bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detailed heat flow measurements over the Juan de Fuca Ridge System
Authors: Davis E. E. , Lister C. R. B. , Wade U. S. , Hyndman R. D. 
Published: February 2008

Eleven detailed profiles of heat flow measurements have been completed over young oceanic crust of the Juan de Fuca ridge system. Individual measurements were spaced typically 0.4–1 km apart along multiple‐penetration lines from 3 to 20 km in total length, and each measurement was located with respect to structural and sedimentary features by simultaneous seismic reflection profiling. In all cases, the average heat flow is well below that predicted by simple conductively cooled spreading models, even when the sediment cover is thick and the nearest basement outcrop is 15 km away. This disparity is attributed to ventilated convective circulation of water in the crust. Large heat flow variability is common along all profiles. Variations are present at two scales. Small‐scale variations (from 1 km to a few kilometers between significant heat flow maxima), present in the younger profiles, probably reflect the influence of local venting and permeability variations on permeable layer cellular convection. Large‐scale variations (10–20 km between significant heat flow maxima), present in all profiles, may reflect the influence of regional circulation driven by cold water recharge at isolated basement outcrops. Laboratory experimental data indicate that normal cellular convection can coexist with larger‐scale bilateral flows, so that there is no simple way to extract the permeable layer thickness from the surface heat flow data. There is a considerable reduction in the amplitude of small‐scale heat flow variability over the range of crustal age studied (0.1–12.5 m.y.). This is probably caused by the thermal filtering effects of the sediment cover which increases from about 50 m near the ridge crests to over 700 m on the flanks.The appendix is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N. W., Washington, D.C. 20009. Document J79‐007; $1.00. Payment must accompany order.
The Iceland Research Drilling Project
Authors: Fridleifsson Ingvar B. , Gibson Ian L. , Hall J. M. , Johnson H. Paul , Christensen N. I. , Schmincke Hans‐Ulrich , Schönharting Gunther 
Published: February 2008

This issue of the Journal of Geophysical Research contains the collected results of the initial studies of a 3‐km vertical section of Icelandic crust. The material described in these papers was largely presented at a meeting of the investigators working in this project held in Reykjavík, Iceland, from May 13 to May 15, 1980Iceland presents a very well exposed example of crust formed at an accretional plate margin, the crest of the Mid‐Atlantic Ridge. The desirability of a detailed study of a long vertical section of Icelandic crust by deep drilling has been expressed in proposals and recommendations of scientists and international scientific committees since the early 1960's. A formal proposal with descriptions of several alternative drill sites was presented in 1975 [Working Group on Deep Crustal Drilling in Iceland, 1975], but difficulties in financing a drill hole that would penetrate into crustal layer 3 (Vp = 6.5 km/s) delayed implementation of the recommendations.
Thermal origin of the Hawaiian swell: Heat flow evidence and thermal models
Authors: Von Herzen R. P. , Detrick R. S. , Crough S. T. , Epp D. , Fehn U. 
Published: February 2008

The lithospheric reheating hypothesis for the origin of the Hawaiian swell has been tested by heat flow measurements along the swell between Hawaii and Midway. Ninety five measurements at eight carefully selected sites show that the heat flux on the swell increases systematically from near‐normal values (52±2 mW m−2) near Hawaii to values near Midway (59±2 mW m−2) about 20–25% higher than normal for lithosphere of that age (110 m.y.). This heat flow pattern is qualitatively consistent with a deep‐seated thermal anomaly created in a lithospheric plate moving across a fixed heat source. Modeling of the heat flow and bathymetry data on the Hawaiian swell strongly suggest that the swell is caused by a rapid heating (within <5 m.y.) of the lower part (>40‐ to 50‐km depth) of normal 90‐m.y.‐ old lithosphere over a relatively broad (500–1000 km) region near Hawaii. This model is also consistent With gravity and geoid anomalies associated with the swell, which require a low‐density region in the lower lithosphere, and with flexure studies of seamounts in the Hawaiian chain, which indicate that the rigidity of the lithosphere is not significantly reduced by the reheating.Appendices A‐C are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J82‐005; $1.00. Payment must accompany order.
Origin of hematite and its associated remanence in the Copper Harbor Conglomerate (Keweenawan), upper Michigan
Authors: Elmore R. Douglas , Van der Voo Rob 
Published: February 2008

