Spectral-type simulation of spatially correlated fracture set properties

Fracture set properties such as orientation, spacing, trace length, and waviness tend to be spatially correlated. These properties can be efficiently simulated by spectral analysis procedures that take advantage of the computational speed of the fast Fourier transform. The covariance function of each property to be simulated is obtained from the variogram function estimated from mapped fracture set data and is typically referenced to the mean vector of the set. Simulation procedures for normally and exponentially distributed data involve generating uncorrelated Fourier coefficients that are assigned proper variance according to the spectral density, which is the Fourier transform of the covariance function. These coefficients are then reverse Fourier transformed to produce simulated set properties that have the desired variance and variogram function.     

Recognizing mercurian meteorites

Abstract— With the recent realization that some meteorites may come from Mars and the Moon, it is worthwhile to consider whether meteorites from Mercury could exist in our collections and, if so, whether they could be recognized. The current state of ignorance about Mercury both increases the potential scientific value of mercurian meteorites and aggravates the problem of identifying them. Here, we review evidence supporting the possibility of impact launch and subsequent orbital evolution that could deliver rocks from Mercury to Earth and suggest criteria that could help identify a mercurian meteorite. Mercurian rocks are probably differentiated igneous rocks or breccias or melt rocks derived therefrom. Solar nebula models suggest that they are probably low in volatiles and moderately enriched in Al, Ti, and Ca oxides. Mercurian surface rocks contain no more than 5% FeO and may contain plagioclase. A significant fraction may be volcanic. They may possess an unusual isotopic composition. Most pristine mercurian rocks should have solidification ages of ～3.7 to ～4.4 Ga, but younger impact-remelted materials are possible. Because we know more about the space environment of Mercury than we do about the planet itself, surface-exposed rocks would be easiest to identify as mercurian. The unique solar-to-galactic cosmic-ray damage track ratio expected in materials exposed near the Sun may be useful in identifying a rock from Mercury. Mercury's magnetic field stands off the solar wind, so that solar-wind implants in mercurian regolith breccias may be scarce or fractionated compared to lunar ones. Mercurian regolith breccias should contain more agglutinates (or their recrystallized derivatives) and impact vapor deposits than any other and should show a higher fraction of exogenic chondritic materials than analogous lunar breccias. No known meteorite group matches these criteria. A misclassified mercurian meteorite would most likely be found among the aubrites or the anorthositic lunar meteorites.     

RETRACTED ARTICLE: Space and time distributions of major winter storms in the United States

Winter storms are a major weather problem in the United States and their losses have been rapidly increasing. A total of 202 catastrophic winter storms involving ice storms, blizzards, and snowstorms, each causing >$5 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous United States, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of nine storms, and one year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differences in storm-producing weather conditions over time. The time distribution of the nation’s 202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.     

Losses from sleet storms in the United States

Increasing losses of life and property and damages to the environment due to sleet and related winter storm conditions have increased the need for long-term sleet storm data to better assess the point and regional risks of sleet and their long-term variations. The areas of greatest losses and frequency of catastrophes caused by sleet during 1971–2007 are the Northeast and Central regions of the U.S. These two regions experienced 72% of all the nation’s sleet losses. Most of the western U.S. had no damaging sleet-related events or losses. When sleet losses occurred, they tended to be in 2, 3, or 4 adjacent states. Sleet catastrophes were most common in January with 15 of the 30 events. The earliest storm occurred in October and the latest in March. The temporal distributions of catastrophes and their losses during 1971–2007 were similar. Both showed a secondary peak in 1976–1979, a low in 1988–1991, and then high values during the 1996–2007 period. The temporal distributions of damaging storms and losses indicate an upward trend over time.     

Support for,and Impacts of Publishing in the Annals of the AAG: The Authors and and Editor Speak

A survey of 176 authors who published in the Annals between 1988 and 1993 provides insights into why authors submitted their research to the journal, what support they received, and the impacts of the publication on their careers. Most decided themselves to submit their work, and one-third received support from research grants; cartographic assistance and graduate assistants were less important. The major benefits of publishing in the Annals were visibility in one's department, contact with other geographers, and requests for reprints. Most authors presented their ideas at professional meetings prior to submission. Promotion and salary Inc.reases were benefits for women, assistant professors, associate professors, and physical geographers. Authors considered their articles as original examinations that yielded new results, contributed to theory, stimulated debate, and helped bridge gaps inside and outside of geography. These results are useful in helping individual authors and for administrators in identifying the kinds of research support needed by authors publishing in the Annals.     

A Proposal to Use Chlorine-36 for Monitoring the Movement of Radionuclides from Nuclear Explosions

Chlorine-36 has been produced in large amounts by hundreds of nuclear explosions on the Nevada Test Site as well as 12 off-site explosions at eight locations in five states. Continued monitoring of the redistribution of radionuclides by subsurface water is of concern in most of the areas affected by the detonations. Chlorine-36 has the following advantages as a built-in tracer for this redistribution: its mobility is equal to or greater than water, its long half-life assures its continued usefulness over long periods, collection and storage of samples is simple, it is not subject to vapor transport at ordinary temperatures, its natural background is very low, and it does not form insoluble precipitates. Chlorine-36 from the Gnome event near Carlsbad, New Mexico, illustrates how ³⁶C1 can be used to help study the redistribution of radionuclides in the soil profile. Chlorine-36 is also potentially useful as a tracer to study movement of contaminants around large nuclear reactor complexes and near respositories for radioactive waste.     

Descriptive statistics forN-dimensional closed arrays: A spherical coordinate approach

Recent publications have demonstrated that the composition of a system can be described by the angles which define the vector resulting from the projection of the composition onto the unit hypersphere. Although published trigonometric relationships allow determination of the angles in any number of dimensions, no general hyperdimensional recursive formulae exist for the calculation of these quantities and their variances and covariances. A general methodology for calculating the angles which describe the compositions of systems in any number of dimensions is presented. These angles can be used to calculate statistics (central moments and resultant vectors) describing the central tendency and dispersion among rock compositions, as well as to quantify the angular differences between compositions. Equations that relate the variances and covariances of these angular variables to the variances and covariances of the actual component proportion variables are presented, allowing projection of these measurements from one reference frame to another (cartesian to spherical and vice versa).     

Do predatory fish of benthic crustaceans vary between kelp and barren reef habitats in northeastern New Zealand?

Fish assemblages that included known predators of benthic crustaceans were compared between kelp and barren habitats in northeastern New Zealand using baited underwater video census methods. The benthic-feeding fish were observed in winter, spring/summer and autumn, as well as during night-time in spring/summer. Overall, the fish assemblages varied between barren and kelp habitat, being most marked in winter. Individual benthic-feeding species, such as grey mao mao (Scorpis lineolatus) and leatherjacket (Meuschenia scaber) were associated with barren habitat, while the spotted wrasse (Notolabrus celidotus) was more strongly associated with kelp habitat. The results suggest that changes in habitats on coastal reefs affect populations of species that are benthic predators, which may in turn influence the distribution and abundance of their prey species, such as juvenile spiny lobsters.