scholarly journals Amplitudes of P, PP, and S and magnitude of shallow earthquakes*

1945 ◽  
Vol 35 (2) ◽  
pp. 57-69
Author(s):  
B. Gutenberg
Keyword(s):  
Absorption Coefficient ◽  
Shallow Earthquake ◽  
Transverse Waves ◽  
Longitudinal Waves ◽  
Longitudinal And Transverse Waves ◽  
The Core ◽  
The Earth ◽  
Shallow Earthquakes

Summary It is found that the absorption coefficient for longitudinal and transverse waves in the mantle of the earth as well as for longitudinal waves through the core is 0.00012 per km. In the average shallow earthquake about equal amounts of energy go into longitudinal and transverse waves. Equation (18), together with tables 2 and 4, permits the calculation of the magnitude of a shallow earthquake from the amplitudes of P, PP, or S.

scholarly journals Observations on seismic waves reflected at the core boundary of the earth*

1950 ◽  
Vol 40 (2) ◽  
pp. 95-109
Author(s):  
Samuel T. Martner
Keyword(s):  
Observational Data ◽  
Seismic Waves ◽  
Outer Boundary ◽  
Body Waves ◽  
Longitudinal Waves ◽  
The Core ◽  
The Earth ◽  
Core Boundary ◽  
Direct Body

Abstract Waves reflected from the outer boundary of the core of the earth often record trace amplitudes that appear excessive. A comparison of the observed displacements of these phases and the direct body waves is presented. Observational data seem to confirm the idea that the displacement ratios of the longitudinal waves reflected at the core to the longitudinal direct waves is larger than the presently recognized theory indicates. A discussion is included of some possible causes for this difference, but reasonable changes in accepted assumptions fail to explain the entire discrepancy.

scholarly journals Attenuation of seismic waves in the earth's mantle

1958 ◽  
Vol 48 (3) ◽  
pp. 269-282 ◽  
Author(s):  
B. Gutenberg
Keyword(s):  
Absorption Coefficient ◽  
Elastic Waves ◽  
Laboratory Experiments ◽  
Seismic Waves ◽  
Body Waves ◽  
The Core ◽  
Earth’S Mantle ◽  
The Earth ◽  
Theoretical Considerations

Abstract Contrasting with conclusions from laboratory experiments that the absorption coefficient k for amplitudes of elastic waves is proportional to 1/T, or, from theoretical considerations, that it should be proportional to 1/T or to 1/T2, observations of body waves through the mantle of the earth show little if any decrease in absorption with increasing period T. In teleseismic records S rarely shows periods of less than 4 seconds, while in P periods of 1 second are observed to the greatest distances. The value k = 0.06 per 1,000 km., found previously for P, P′P′ and P′P′P′ through the mantle and the core, is confirmed for P and PP and is found also for S in the mantle.

Ups and Downs

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Mantle Convection ◽  
Laboratory Experiments ◽  
Inner Core ◽  
Computer Modelling ◽  
Great Depth ◽  
New Horizons ◽  
The Core ◽  
The Earth ◽  
The World ◽  
The 1960S

Despite the dumbing-down of education in recent years, it would be unusual to find a ten-year-old who could not name the major continents on a map of the world. Yet how many adults have the faintest idea of the structures that exist within the Earth? Understandably, knowledge is limited by the fact that the Earth’s interior is less accessible than the surface of Pluto, mapped in 2016 by the NASA New Horizons spacecraft. Indeed, Pluto, 7.5 billion kilometres from Earth, was discovered six years earlier than the similar-sized inner core of our planet. Fortunately, modern seismic techniques enable us to image the mantle right down to the core, while laboratory experiments simulating the pressures and temperatures at great depth, combined with computer modelling of mantle convection, help identify its mineral and chemical composition. The results are providing the most rapid advances in our understanding of how this planet works since the great revolution of the 1960s.

scholarly journals Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

Dead-Ends and New Directions

2021 ◽  
Vol 15 (4) ◽  
pp. 327-347
Author(s):  
Jean Francesco A.L. Gomes
Keyword(s):  
Natural History ◽  
Scientific Theory ◽  
Good Science ◽  
Orthodox Christian ◽  
The Core ◽  
The Earth ◽  
New Directions ◽  
History Of ◽  
Evolutionary Science ◽  
Doctrine Of Creation

Abstract The aim of this article is to investigate how Abraham Kuyper and some late neo-Calvinists have addressed the doctrine of creation in light of the challenges posed by evolutionary scientific theory. I argue that most neo-Calvinists today, particularly scholars from the Vrije Universiteit Amsterdam (VU), continue Kuyper’s legacy by holding the core principles of a creationist worldview. Yet, they have taken a new direction by explaining the natural history of the earth in evolutionary terms. In my analysis, Kuyper’s heirs at the VU today offer judicious parameters to guide Christians in conversation with evolutionary science, precisely because of their high appreciation of good science and awareness of the nonnegotiable elements that make up the orthodox Christian narrative.

The density variation of the earth's central core*

1942 ◽  
Vol 32 (1) ◽  
pp. 19-29
Author(s):  
K. E. Bullen
Keyword(s):  
Pure Iron ◽  
Outer Boundary ◽  
Density Variation ◽  
Central Core ◽  
Good Precision ◽  
Wide Margin ◽  
The Core ◽  
The Earth ◽  
The Mean ◽  
Published Paper

ABSTRACT A detailed analysis of the problem of the earth's density variation has been extended to the earth's central core. It is shown that in the region between the outer boundary of the core and a distance of about 1400 km. from the earth's center the density ranges from 9.4 gm/cm.3 to 11.5 gm/cm.3 within an uncertainty which, if certain general assumptions are true, does not exceed 3 per cent. The density and pressure figures are, moreover, compatible with the existence of fairly pure iron in this part of the earth. The result for the earth's outer mantle as given in a previously published paper, together with those in the present paper, are found to give with good precision the density distribution in a region occupying 99 per cent of the earth's volume. Values of the density within 1400 km. of the earth's center are subject, however, to a wide margin of uncertainty, and there appears to be no means of resolving this uncertainty for the present. The most that can be said is that the mean density in the latter region is greater than 12.3 gm/cm.3 and may quite possibly be several gm/cm.3 in excess of this figure. In the present paper figures are also included for the variation of gravity and the distribution of pressure within the central core. The gravity results are shown to be subject to an appreciable uncertainty except within about 1000 km. of the outer boundary of the core, but the pressure results are expected to be closely accurate at all depths.

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