To study further the origin remanence in red beds, the volcanogenic Copper Harbor Conglomerate has been investigated using both paleomagnetic and petrographic techniques. Paleomagnetic results suggest the presence of two magnetic components, both possessing a westerly and shallow or normal Keweenawan direction. One component (in the vicinity of declination 294°, inclination −7.6) comprises approximately 30% of the total natural remanent magnetization, is removed by alternating field demagnetization following chemical demagnetization, and shows a consistent inclination error that is controlled in sense and amount by the dip of the cross beds in which the samples were taken. The low coercivities of this component suggest that the magnetization resides in magnetite. This and the inclination error due to the bedding indicate that the component is a detrital remanent magnetization.The predominant component (declination 286.5°, inclination 0.0°, based on six sites) is removed by chemical demagnetization and shows no consistent relationship between inclination and dip of the cross beds, which suggests that it is a postdepositional magnetization. This component resides in hematite that is removed during the chemical demagnetization procedure. Petrographic studies show that hematite is present authigenically as pigment and as partly to wholly martitized grains. Martitization may have occurred before or after deposition; petrographic results are at present inconclusive. A pole position calculated from this postdepositional component (168.3°E, 11.2°N) is similar to poles from the overlying Nonesuch Shale and Freda Sandstone, which suggests that the remanence was acquired before the end of Freda deposition.
The 1982 Control Network of Mars
Authors: Davies Merton E. , Katayama Frank Y. 
Published: February 2008

Summary and entire article are available on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document B93‐005; $2.50. Payment must accompany order.A new planet‐wide control network of Mars was computed in September 1982 using a large single‐block analytical triangulation with 47,524 measurements of 6853 control points on 1054 Mariner 9 and 757 Viking pictures. A total of 19,139 normal equations were solved, and the resulting standard error of measurement was 18.06 μm. Appendix A lists those control points that are identified by name and letter designation; Appendix B gives the areographic coordinates of the control points. Both appendices are available on microfiche. The coordinates of the Viking 1 lander site are latitude 22.480°, longitude 47.962°, and radius 3389.32 km.
Cratering experiments in sands and a trial for general scaling law
Authors: Mizutani Hitoshi , Kawakami Shin‐ichi , Takagi Yasuhiko , Kato Manabu , Kumazawa Mineo 
Published: February 2008

We report results of vertical impacts of aluminum projectiles into quartz sand. The impacts were performed at velocities of 35 to 830 m/sec with a single stage powder gun. Morphology of craters formed in loose sands is generally conical, whereas morphology of craters formed in self‐compacted sands varies from a flat‐floor type to a double ring type, with increasing impact velocity. The present data together with previous experimental data and Dienes and Walsh's ‘late‐stage equivalence’ indicate that crater diameter is expressed by a function of the ‘late‐stage effective energy’ but not of the impact kinetic energy. The diameter of a crater formed in a noncohesive sand was found to be proportional to one‐fourth the power of the late‐stage effective energy. For a general impact cratering in a target with a finite strength, the diameter, D, versus impact velocity, v, relation is written as follows:

urn:x-wiley:01480227:media:jgrb4659:jgrb4659-math-0001
where v* and D* are normalizing values of the impact velocity and diameter, and K is a constant related to target and projectile properties. The relation suggests that there are four regimes in crater diameter versus the kinetic energy relation.
Constraints on plate motions in southern Pakistan and the northern Arabian Sea from the focal mechanisms of small earthquakes
Authors: Quittmeyer Richard C. , Kafka Alan L. 
Published: February 2008

