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J. C. Roller

Publications and source records attributed to J. C. Roller.

13 recordsLinked to original sources
USGS1979

Magnitude of shear stress on the San Andreas fault: Implications of a stress measurement profile at shallow depth

A profile of measurements of shear stress perpendicular to the San Andreas fault near Palmdale, California, shows a marked increase in stress with distance from the fault. The pattern suggests that shear stress on the fault increases slowly with depth and reaches a value on the order of the average stress released during earthquakes. This result has important implications for both long- and short-term prediction of large earthquakes.

California↗
USGS1977

Preliminary stress measurements in central California using the hydraulic fracturing technique

Use of the hydraulic fracturing technique for determining in situ stress is reviewed, and stress measurements in wells near the towns of Livermore, San Ardo, and Menlo Park, California are described in detail. In the Livermore well, four measurements at depths between 110 and 155 m indicate that the least principal compressive stress is horizontal and increases from 1.62 to 2.66 MPa. The apparent direction of maximum compression is N 70?? E (??40??). At the San Ardo site the least principal stress is that due to the overburden weight. At depths of 240.2 and 270.7 m the minimum and maximum horizontal stresses are estimated to be 11.4 and 22.5 MPa, and 12.0 (??1.1) and 15.8 (??3.3) MPa, respectively. From an impression of the fracture at 240.2 m, the direction of maximum compression appears to be about N 15?? E. The rock in the Menlo Park well is too highly fractured to yield a reliable measurement of the horizontal stresses. The data indicate, however, that the least principal stress is vertical (due to the overburden weight) to a depth of 250 m. ?? 1977 Birkha??user Verlag.

Pure and Applied Geophysics PAGEOPH↗
USGS1964

A preliminary summary of a seismic-refraction survey in the vicinity of the Tonto Forest Observatory, Arizona

The U.S. Geological Survey complete d a seismic-refraction survey in the vicinity of the Tonto Forest Seismological Observatory (T.F.S.O.) in April and May 1964. More than 1200 km of reversed profiles were surveyed to determine the crustal structure and crustal and upper mantle velocities in this area. The purpose of this work was to provide information on wave-propagation paths of seismic events recorded at T.F.S.O. and to improve the performance of the Observatory in locating and identifying these events. First arrivals indicate that the Mohorovicic discontinuity dips to the northeast by as much as 6 degrees under T.F.S.O., and may even be displaced vertically by as much as 5 km immediately north of the Observatory near the boundary of the Basin and Range and the Colorado Plateau Provinces. A preliminary examination of the first arrivals indicates that the crust at T.F.S.O. is at least 30 km thick and is made up of at least two seismic layers. A thin veneer at the surface with a velocity of approximately 4 km/sec is underlain by a layer with a velocity of approximately 5.9 km/sec to 6.1 km/sec. An intermediate layer with velocity of 6.6 to 7.0 km/sec is probably present in the lower crust, but is not revealed by first arrivals. The velocity of seismic waves in the upper mantle is about 7.9 km/sec.

Arizona↗
USGS1964

Seismic-refraction measurements of crustal structure between Nevada Test Site and Ludlow, California

Seismic-refraction measurements from nuclear and chemical explosions were made along a line from the Nevada Test Site (NTS) to Ludlow, California, and additional recordings from nuclear explosions were made southward toward Calexico, California. The time of first arrivals from the Ludlow shotpoint is expressed as T 0 = 0.00 + Δ/2.50 (assumed), T 1 = 1.00 + Δ6.10, T 2 = 2.81 + Δ/6.80, and T 3 = 5.48 + ~7.76, where T is in seconds and distance Δ is in km. First arrival times from NTS fit the lines T 1 = 0.74 + Δ/6.10, T 2 = 2.81 + Δ/6.80 (assumed), T 3 = 6.70 + Δ/8.04 to a distance of 265 km, beyond 265 km T 3 = 5.83 + Δ/7.75. The difference in the apparent velocities of the P n (T 3 ) arrival is caused by variations in the dip of the Mohorovicic discontinuity. The thickness of the successive layers at NTS are H 0 s 1.0 km (V 0 ~ 2.5 km/sec), H 1 = 13 km (v 1 = 6.1 km/sec), and H 2 = 20 km (v 2 = 6.8 km/ sec); the total crustal thickness is 34 km. The successive crustal layers at Ludlow have a thickness of H 0 = 1.4 km, H 1 = 13 km, and H 2 = 13 km; the total crustal thickness is 27 km.

