The depth of focus of two recent earthquakes and the depth of the surface layer of the earth in California

1926 ◽  
Vol 16 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Perry Byerly
Keyword(s):  
Surface Layer ◽  
Depth Of Focus ◽  
The Earth ◽  
Recent Earthquakes

The Distribution of Deep-focus Earthquakes

1937 ◽  
Vol 74 (7) ◽  
pp. 316-324 ◽  
Author(s):  
Charles Davison
Keyword(s):  
Northern Hemisphere ◽  
Depth Of Focus ◽  
The Earth ◽  
Deep Focus

During the years 1918–1931, there were 270 earthquakes with unusually deep foci, 167 in the Northern Hemisphere, 101 in the Southern, and two with epicentres on the equator. The normal depth of focus is assumed to be about 50 km. or ·008 of the earth's radius. The focal depths of the above earthquakes range from ·005 to ·090 of the earth's radius below the normal depth, or from 50 to 380 miles beneath the surface. Throughout this paper, the depth, when given in terms of the earth's radius, is referred to the normal depth; when given in miles, to the surface of the earth.

A PLANE-WAVE ANALOGUE MODEL FOR STUDYING ELECTROMAGNETIC VARIATIONS

1966 ◽  
Vol 44 (1) ◽  
pp. 67-80 ◽  
Author(s):  
H. W. Dosso
Keyword(s):  
Surface Layer ◽  
Plane Wave ◽  
Geological Structures ◽  
Analogue Model ◽  
The Earth ◽  
Phase Angles

A plane-wave analogue model for studying the effect that various geological structures have on the natural electromagnetic variations observed at the surface of the earth is discussed. The validity of the model is discussed, and measurements of amplitudes and phase angles are obtained for a model flat earth and for cylindrical bodies embedded in the surface layer.

Prompt gamma rays and X rays from supernovae

1968 ◽  
Vol 46 (10) ◽  
pp. S476-S480 ◽  
Author(s):  
Stirling A. Colgate
Keyword(s):  
Surface Layer ◽  
Gamma Rays ◽  
Lower Energy ◽  
Mean Free Path ◽  
Prompt Gamma ◽  
X Rays ◽  
Energy Factor ◽  
The Earth ◽  
Photon Pulse ◽  
Energy Formula

The hydrodynamic origin of cosmic rays (Colgate and Johnson 1960) depends upon the shock ejection of the outer layers of the supernova. The increase in energy of the shock to c2 per gram occurs relatively deep within the star where the fraction, F, of mass external to this layer is 10−4. The relativistic shock wave continues to increase in strength in the decreasing density of the envelope. When the shock "breaks through" the surface denned as one Compton scattering mean free path at radius R, then the energy factor [Formula: see text]. The temperature in the proper frame of the shock is determined by the condition aT4 = 2γs2ρ0, where ρ0 is the initial rest density ahead of the shock. For a typical presupernova star, [Formula: see text], and polytrope of index 3, the temperature becomes (1.7–2) × 105 eV at the surface layer. Photons emitted from the moving surface layer will be Doppler-shifted from their mean proper frame value of 3kT to a final energy [Formula: see text].Photons originating in, and emitted from, the surface layer before the layer expands adiabatically will have the upper limiting energy. As adiabatic expansion of subsequent layers takes place, photons diffusing from greater depths will be emitted at sequentially lower energy. The total energy in the photon pulse from the surface layer becomes [Formula: see text] ergs, or 50 ergs/cm2 at the earth for a supernova within our galaxy. The time of emission becomes [Formula: see text] (Petschek 1967).

The times of origin and depths of focus of intermediate and deep focus earthquakes: Model calculations

1981 ◽  
Vol 71 (5) ◽  
pp. 1539-1552
Author(s):  
A. L. Hales ◽  
K. J. Muirhead ◽  
L. Maki-Lopez
Keyword(s):  
Average Velocity ◽  
Epicentral Distance ◽  
Depth Range ◽  
Depth Of Focus ◽  
P Waves ◽  
Model Calculations ◽  
The Earth ◽  
Deep Focus ◽  
The Times ◽  
Time Of Origin

abstract Two methods for determining the time of origin, depth of focus, and the average velocities from the focus to the surface are described. The first stage in the first method is to determine the time of origin using a modification of the Wadati method. As was pointed out in 1973 by Kisslinger and Engdahl, the relation between (ts − tp and tp is nonlinear and it is necessary to allow for this nonlinearity by including a term in tp2 in the analysis. Thereafter the depth of focus and the average velocity can be found by a modification of the procedure used to determine the depth to a reflector in seismic reflection prospecting. It is necessary to allow for the sphericity of the Earth in this analysis. In the second method, the depth of focus is determined first by analyzing (ts − tp)2 as a function of x2, x being the epicentral distance. The average velocity of separation of S and P waves is also determined at this stage. Thereafter the time of origin and the average P and S velocities are determined. The results of the analysis of the calculated travel times for three models show that systematic errors in the depth of focus using these procedures are less than 2 km over the depth range of 60 to 640 km. Preliminary results of the analysis of a limited set of Japanese earthquakes by these methods give estimates of depth smaller than those given by ISC for depths less than 300 km. For deeper earthquakes, these methods give foci deeper than the ISC, but in these cases the observations close to the epicenter are inadequate for reliable analysis.

Turbulent Motion

1914 ◽  
Vol 34 ◽  
pp. 112-112
Keyword(s):  
Surface Layer ◽  
Great Circle ◽  
Turbulent Motion ◽  
The Earth ◽  
The Subject ◽  
Rotation Of The Earth

In the study which has been the subject of the foregoing pages we have always considered the motion of the air to be regulated by a distribution of pressure balanced by the rotation of the earth, except in regard to the surface layer and one other suggested exception when the momentum of the general westerly circulation was invoked. It should here be noted that by this limitation to what may perhaps be called “great circle motion,” we are considering almost exclusively the circulation above that half of the earth's surface which is north of the northern tropic and south of the southern one.

Subdivided Buildings—Developments in Australia, Singapore and England

1996 ◽  
Vol 45 (2) ◽  
pp. 343-364 ◽  
Author(s):  
Alice Christudason
Keyword(s):  
Surface Layer ◽  
The Earth ◽  
The Law

This article considers the development in several Commonwealth jurisdictions of the law relating to “horizontal subdivisions”2, or subdivided buildings. The latter expression describes the situation where title to land can relate to a slice of defined area or cubic space, which is not grounded on the surface layer of the earth, and is divided not only horizontally, but vertically as well.

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