EARTHQUAKE FAULT ZONE OF REQUIRED INVESTIGATION These zones are delineated to assist cities and counties in fulfilling their responsibilities for protecting the public safety from the effects of earthquake fault rupture as required by the Alquist-Priolo Earthquake Fault Zoning Act (Public Resources Code Sections 2623 et seq). For a general description of the Alquist-Priolo Earthquake Fault Zoning Act and regulations, downloadable official zones and related information, please refer to the California Geological Survey Website at (http://www.conservation.ca.gov/cgs/rghm/ap/Pages/index.aspx) FAULT TRACES Fault trace features are from the California Geological Survey 2010 Fault Map of California and show the location of the ground surface trace of faults that are categorized by age for the past 1.6 million years (previously-defined Quaternary Period). Users of this information should be aware that active faults and earthquakes are the subject of continuing research and that refinement of the interpretations given here are sure to come within a few years. California Geological Survey Bulletin 201, “An Explanatory Text to Accompany the Geologic Map of California,” published separately, contains detailed source index maps and references to all the published and unpublished reports and information used in compiling the 1975 Fault Map of California. For additional information about the 2010 version of this map go to the following (http://www.conservation.ca.gov/cgs/cgs_history/Pages/2010_geologicmap.aspx)

LIMITATIONS 1)This site is not designed for official natural hazards disclosure determination. “Official” natural hazard zones viewed on this site are of insufficient resolution to definitively determine in all cases whether an individual property lies within a earthquake fault zone for disclosure purposes pursuant to California Civil Code Section 1103 et seq.
2)This map may not show all potentially active faults, either within the earthquake fault zones or outside their boundaries. 3)Faults shown within earthquake fault zones are the basis for establishing the zone boundaries. 4)The identification of faults and the location of fault traces are based on based on available data at various scales of accuracy, and have not been field checked. Overlay of zones on other base maps can result in discordance with base map features. 5)DISCLAIMER: The State of California and the Department of Conservation make no representations or warranties regarding the accuracy of these zones or fault traces, or the data from which these zones and fault traces were derived. Neither the State nor the Department shall be liable under any circumstances for any direct, indirect, special, incidental or consequential damages with respect to any claim by any user or any third party on account of or arising from the use of this information.

Liquefaction Zones (Feature Service)This is a digital Seismic Hazard Zone Map presenting areas where liquefaction and landslides may occur during a strong earthquake. Three types of geological hazards, referred to as seismic hazard zones, may be featured on the map: 1) liquefaction, 2) earthquake-induced landslides, and 3) overlapping liquefaction and earthquake-induced landslides. In addition, a fourth feature may be included representing areas not evaluated for liquefaction or earthquake-induced landslides. Developers of properties falling within any of the three zones may be required to investigate the potential hazard and mitigate its threat during the local permitting process.

This layer is a component of Web server for AP and SHZ zones.

This is a digital Seismic Hazard Zone Map presenting areas where liquefaction and landslides may occur during a strong earthquake. Three types of geological hazards, referred to as seismic hazard zones, may be featured on the map: 1) liquefaction, 2) earthquake-induced landslides, and 3) overlapping liquefaction and earthquake-induced landslides. In addition, a fourth feature may be included representing areas not evaluated for liquefaction or earthquake-induced landslides. Developers of properties falling within any of the three zones may be required to investigate the potential hazard and mitigate its threat during the local permitting process.

© Seismic Hazards Progam, California Geological Survey, California Department of Conservation

