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USGS1995

Saving lives through better design standards

Over the past 30 years, scientists have put together a more complete picture of how the ground shakes during earthquakes. They have learned that shaking near the source of earthquakes is far more severe than once thought and that soft ground shakes more strongly than hard rock.This knowledge has enabled engineers to improve design standards so that structures arebetter able to survive strong earthquakes. When the 1989 Loma Prieta earthquake struck, 42 people tragically lost their lives in the collapse of a half-mile-long section of the Cypress structure, an elevated double-decker freeway in Oakland, California.Yet adjacent parts of this structure withstood the magnitude 6.9 temblor—why? The part that collapsed was built on man-made fill over soft mud, whereas adjacent sections stood on older, firmer sand and gravel deposits. Following the collapse, scientists set out instruments in the area to record the earthquake's many strong aftershocks. These instruments showed that the softer ground shook more forcefully than the firmer material-even twice as violently

California↗
USGS1968

Geological literature on the San Joaquin Valley of California

The following list of references includes most of the geological literature on the San Joaquin Valley and vicinity in central California (see figure 1) published prior to January 1,1968. The San Joaquin Valley comprises all or parts of 11 counties -- Alameda, Calaveras, Contra Costa, Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus, and Tulare (figure 2). As a matter of convenient geographical classification, the boundaries of the report area have been drawn along county lines, and to include San Benito and Santa Clara Counties on the west and Mariposa and Tuolumne Counties on the east. Therefore, this list of geological literature includes some publications on the Diablo and Temblor Ranges on the west, the Tehachapi Mountains and Mojave Desert on the south, and the Sierra Nevada Foothills and Mountains on the east.

California↗
USGS1991

Cenozoic giant pectinids from California and the Tertiary Caribbean Province: Lyropecten, "Macrochlamis," Vertipecten, and Nodipecten species

Tertiary pectinids recognized for more than 125 years by field geologists can now be used to date and correlate 3-4 m.y. increments of the geologic record and to determine faunal distributions in relation to tectonic terranes. Fossil pectinids are commonly preserved in shallowmarine clastic deposits that mostly lack microfossils. The stratigraphic ranges of Lyropecten, "Macrochlamis," Vertipecten , and Nodipecten can be used to subdivide provincial megafaunal stages in California and to correlate chronostratigraphic units in the Pacific Northwest and Atlantic Coastal Plain. One New World taxon, "Macrochlamis" magnolia ojaiensis, n. subsp., supports a direct correlation between the middle "Vaqueros" Stage of California (interpolated as 27-23 m.y. B.P.) and an Upper Chattian-Lower Aquitanian Stage section in southwestern Switzerland. Two lithologic units widespread in California, the Vaqueros Formation (spanning 12 m.y., from the late Oligocene into the early Miocene) and Temblor Formation (deposited over a period of 26 m.y., from the late Eocene or early Oligocene to the middle Miocene), transgress much longer periods of time than have been generally recognized. Certain species pairs are identified as cognates, close relatives descended from a common ancestor. Close similarities are found between widely separated assemblages from the Salton Trough of California and the Caribbean, the Gulf Coastal Plain of eastern Mexico and the Sinu Valley of western Colombia, the Santa Rosalia area in Baja California Sur, Mexico, and the Paraguana Peninsula of Venezuela. Distribution patterns for relatively recently dispersed taxa have important implications for middle to late Cenozoic paleogeography and tectonic history, especially in west Mexico and the Caribbean. Speciation was concurrent with the closure of the Isthmus of Panama, the opening of the Gulf of California, and possibly with the northward translation of segments of the California Continental Borderland. Tertiary Caribbean and PacificPanamic Lyropectens and Nodipectens are plotted on a simplified tectonic map as an early step in considering Cenozoic molluscan distributions in relation to major plate boundaries. Taxa having unusual distributions are tabulated with the tectonic events that may have modified their observed geographic ranges. Southern California and the Baja California peninsula include tectonostratigraphic terranes and tectonic slivers that may have moved on the order of hundreds or thousands of kilometers in the Paleogene. Relations between recently dispersed faunas and tectonic terrane boundaries are further complicated by short-term variations in oceanographic phenomena such as currents, El Nino events, and shifts in areas of upwelling. Lyropecten evolved in the late Oligocene or early Miocene, Nodipecten by the late middle Miocene. According to the classification used here, Lyropecten still lives in the Galapagos. Holocene Nodipectens divide the Pacific-Panamic and Caribbean provinces into two subprovinces each. Habitat, life history, dispersal, and growth data are summarized for living Nodipectens, whose distinctive shell features include ledges and hollow nodes. Phylogenetic lineages are based on progressive trends in node formation and rib schemes, some of which have biostratigraphic significance.

