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Articles 1 - 14 of 14
Full-Text Articles in Physical Sciences and Mathematics
Determination Of Paleoearthquake Timing And Magnitudes On The Southern Segment Of The East Cache Fault, Utah, James P. Mccalpin
Determination Of Paleoearthquake Timing And Magnitudes On The Southern Segment Of The East Cache Fault, Utah, James P. Mccalpin
James P. McCalpin
We investigated the late Quaternary rupture history of the southern East Cache Fault zone [ECFZ], northern Utah with geologic mapping, paleoseismic logging of fault trenches, ground-penetrating radar, and optically stimulated luminescence dating. McCalpin (1989) indicated that the southern segment of the ECFZ consisted of three strands. We excavated four trenches across these strands, and evaluate the stratigraphy and structure of the sites. We conclude that the western fault strand of the ECFZ has had no late Quaternary displacement or does not exist; the central strand has not had any late Quaternary movement and may be a drape fold; and the …
Quaternary Geology And Geochronology Of The Uppermost Arkansas Valley, Colorado- Glaciers, Ice Dams, Landslides, And Floods, James P. Mccalpin
Quaternary Geology And Geochronology Of The Uppermost Arkansas Valley, Colorado- Glaciers, Ice Dams, Landslides, And Floods, James P. Mccalpin
James P. McCalpin
This field trip to the uppermost Arkansas Valley of central Colorado is based mainly on work performed since 2008, in an area with a long history of bedrock mapping by renowned geologists of the U.S. Geological Survey beginning in the 1880s (e.g. Emmons, 1886). The Quaternary features of the region were first described by Capps in 1909. Despite over 100 years of intermittent geologic studies here, there were still new discoveries to be made in the past few years. Day 1 of the trip emphasizes landslides (in the morning) and glacial deposits (in the afternoon). The “take-home messages” of the …
Refine Slip Rates And Segmentation Of The Northern Sangre De Cristo Fault, Colorado’S Largest Active Fault, James P. Mccalpin
Refine Slip Rates And Segmentation Of The Northern Sangre De Cristo Fault, Colorado’S Largest Active Fault, James P. Mccalpin
James P. McCalpin
We excavated a 25 m-long trench on the northern part of the Crestone section of the Northern Sangre de Cristo fault zone, to see whether the Crestone section might be composed of more than one (independent) rupture segments. The Carr Gulch trench exposed evidence for 3 paleoearthquake displacements in the past 27.4 ka. The existence of 3 colluvial deposits (units 2, 3, 4) indicates that the ca. 4.5 m of surface offset was formed during 3 surface-faulting events with an average displacement of about 1.5 m each. The events occurred at about 8 ka, 20 ka, and between 22.5 and …
Long Recurrence Records From The Wasatch Fault Zone, Utah, James P. Mccalpin
Long Recurrence Records From The Wasatch Fault Zone, Utah, James P. Mccalpin
James P. McCalpin
The Wasatch fault "megatrench" was excavated in September 1999 across two fault scarps totaling 18 meters high on the Salt Lake City segment of the Wasatch fault zone (WFZ). The purpose of the megatrench was to date a long series of consecutive earthquakes (8-12 events?) on the WFZ and measure the variability of recurrence times between the events.This variability could then be used in calculating the future probability of large earthquakes on the WFZ. The trench was located 1 km north of the mouth of Little Cottonwood Canyon, at an elevation of 1525 m, between the Bonneville highstand (ca. 17.5 …
Paleoseismicity Of Quaternary Faults Near Albuquerque, New Mexico: The Zia Fault, James P. Mccalpin
Paleoseismicity Of Quaternary Faults Near Albuquerque, New Mexico: The Zia Fault, James P. Mccalpin
James P. McCalpin
This study continues USGS-funded efforts to assess the activity and earthquake hazard potential of Quaternary faults in the Albuquerque metropolitan region. Our target in 2000 was the Zia fault, a 37 km-long normal fault that trends N-S in northern Llano de Albuquerque (LdA). The Zia fault is one of three major east-dipping normal faults that define the western margin of the Rio Grande rift in the northern Albuquerque basin, the other faults being the Calabacillas fault (to the west of the Zia fault) and the County Dump fault (to the east of the Zia fault) (Machette et al., 1998). In …
Ridgetop Splitting, Spreading, And Shattering Related To Earthquakes In Southern California, James P. Mccalpin
Ridgetop Splitting, Spreading, And Shattering Related To Earthquakes In Southern California, James P. Mccalpin
James P. McCalpin
Our mapping documents that anomalous ridgetop landforms are numerous in the San Gabriel and Santa Susana Mountains, and that many sites (37% of the San Gabriel sites, 16% of the Santa Susana sites) are not associated with any visible signs of landsliding. These sites may represent deep-seated gravitational spreading due to earthquake shaking. However, our factor analysis indicates that the spatial distribution of these suspected spreading landforms, with respect to ridge relief and distance to Late Quaternary faults, is essentially identical to that of landslides. Thus, it seems that if these spreading landforms represent the results of earthquake shaking, than …
Statistics Of Paleoseismic Data, James P. Mccalpin
Statistics Of Paleoseismic Data, James P. Mccalpin
James P. McCalpin
Compiled data from numerous neotectonic-geomorphic and trench studies reveals patterns in the spatial and temporal variation of coseismic fault displacement. Recurrence intervals between successive large earthquakes on faults define a near-symmetrical probability distribution with a coefficient of variance of 0.36. Normal faults have the most regular recurrence, and subduction zones the most variable. Variability in recurrence times at a site is not dependent on the number of recurrence intervals dated at that site. During historic surface-rupturing earthquakes slip has varied widely along strike. Based on 56 ruptures where more than 15 displacement measurements were made, the generic pattern is for …
Surficial Geologic Map Of The East Cache Fault Zone, Cache County, Utah, James P. Mccalpin
Surficial Geologic Map Of The East Cache Fault Zone, Cache County, Utah, James P. Mccalpin
James P. McCalpin
The 1:50,000-scale map shows surficial geologic deposits and the faults that displace them along the East Cache fault zone in northern Utah. The East Cache fault is a north-trending normal fault that extends about 77 km along the eastern side of Cache Valley (an east-tilted graben) at the base of the Bear River Range. The map includes a description of Quaternary deposits along the fault zone, a description of the fault segments, and estimates of the age, size, and distribution of fault scarps in the fault zone.