The focal mechanism and depth were determined for nine small earthquakes (M0<1025 dyn cm, M<5.5) that occurred in southern Pakistan and the northern Arabian Sea from an analysis of the vertical component of Rayleigh waves in combination with limited first‐motion data. Focal parameters were determined from the Rayleigh waves by using an event‐pair method of analysis. For earthquakes that are located very close to each other (<≈ 50 km), the event‐pair method is able to remove a significant proportion of propagation effects at all periods in the range of interest (20–50 s). For events separated by more than ≈ 100 km the propagation effects are reduced for only the longer periods (≈ 40–50 s). The earthquakes that were studied provide evidence for a model of plate interactions in the vicinity of the southern Pakistan triple junction. The Owen fracture zone is a transform fault that accommodates right‐lateral motion between the Indian and Arabian plates. The plate boundary in the vicinity of the Murray ridge is also partially made up of transform segments that strike subparallel to the Owen fracture zone. Spreading centers may also exist in the vicinity of the Murray ridge but were not documented by seismic or other evidence. The slip azimuths for earthquakes along this boundary are significantly more northerly than those predicted by various regional and worldwide models of plate motion. The Arabian plate is being subducted beneath the Eurasian plate along the southern coast of Pakistan. Slip vectors for earthquakes along this boundary trend northnortheasterly in general agreement with predicted directions. Left‐lateral motion is documented along the boundary between the Indian and Eurasian plates in southern Pakistan. The predicted direction of relative motion between these plates is not significantly different from that observed. Two of the earthquakes studied appear to be intraplate in nature. The depth and focal mechanism of one intraplate event, which may have occurred within the accretionary prism along the Makran coast, however, are based on limited data. The other intraplate earthquake occurred within the sedimentary deposits along the western edge of the Indian subcontinent near the Indian‐Eurasian plate boundary.Appendix is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document B83‐009; $2.50. Payment must accompany order.
A detailed magnetotelluric/audiomagnetotelluric study of the Jemez Volcanic Zone, New Mexico
Authors: Ander Mark E. , Goss Ron , Strangway David W. 
Published: February 2008

Supplement is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W.,Washington, D.C. 20009. Document B84‐003; $10.00. Payment must accompany order.The Jemez volcanic zone is an alignment of late Cenozoic volcanic centers located in northern New Mexico and Arizona. It trends N52°E and is >500 km in length. Previous investigators suggest the zone is associated with elevated heat flow and anomalously low P wave velocity from 25 to 140 km depth measured along a line from Mount Taylor to the Jemez Mountains. It may also be associated with a Precambrian crustal‐age boundary. A detailed study, consisting of 119 audiomagnetotelluric (AMT) and 25 magnetotelluric (MT) soundings, was performed in a 161 km2 area located ∼50 km NW of the zone center. The AMT soundings were spaced 1.6 km apart in a grid pattern and had a frequency range from 12 Hz to 10.2 kHz. The AMT soundings were used to detect any near‐surface electrical structures or lateral variations. None were found, although terrain effects near the edges of mesas were observed. Agreement between the AMT and MT results from 12 to 50 Hz was excellent. Electrical strike direction is undefined at less than 1‐s period. From 1 to 100 s the average tipper strike is N30°W, aligning with the dominant surface structures. Greater than 100 s, it rotates abruptly to ∼N60°. This direction represents the electrical strike within metamorphic Precambrian basement rocks and suggests control of the deep electrical structure beneath the study area by the Jemez zone. Two‐dimensional MT modeling indicates three relatively homogeneous layers. The resistivity of the deepest layer, ≥15 km depth, is 50 ohm‐m in the northwest but decreases to 5 ohm‐m southeastward, toward the zone. These results, plus preliminary results from a regional MT study that surrounds the detailed AMT/MT study, suggest that the Jemez zone is associated with anomalously high electrical conductivity at shallow depths relative to surrounding regions. Magma intrusion along the zone is the most probable explanation for this anomaly.
Moho orientation beneath central California from regional earthquake travel times
Authors: Oppenheimer David H. , Eaton Jerry P. 
Published: February 2008