Professional Paper↗
USGS1991

The Cenozoic evolution of the San Joaquin Valley, California

The San Joaquin Valley, which is the southern part of the 700-km-long Great Valley of California, is an asymmetric structural trough that is filled with a prism of upper Mesozoic and Cenozoic sediments up to 9 km thick; these sediments rest on crystalline basement rocks of the southwestward-tilted Sierran block. The San Joaquin sedimentary basin is separated from the Sacramento basin to the north by the buried Stockton arch and associated Stockton fault. The buried Bakersfield arch near the south end of the valley separates the small Maricopa-Tejon subbasin at the south end of the San Joaquin basin from the remainder of the basin. Cenozoic strata in the San Joaquin basin thicken southeastward from about 800 m in the north to over 9,000 m in the south. The San Joaquin Valley can be subdivided into five regions on the basis of differing structural style. They are the northern Sierran block, the southern Sierran block, the northern Diablo homocline, the westside fold belt, and the combined Maricopa-Tejon subbasin and southmargin deformed belt. Considerable facies variation existed within the sedimentary basin, particularly in the Neogene when a thick section of marine sediment accumulated in the southern part of the basin, while a relatively thin and entirely nonmarine section was deposited in the northern part. The northern Sierran block, the stable east limb of the valley syncline between the Stockton fault and the San Joaquin River, is the least deformed region of the valley. Deformation consists mostly of a southwest tilt and only minor late Cenozoic normal faulting. The southern Sierran block, the stable east limb of the valley syncline between the San Joaquin River and the Bakersfield arch, is similar in style to the northern part of the block, but it has a higher degree of deformation. Miocene or older normal faults trend mostly north to northwest and have a net down-to-the-west displacement with individual offsets of as much as 600 m. The northern Diablo homocline, the western limb of the valley syncline between the Stockton arch and Panoche Creek, consists of a locally faulted homocline with northeast dips. Deformation is mostly late Cenozoic, is complex in its history, and has included up-to-the-southwest reverse faulting. The west-side fold belt, the southwestern part of the valley syncline between Panoche Creek and Elk Hills and including the southern Diablo and Temblor Ranges, is characterized by a series of folds and faults trending slightly oblique to the San Andreas fault. Paleogene folding took place in the northern part of the belt; however, most folding took place in Neogene time, during which the intensity of deformation increased southeastward along the belt and southwestward toward the San Andreas fault. The Maricopa-Tejon subbasin and the south-margin deformed belt are structurally distinct, but genetically related, regions bounded by the Bakersfield arch on the north, the San Emigdio Mountains on the south, the Tehachapi Mountains on the east, and the southeast end of the fold belt on the west. This combined region, which is the most deformed part of the basin, has undergone significant late Cenozoic shortening through north-directed thrust faulting at the south margin, as well as extreme Neogene basin subsidence north of the thrust belt. The sedimentary history of the San Joaquin basin, recorded in terms of unconformity-bounded depositional sequences, has been controlled principally by tectonism, but it has also been controlled by eustatic sea-level changes and, to a lesser degree, by climate. Plate tectonic events that had an influence on the basin include (1) subduction during the early Tertiary that changed from oblique to normal convergence in the later part of the Eocene, (2) the mid-Oligocene encounter of the Pacific-Farallon spreading ridge with the trench, and the consequent establishment of the San Andreas transform, (3) the northwestward migration of the Mendocino triple junction that in

Professional Paper↗
USGS2009

Eocene total petroleum system — North and East of the Eocene West Side Fold Belt Assessment Unit of the San Joaquin Basin Province

