摘要:

Recently, geodesy has witnessed a renaissance in geoid computation. The advances over the past decade have taken place at all wavelengths, and have brought forth major improvements in accuracy. An example of a long‐wavelength global gravitation model is the GEM‐T2 (Goddard Earth Model) solution ofMarsh et al.[1989], which is complete to degree and order 36, and incomplete to degree 50.Rapp and Pavlis[1990] have computed a pair of solutions, 0SU89A and 0SU89B (Ohio State University), which are spherical harmonic models of the Earth's geopotential complete to degree and order 360. Although termed high degree global models, these solutions provide the geoid to what we may now consider a medium length scale–about 50‐km resolution. High‐resolution geoid height modeling has shown the greatest advances in accuracy.Forsberg[1990] computed a geoid model for the Nordic area on a 5‐km grid, and obtained 3–7 cm standard deviations when compared to Global Positioning System (GPS) and leveling in local networks of 50–1

ISSN:0002-8606    

DOI:10.1029/EO072i049p00545-01

年代:1991

数据来源: WILEY

摘要:

On June 4, 1991, AGU Fellow Joseph Fairfield Poland died in a Sacramento, Calif., hospital at the age of 83 after a long fight with Parkinson's Disease. A recognized expert on land subsidence and a retiree from the U.S. Geological Survey's Water Resources Division, his death occurred only 2 weeks after the end of the 4th International Symposium on Land Subsidence, held in Houston, Tex. Frequently known as “Mr. Land Subsidence,” it was appropriate that the proceedings of that symposium had been dedicated to him.Born in Boston, Poland earned a bachelor's degree in geology from Harvard University in 1929. He was resident geologist for Tropical Oil Company in Colombia from 1929 to 1931. After returning to the United States, Poland earned his master's degree in geology from Stanford University in 1935, taught groundwater hydrology, and consulted on groundwater and geophysical problems in the West and Southw

ISSN:0002-8606    

DOI:10.1029/90EO00389

年代:1991

数据来源: WILEY

摘要:

Five students from the Solar‐Planetary Relationships section were cited for their outstanding papers delivered at the AGU 1991 Spring Meeting in Baltimore.Steve Benka, who presented “A Thermal/Non‐thermal (TNT) Model for Solar Microwave Bursts,” successfully completed the doctoral program at the University of North Carolina at Chapel Hill in August 1991. His research interests include the interpretation of high‐resolution spectra of solar flare hard X‐ray and microwave emissions. Benka is interested in extending the usefulness of concepts learned in physics to other phenomena, both atrophysical and within the solar system. Benka received a B.S. in both physics and mathematics from Metropolitan State Coll

ISSN:0002-8606    

DOI:10.1029/EO072i049p00547-01

年代:1991

数据来源: WILEY

摘要:

On the evening of March 2, 1991, the research vesselJOIDES Resolutiondeparted from Honolulu harbor for a 17‐day mission that reflects an important new trend in the international Ocean Drilling Program (ODP). The primary objective of ODP Leg 136 was to prepare a seafloor site for future experiments needed to develop the Ocean Seismographic Network (OSN). The focus of OSN is much deeper than the strata reached by the drill bit of the Resolution, and this cooperative effort will enable the drilling ship's resources to be shared with a community whose interests extend to the inner core of the Earth.During Leg 136, ODP Hole 843B (proposed Site OSN‐1) was established on the Hawaiian Arch, approximately 225 km south‐southwest of the island of Oahu (Figure 1). The hole was drilled through 242 m of sediment and 70 m into the basaltic basement. It will provide a site for performing borehole seismometer experiments that include noise measurements, recording data from teleseismic events for comparison with an existing high‐quality station on Oahu, and testing new broad‐band sensors and other instrumentation for long‐term deployment. A significant part of this report will be devoted to providing the reader with the background and objectives

ISSN:0002-8606    

DOI:10.1029/EO072i049p00548

年代:1991

数据来源: WILEY

摘要:

As a sequel to the saga “As the World Turns” [Chao, 1985], which strolls through the kinematics of the Earth's rotation, this episode relates a close encounter of the dynamic kind with our turning world. First, this article elucidates the distinction between relative and absolute rotations. Then it argues that the instruments that respond to absolute rotation with sufficient sensitivity can potentially detect the Earth's rotational variations under certain conditions; hence, the instruments are complementary and present interesting alternatives to conventional geodetic techniques that measure relative rotat

ISSN:0002-8606    

DOI:10.1029/EO072i049p00550

年代:1991

数据来源: WILEY