The map shows faults with historic and Holocene movement. Because the unit is undifferentiated in our digital geologic data set, we have no basis for identifying the slower-velocity soils. While the average velocity is within the range of soil-type C, some of the slower-velocity soils within the unit fall into the range of soil-type D. For example, there is a widespread unit consisting of Quaternary sand, gravel, silt and mud. Some inaccuracy is introduced by assigning NEHRP soil-types to a geologic unit on the basis of the average velocity for that unit.
Bay area earthquake | bay area earthquake monitor | milpitas earthquake | bay area news - Sites on thin layers of soft soil overlying stiff soil will behave more like sites on stiff soil. Soft soils tend to overlie stiffer soils and bedrock. Map boundaries are accurate only to within about 50 meters. Surface geology provides only a rough estimate of the site effect. The strongest amplification of shaking due is expected for this soil type. Includes water-saturated mud and artificial fill. Significant amplification of shaking by these soils is generally expected. Includes some Quaternary sands, sandstones and mudstones, some Upper Tertiary sandstones, mudstones and limestone, some Lower Tertiary mudstones and sandstones, and Franciscan melange and serpentinite. Includes volcanics, most Mesozoic bedrock, and some Franciscan bedrock. Soil types A and B do not contribute greatly to shaking amplification.
Bay area earthquake | bay area earthquake monitor | milpitas earthquake | bay area news - Occurs infrequently in the bay area. Includes unweathered intrusive igneous rock. We have modified these definitions slightly, based on studies of earthquake damage in the Bay Area. The National Earthquake Hazards Reduction Program has defined 5 soil types based on their shear-wave velocity.
Bay area earthquake | bay area earthquake monitor | milpitas earthquake | bay area news - Sites on thin layers of soft soil overlying stiff soil will behave more like sites on stiff soil. Soft soils tend to overlie stiffer soils and bedrock. Map boundaries are accurate only to within about 50 meters. Surface geology provides only a rough estimate of the site effect. The strongest amplification of shaking due is expected for this soil type. Includes water-saturated mud and artificial fill. Significant amplification of shaking by these soils is generally expected. Includes some Quaternary sands, sandstones and mudstones, some Upper Tertiary sandstones, mudstones and limestone, some Lower Tertiary mudstones and sandstones, and Franciscan melange and serpentinite. Includes volcanics, most Mesozoic bedrock, and some Franciscan bedrock. Soil types A and B do not contribute greatly to shaking amplification.
Bay area earthquake | bay area earthquake monitor | milpitas earthquake | bay area news - Occurs infrequently in the bay area. Includes unweathered intrusive igneous rock. We have modified these definitions slightly, based on studies of earthquake damage in the Bay Area. The National Earthquake Hazards Reduction Program has defined 5 soil types based on their shear-wave velocity.
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