SEISMIC HAZARD ZONES OF REQUIRED INVESTIGATION These zones are delineated to assist cities and counties in fulfilling their responsibilities for protecting the public safety from the effects of earthquake-triggered ground failure as required by the Seismic Hazards Mapping Act (Public Resources Code Sections 2690-2699.6). For general information regarding the designation of seismic hazard zones, see California Geological Survey Special Publication 118, Recommended Criteria for Delineating Seismic Hazard Zones in California. For information regarding the scope and recommended methods to be used in conducting the required site investigations, see California Geological Survey Special Publication 117A, Guidelines for Evaluating and Mitigating Seismic Hazards in California. For a general description of the Seismic Hazards Zonation Program, the Seismic Hazards Mapping Act and regulations, downloadable official zones and related information, please refer to the California Geological Survey Website at http://www.conservation.ca.gov/cgs/shzp/.
LIMITATIONS 1) This site is not designed for official natural hazards disclosure determination. “Official” natural hazard zones viewed on this site have been modified for display purposes, and are of insufficient resolution to definitively determine in all cases whether an individual property lies within a seismic hazard zone for disclosure purposes pursuant to California Civil Code Section 1103 et seq.
2) These zones may not include all areas that have the potential for liquefaction, landsliding, strong earthquake ground shaking or other earthquake and geologic hazards. Also, a single earthquake capable of causing liquefaction or triggering landslide failure will not uniformly affect the entire area zoned. 3) Delineation of official seismic hazard zones was done in accordance with U.S. Geological Survey 1:24,000 base map standards which provides that 90 percent of cultural features be located within 40 feet (horizontal accuracy). Overlay of zones on other base maps can result in discordance with base map features. 4) DISCLAIMER: The State of California and the Department of Conservation make no representations or warranties regarding the accuracy of these zones, or the data from which these zones were derived. Neither the State nor the Department shall be liable under any circumstances for any direct, indirect, special, incidental or consequential damages with respect to any claim by any user or any third party on account of or arising from the use of this information.

Note: The DOC hosted version will be maintained through 2022, but is being retired in favor of an ArcGIS Online Hosted version of the same data. Those data can be found at: https://cadoc.maps.arcgis.com/home/item.html?id=921a7c243d074fa081af2b9d19be0315This is a digital Seismic Hazard Zone Map presenting areas where liquefaction and landslides may occur during a strong earthquake. Three types of geological hazards, referred to as seismic hazard zones, may be featured on the map: 1) liquefaction, 2) earthquake-induced landslides, and 3) overlapping liquefaction and earthquake-induced landslides. In addition, a fourth feature may be included representing areas not evaluated for liquefaction or earthquake-induced landslides. Developers of properties falling within any of the three zones may be required to investigate the potential hazard and mitigate its threat during the local permitting process.

County Faults/Fault Zones (Per Riverside County General Plan 10/2003). Alquist-Priolo Earthquake Fault Zones have been designated by the California Division of Mines and Geology for the Elsinore, San Jacinto, and San Andreas fault zones in Riverside County. Within the rapidly growing county, State A-P mapping has not kept pace with development. The County of Riverside has zoned fault systems and required similar special studies prior to development. These are referred to as County Fault Zones on Figure S-2 and in the Technical Background Report. Within A-P and County Fault Zones, proposed tracts of four or more dwelling units must investigate the potential for and setback from ground rupture hazards. As there are many active faults in Riverside County, with new fault strands being continually discovered, all proposed structures designed for human occupancy should be required to investigate the potential for and setback from ground rupture. Also of concern are structures, not for human occupancy, that can cause harm if damaged by an earthquake, such as utility, communications, and transportation lifelines. The County regulates most development projects within earthquake fault zones (Figure S-2). Projects include all land divisions and most structures for human occupancy. Before a project can be permitted within an A-P Earthquake Fault Zone, County Fault Zone, or within 150 feet of any other potentially active or active fault mapped in published United States Geological Survey (USGS) or California Division of Mining and Geology (CDMG) reports, a geologic investigation must demonstrate that proposed buildings will not be constructed across active faults.Updated 2/2016 with Thermal and Indio California Geologic Survey Quads

