A NOTE ON THE USE OF MICROSEISMS IN DETERMINING THE SHALLOW STRUCTURES OF THE EARTH’S CRUST

Geophysics ◽  
1965 ◽  
Vol 30 (4) ◽  
pp. 665-666 ◽  
Author(s):  
Keiiti Aki
Keyword(s):  
Phase Velocity ◽  
Japanese Journal ◽  
The United States ◽  
Earth’S Crust ◽  
Random Waves ◽  
Frequency Range ◽  
Special Issue ◽  
Unknown Parameters ◽  
Earth's Crust ◽  
Partial Success

In the VELA UNIFORM Special Issue I of Geophysics, M. N. Toksöz presented the result of his attempt at determining the shallow structures of the earth’s crust from the phase velocity of microseisms. He stated that his attempt resulted only in partial success on account of the fact that the microseisms arrived from more than one direction at the same time with comparable strength. He also concluded that there was no way of improving the results by the use of special arrays because, according to him, there were two unknown parameters, direction and phase velocity, and without the knowledge of one the other cannot be found. I thought this problem was already solved in my paper (Aki, 1957), in which a statistical theory of determining the phase velocity of random waves was given with a successful application to microseisms in Tokyo in the frequency range of 5 to 15 cps. Since Toksöz’s conclusion might have given a pessimistic view on the use of microseisms, I feel it is necessary to report a brief summary of my old paper published in a Japanese journal which might not be well circulated in the United States.

On the calculation of AFMAG *AFMAG—Audio Frequency Magnetics.anomalies

Geophysics ◽  
1960 ◽  
Vol 25 (6) ◽  
pp. 1290-1293
Author(s):  
JAMES Richard WAIT
Keyword(s):  
Geomagnetic Field ◽  
The Other ◽  
Earth’S Crust ◽  
Audio Frequency ◽  
Geophysical Prospecting ◽  
Frequency Range ◽  
Horizontal Stratification ◽  
Charles Wright ◽  
Earth's Crust ◽  
Practical Scheme

It has been proposed by S. H. Ward (1959) and C. S. Wright et al. (1960) that nonuniformity in the earth's crust will tend to tilt the direction of the fluctuating components of the geomagnetic field from its normal horizontal direction. In fact, Ward and colleagues have developed a practical scheme (AFMAG) for geophysical prospecting which makes use of this phenomenon in the frequency range from 100 to 400 c/s. Sir Charles Wright et al., on the other hand, have found that at much lower frequencies, .005 to 1 c/s, a substantial verticalcomponent of the field in the vicinity of coast lines or other situations where the earth's crust departs from horizontal stratification.

scholarly journals Editorial for Special Issue “Clays, Clay Minerals, and Geology”

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1057
Author(s):  
Francesco Cavalcante
Keyword(s):  
Clay Minerals ◽  
Sedimentary Rocks ◽  
Earth’S Crust ◽  
Special Issue ◽  
Earth's Crust

Sedimentary rocks covering most of the Earth’s crust are mainly composed of clays, making clay minerals widespread globally. [...]

scholarly journals Editorial for the Special Issue “The Rietveld Method in Geomaterials Characterisation”

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 814
Author(s):  
Thomas N. Kerestedjian
Keyword(s):  
Raw Materials ◽  
Rietveld Method ◽  
Earth’S Crust ◽  
Fundamental Importance ◽  
Special Issue ◽  
Wide Range ◽  
Earth's Crust

The raw materials obtained from the Earth’s crust (Geomaterials) are of fundamental importance for a wide range of industries [...]

scholarly journals Editorial for Special Issue “Mineralogy of Quartz and Silica Minerals”

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 467
Author(s):  
Jens Götze
Keyword(s):  
Earth’S Crust ◽  
Special Issue ◽  
Earth's Crust

Quartz and other silica minerals make up 12.6 wt % of the Earth’s crust and belong to the most frequent rock-forming constituents. [...]

scholarly journals Editorial for Glacial and Geomorphological Cartography Special Issue

Geosciences ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 424
Author(s):  
Ramón Pellitero Ondicol
Keyword(s):  
Earth’S Crust ◽  
Special Issue ◽  
Earth's Crust

Landforms are the most superficial part of the earth’s crust. [...]

scholarly journals A SEISMIC MODEL STUDY OF THE PHASE VELOCITY METHOD OF EXPLORATION

Geophysics ◽  
1957 ◽  
Vol 22 (2) ◽  
pp. 275-285 ◽  
Author(s):  
Frank Press
Keyword(s):  
Phase Velocity ◽  
Surface Waves ◽  
Earth’S Crust ◽  
Velocity Variation ◽  
Seismic Model ◽  
Additional Information ◽  
Model Study ◽  
Unique Interpretation ◽  
Ground Roll ◽  
Earth's Crust

Variations in the phase velocity of earthquake‐generated surface waves have been used to determine local variations in the thickness of the earth’s crust. It is of interest to determine whether this method can be used to delineate structures encountered by the exploration geophysicist. A seismic model study of the effect of thickness changes, lithology changes, faults and scarps, on the phase velocity of surface waves was carried out. It is demonstrated that all of these structures produce measurable variations in the phase velocity of surface waves. Additional information is required, however, to give a unique interpretation of a given phase velocity variation in terms of a particular structure. Some remarks on the phenomenon of returning ground roll are made.

Tides in the Earth's Crust

1915 ◽  
Vol 79 (2058supp) ◽  
pp. 382-383
Author(s):  
Alphonse Berget
Keyword(s):  
Earth’S Crust ◽  
Earth's Crust

EDITORIAL: Migration and competitiveness: Japan and the United States

2013 ◽  
Vol 10 (2) ◽  
pp. 115-124
Author(s):  
Philip L. Martin
Keyword(s):  
United States ◽  
The United States ◽  
Variable Cost ◽  
Fixed Cost ◽  
Special Issue ◽  
Science And Engineering ◽  
The Past ◽  
Past Half Century ◽  
Key Sectors ◽  
Past Half

Japan and the United States, the world’s largest economies for most of the past half century, have very different immigration policies. Japan is the G7 economy most closed to immigrants, while the United States is the large economy most open to immigrants. Both Japan and the United States are debating how immigrants are and can con-tribute to the competitiveness of their economies in the 21st centuries. The papers in this special issue review the employment of and impacts of immigrants in some of the key sectors of the Japanese and US economies, including agriculture, health care, science and engineering, and construction and manufacturing. For example, in Japanese agriculture migrant trainees are a fixed cost to farmers during the three years they are in Japan, while US farmers who hire mostly unauthorized migrants hire and lay off workers as needed, making labour a variable cost.

Sign in / Sign up

Export Citation Format

Share Document