A new heat-flow contour map of the conterminous United States

Sass, J.H.; Diment, W.H.; Lachenbruch, Arthur H.; Marshall, B.V.; Munroe, Robert J.; Moses, T.H.; Urban, T.C.

doi:10.3133/ofr76756

Cited by 19 publications

(5 citation statements)

References 25 publications

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“…The upper crust of the Basin and Range province is seismically active, with over 95% of earthquakes occ•g in the upper 15 km of the crust and virtually none below 20 km [Smith, 1978]. A region of high heat flow encompassing the Basin and Range was identified by Blackwell [1969] and confirmed by later workers [Roy et al, 1972;Sass et al, 1976;Ixtchenbruch and Sass, 1978].…”

Section: ;mentioning

confidence: 83%

The crustal structure of the Northwestern Basin and Range Province, Nevada, from wide‐angle seismic data

Holbrook¹

1990

J. Geophys. Res.

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I present a model of lithospheric P‐wave velocity structure in the northwestern Basin and Range province, Nevada, based on wide‐angle seismic data collected in 1986 under the auspices of the Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL). The lithosphere in the Basin and Range consists of (1) 2‐ to 3‐km‐thick low‐velocity (2.5–4.0 km/s) sedimentary basins and high‐velocity (>4.5 km/s) ranges overlying a basement of velocity 5.5–6.1 km/s, (2) a mid‐crust (6.1–6.2 km/s) which consists of rocks of probable granitic to granodioritic composition in greenschist to amphibolite facies and which includes two local low‐velocity zones (5.5–5.7 km/s), (3) a laterally varying lower crust which consists of rocks of probable gabbroic composition in upper amphibolite to granulite fades and which comprises layers of 6.6 and 7.0–7.2 km/s average velocity, (4) a complex crust‐mantle transition best modeled as a velocity gradient zone 1–2 km thick, and (5) an upper mantle with velocities of 7.7–7.9 km/s which includes a local low‐velocity zone (7.5 km/s). Crustal thickness in the region varies laterally from 28 to 37 km, significantly thicker than several previous estimates. The upper mantle velocities and velocity gradients differ slightly on the two perpendicular profiles, suggesting possible azimuthal anisotropy. A wedge‐shaped, eastward‐thickening lower crust of high seismic velocity (7.0–7.2 km/s) on the eastern pan of the survey may represent the westward edge of “rift‐stage” Précambrien continental crust or, alternatively, mafic material underplated and intruded into the crust during Cenozoic extension. Comparison of the velocity model with coincident seismic reflection data shows that the reflection and refraction Mohos are coincident across the entire profile, thus indicating that deep reflections (4–10 sec two‐way travel time) seen on COCORP and PASSCAL‐piggyback reflection profiles originate entirely within the crust. The top of the reflective zone, however, lies consistently above the mid‐crustal increase in average velocity, indicating that the reflectivity is not restricted to the mafic part of the crust; on PASSCAL piggyback profiles, in fact, the middle (silicic) crust appears more reflective than the lower (mafic) crust This can be explained as the result of either mafic, sill‐like intrusions or ductile strain fabrics. Both of these processes are likely to have accompanied Cenozoic extension in the region.

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Section: ;mentioning

confidence: 83%

The crustal structure of the Northwestern Basin and Range Province, Nevada, from wide‐angle seismic data

Holbrook¹

1990

J. Geophys. Res.

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“…and eastern United States, Pn exhibits no correlation with P wave amplitude. Heat flow in the western United States[Sass et al, 1971[Sass et al, , 1976 Dintent et al, 1975] correlates well with P wave amplitudes. High heat flow along the Rocky Mountain front and the Rio Grande rift and in the Battle Mountain area of northern Nevada and southwest Oregon correlate with low P wave amplitudes.…”

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confidence: 99%

Azimuth, energy, Q, and temperature: Variations on P wave amplitudes in the United States

Butler¹

1984

Reviews of Geophysics

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Mean relative P wave (1 s) amplitude characteristics are determined for standardized seismic stations in the United States. Data are compiled from three azimuths: to the north, explosions in Russia; to the northwest, earthquakes along the Asian‐Pacific arc; and to the south‐southeast, earthquakes in South America. Characteristic receiver amplitudes are found to be azimuthally dependent. High‐amplitude areas occur in the central United States, and lowest amplitudes occur along the Rocky Mountain front range and the Rio Grande rift zone. Amplification effects of low‐velocity sediments are significant in the central United States. Azimuthal amplitude variations in the eastern United States are consistent with an anomalous attenuating or defocusing body in the lower mantle beneath Colombia, South America. Nonazimuthal amplitude studies are tied to the azimuthal data set to increase station amplitude coverage. The regional and local stability of amplitudes is analyzed. Amplitudes are stable with an average variation of a factor of about 1.3 around the regional mean. For seismic stations situated on hard bedrock, the squared amplitude variations are related to energy variations in the P wave fronts. Acknowledging the likely importance of elastic focusing/defocusing and scattering effects at individual stations, variations of anelastic attenuation are derived that are consistent with the observed energy‐amplitude variations. Assuming that the variations of anelastic attenuation occur in the upper 400 km of the earth, high‐amplitude stations may be unattenuated, low‐amplitude stations are consistent with Q ∼ 110, and a mean amplitude implies Q ∼ 220–240. The range of variation of Q is mapped into temperature variations, assuming a thermally activated Q mechanism and an olivine activation energy for the upper mantle. The apparent Q variations are consistent with temperature variations of 135°–287°C between high‐ and low‐amplitude seismic station sites. Geophysical and physiographic correlations with the P wave amplitude variations are discussed. Accounting for the motion of the North American plate, low P wave amplitudes along the Rocky Mountain front may be related to the uplift of the Colorado Plateau. Low amplitudes extending from northern Texas to New England lie along the approximate boundary of the continental craton.

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“…This large volume of hot rock (or magma) is the obvious heat source for the surface hydrothermal activity within the Long Valley caldera (Sorey and Lewis, 1976). However, thermal calculations based on the work of Lachenbruch, Sass, Monroe, and Moses (1976) suggest that in spite of its proximity to the study area, a magma chamber beneath the Long Valley caldera could contribute little to conductive surface heat flow within the study area.…”

Section: Geothermal-resource Evaluation 81mentioning

confidence: 97%

Mineral resources of the Minarets Wilderness and adjacent areas, Madera and Mono counties, California

Huber¹,

Oliver²,

Bailey³

et al. 1982

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A new heat-flow contour map of the conterminous United States

Cited by 19 publications

References 25 publications

The crustal structure of the Northwestern Basin and Range Province, Nevada, from wide‐angle seismic data

The crustal structure of the Northwestern Basin and Range Province, Nevada, from wide‐angle seismic data

Azimuth, energy, Q, and temperature: Variations on P wave amplitudes in the United States

Mineral resources of the Minarets Wilderness and adjacent areas, Madera and Mono counties, California

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