Table Al is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document B84‐011; $2.50. Payment must accompany order.Analysis of relative Pn travel times recorded by 238 stations of the U.S. Geological Survey central California seismic network (CALNET) from 77 regional earthquakes and explosions shows that arrivals are progressively delayed to the northeast in both the Coast Ranges and Sierra Nevada foothills. By dividing the CALNET into 10 subarrays and assuming laterally uniform velocities for a crust over an upper mantle half space, the orientation of a planar Moho beneath each subarray is calculated by inversion of relative Pn arrival times. The results show that the Moho dips to the northeast between 3° and 6° beneath the Coast Ranges and 8°–17° beneath the Great Valley and is horizontal beneath the foothills. Pn residuals west of the San Andreas fault are relatively early by 0.35 s but are interpreted as resulting from a lateral velocity contrast across the fault rather than variations in crustal thickness. Unexplained Pn travel time variance improves by approximately 60% after correction for the travel time due to dip and mean Pn residual at each station. The Pn data corrected for the travel time due to a dipping Moho indicate an isotropic upper mantle velocity of 7.97±0.05 km/s beneath the Coast Ranges, Great Valley, and foothills. Evidence of upper mantle velocity anisotropy in the azimuthal variation in Pn apparent velocity corrected for dip is only marginally significant at the 5% level. However, large azimuthal variations in corrected apparent velocity do exist and may be attributed to velocity heterogeneities in the crust, unmodeled higher‐order mantle structure, and gradients in upper mantle velocity. Arrival times of Cape Mendocino earthquakes recorded in the Coast Ranges south of San Francisco Bay indicate lateral variations in upper mantle velocity. The 7.4 km/s apparent velocity estimate from travel times of the Oroville earthquake recorded in the Coast Ranges out to distances greater than 400 km is anomalous in that Pn is normally observed at distances greater than 200 km. These arrivals may originate from updip propagation along a 6.9 km/s layer in the lower crust of the Coast Ranges subparallel to the Moho.
Symmetrical and upward shallowing cycles in the Middle Devonian of New York State and their implications for the punctuated Aggradational Cycle Hypothesis
Authors: Brett Carlton E. , Baird Gordon C. 
Published: February 2008

The Middle Devonian (Eifelian and Givetian) Hamilton Group in western and central New York, composed largely of fossil‐rich marine shelf and slope facies, is subdivisible into repetitive facies sequences of varying thicknesses. Minor cycles include 1‐ to 3‐m‐thick, upward coarsening shale to siltstone hemicycles, resembling sixth‐order punctuated aggradational cycles (PACs), in central New York; probably correlative (0.5‐1.0 m) shale to argillaceous, nodular limestone couplets occur in western areas.Major cycles in western New York include subsymmetrical 3‐ to 5‐m‐thick packages with medial limestone beds, analogous to “upper limestones” of Pennsylvanian cyclothems. The center of each cycle marks a regressive maximum and grades vertically, above and below, into black shale or dark gray mudstone, corresponding, in a facies sense, to cyclothemic “core shales” in the midcontinent Pennsylvanian. These widespread units appear to be allocyclic in nature and approximate fifth‐order transgressive‐regressive cycles, based upon average unit thickness relative to the encompassing, well‐zoned, Hamilton sequence. Correlations show that most key regressive events marked by limestones in western New York are expressed by equivalent siltstone or fine sandstone units in central New York. Most cycles, which are nearly symmetrical in western New York, grade eastward into 5‐ to 20‐m upward coarsening (PAC motif) hemicycles. These asymmetric cycles apparently reflect rapid sediment aggradation to limits imposed by wave energy in a region of abundant sediment supply. Further minor shallowing was accompanied by winnowing and bypass of fine‐grained sediments, generating condensed, capping deposits of coarser silt and sand, reworked shells and, commonly, phosphatic nodules. Ensuing sea level rises were accompanied by initial sediment starvation followed by sedimentation in deeper water. Hence asymmetrical, upward shallowing hemicycles (PACs) appear to grade offshore into thin but symmetrical cycles. Both PAC and symmetrical motifs are local responses to the same, probably allocyclic, sea level fluctuations. We suggest that the PAC motif is partially facies controlled, being largely restricted to shallow shelf settings with relatively high rates of sediment accumulation.
History of the lunar orbit
Authors: Goldreich Peter 
Published: February 2008

