THE PROPAGATION OF THE COMPRESSIONAL WAVE IN THE CRUST: I. A SIMPLE TREATMENT OF THE DATA

1965 ◽  
Vol 2 (6) ◽  
pp. 543-559 ◽  
Author(s):  
M. J. Keen ◽  
C. F. Tsong ◽  
J. E. Blanchard
Keyword(s):  
Nova Scotia ◽  
Velocity Gradient ◽  
Atlantic Coast ◽  
Compressional Wave ◽  
Earth’S Crust ◽  
Head Wave ◽  
Propagation Mechanism ◽  
Half Cycle ◽  
Simple Treatment ◽  
Earth's Crust

Seismic experiments have been undertaken along the Atlantic coast of Nova Scotia, and an attempt has been made to determine by what mechanism the compressional wave which is recorded as the first event in the range of distance 10 km to 180 km propagates, and to describe its attenuation. In this part of the paper the change in amplitude of the first half-cycle of the first event is investigated, and compared with the change in amplitude which might be expected if propagation occurred as a "head wave", and if propagation occurred because of the presence of a velocity gradient in the upper few kilometers of the earth's crust. We find that we cannot distinguish between the two mechanisms of propagation with any certainty, and although the suggestion is made that the value of Q is in the range 90 to 300, depending upon the propagation mechanism, the assumptions which underlie the approach are criticized, and a more reasonable one put forward.

SEISMIC STUDIES ON THE EASTERN SEABOARD OF CANADA: THE ATLANTIC COAST OF NOVA SCOTIA

1964 ◽  
Vol 1 (1) ◽  
pp. 10-22 ◽  
Author(s):  
D. L. Barrett ◽  
M. Berry ◽  
J. E. Blanchard ◽  
M. J. Keen ◽  
R. E. McAllister
Keyword(s):  
Nova Scotia ◽  
Upper Mantle ◽  
Atlantic Coast ◽  
Seismic Refraction ◽  
Compressional Wave ◽  
Crust And Upper Mantle ◽  
Compressional Waves ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Eastern Seaboard

The results of seismic refraction profiles on the Atlantic coast of Nova Scotia and on the continental shelf off Nova Scotia are presented. Compressional and shear waves have been observed in the crust and mantle and suggest that the thickness of the crust is about 34 km. The compressional wave velocities recorded in the main crust and upper mantle are 6.10 and 8.11 km s−1 respectively. No compressional waves with values of velocity between these values can be identified, and this suggests that any "intermediate" layer is thin or absent. The corresponding shear wave velocities are 3.68 and 4.53 km s−1. Values of Poisson's ratio in the crust and mantle are 0.22 and 0.28. Alternative models of the crust which, on the evidence of travel times, might fit the observed results are discussed.

HEAD WAVE TIME SECTIONS OF THE UPPER EARTH’S CRUST ALONG THE SURVEY BASE LINE 3-DV (NORTHEASTERN BLOCK)

2016 ◽  
pp. 86-95
Author(s):  
P. O. Polyansky ◽  
◽  
A. S. Salnikov ◽  
A. F. Emanov ◽  
V. V. Zhabin ◽  
...  
Keyword(s):  
Earth’S Crust ◽  
Head Wave ◽  
Base Line ◽  
Earth's Crust

scholarly journals Study on the inter-annual hydrology-induced deformations in Europe using GRACE and hydrological models

2020 ◽  
Vol 14 (4) ◽  
pp. 393-403
Author(s):  
Artur Lenczuk ◽  
Grzegorz Leszczuk ◽  
Anna Klos ◽  
Wieslaw Kosek ◽  
Janusz Bogusz
Keyword(s):  
Atlantic Coast ◽  
Singular Spectrum Analysis ◽  
River Basins ◽  
Earth’S Crust ◽  
Hydrological Models ◽  
European Area ◽  
High Precipitation ◽  
Earth's Crust ◽  
Land Data Assimilation System ◽  
Gravity Recovery

