will be specified in the revision list and will result in the recording of a new version number for the report. Small changes will be indicated by decimal increments and larger changes by integer increments in the version number. Revisions will be announced and maintained on the Web page for this report on the U.S. Geological Survey publications web server. Consult the revision list there to determine if a revision is significant for your purposes. MAP COMPILATION The Quaternary deposits database was compiled digitally in vector form in workstation ArcInfo as individual 7.5-minute quadrangles at a scale of 1:24,000 in State Plane projection. Original linework was scanned, vectorized, and edited on-screen over the scanned raster background. The 68 individual quadrangles were then converted to UTM projection and assembled into a single regional layer. Quadrangle boundary problems were resolved where possible, although some remain. Much of the fine detail in the spatial database is too small for legible portrayal at the regional scale of the colored maps (1:200,000). SPATIAL RESOLUTION The digital database should not be used in ways that violate the spatial resolution of the data. Although the digital form of the data removes the physical constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. Use of the database at a scale larger than 1:24,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, where this database is used in combination with other data of higher resolution, the resolution of the combined output will be limited by the lower resolution of this data. DESCRIPTION OF THE SPATIAL DATABASE The spatial database consists of the data layer for Quaternary deposits and liquefaction susceptibility. The database structure follows the ALACARTE data model, such that the primary line attribute is LTYPE and the primary polygon attribute is PTYPE. Definition files are also included, however, after the SGM data model of Gautier (1999). The ArcInfo layer (coverage) SF-QUAT2 is stored in UTM projection (table 1), whereas the shape files are in decimal degrees of longitude and latitude (NAD27). These were prepared by projecting SF-QUAT2 to decimal degrees as SFQ2 and converting this coverage using the Arc command arcshape. (Note that this procedure has resulted in the modification of the names of some database fields.) Descriptions of the coverage database fields (items) use the terms of table 2. Table 1. Map Projection for Arc coverage Projection UTM (Universal Transverse Mercator) Units METERS Zone 10 Datum NAD27 Spheroid CLARKE1866 Table 2. Field Definition Terms ITEM NAME name of the database field (item) WIDTH maximum number of digits or characters stored OUTPUT output width TYPE B- binary integer, F- binary floating point number, I- ASCII integer, C- ASCII character string N.DEC number of decimal places maintained for floating point numbers The Quaternary deposits layer contains attributed lines and polygons and requires polygon topology for effective use. The lines and polygons are described here through their feature attribute tables and associated definition tables (table 3). Table 3. Definition Tables Included as INFO Files in the Arc Coverage SF-QUAT2 Table Name Function SF-QUAT2.LN defines line types (LTYPE) SF-QUAT2.UN lists names of map units by PTYPE (polygon label) SF-QUAT2.QDEF defines polygon LIQ values SF-QUAT2.LIQ lists standard LIQ rating by PTYPE (map unit) The attribute table for lines (SF-QUAT2.AAT, table 4) contains the topical attribute field LTYPE, the 12 different values of which are described in table 4 and in digital form as part of the sf-quat2 coverage in the INFO definition table SF-QUAT2.LN. Table 4. Structure of the Arc Attribute Table (SF-QUAT2.AAT) ITEM NAME WIDTH OUTPUT TYPE N.DEC FNODE# 4 5 B - starting node of arc (from node) TNODE# 4 5 B - ending node of arc (to node) LPOLY# 4 5 B - polygon to the left of the arc RPOLY# 4 5 B - polygon to the right of the arc LENGTH 4 12 F 3 length of arc in meters SF-QUAT# 4 5 B - unique internal control number SF-QUAT-ID 4 5 B - unique identification number LTYPE 35 35 C - line type Table 5. Line Types Recorded in the Quaternary-Deposits LTYPE Field This table lists the contents