A method of calculating the past states of the earth‐moon system is developed. The method is based on the existence of three distinct time scales for dynamical change. The short time scale is determined by the revolution periods of the sun and moon about the earth or, equivalently, by the year and current month. The intermediate time scale is set by the precessional motions of the lunar orbit plane and the earth's equator plane. The rate at which tidal friction alters the state of the earth‐moon system defines the long time scale. The equations of motion governing the earth‐moon system are successively averaged over the short and then the intermediate time scales. These averaged equations are then integrated back a short interval on the long time scale. The equations of motion appropriate to this new state of the earth‐moon system are then re‐averaged on the short and intermediate time scales, and once again the averaged eqations are stepped back on the tidal time scale. The first step in this procedure (i.e. averaging on the short time scale) is performed analytically, whereas the calculations on the intermediate and long time scales require the use of a large computer.At present, the inclination of the lunar orbit plane to the ecliptic remains nearly constant during the precessional motion. On the other hand, if the moon's semimajor axis were ever less than 10R⨁, the inclination of the lunar orbit plane would have maintained a fixed value with respect to the earth's equator plane. The current investigation shows that this inclination could never have been less than 10° and, therefore, that the moon could never have moved on an equatorial orbit. This result contradicts theories that postulate fission of the earth to form the moon and also those which propose that the moon formed by accretion within 10R⨁
Surface waters
Authors: Schaake John C. 
Published: February 2008

Research in surface water hydrology made important advances in the areas of river mechanics and streamflow routing, experimental study of overland flow, surface runoff models, partial area processes, effects of land use on surface runoff, and probability, statistics and analysis of uncertainty. In each area there was a fundamental need to apply mathematical and computer methods, and this is reflected in the following review of progress in each of these areas.A broad‐based effort went into developing numerical solutions of the Saint Venant partial differential equations for unsteady flow in open channels. Some papers suggested a numerical procedure; some looked at computational efficiency; some looked at convergence and/or stability properties; some looked at the importance of various terms; some looked at prediction accuracy; and some suggested procedures for branched or looped river networks. These papers offer testimony to widespread use in hydrology practice of models based either on the full Saint Venant equations or on one of many approximations to these equations, including both linear approximations with one or more terms neglected and nonlinear approximations with several terms neglected. Because some of these approximations have the same mathematical structure as certain well‐known hydrologic routing techniques, it is now possible to give clearer physical meaning to the better established hydrologic methods such as the Muskingum method. Hopefully, this will stimulate more intelligent use of all of these techniques (e.g., through new physically based criteria for applying the lag and route model or new criteria for judging when the full nonlinear Saint Venant equations must be used rather than some approximation, etc.). Following is a review of some specific contributions.
Water resource systems and relations
Authors: Schwarz Harry E. 
Published: February 2008

The analyses of water resource systems and the application of mathematical statistics and operations research in the planning, operation, and management of water resource developments are continuing. Systems analyses as a tool of the hydrologist and water resource engineer are coming of age in the United States. In addition to the use of these techniques in analyzing and synthesizing physical systems, significant inputs are being made to broaden the analysis to social, economic, and environmental considerations.Water resource systems analysis has come to mean the use of mathematical programing and simulation techniques in the study of large‐scale systems which control the movement of water on and under the surface of the earth. Included in the discussion which follows will be a review of surface water systems, groundwater systems, water quality systems, stochastic flow models, decision theory, and network theory.