Abstract:This is a digital Seismic Hazard Zone Map presenting areas where liquefaction and landslides may occur during a strong earthquake. Three types of geological hazards, referred to as seismic hazard zones, may be featured on the map: 1) liquefaction, 2) earthquake-induced landslides, and 3) overlapping liquefaction and earthquake-induced landslides. In addition, a fourth feature may be included representing areas not evaluated for liquefaction or earthquake-induced landslides. Developers of properties falling within any of the three zones may be required to investigate the potential hazard and mitigate its threat during the local permitting process.Purpose:The map is used by cities and counties to regulate development and by property owners selling property within areas where seismic hazard zones have been identified. Local governments can withhold development permits until geologic or soils investigations are conducted for specific sites and mitigation measures are incorporated into development plans. Sellers of property use the maps to check the location of their specific site and, if applicable, disclose to the buyer that the property lies within a seismic hazard zone as required by the Seismic Hazards Mapping Act of 1990 (Public Resources Code, Division 2, Chapter 7.8). For information regarding the scope and recommended methods to be used in conducting the required site investigations, see California Geological Survey Special Publication 117A, Guidelines for Evaluating and Mitigating Seismic Hazards in California.Supplemental Information:This map may not show all areas that have potential for liquefaction or landsliding. Also, a single earthquake capable of causing liquefaction or triggering landslide failure will not uniformly affect the entire area zoned. The identification and location of liquefaction and earthquake-induced landslide zones are based on the best available data. However, the quality of data used is varied. Zone boundaries have been drawn as accurately as possible at the map scale.Full detail of metadataReferenced from external source.

The California parcel dataset was processed to determine whether a parcel is within an earthquake fault zone, a liquefaction zone, and/or a landslide zone. The main purpose of these data are to be used in the Earthquake Zones of Required Investigation GeoApp.

This is a digital Seismic Hazard Zone Map presenting areas where liquefaction and landslides may occur during a strong earthquake. Three types of geological hazards, referred to as seismic hazard zones, may be featured on the map: 1) liquefaction, 2) earthquake-induced landslides, and 3) overlapping liquefaction and earthquake-induced landslides. Developers of properties falling within any of the three zones may be required to investigate the potential hazard and mitigate its threat during the local permitting process.

This is a digital Seismic Hazard Zone Map presenting areas where liquefaction and landslides may occur during a strong earthquake. Three types of geological hazards, referred to as seismic hazard zones, may be featured on the map: 1) liquefaction, 2) earthquake-induced landslides, and 3) overlapping liquefaction and earthquake-induced landslides. In addition, a fourth feature may be included representing areas not evaluated for liquefaction or earthquake-induced landslides. Developers of properties falling within any of the three zones may be required to investigate the potential hazard and mitigate its threat during the local permitting process.