AbstractEarth’s crust deforms in various time and spatial resolutions. To estimate them, geodetic observations are widely employed and compared to geophysical models. In this research, we focus on the Earth’s crust deformations resulting from hydrology mass changes, as observed by GRACE (Gravity Recovery and Climate Experiment) gravity mission and modeled using WGHM (WaterGAP Global Hydrological Model) and GLDAS (Global Land Data Assimilation System), hydrological models. We use the newest release of GRACE Level-2 products, i. e. RL06, provided by the CSR (Center for Space Research, Austin) analysis center in the form of a mascon solution. The analysis is performed for the European area, divided into 29 river basins. For each basin, the average signal is estimated. Then, annual amplitudes and trends are calculated. We found that the eastern part of Europe is characterized by the largest annual amplitudes of hydrology-induced Earth’s crust deformations, which decrease with decreasing distance to the Atlantic coast. GLDAS largely overestimates annual amplitudes in comparison to GRACE and WGHM. Hydrology models underestimate trends, which are observed by GRACE. For the basin-related average signals, we also estimate the non-linear variations over time using the Singular Spectrum Analysis (SSA). For the river basins situated on the southern borderline of Europe and Asia, large inter-annual deformations between 2004 and 2009 reaching a few millimeters are found; they are related to high precipitation and unexpectedly large drying. They were observed by GRACE but mismodelled in the GLDAS and WGHM models. Few smaller inter-annual deformations were also observed by GRACE between 2002-2017 for central and eastern European river basins, but these have been also well-covered by the WGHM and GLDAS hydrological models.

Use of amplitudes, Part I: Pn from 3° to 23°*

1955 ◽  
Vol 45 (3) ◽  
pp. 219-244
Author(s):  
J. Cl. De Bremaecker
Keyword(s):  
Density Ratio ◽  
Limited Range ◽  
Theoretical Explanation ◽  
Earth’S Crust ◽  
Head Wave ◽  
Rate Of Increase ◽  
Earth's Crust ◽  
Mohorovičić Discontinuity

Abstract Ten seisms with epicentral distances between 3° and 23° are studied. Gutenberg's method to find the variation of Pn amplitudes with distance is applied. It results in observations too scattered to permit any conclusion. The second method uses a combination of seisms, each observed in a limited range. A minimum is found around 7° and a maximum around 13⋅∘5. The essence of the proposed theoretical explanation is the coexistence of “Muskat's rays”† (refracted rays) and of “direct rays” and the existence of “Muskat's rays” along the boundary of two media, in one of which the velocity increases with depth. The results are well explained by comparing the amplitudes due to these two rays. The following structure of the earth's crust best explains the results: speed above the Mohorovičić discontinuity, 6.3 km/sec.; speed immediately below it, 8.1 km/sec.; speed at 80 km. depth, between 8.10 km/sec. and 8.128 km/sec.; around 80 km., decrease in the rate of increase of speed with depth, or decrease of speed with depth < 0.001293 km/sec/km.; depth of the discontinuity, 35 km.; σ1 = σ2 = 0.25; density ratio = 1.103. † Note added in proof: Since the time of this writing, various papers have been published by Macelwane's students using the term “head-wave” for what is here called “Muskat's rays.” As the former term is not ambiguous and is now in current use, it should be preferred.

THE PROPAGATION OF THE COMPRESSIONAL WAVE IN THE CRUST: II. SYNTHETIC SEISMOGRAMS

1965 ◽  
Vol 2 (6) ◽  
pp. 560-576 ◽  
Author(s):  
M. J. Keen ◽  
C. F. Tsong
Keyword(s):  
Nova Scotia ◽  
Wave Velocity ◽  
Atlantic Coast ◽  
Compressional Wave ◽  
Synthetic Seismograms ◽  
The Other ◽  
Compressional Wave Velocity ◽  
Compressional Waves ◽  
The One

Synthetic seismograms have been generated in an attempt to measure the attenuation of compressional waves beneath the Atlantic coast of Nova Scotia; the results suggest that the value of Q must be of the order of 300 whatever the mechanism of propagation may be. Comparison with results of experiments in the Gulf of St. Lawrence shows that attenuation of first events in the range of distance up to 60 km is more rapid in the rocks beneath the Gulf than in those beneath the Atlantic coast of Nova Scotia, This may be due either to attenuation in the upper sedimentary layers, present in the one place but not in the other, or to greater attenuation within rocks in which the compressional wave velocity is the same as in those beneath the Atlantic coast.

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

MAGNETOELASTIC MODEL OF THE EARTH’S CRUST FOR THE WESTERN TERMINATION OF THE SOUTH BAIKAL BASIN

2017 ◽  
Vol S36 ◽  
pp. 3-10
Author(s):  
P. G. Dyadkov ◽  
◽  
L. V. Tsibizov ◽  
M. P. Kozlova ◽  
A. V. Levicheva ◽  
...  
Keyword(s):  
Earth’S Crust ◽  
The South ◽  
Baikal Basin ◽  
Earth's Crust ◽  
South Baikal
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