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Analysis of geomagnetic secular variation during 1980-1985 and 1985- 1990, and geomagnetic models proposed for the 1991 revision of the International Geomagnetic Reference Field Analysis of geomagnetic secular variation during 1980-1985 and 1985- 1990, and geomagnetic models proposed for the 1991 revision of the International Geomagnetic Reference Field

The secular variation of the main geomagnetic field during the periods 1980-1985 and 1985-1990 was analyzed in terms of spherical harmonics up to the eighth degree and order. Data from worldwide magnetic observatories and the Navy's Project MAGNET aerial surveys were used. The resulting pair of secular-variation models was used to update the Definitive Geomagnetic Reference Field (DGRF)...
Authors
N.W. Peddie

Hayward fault: Large earthquakes versus surface creep Hayward fault: Large earthquakes versus surface creep

The Hayward fault, thought a likely source of large earthquakes in the next few decades, has generated two large historic earthquakes (about magnitude 7), one in 1836 and another in 1868. We know little about the 1836 event, but the 1868 event had a surface rupture extending 41 km along the southern Hayward fault. Right-lateral surface slip occurred in 1868, but was not well measured...
Authors
James J. Lienkaemper, Glenn Borchardt

Quiet geomagnetic field representation for all days and latitudes Quiet geomagnetic field representation for all days and latitudes

This paper describes a technique for obtaining the quiet-time geomagnetic field variation expected for all days of the year and distribution of latitudes from a limited set of selected quiet days within a year at a discrete set of locations. We used a data set of observatories operated by Indian and USSR scientists in 1976 and 1977 near 75°E longitude as illustration. Our method relies...
Authors
W.H. Campbell, E.R. Schiffmacher, B.R. Arora

Fault growth and acoustic emissions in confined granite Fault growth and acoustic emissions in confined granite

The failure process in a brittle granite was studied by using acoustic emission techniques to obtain three dimensional locations of the microfracturing events. During a creep experiment the nucleation of faulting coincided with the onset of tertiary creep, but the development of the fault could not be followed because the failure occurred catastrophically. A technique has been developed...
Authors
David A. Lockner, James D. Byerlee
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