TheMw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earth... more TheMw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike the greater San Francisco Bay area since the Mw 6.9 1989 Loma Prieta earthquake. The rupture from this right-lateral earth-
As part of the U.S. National Seismic Hazard Model (NSHM) update planned for 2023, two databases w... more As part of the U.S. National Seismic Hazard Model (NSHM) update planned for 2023, two databases were prepared to more completely represent Quaternary-active faulting across the western United States: the NSHM23 fault sections database (FSD) and earthquake geology database (EQGeoDB). In prior iterations of NSHM, fault sections were included only if a field-measurement-derived slip rate was estimated along a given fault. By expanding this inclusion criteria, we were able to assess a larger set of faults for use in NSHM23. The USGS Quaternary Fault and Fold Database served as a guide for assessing possible additions to the NSHM23 FSD. Reevaluating available data from published sources yielded an increase of fault sections from ~650 faults in NSHM18 to ~1,000 faults proposed for use in NSHM23. EQGeoDB, a companion dataset linked to NSHM23 FSD, contains geologic slip rate estimates for fault sections included in FSD. Together, these databases serve as common input data used in deformatio...
This Data Release contains preliminary versions of two related databases: 1) A fault sections dat... more This Data Release contains preliminary versions of two related databases: 1) A fault sections database ("NSHM2023_FaultSections_v1"), which depicts the geometry of faults capable of hosting independent earthquakes, and 2) An earthquake geology site information database ("NSHM2023_EQGeoDB_v1"), which contains fault slip-rate constraints at points. These databases were prepared in anticipation of updates to the National Seismic Hazard Model (NSHM) 2023. Fault-specific geologic parameters for the NSHM have not been updated since the 2014 NSHM release. The datasets include the states of Washington, Oregon, California, Idaho, Nevada, Arizona, Montana, Wyoming, Colorado, New Mexico and Texas. Datasets containing fault information for Alaska and the Central and Eastern United States will be the subject of future efforts. These databases are provided as geospatial data (e.g., .SHP, .KML, .GeoJSON file formats) and tables (.CSV format).
In the minutes to hours after a major earthquake, such as the recent 2018 Mw 7.1 Anchorage event,... more In the minutes to hours after a major earthquake, such as the recent 2018 Mw 7.1 Anchorage event, the U.S. Geological Survey (USGS) produces a suite of interconnected earthquake products that provides diverse information ranging from basic earthquake source parameters to loss estimates. The 2018 Anchorage earthquake is the first major domestic earthquake to occur since several new USGS products have been developed, thus providing an opportunity to discuss the newly expanded USGS earthquake product suite, its timeliness, performance, and reception. Overall, the products were relatively timely, accurate, well received, and widely used, including by the media, who used information and visualizations from many products to frame their early reporting. One downside of the codependence of multiple products is that reasonable updates to upstream products (e.g., magnitude and source characterization) can result in significant changes to downstream products; this was the case for the Anchorag...
Earthquake-induced ground failures such as liquefaction have historically brought loss of life an... more Earthquake-induced ground failures such as liquefaction have historically brought loss of life and damage to property and infrastructure. Observations of the effects of historical large-magnitude earthquakes show that the distribution of liquefaction phenomena is not random. Liquefaction is restricted to areas underlain by loose, cohesionless sands and silts that are saturated with water. These areas can be delineated on the basis of thorough geologic, geomorphic, and hydrologic mapping and map analysis (Tinsley and Holzer, 1990; Youd and Perkins, 1987). Once potential liquefaction zones are delineated, appropriate public and private agencies can prepare for and mitigate seismic hazard in these zones. In this study, we create a liquefaction susceptibility map of the Napa 1:100,000 quadrangle using Quaternary geologic mapping, analysis of historical liquefaction information, groundwater data, and data from other studies. The study is patterned after state-of-the-art studies by Youd (1973) Dupré and Tinsley (1980) and Dupré (1990) in the
Geotechnical Earthquake Engineering and Soil Dynamics IV, 2008
A deformation-based approach for mapping earthquake-induced liquefaction hazard has been develope... more A deformation-based approach for mapping earthquake-induced liquefaction hazard has been developed that utilizes recently generated predictive relationships for shear-strain potential. These new relationships are used to calculate Displacement Potential Index given induced cyclic stress ratio and normalized fines-corrected standard penetration resistance. Conventional liquefaction hazard mapping is based on qualitative assessments of surface deposits, their geomorphology, environment and recency of deposition, and past performance from post-earthquake investigations. This new method is a more quantitative, deformation-based approach that emphasizes the severity of ground failure rather than mere likelihood of liquefaction. These new methods are being investigated for use in improving delineation of California's regulatory liquefaction hazard zones. Over 650 boring logs have been analyzed for 18 Quaternary geologic map units in a pilot study covering a portion of the southern San Francisco Bay Area in Santa Clara County. A sufficient number of boring logs were available for nine of the Quaternary units to permit reclassification into four liquefaction susceptibility units, for which parametric modeling was performed and ground deformation hazard mapped over the test area. Pilot study results show good agreement with historical occurrences of liquefaction.