This part of DS 781 presents data for faults for the geologic and geomorphic map of the Offshore of Salt Point map area, California. The vector data file is included in "Faults_OffshoreSaltPoint.zip," which is accessible from http://pubs.usgs.gov/ds/781/OffshoreSaltPoint/data_catalog_OffshoreSaltPoint.html. The onshore part of the Offshore of Salt Point map area is cut by the northwest-trending San Andreas Fault, the right-lateral transform boundary between the North American and Pacific tectonic plates. The San Andreas extends extends into the offshore about 5 km south of the map area near Fort Ross, and about 50 km north of the map area on the east flank of Point Arena. The coast between Fort Ross and Point Arena, the northwesternmost exposed section west of the San Andreas Fault, is known as the "Gualala Block" (fig. 1) on the basis of its distinctive geology, which has been widely used to develop paleogeographic reconstructions of coastal California that restore as much as 150 to 180 km of right-lateral slip on the combined San Andreas and San Gregorio Fault systems (see, for example, Wentworth, (1968); Wentworth and others (1998); Jachens and others (1998); Dickinson and others (2005); Burnham (2009). The Gualala Block is underlain by a thick (as much as 9 to 11 km, in aggregate), discontinuous Upper Cretaceous to Miocene stratigraphic section (summarized in Wentworth and others, 1998), however only the Eocene and Paleocene German Rancho Formation (unit Tgr) is exposed onshore and is inferred to form seafloor bedrock outcrops in the Offshore of Salt Point map area. The German Rancho Formation consists of sandstone, mudstone, and conglomerate interpreted as deep-water, submarine-fan deposits. The western boundary of the Gualala Block lies offshore. Using seismic-reflection data, McCulloch (1987; his fig. 14) mapped a shore-parallel fault about 3 to 5 km offshore, which Dickinson and others (2005) subsequently named the Gualala Fault. Jachens and others (1998) evaluated aeromagnetic and gravity data across this zone and modeled this structure as a steep fault within the Salinian basement block, characterized by 3 to 5 km of right-lateral offset. In contrast, Dickinson and others (2005) consider the Gualala fault a Late Miocene strand of the San Andreas fault, separating Salinian and Franciscan basement rocks, with minimum right-lateral slip of 70 km. Our analysis of deeper industry seismic-reflection data within California State Waters shows the Gualala fault as a steep, northeast-dipping structure. Shallower seismic-reflection crossing the Gualala fault reveal a thick late(?) Pleistocene section characterized by recent faulting and gentle asymmetric folding. Hence, the Gualala fault appears to be a recently active "blind" structure that has deformed young sediments. Our mapping also documents a more nearshore zone of deformation that we refer to as the "east Gualala deformation zone." This zone extends through the central and southern parts of the Offshore of Salt Point map area and is similarly charcterized by steep faults and gentle folds that deform inferred late Pleistocene strata. This section of the San Andreas Fault onland has an estimated slip rate of about 17 to 25 mm/yr (Bryant and Lundberg, 2002). The devastating Great 1906 California earthquake (M 7.8) is thought to have nucleated on the San Andreas Fault about 100 kilometers south of this map area offshore of San Francisco (e.g., Bolt, 1968; Lomax, 2005), with the rupture extending northward through the onshore part of the Offshore of Salt Point map area to the south flank of Cape Mendocino (Lawson, 1908; Brown and Wolfe, 1972). Emergent marine terraces along the coast in the Offshore of Salt Point map area record recent contractional deformation associated with the San Andreas Fault system. Prentice and Kelson (2006) reported uplift rates of 0.3 to 0.6 mm/yr for a nearby late Pleistocene terrace (exposed at Fort Ross, about 5 km south of the map area) and this recent uplift must also have affected the nearshore and inner shelf, at least as far west as the Gualala fault. Faults were primarily mapped by interpretation of seismic reflection profile data (see field activity S-8-09-NC). The seismic reflection profiles were collected between 2007 and 2010. References Cited Bolt, B.A., 1968, The focus of the 1906 California earthquake: Bulletin of the Seismological Society of America, v. 58, p. 457-471. Brown, R.D., Jr., and Wolfe, E.W., 1972, Map showing recently active breaks along the San Andreas Fault between Point Delgada and Bolinas Bay, California: U.S. Geological Survey Miscellaneous Investigations Map I-692, scale 1:24,000. Bryant, W.A., and Lundberg, M.M., compilers, 2002, Fault number 1b, San Andreas fault zone, North Coast section, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, accessed April 4, 2013 at http://earthquakes.usgs.gov/hazards/qfaults. Burnham, K., 2009, Predictive model of San Andreas Fault system paleogeography, Late Cretaceous to early Miocene, derived from detailed multidisciplinary conglomerate correlations: Tectonophysics 464, p. 195-208. Dickinson, W.R., Ducea, M., Rosenberg, L.I., Greene, H.G., Graham, S.A., Clark, J.C., Weber, G.E., Kidder, S., Ernst, W.G., and Brabb, E.E., 2005, Net dextral slip, Neogene San Gregorio-Hosgri Fault Zone, coastal California: Geologic evidence and tectonic implications: Geological Society of America Special Paper 391, 43 p. Jachens, R.C., Wentworth, C.M., and McLaughlin, R.J., 1998, Pre-San Andreas location of the Gualala Block inferred from magnetic and gravity anomalies, in Elder, W.P., ed., Geology and tectonics of the Gualala block, northern California: Pacific Section, Society of Economic Paleontologists and Mineralogists, Book 84, p. 27-53. Lawson, A.C., ed., 1908, The California earthquake of April 18, 1906, Report of the State Earthquake Investigation Commission: Carnegie Institution of Washington Publication 87, v. 1, 1451 p. and atlas. Lomax, A., 2005, A reanalysis of the hypocentral location and related observations for the Great 1906 California earthquake: Bulletin of the Seismological Society of America, v. 95, p. 861-877. McCulloch, D.S., 1987, Regional geology and hydrocarbon potential of offshore central California, in Scholl, D.W., Grantz, A., and Vedder, J.G., eds., Geology and Resource Potential of the Continental Margin of Western North America and Adjacent Oceansâ Beaufort Sea to Baja California: Houston, Texas, Circum-Pacific Council for Energy and Mineral Resources, Earth Science Series, v. 6., p. 353-401. Prentice, C.S., and Kelson, K.I., 2006, The San Andreas fault in Sonoma and Mendocino counties, in Prentice, C.S., Scotchmoor, J.G., Moores, E.M., and Kiland, J.P., eds., 1906 San Francisco Earthquake Centennial Field Guides: Field trips associated with the 100th Anniversary Conference, 18-23 April 2006, San Francisco, California: Geological Society of America Field Guide 7, p. 127-156, Wentworth, C.M., 1968, Upper Cretaceous and lower Tertiary strata near Gualala, California, and inferred large right slip on the San Andreas fault, in Dickinson, W.R., and Grantz, A., eds. Proceedings of conference on geologic problems of San Andreas fault system: Stanford University Publications, Geological Sciences, v. 11, p. 130-143. Wentworth, C.M., Jones, D.L., and Brabb, E.E., 1998, Geology and regional correlation of the Cretaceous and Paleogene rocks of the Gualala block, California, in Elder, W.P., ed., Geology and tectonics of the Gualala block, northern California: Pacific Section, Society of Economic Paleontologists and Mineralogists, Book 84, p. 3-26.

