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Filter Total Items: 1976

Geomagnetic paleointensities from excursion sequences in lavas on Oahu, Hawaii

Paleomagnetic data demonstrating three late Tertiary excursions in the direction of the geomagnetic field recorded in sequences of basaltic lavas on the island of Oahu, Hawaii were published by R. R. Doell and G. B. Dalrymple in 1973. We have determined geomagnetic paleointensities by the Thelliers' method for 14 lavas from the three sites. During these experiments, considerable difficulty was enc

Book review: Geomagnetism of baked clays and recent sediments

This book is an outgrowth of the symposium entitled “Time Scales of Geomagnetic Secular Variations,” which was held at the 4th Assembly of the International Association of Geomagnetism and Aeronomy (Edinburgh, U.K., August 1981). The volume includes many of the papers presented, which described paleomagnetic results from both archeologic materials and Holocene geologic deposits, as well as contrib

Pedimentation versus debris-flow origin of plateau-side desert terraces in southern Utah.

Plateau-side terraces in arid areas around the world are commonly described as pediment remnants, although, in many cases, they may have been formed by debris-flow deposition. Pediments do exist in the area of the Aquarius and Kaiparowits Plateaus of southern Utah; however, many alluvial terraces that were classified by previous workers as pediments are actually formed of thick deposits of sedimen

Landslides caused by earthquakes.

Data from 40 historical world-wide earthquakes were studied to determine the characteristics, geologic environments, and hazards of landslides caused by seismic events. This sample was supplemented with intensity data from several hundred US earthquakes to study relations between landslide distribution and seismic parameters. Correlations between magnitude (M) and landslide distribution show that

Transitional paleointensities from Kauai, Hawaii, and geomagnetic reversal models

Previously presented paleointensity results from an R-N transition zone in Kauai, Hawaii, show that field intensity dropped from 0. 431 Oe to 0. 101 Oe while the field remained within 30 degree of the reversed axial dipole direction. A recovery in intensity and the main directional change followed this presumably short period of low field strength. As the reversal neared completion, the field has

High paleointensities of the geomagnetic field from thermomagnetic studies on rift valley pillow basalts from the Mid- Atlantic Ridge.

Nineteen pillow basalts dredged within the rift valley of the Mid-Atlantic Ridge at 36.8oN were studied by the Thellier stepwise heating method in order to determine the paleointensity of the geomagnetic field when they erupted on to the sea floor. Previously reported fission track ages are 2000-6000 yr for the youngest rocks (mainly olivine basalts) and 10 000-100 000 yr for the others (mainly pl

Landslide risk assessment

Landslide risk can be assessed by evaluating geological conditions associated with past events. A sample of 2,4 16 slides from urban areas in West Virginia, each with 12 associated geological factors, has been analyzed using SAS computer methods. In addition, selected data have been normalized to account for areal distribution of rock formations, soil series, and slope percents. Final calculations

PREPARING A DETAILED LANDSLIDE-INVENTORY MAP FOR HAZARD EVALUATION AND REDUCTION.

A method of preparing a detailed landslide-inventory map has been developed which provides the engineering geologist with the basic information for evaluating and reducing landslide hazards or risk on a regional or community level. For each landslide, the map depicts state of activity, certainty of identification, dominant type of slope movement, primary direction of movement, estimated thickness

Sensitivity of selected geomagnetic properties to truncation level of spherical harmonic expansions

A two day selection of MAGSAT data is fit by spherical harmonic series truncated at increasing levels NF in the range 2

Paleomagnetic data from the Coso Range, California and current status of the Cobb Mountain normal geomagnetic polarity event

Two basalt flows which erupted about 1.08 m.y. ago in the Coso Range, California, have normal magnetic polarity and thus provide additional evidence for the Cobb Mountain normal polarity event. A review of available data confirms that this event was of geomagnetic origin. A mean age of 1.10 ± 0.02 m.y. B.P. for the Cobb Mountain normal polarity event was found to best fit all available radiometric