The Quake `06 Campaign is a volunteer effort capitalizing on the extraordinary earthquake risk ma... more The Quake `06 Campaign is a volunteer effort capitalizing on the extraordinary earthquake risk management expertise in the San Francisco Bay area. Begun in April 2002, Quake `06 is a four-year campaign to reduce earthquake risk in the Bay Area by the hundredth ...
We describe an approach to model liquefaction extent that focuses on identifying broadly availabl... more We describe an approach to model liquefaction extent that focuses on identifying broadly available geospatial variables (e.g., derived from digital elevation models) and earthquake-specific parameters (e.g., peak ground acceleration, PGA). A key step is database development: We focus on the 1995 Kobe and 2010–2011 Christchurch earthquakes because the presence/absence of liquefaction has been mapped so that the database is unbiased with respect to the areal extent of liquefaction. We derive two liquefaction models with explanatory variables that include PGA, shear-wave velocity, compound topographic index, and a newly defined normalized distance parameter (distance to coast divided by the sum of distance to coast and distance to the basin inland edge). To check the portability/reliability of these models, we apply them to the 2010 Haiti earthquake. We conclude that these models provide first-order approximations of the extent of liquefaction, appropriate for use in rapid response, lo...
Bulletin of the Seismological Society of America, 2002
Evidence of rapid relative sea level changes preserved in sediment of coastal estuaries along the... more Evidence of rapid relative sea level changes preserved in sediment of coastal estuaries along the north coast segment of the San Andreas fault provides information on the dates of past earthquakes. This approach, although successfully used to document large subduction zone earthquakes, has not been used previously to constrain the dates of San Andreas fault or other strike-slip fault earthquakes. Data on prehistoric San Andreas fault earthquakes is needed for development of robust probabilistic hazard assessments in northern California and the San Francisco Bay area. Evidence of earthquake-induced subsidence is preserved in marshes at the northern margin of Bolinas Lagoon and the southeastern margin of Bodega Harbor. These sites occupy structural basins or troughs along the northern San Andreas fault. Radiocarbon dating and identification of the first occurrence of nonnative pollen near abrupt sedimentological changes in cores are used to constrain the dates of San Andreas fault earthquakes over about the last 800 years. Estuarine sediment from northern Bolinas Lagoon preserves evidence of an earthquake that occurred about 750 years ago. Evidence for this earthquake includes a marsh soil that was abruptly buried by tidal flat mud or coarse, poorly sorted deltaic deposits containing a mixture of terrestrial sediment and marine mud. Evaluation of diatom assemblages from above and below the buried soil horizon provides evidence of at least several decimeters of sustained relative sea level rise. Three buried soils in a marsh at the southern end of Bodega Harbor are likely a result of coseismic subsidence. All three buried marsh soils have abrupt upper contacts, although diatom evidence for decimeters of sustained subsidence is not as strong as it is for the buried soil in Bolinas Lagoon. Existing paleoseismic data on the northern San Andreas fault is compared with results of this study in order to evaluate the dates of prehistoric large earthquakes and length of past ruptures. These data indicate that an earthquake occurred about 400 years ago and another earthquake occurred about 700 years ago. The data allow for 1906-type ruptures of the fault from the Santa Cruz Mountains to at least Point Arena. However, a sequence of closely timed, smaller earthquakes would produce a similar set of paleoseismic data.