The North and East of Eocene West Side Fold Belt Assessment Unit (AU) of the Eocene Total Petroleum System of the San Joaquin Basin Province comprises all hydrocarbon accumulations within the geographic and stratigraphic limits of this confirmed AU. Oil and associated gas accumulations occur in Paleocene through early middle Miocene marine to nonmarine sandstones found on the comparatively stable northeast shelf of the basin. The assessment unit is located north and east of the thickest accumulation of Neogene sediments and the west side fold belt. The area enclosed by the AU has been affected by only mild deformation since Eocene time. Traps containing known accumulations are mostly low-relief domes, anticlines, and up-dip basin margin traps with faulting and stratigraphic components. Map boundaries of the assessment unit are shown in figures 19.1 and 19.2; this assessment unit replaces the Northeast Shelf of Neogene Basin play 1006, the East Central Basin and Slope North of Bakersfield Arch play 1010, and part of the West Side Fold Belt Sourced by Pre-middle Miocene Rocks play 1005 considered by the U.S. Geological Survey (USGS) in their 1995 National Assessment (Beyer, 1996). Stratigraphically, the AU includes rocks from the uppermost crystalline basement to the topographic surface. In the region of overlap with the Central Basin Monterey Diagenetic Traps Assessment Unit, the North and East of Eocene West Side Fold Belt AU extends from basement rocks to the top of the Temblor Formation (figs. 19.3 and 19.4). In map view, the northern boundary of the assessment unit corresponds to the northernmost extent of Eocene-age Kreyenhagen Formation. The northeast boundary is the eastern limit of possible oil reservoir rocks near the eastern edge of the basin. The southeast boundary corresponds to the pinch-out of Stevens sand of Eckis (1940) to the south, which approximately coincides with the northern flank of the Bakersfield Arch (fig. 19.1). The AU is bounded on the southwest by the limit of major west side structural deformation and to the northwest by the San Andreas Fault and the limit of hydrocarbon-prospective strata in the Coast Ranges. As described by Gautier and others (this volume, chapter 2), existing oil fields in the San Joaquin Basin Province were assigned to assessment units based on the identified petroleum system and reservoir rocks in each field. Vallecitos oil field in the extreme northwest corner of the basin was assigned to the Eocene Total Petroleum System, because oil analyses conducted for this San Joaquin Basin assessment indicate that Eocene oil charged the reservoir rocks (Lillis and Magoon, this volume, chapter 9). Some literature classifies the Vallecitos oil field as part of the northernmost fold of the basin’s west side fold belt (see, for example, Rentschler, 1985; Bartow, 1991), but because of the oil field’s spatial separation and differing trend from the west side fold belt, Vallecitos field was considered here to be within the North and East of Eocene West Side Fold Belt Assessment Unit rather than in the other assessment unit in the Eocene Total Petroleum System, the Eocene West Side Fold Belt. Primary fields in the assessment unit are defined as those containing hydrocarbon resources greater than the USGS minimum threshold for assessment (0.5 million barrels of oil); secondary fields contain smaller volumes of oil but constitute a significant show of hydrocarbons.

California↗
USGS1970

The Alaska earthquake, March 27, 1964: Lessons and conclusions

One of the greatest earthquakes of all time struck south-central Alaska on March 27, 1964. Strong motion lasted longer than for most recorded earthquakes, and more land surface was dislocated, vertically and horizontally, than by any known previous temblor. Never before were so many effects on earth processes and on the works of man available for study by scientists and engineers over so great an area. The seismic vibrations, which directly or indirectly caused most of the damage, were but surface manifestations of a great geologic event-the dislocation of a huge segment of the crust along a deeply buried fault whose nature and even exact location are still subjects for speculation. Not only was the land surface tilted by the great tectonic event beneath it, with resultant seismic sea waves that traversed the entire Pacific, but an enormous mass of land and sea floor moved several tens of feet horizontally toward the Gulf of Alaska. Downslope mass movements of rock, earth, and snow were initiated. Subaqueous slides along lake shores and seacoasts, near-horizontal movements of mobilized soil (“landspreading”), and giant translatory slides in sensitive clay did the most damage and provided the most new knowledge as to the origin, mechanics, and possible means of control or avoidance of such movements. The slopes of most of the deltas that slid in 1964, and that produced destructive local waves, are still as steep or steeper than they were before the earthquake and hence would be unstable or metastable in the event of another great earthquake. Rockslide avalanches provided new evidence that such masses may travel on cushions of compressed air, but a widely held theory that glaciers surge after an earthquake has not been substantiated. Innumerable ground fissures, many of them marked by copious emissions of water, caused much damage in towns and along transportation routes. Vibration also consolidated loose granular materials. In some coastal areas, local subsidence was superimposed on regional tectonic subsidence to heighten the flooding damage. Ground and surface waters were measurably affected by the earthquake, not only in Alaska but throughout the world. Expectably, local geologic conditions largely controlled the extent of structural damage, whether caused directly by seismic vibrations or by secondary effects such as those just described. Intensity was greatest in areas underlain by thick saturated unconsolidated deposits, least on indurated bedrock or permanently frozen ground, and intermediate on coarse well-drained gravel, on morainal deposits, or on moderately indurated sedimentary rocks. Local and even regional geology also controlled the distribution and extent of the earthquake's effects on hydrologic systems. In the conterminous United States, for example, seiches in wells and bodies of surface water were controlled by geologic structures of regional dimension. Devastating as the earthquake was, it had many long-term beneficial effects. Many of these were socioeconomic or engineering in nature; others were of scientific value. Much new and corroborative basic geologic and hydrologic information was accumulated in the course of the earthquake studies, and many new or improved investigative techniques were developed. Chief among these, perhaps, were the recognition that lakes can be used as giant tiltmeters, the refinement of methods for measuring land-level changes by observing displacements of barnacles and other sessile organisms, and the relating of hydrology to seismology by worldwide study of hydroseisms in surface-water bodies and in wells. The geologic and hydrologic lessons learned from studies of the Alaska earthquake also lead directly to better definition of the research needed to further our understanding of earthquakes and of how to avoid or lessen the effects of future ones. Research is needed on the origins and mechanisms of earthquakes, on crustal structure, and on the generation of tsunamis and local waves. Better earthquake-hazard maps, based on improved knowledge of regional geology, fault behavior, and earthquake mechanisms, are needed for the entire country. Their preparation will require the close collaboration of engineers, seismologists, and geologists. Geologic maps of all inhabited places in earthquake-prone parts of the country are also needed by city planners and others, because the direct relationship between local geology and potential earthquake damage is now well understood. Improved and enlarged nets of earthquake-sensing instruments, sited in relation to known geology, are needed, as are many more geodetic and hydrographic measurements. Every large earthquake, wherever located, should be regarded as a full-scale laboratory experiment whose study can give scientific and engineering information unobtainable from any other source. Plans must be made before the event to insure staffing, funding, and coordination of effort for the scientific and engineering study of future earthquakes. Advice of earth scientists and engineers should be used in the decision-making processes involved in reconstruction after any future disastrous earthquake, as was done after the Alaska earthquake. The volume closes with a selected bibliography and a comprehensive index to the entire series of U.S. Geological Survey Professional Papers 541-546. This is the last in a series of six reports that the U.S. Geological Survey published on the results of a comprehensive geologic study that began, as a reconnaissance survey, within 24 hours after the March 27, 1964, Magnitude 9.2 Great Alaska Earthquake and extended, as detailed investigations, through several field seasons. The 1964 Great Alaska earthquake was the largest earthquake in the U.S. since 1700. Professional Paper 546, in 1 part, describes Lessons and Conclusions.