This is a digital Seismic Hazard Zone Map presenting areas where liquefaction and landslides may occur during a strong earthquake. Three types of geological hazards, referred to as seismic hazard zones, may be featured on the map: 1) liquefaction, 2) earthquake-induced landslides, and 3) overlapping liquefaction and earthquake-induced landslides. In addition, a fourth feature may be included representing areas not evaluated for liquefaction or earthquake-induced landslides. Developers of properties falling within any of the three zones may be required to investigate the potential hazard and mitigate its threat during the local permitting process.

Link to the ScienceBase Item Summary page for the item described by this metadata record. Service Protocol: Link to the ScienceBase Item Summary page for the item described by this metadata record. Application Profile: Web Browser. Link Function: information

Airborne lidar survey of surface ruptures and ground failure features associated with the 4 and 5 July 2019 Ridgecrest Earthquake sequence. This dataset covers the non-tectonic Trona Pinnacles & Argus surface disturbance area. This region is not along the primary tectonic surface rupture , but was collected as part of a larger data collect which covers the areas impacted by the Ridgecrest earthquake. For additional information about this dataset see: Hudnut, K.W., B. Brooks, K. Scharer, J.L. Hernandez, T.E. Dawson, M.E. Oskin, R. Arrowsmith, C.A. Goulet, K. Blake, M.L. Boggs, S. Bork, C.L. Glennie, J.C. Fernandez-Diaz, A. Singhania, D. Hauser, S. Sorhus (2020), Airborne Lidar and Electro-Optical Imagery Along Surface Ruptures of the 2019 Ridgecrest Earthquake Sequence, Southern California, in press, Seismological Research Letters (preprint available upon request)

This map shows the potential of widespread slope failures, in terms of Newmark displacement (measured in centimeters), triggered by a M7.0 scenario earthquake on the Hayward Fault in the 10-county area surrounding the San Francisco Bay region, California. The cumulative downslope displacement of hillslopes is calculated using a simplified Newmark rigid sliding block slope stability model utilizing four primary datasets: a regional-scale geologic map of the study area, geologic strength parameters compiled as part of the California Geological Survey Seismic Hazard Mapping Program, earthquake shaking data from the USGS ShakeMap developed for this scenario, and 10-meter digital elevation data from the USGS 2009 National Elevation Dataset.The seismic-landslide hazard potential map covers the counties of Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz, Solano, and Sonoma. The slope failures are triggered by a hypothetical earthquake with a moment magnitude of 7.0 occurring on April 18, 2018, at 4:18 p.m. on the Hayward Fault in the east bay part of California’s San Francisco Bay region.

In October 2016, we acquired an approximately 15-km-long seismic profile along a linear transect across the East Bay region of the San Francisco Bay area. Our goal was to image previously unknown strands of the Hayward Fault zone and to better delineate the structure and geometry of the main trace of the Hayward Fault. Our profile started near the southern border of San Leandro, California at the San Francisco Bay shoreline, trended ENE through the northern edge of Castro Valley, California, and ended approximately 5 km WSW of San Ramon, California. The data were analyzed using refraction tomography modeling, reflection processing, and guided-wave analysis. The analyzed data are presented in separate reports by Strayer and others (submitted to BSSA).
The seismic data were generated at 26 shotpoints: 16 shotpoints located along the profile (inline shotpoints) and 10 shotpoints offset from the profile and located within known or suspected fault traces (guided-wave shotpoints). Mos ...