of the LTYPE definition table SF-QUAT2.LN. LTYPE LDEF contact, well located depositional contact, location uncertainty less than about 100 m contact, approx. located depositional contact, location uncertainty greater than about 100 m contact, concealed depositional contact concealed beneath water, fill, or levee scratch boundary boundary without geologic attribute, here connecting mismatch of contacts or units at 7.5-minute quadrangle boundary water boundary boundary of open water from 1:24,000 USGS DLGs and published paper topographic maps water boundary, 1800s landward margin of tidal marsh bordering San Francisco Bay in the late 19th century, mainly from Nichols and Wright, 1971 water boundary, 1800s, concealed concealed equivalent of water boundary, 1800s contact, liq depositional contact inferred beneath overlying fill, location uncertainty less that about 100 m contact, liq, queried depositional contact inferred beneath overlying fill, location uncertainty greater that about 100 m liq boundary arbitrary boundary between depositional or liquefaction (PTYPE2) units beneath overlying fill county line boundary of nine-county region, from 1:24,000 USGS DLGs and published paper topographic maps map boundary exterior boundary of 1:24,000 quadrangles composing the map area The Quaternary-deposits polygon attribute table (SF-QUAT2.PAT, table 6) contains the topical field PTYPE, values of which are map-label representations of the Quaternary map units (such as Qt). These labels and their equivalent unit names are listed in table 8 and in the INFO definition table SF-QUAT2.UN, and are described in Appendix A of part 3. The Quaternary map unit(s) underlying each artificial fill is recorded in the PTYPE2 field as unit map labels in order to permit liquefaction susceptibility of fills to be represented by that of the underlying natural deposit. PTYPE2 for all natural deposits is the same as PTYPE. PTYPE2 for most narrow fills is a combination of adjacent natural units (such as Qhc-Qhf). Table 6. Structure of the Quaternary-Deposits Polygon Attribute Table (SJ-GEOL.PAT) ITEM NAME WIDTH OUTPUT TYPE N.DEC FNODE# 4 5 B - starting node of arc (from node) AREA 4 12 F 3 area of polygon in square meters PERIMETER 4 12 F 3 length of perimeter in meters SF-QUAT2# 4 5 B - unique internal control number SF-QUAT2-ID 4 5 B - unique identification number PTYPE 35 35 C - Quaternary unit label PTYPE2 35 35 C - Quaternary unit underlying fills LIQ 8 8 C - liquefaction susceptibility LIQ-SOURCE 1 1 I - 1 where custom LIQ value assigned, otherwise 0 The codes for liquefaction susceptibility in the LIQ field are defined in table 7 and in the INFO definition table SF-QUAT2.QDEF. The susceptibility ratings for most natural deposits are based on map unit (LIQ- SOURCE = 0), although some are assigned custom ratings (LIQ-SOURCE = 1) based on such local information as depth to ground water or historical occurrence of liquefaction. Susceptibility of fills other than dams (adf) is based on the underlying natural unit (PTYPE2; where PTYPE2 consists of dual (or triple) units, the highest susceptibility of those units is used); the minimum susceptibility of af is L, of alf is M, and of ac is L. The standard correlations between map unit and susceptibility are listed in Table 8 and the INFO definition table SF-QUAT2.LIQ, and are described in table 3 of Part 3, Description of Mapping. Table 7. Meanings of liquefaction susceptibility codes in the LIQ field (SF-QUAT2.PAT) This table lists the contents of the LIQ definition table SF-QUAT2.QDEF. LIQ CODE (LIQ) DEFINITION (QDEF) VH VERY HIGH H HIGH M MODERATE L LOW VL VERY LOW W WATER NM AREA NOT MAPPED Table 8. Unit PTYPEs, Liquefaction Susceptibility Ratings, and Unit Names This table lists in stratigraphic order the combined contents of the PTYPE definition table (SF-QUAT2.UN) and the PTYPE/LIQ correlation table SF-QUAT2.LIQ. PTYPE LIQ NAME MODERN af L Artificial fill (historical) afbm VH Artificial fill over San Francisco Bay mud (historical) alf H Artificial levee fill (historical) acf VH Artificial channel fill (historical) adf L Artificial dam fill (historical) gq M gravel quarries and percolation ponds ac H Artificial stream channel (historical) Qhc VH Modern stream channel deposits LATEST HOLOCENE Qhfy H Latest Holocene alluvial fan deposits Qhly VH Latest Holocene alluvial fan levee deposits Qhty H Latest Holocene stream terrace deposits Qhty1 H Younger latest Holocene stream terrace deposits Qhty2 H Older latest Holocene stream terrace deposits Qhay H Latest Holocene alluvial deposits, Undifferentiated Qhbs VH Latest Holocene beach sand HOLOCENE Qhds M Holocene dune sand Qhbm M Holocene San Francisco Bay Mud Qhed H Holocene estuarine delta deposits Qhb M Holocene basin deposits Qhfe H Holocene alluvial fan-estuarine complex deposits Qhff M Holocene alluvial fan deposits, fine facies Qhf M Holocene alluvial fan deposits Qhf1 M Younger Holocene alluvial fan deposits Qhf2 M Older Holocene alluvial fan deposits Qhl M Holocene alluvial fan levee deposits Qhl1 M Younger Holocene alluvial fan levee deposits Qhl2 M Older Holocene alluvial fan levee deposits Qht M Holocene stream terrace deposits Qht1 M Younger Holocene stream terrace deposits Qht2 M Older Holocene stream terrace deposits Qha M Holocene alluvium, undifferentiated HOLOCENE TO LATEST PLEISTOCENE Qds M Latest Pleistocene to Holocene dune sand Qb L Latest Pleistocene to Holocene basin deposits Qf M Latest Pleistocene to Holocene alluvial fan deposits Qt M Latest Pleistocene to Holocene stream terrace deposits Qa M Latest Pleistocene to Holocene alluvium, undifferentiated LATEST PLEISTOCENE Qpf L Latest Pleistocene alluvial fan deposits Qpt L Latest Pleistocene stream terrace deposits Qpa L Latest Pleistocene alluvium, undifferentiated PLEISTOCENE Qmt L Pleistocene marine terrace deposits Qmt1 L Youngest (of 4) Pleistocene marine terrace deposits Qmt2 L Second youngest (of 4) Pleistocene marine terrace deposits Qmt3 L Second oldest (of 4) Pleistocene marine terrace deposits Qmt4 L Oldest (of 4) Pleistocene marine terrace Deposits Qbt L Pleistocene bay terrace deposits EARLY TO LATE PLEISTOCENE Qop VL Early to late Pleistocene pediment deposits Qof VL Early to late Pleistocene alluvial fan deposits Qof1 VL Younger early to late Pleistocene alluvial fan deposits Qof2 VL Older early to late Pleistocene alluvial fan deposits Qot VL Early to late Pleistocene stream terrace deposits Qoa VL Early to late Pleistocene alluvial deposits, undifferentiated Qoa1 VL Younger early to late Pleistocene alluvial deposits, undifferentiated Qoa2 VL Older early to late Pleistocene alluvial deposits, undifferentiated PRE-QUATERNARY br VL pre-Quaternary deposits and bedrock REFERENCES CITED Fitzgibbon, T.T., 1991, ALACARTE installation and system manual (version 1.0): U.S. Geological Survey, Open-File Report 91-587B. Fitzgibbon, T.T., and Wentworth, C.M., 1991, ALACARTE user interface - AML code and demonstration maps (version 1.0): U.S. Geological Survey, Open-File Report 91-587A. Gautier, D.L., 1999, Data model for single geologic maps: an application of the national geologic map data model, in, Soller, D.R., ed., Digital mapping techniques '99 -- workshop proceedings: U.S. Geological Survey Open-File Report 99-386. Knudsen, K.L, Sowers, J.M., Witter, R.C., Wentworth, C.M., and Helley, E.J., 2000, Preliminary maps of Quaternary deposits and liquefaction susceptibility, nine-county San Francisco Bay Region, California: a digital database: U.S. Geological Survey Open-File Report 00-444. Nichols, D.R., and Wright, N.A., 1971, Preliminary map of historical margins of marshland, San Francisco Bay, California: U.S. Geological Survey Open-File Report, Basic Data Contribution 9, scale 1:125,000. Wentworth, C.M., and Fitzgibbon, T.T., 1991, ALACARTE user manual (version 1.0):U.S. Geological Survey, Open-File Report 91-587B. Witter, R.C., Knudsen, K.L., Sowers, J.M., Wentworth, C.M., Koehler, R.D., and Randolph, C.E., 2005, Maps of Quaternary deposits and liquefaction susceptibility in the San Francisco Bay area urban core, California: Final Technical Report to National Earthquake Hazards Reduction Program, U.S. Geological Survey Award Number 99-HQ-GR-0095. Working Group on California Earthquake Probabilities, 1999, Earthquake in the San Francisco Bay Region: 2000 to 2030 - A summary of: U.S. Geological Survey Open File Report 99-517, Online Version 1.0.