Bulletin of the Seismological Society of America, 2011
To assess the level and nature of ground shaking in Hawaii for the purposes of earthquake hazard ... more To assess the level and nature of ground shaking in Hawaii for the purposes of earthquake hazard mitigation and seismic design, empirical groundmotion prediction models are desired. To develop such empirical relationships, knowledge of the subsurface site conditions beneath strong-motion stations is critical. Thus, as a first step to develop ground-motion prediction models for Hawaii, spectralanalysis-of-surface-waves (SASW) profiling was performed at the 22 free-field U.S. Geological Survey (USGS) strong-motion sites on the Big Island to obtain shear-wave velocity (V S) data. Nineteen of these stations recorded the 2006 Kiholo Bay moment magnitude (M) 6.7 earthquake, and 17 stations recorded the triggered M 6.0 Mahukona earthquake. V S profiling was performed to reach depths of more than 100 ft. Most of the USGS stations are situated on sites underlain by basalt, based on surficial geologic maps. However, the sites have varying degrees of weathering and soil development. The remaining strong-motion stations are located on alluvium or volcanic ash. V S30 (average V S in the top 30 m) values for the stations on basalt ranged from 906 to 1908 ft=s [National Earthquake Hazards Reduction Program (NEHRP) site classes C and D], because most sites were covered with soil of variable thickness. Based on these data, an NEHRP site-class map was developed for the Big Island. These new V S data will be a significant input into an update of the USGS statewide hazard maps and to the operation of ShakeMap on the island of Hawaii.
Appendix A-Sources of geologic information used by site investigators when compiling time-average... more Appendix A-Sources of geologic information used by site investigators when compiling time-averaged shear-wave velocity to a depth of 30 meters (V S30) data.
The U.S. Geological Survey (USGS) Earthquake Hazards and Landslide Hazards Programs are developin... more The U.S. Geological Survey (USGS) Earthquake Hazards and Landslide Hazards Programs are developing plans to add quantitative hazard assessments of earthquake-triggered landsliding and liquefaction to existing real-time earthquake products (ShakeMap, ShakeCast, PAGER) using open and readily available methodologies and products. To date, prototype global statistical models have been developed and are being refined, improved, and tested. These models are a good foundation, but much work remains to achieve robust and defensible models that meet the needs of end users. In order to establish an implementation plan and identify research priorities, the USGS convened a workshop in Golden, Colorado, in October 2015. This document summarizes current (as of early 2016) capabilities, research and operational priorities, and plans for further studies that were established at this workshop. Specific priorities established during the meeting include (1) developing a suite of alternative models; (2) making use of higher resolution and higher quality data where possible; (3) incorporating newer global and regional datasets and inventories; (4) reducing barriers to accessing inventory datasets; (5) developing methods for using inconsistent or incomplete datasets in aggregate; (6) developing standardized model testing and evaluation methods; (7) improving ShakeMap shaking estimates, particularly as relevant to ground failure, such as including topographic amplification and accounting for spatial variability; and (8) developing vulnerability functions for loss estimates.
TheMw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earth... more TheMw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike the greater San Francisco Bay area since the Mw 6.9 1989 Loma Prieta earthquake. The rupture from this right-lateral earth-
As part of the U.S. National Seismic Hazard Model (NSHM) update planned for 2023, two databases w... more As part of the U.S. National Seismic Hazard Model (NSHM) update planned for 2023, two databases were prepared to more completely represent Quaternary-active faulting across the western United States: the NSHM23 fault sections database (FSD) and earthquake geology database (EQGeoDB). In prior iterations of NSHM, fault sections were included only if a field-measurement-derived slip rate was estimated along a given fault. By expanding this inclusion criteria, we were able to assess a larger set of faults for use in NSHM23. The USGS Quaternary Fault and Fold Database served as a guide for assessing possible additions to the NSHM23 FSD. Reevaluating available data from published sources yielded an increase of fault sections from ~650 faults in NSHM18 to ~1,000 faults proposed for use in NSHM23. EQGeoDB, a companion dataset linked to NSHM23 FSD, contains geologic slip rate estimates for fault sections included in FSD. Together, these databases serve as common input data used in deformatio...
This Data Release contains preliminary versions of two related databases: 1) A fault sections dat... more This Data Release contains preliminary versions of two related databases: 1) A fault sections database ("NSHM2023_FaultSections_v1"), which depicts the geometry of faults capable of hosting independent earthquakes, and 2) An earthquake geology site information database ("NSHM2023_EQGeoDB_v1"), which contains fault slip-rate constraints at points. These databases were prepared in anticipation of updates to the National Seismic Hazard Model (NSHM) 2023. Fault-specific geologic parameters for the NSHM have not been updated since the 2014 NSHM release. The datasets include the states of Washington, Oregon, California, Idaho, Nevada, Arizona, Montana, Wyoming, Colorado, New Mexico and Texas. Datasets containing fault information for Alaska and the Central and Eastern United States will be the subject of future efforts. These databases are provided as geospatial data (e.g., .SHP, .KML, .GeoJSON file formats) and tables (.CSV format).