Alaska↗
USGS1973

Geological literature on the San Joaquin Valley of California

The following list of references includes most of the geological literature on the San Joaquin Valley and vicinity in central California (see figure 1) published prior to January 1, 1973. The San Joaquin Valley comprises all or parts of 11 counties -- Alameda, Calaveras, Contra Costa, Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus, and Tulare (figure 2). As a matter of convenient geographical classification the boundaries of the report area have been drawn along county lines, and to include San Benito and Santa Clara Counties on the west and Mariposa and Tuolumne Counties on the east. Therefore, this list of geological literature includes some publications on the Diablo and Temblor Ranges on the west, the Tehachapi Mountains and Mojave Desert on the south, and the Sierra Nevada Foothills and Mountains on the east.

California↗
USGS2012

New Zealand’s deadliest quake sounds alarm for cities on fault lines

The catastrophic Christ Church Earthquake is a strong reminder to engineers and scientists of the hazards pose by fault lines, both mapped and unknown, near major cities. In February 2011, the relatively moderate earthquake that struck the cities of Christchurch and Lyttleton in the Canterbury region of New Zealand's South Island surprised many with its destructive power. The magnitude 6.2 temblor killed 181 people, 118 of whom were killed in the collapse of a single building in the city center. The quake damaged or destroyed more than 100,000 buildings. It was the deadliest quake to strike the nation in 80 years-since the 1931 earthquake that struck the Napier and Hastings area of the North Island. The Christchurch quake was part of the aftershock sequence following the September 2010 magnitude 7.1 earthquake near Darfield, 40 kilometers west of the city. The Darfield earthquake was in a sparsely populated area, causing to loss of life. By contrast, the Christchurch earthquake was generated on a fault in close proximity to the city.

Christchurch↗
USGS2001

Magnetic stratigraphy of the lower middle Eocene (type Ulatsian) Vacaville Shale, Solano County, California

Mallory (1959) designated exposures of the Vacaville Shale on Ulatis Creek, northwest o Vacaville, California, as the type section of his lower middle Eocene Ulatisian benthic foraminiferal stage. Magnetic samples were taken from the 75 m of exposed section, and yielded a stable remanence held mainly in magnetite which passed a reversal test. The section showed two normal zones and three reversed magnetozones. Based on calcareous nannofossils and planktonic foraminifera, we correlate the type Ulatisian with Chron C20r-C22r (45.0-50.5 Ma), which is latest early Eocene to early middle Eocene on the global time scale. Our data calibrate what has been previously suggested by micropaleontologists: the base of the Ulatisian in the Vacaville Shale is 2 million years older (50.5 Ma) than it is in Media Agua Creek in the Temblor Range (48.5 Ma), and that the top of the Ulatisian is a million years younger (46.5 Ma) in the Vacaville section then it is at Media Agua Creek (47.5 Ma). This is another example of the problems with time-transgressive benthic foraminiferal stages.

Book chapter↗