This part of DS 781 presents data for folds for the geologic and geomorphic map of the Offshore of Bodega Head map area, California. The vector data file is included in "Folds_OffshoreBodegaHead.zip," which is accessible from http://pubs.usgs.gov/ds/781/OffshoreBodegaHead/data_catalog_OffshoreBodegaHead.html. Onshore investigations indicate that this section of the San Andreas Fault onland has an estimated slip rate of about 17 to 25 mm/yr (Bryant and Lundberg, 2002). Emergent marine terraces at Bodega Bay record uplift rates associated with the fault system of about 0.1 mm/yr (Landis and others, 2004). The devastating Great 1906 California earthquake (M 7.8) is thought to have nucleated on the San Andreas Fault about 70 kilometers south of this map area offshore of San Francisco (e.g., Bolt, 1968; Lomax, 2005), with the rupture extending northward through the Offshore of Bodega Head map area to the south flank of Cape Mendocino. Folds were primarily mapped by interpretation of seismic reflection profile data (see field activity S-15-10-NC). The seismic reflection profiles were collected in 2010. References Cited Bolt, B.A., 1968, The focus of the 1906 California earthquake: Bulletin of the Seismological Society of America, v. 58, p. 457-471. Bryant, W.A., and Lundberg, M.M., compilers, 2002, Fault number 1b, San Andreas fault zone, North Coast section, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, accessed April 4, 2013, at http://earthquakes.usgs.gov/hazards/qfaults. Landis, P.S., Gardner, T.W., and Merritts, D.J., 2004, Deformation of marine terraces along the western edge of the North American Plate, Bodega Bay to the Russian River, CA: Geological Society of America Abstracts with Programs, South-Central Section, Paper 6-3. Lomax, A., 2005, A reanalysis of the hypocentral location and related observations for the Great 1906 California earthquake: Bulletin of the Seismological Society of America, v. 95, p. 861-877.

Since 1967 the U.S. Geological Survey has operated the Northern California Seismic Network (NCSN) to provide earthquake data for a wide range of research topics and hazard-reduction activities. The NCSN is designed to detect all local earthquakes having signal strength above the background level of microseisms. The network configuration was motivated by the need to monitor active faults and volcanoes with a station density sufficient to determine the focal depth of shallow (0-15 km) crustal earthquakes. Depending on the concentration of stations in a region, the magnitude (M) level at which earthquake detection is complete varies from approximately 1.4 in parts of the central Coast Ranges to 2.6 in the Klamath Mountain range. However, earthquakes with M<1.0 are routinely detected throughout the network.

The NCSN operates 412 stations in northern and central California and records an additional 100 stations maintained by 4 other institutions. It records a total of 924 channels of data using a mix of digital and analog systems. Nearly one fourth of the stations in the network are now digital, and 11 of the digital stations have broadband sensors, 92 have strong-motion sensors, and 11 are borehole installations. The remainder of the stations are mostly comprised of short-period vertical-component sensors. The NCSN telemetry system utlizes local collection nodes which are linked to Menlo Park via analog microwave, digital satellite telemetry, and leased digital circuits. The network also utilizes direct radio telemetry to Menlo Park and operates an extensive LAN that links urban stations located in the San Francisco Bay region.

NCSN network geometry is illustrated in a map of northern and central California located at the following URL: "http://quake.geo.berkeley.edu/ncsn/map.html".

Data Access: An earthquake catalog is produced from analysis of the NCSN data. Locations, magnitude, phases, coda durations, and first-motion mechanisms are available using the earthquake catalog search, "http://quake.geo.berkeley.edu/ncedc/catalog-search.html".

At this point in time, NCSN waveform data are not available in SEED format. However, effort is underway to provide this capability. For the present, NCSN waveform data are available through the EVT_FAST waveform request form, "http://quake.geo.berkeley.edu/ncedc/evt_fast_form.html", or through research accounts.