In the minutes to hours after a major earthquake, such as the recent 2018 Mw 7.1 Anchorage event,... more In the minutes to hours after a major earthquake, such as the recent 2018 Mw 7.1 Anchorage event, the U.S. Geological Survey (USGS) produces a suite of interconnected earthquake products that provides diverse information ranging from basic earthquake source parameters to loss estimates. The 2018 Anchorage earthquake is the first major domestic earthquake to occur since several new USGS products have been developed, thus providing an opportunity to discuss the newly expanded USGS earthquake product suite, its timeliness, performance, and reception. Overall, the products were relatively timely, accurate, well received, and widely used, including by the media, who used information and visualizations from many products to frame their early reporting. One downside of the codependence of multiple products is that reasonable updates to upstream products (e.g., magnitude and source characterization) can result in significant changes to downstream products; this was the case for the Anchorag...
Earthquake-induced ground failures such as liquefaction have historically brought loss of life an... more Earthquake-induced ground failures such as liquefaction have historically brought loss of life and damage to property and infrastructure. Observations of the effects of historical large-magnitude earthquakes show that the distribution of liquefaction phenomena is not random. Liquefaction is restricted to areas underlain by loose, cohesionless sands and silts that are saturated with water. These areas can be delineated on the basis of thorough geologic, geomorphic, and hydrologic mapping and map analysis (Tinsley and Holzer, 1990; Youd and Perkins, 1987). Once potential liquefaction zones are delineated, appropriate public and private agencies can prepare for and mitigate seismic hazard in these zones. In this study, we create a liquefaction susceptibility map of the Napa 1:100,000 quadrangle using Quaternary geologic mapping, analysis of historical liquefaction information, groundwater data, and data from other studies. The study is patterned after state-of-the-art studies by Youd (1973) Dupré and Tinsley (1980) and Dupré (1990) in the
Geotechnical Earthquake Engineering and Soil Dynamics IV, 2008
A deformation-based approach for mapping earthquake-induced liquefaction hazard has been develope... more A deformation-based approach for mapping earthquake-induced liquefaction hazard has been developed that utilizes recently generated predictive relationships for shear-strain potential. These new relationships are used to calculate Displacement Potential Index given induced cyclic stress ratio and normalized fines-corrected standard penetration resistance. Conventional liquefaction hazard mapping is based on qualitative assessments of surface deposits, their geomorphology, environment and recency of deposition, and past performance from post-earthquake investigations. This new method is a more quantitative, deformation-based approach that emphasizes the severity of ground failure rather than mere likelihood of liquefaction. These new methods are being investigated for use in improving delineation of California's regulatory liquefaction hazard zones. Over 650 boring logs have been analyzed for 18 Quaternary geologic map units in a pilot study covering a portion of the southern San Francisco Bay Area in Santa Clara County. A sufficient number of boring logs were available for nine of the Quaternary units to permit reclassification into four liquefaction susceptibility units, for which parametric modeling was performed and ground deformation hazard mapped over the test area. Pilot study results show good agreement with historical occurrences of liquefaction.
The Quake `06 Campaign is a volunteer effort capitalizing on the extraordinary earthquake risk ma... more The Quake `06 Campaign is a volunteer effort capitalizing on the extraordinary earthquake risk management expertise in the San Francisco Bay area. Begun in April 2002, Quake `06 is a four-year campaign to reduce earthquake risk in the Bay Area by the hundredth ...
We describe an approach to model liquefaction extent that focuses on identifying broadly availabl... more We describe an approach to model liquefaction extent that focuses on identifying broadly available geospatial variables (e.g., derived from digital elevation models) and earthquake-specific parameters (e.g., peak ground acceleration, PGA). A key step is database development: We focus on the 1995 Kobe and 2010–2011 Christchurch earthquakes because the presence/absence of liquefaction has been mapped so that the database is unbiased with respect to the areal extent of liquefaction. We derive two liquefaction models with explanatory variables that include PGA, shear-wave velocity, compound topographic index, and a newly defined normalized distance parameter (distance to coast divided by the sum of distance to coast and distance to the basin inland edge). To check the portability/reliability of these models, we apply them to the 2010 Haiti earthquake. We conclude that these models provide first-order approximations of the extent of liquefaction, appropriate for use in rapid response, lo...