Arizona, California, Nevada↗
USGS1963

Crustal structure in the western United States; study of seismic propagation paths and regional traveltimes in the California-Nevada region

The U.S. Geological Survey, with the assistance of United ElectroDynamics, Inc., completed ten weeks of seismic-refraction field work during the summer of 1962 in the southwestern part of the United States. This work was a continuation of a program initiated in 1961 to study traveltimes and seismic propagation paths in the earth?s crust and upper mantle in the western United States. A total of 761 seismograms were recorded along 10 profiles from 86 explosions at 18 shotpoints. Analysis of the data is continuing, but a few conclusions can be made from a preliminary study: (1) Variations in traveltimes in the Basin and Range province are large but measurable, and perhaps predictable. (2) Traveltimes of seismic waves in adjacent geologic provinces are usually significantly different. (3) The velocity of P g along all of the profiles recorded in 1962 ranges from 5.0 to 6.5 km/sec, and averages 6.0 km/sec. (4) The average velocity of P g in extreme northern Nevada and southern Idaho is 5.6 km/sec, and it is 6.1 km/sec in most of Nevada and California. (5) The average velocity of P n is 7–9 km/ sec and ranges from 7.85 to 7.95 km/sec on reversed profiles where the true P n velocity could be computed. (6) A shallow "intermediate" layer with a velocity of approximately 6.8 km/sec was found in the Snake River Plain. (7) Refraction arrivals from the mantle (P n ) were recorded in the Sierra Nevada. They indicate that the thickness of the crust in the Sierra Nevada is much greater than that in the Basin and Range province. (8) Many refinements in field techniques were made during the 1962 field season.

California;Nevada;Idaho↗
USGS1963

Preliminary report on seismic-reflection studies of crustal structure in the western, central, and southern United States

During 1963 the U.S. Geological Survey, with the assistance of United ElectroDynamics, Inc., recorded five separate reversed seismic profiles. In addition to these profiles, the U.S. Geological Survey participated in a seismic-calibration program for the DRIBBLE experiment at Tatum Dome, Mississippi, a 20,000-pound shot near Dexter, Missouri, and in a cooperative seismic experiment in the Lake Superior region. This work is a continuation of the program started in 1961; however, the emphasis has shifted from a detailed study of the earth's crust in the western United States to a study of crustal structure in various geologic environments including the Wyoming thrust belt, Colorado Plateau, Central Lowlands, the Gulf Coastal Plain, and the southern part of the Canadian Shield. The U.S. Geological Survey has now completed reversed seismic-refraction profiles in nine different geologic provinces. These data present a promising indication that it may be possible to predict the crustal structure in unexplored areas by considering the regional geologic and physiographic environment. The following P n velocities have been determined: 8.2 km/sec in the Wyoming thrust belt, 7.9 km/sec in the Colorado Plateau, 8.1 km/sec in the Central Lowlands, and about 8.2 km/sec in the Gulf Coastal Plain. The data from the Lake Superior region have not yet been interpreted.

Arizona;Idaho;Mississippi;Missouri;Utah↗
USGS1959

Gravity and seismic exploration in Yucca Valley, Nevada test site, January-April, 1959

The thickness of the alluvial and tuffaceous deposits that overlie bedrock in Yucca Valley has been inferred from gravity and seismic measurements. Preliminary interpretations indicate that these deposits are thickest in a narrow north-trending trough in the eastern part of the valley. The gravity data delineate a buried north-trending ridge of bedrock that extends from Mine Mountain almost to Quartzite Ridge. Seismic refraction measurements confirm the existence of the bedrock ridge and indicate that the bedrock is as close as 100 feet to the surface. The buried bedrock high is important because it may alter concepts of the movement of groundwater within the valley. A single seismic-refraction profile was located near the area of thickest alluvium and tuff to determine the feasibility of using refraction techniques for determining the depth to bedrock where it is covered with several thousand feet of alluvium and tuff. The results are encouraging but not enough data were acquired to give a reliable depth estimate. Seismic-refraction measurements were used successfully to determine the thickness of alluvium in narrow valleys partly filled with alluvium. This work was in the northwestern part of Yucca Valley and was done to choose drilling sites for studies of ground-water movement.

Nevada↗