Spatial And Temporal Analysis Of 1200 Landslides In A 900km2 Area, Middle Rocky Mountains, Wyoming, U.S.A., James P. Mccalpin
Spatial And Temporal Analysis Of 1200 Landslides In A 900km2 Area, Middle Rocky Mountains, Wyoming, U.S.A., James P. Mccalpin
James P. McCalpin
An inventory of approximately 1200 landslides in a 900 km2 area in the Salt River Range, western Wyoming, U.S.A., reveals regional and temporal controls on the landsliding process. Sliding is strongly controlled by eight weak formations in the 21 stratigraphic units of Cambrian through Cretaceous age. Morphologic dating of slides suggests that rockslides, slump-flows, and debris flows have occurred rather uniformly in time within the Holocene. In contrast, earthflows seem to be triggered more by cool/wet climatic epicycles in the last 5,000 years.
Field Trip Roadlog For The Bear River Landslide Complex, James P. Mccalpin
Field Trip Roadlog For The Bear River Landslide Complex, James P. Mccalpin
James P. McCalpin
The Bear River Landslide Complex occurs where the unconsolidated sediments of the Bear River Delta have been incised to a depth of 350 to 490 feet (106-150 m) north of Preston, Idaho. The slides are the result of the high pore pressure in confined aquifers in the deltaic sediments. High but variable volumes of groundwater flow and the laterally discontinuous nature of the deltaic sediments result in the varied types of earth movements found within the Landslide Complex. Landslide activity occurs during years of above average precipitation, and has been exacerbated by increased recharge from reservoirs and irrigation canals constructed …
Recommended Setback Distances From Active Normal Faults, James P. Mccalpin
Recommended Setback Distances From Active Normal Faults, James P. Mccalpin
James P. McCalpin
The geometry of near-surface ground breakage was analyzed from 40 trenches across Quaternary normal faults to help define reasonable setback distances. From each of the trench logs (28 on the Wasatch Fault, 11 on other Great Basin faults) eight parameters characteristic of surface rupture style were measured. Parameters included: 1) position of the main fault in relation to scarp morphology. 2) dip of the main fault. 3) number of faults on the upthrown block, 4) width of the upthrown block fault zone. 5) number of faults in the downthrown block. 6) width of the downthrown deformation zone, 7) ratio of …
The Bear River Landslide Complex, Preston, Idaho: Geologic Considerations And Historical Perspectives, James P. Mccalpin
The Bear River Landslide Complex, Preston, Idaho: Geologic Considerations And Historical Perspectives, James P. Mccalpin
James P. McCalpin
The Bear River Landslide Complex is a series of earth movements in northern Cache Valley, north of Preston, Idaho. The landslides occur in unconsolidated sediments of the Pleistocene Bear River Delta which formed where the river entered Lakes Bonneville and Provo. The Lake Bonneville delta deposits are up to 490 feet (150 m) thick and consist of a lower alluvial coarse sand and gravel unit, a middle delta front fine sand and silt unit, and an upper pro-delta clay up to 50 feet (15 m) thick. The interbedded character of the fine sands, silts, and clays, together with abrupt lateral …
Thermoluminescence (Tl) Dating In Seismic Hazard Evaluations: An Example From The Bonneville Basin, Utah, James P. Mccalpin
Thermoluminescence (Tl) Dating In Seismic Hazard Evaluations: An Example From The Bonneville Basin, Utah, James P. Mccalpin
James P. McCalpin
Thermoluminescence (TL) of minerals is the release of light when grains are heated to 1500 -5000 C. As sediments are buried longer they progressively acquire more TL from accumulated radiation damage from alpha, beta, and gamma rays and cosmic radiation. If the total amount of radiation dose received can be calculated, and the current dose rate measured, then dividing the total dose by the yearly dose rate will yield a TL age. Total doses are calculated by heating the sample until all TL is released, then re-irradiating the sample in the lab with known doses until the natural TL is …
Preliminary Age Classification Of Landslides For Inventory Mapping, James P. Mccalpin
Preliminary Age Classification Of Landslides For Inventory Mapping, James P. Mccalpin
James P. McCalpin
A preliminary age classification for landslides is proposed for inventory mapping, based on morphologic criteria visible on aerial photographs. Because landslide scars and deposits are generally disequilibrium landforms, they progress through observable morphologic stages as they age. Four age classes are distinguished: 1) active; 2) inactive-young; 3) inactive-mature; 4) inactive-old. Each age class reflects the age of latest movement only. The morphologic "freshness" of each part of the landslide must be evaluated, including: the head scarp, lateral scarps, marginal drainage, internal scarps and blocks, internal drainage pattern, vegetation type and density, and toe morphology. Morphologic parameters defined from air photos …