Bulletin of the Seismological Society of America, 2002
Evidence of rapid relative sea level changes preserved in sediment of coastal estuaries along the... more Evidence of rapid relative sea level changes preserved in sediment of coastal estuaries along the north coast segment of the San Andreas fault provides information on the dates of past earthquakes. This approach, although successfully used to document large subduction zone earthquakes, has not been used previously to constrain the dates of San Andreas fault or other strike-slip fault earthquakes. Data on prehistoric San Andreas fault earthquakes is needed for development of robust probabilistic hazard assessments in northern California and the San Francisco Bay area. Evidence of earthquake-induced subsidence is preserved in marshes at the northern margin of Bolinas Lagoon and the southeastern margin of Bodega Harbor. These sites occupy structural basins or troughs along the northern San Andreas fault. Radiocarbon dating and identification of the first occurrence of nonnative pollen near abrupt sedimentological changes in cores are used to constrain the dates of San Andreas fault earthquakes over about the last 800 years. Estuarine sediment from northern Bolinas Lagoon preserves evidence of an earthquake that occurred about 750 years ago. Evidence for this earthquake includes a marsh soil that was abruptly buried by tidal flat mud or coarse, poorly sorted deltaic deposits containing a mixture of terrestrial sediment and marine mud. Evaluation of diatom assemblages from above and below the buried soil horizon provides evidence of at least several decimeters of sustained relative sea level rise. Three buried soils in a marsh at the southern end of Bodega Harbor are likely a result of coseismic subsidence. All three buried marsh soils have abrupt upper contacts, although diatom evidence for decimeters of sustained subsidence is not as strong as it is for the buried soil in Bolinas Lagoon. Existing paleoseismic data on the northern San Andreas fault is compared with results of this study in order to evaluate the dates of prehistoric large earthquakes and length of past ruptures. These data indicate that an earthquake occurred about 400 years ago and another earthquake occurred about 700 years ago. The data allow for 1906-type ruptures of the fault from the Santa Cruz Mountains to at least Point Arena. However, a sequence of closely timed, smaller earthquakes would produce a similar set of paleoseismic data.
Bulletin of the Seismological Society of America, 2011
To assess the level and nature of ground shaking in Hawaii for the purposes of earthquake hazard ... more To assess the level and nature of ground shaking in Hawaii for the purposes of earthquake hazard mitigation and seismic design, empirical groundmotion prediction models are desired. To develop such empirical relationships, knowledge of the subsurface site conditions beneath strong-motion stations is critical. Thus, as a first step to develop ground-motion prediction models for Hawaii, spectralanalysis-of-surface-waves (SASW) profiling was performed at the 22 free-field U.S. Geological Survey (USGS) strong-motion sites on the Big Island to obtain shear-wave velocity (V S) data. Nineteen of these stations recorded the 2006 Kiholo Bay moment magnitude (M) 6.7 earthquake, and 17 stations recorded the triggered M 6.0 Mahukona earthquake. V S profiling was performed to reach depths of more than 100 ft. Most of the USGS stations are situated on sites underlain by basalt, based on surficial geologic maps. However, the sites have varying degrees of weathering and soil development. The remaining strong-motion stations are located on alluvium or volcanic ash. V S30 (average V S in the top 30 m) values for the stations on basalt ranged from 906 to 1908 ft=s [National Earthquake Hazards Reduction Program (NEHRP) site classes C and D], because most sites were covered with soil of variable thickness. Based on these data, an NEHRP site-class map was developed for the Big Island. These new V S data will be a significant input into an update of the USGS statewide hazard maps and to the operation of ShakeMap on the island of Hawaii.
Appendix A-Sources of geologic information used by site investigators when compiling time-average... more Appendix A-Sources of geologic information used by site investigators when compiling time-averaged shear-wave velocity to a depth of 30 meters (V S30) data.
The U.S. Geological Survey (USGS) Earthquake Hazards and Landslide Hazards Programs are developin... more The U.S. Geological Survey (USGS) Earthquake Hazards and Landslide Hazards Programs are developing plans to add quantitative hazard assessments of earthquake-triggered landsliding and liquefaction to existing real-time earthquake products (ShakeMap, ShakeCast, PAGER) using open and readily available methodologies and products. To date, prototype global statistical models have been developed and are being refined, improved, and tested. These models are a good foundation, but much work remains to achieve robust and defensible models that meet the needs of end users. In order to establish an implementation plan and identify research priorities, the USGS convened a workshop in Golden, Colorado, in October 2015. This document summarizes current (as of early 2016) capabilities, research and operational priorities, and plans for further studies that were established at this workshop. Specific priorities established during the meeting include (1) developing a suite of alternative models; (2) making use of higher resolution and higher quality data where possible; (3) incorporating newer global and regional datasets and inventories; (4) reducing barriers to accessing inventory datasets; (5) developing methods for using inconsistent or incomplete datasets in aggregate; (6) developing standardized model testing and evaluation methods; (7) improving ShakeMap shaking estimates, particularly as relevant to ground failure, such as including topographic amplification and accounting for spatial variability; and (8) developing vulnerability functions for loss estimates.
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