Deep-Focus Mantle Earthquakes in the Eastern Part of the Caucasian Isthmus

2020 ◽  
Vol 56 (2) ◽  
pp. 189-206
Author(s):  
V. I. Shevchenko ◽  
A. A. Lukk
Keyword(s):  
Deep Focus ◽  
Mantle Earthquakes

scholarly journals Internal melt figures in ice by rapid adiabatic compression

1994 ◽  
Vol 40 (134) ◽  
pp. 132-134
Author(s):  
R.E. Gagnon ◽  
C. Tulk ◽  
H. Kiefte
Keyword(s):  
Phase Transformations ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Adiabatic Compression ◽  
Air Bubbles ◽  
Water Ice ◽  
Deep Focus ◽  
And Behavior ◽  
First Time

AbstractSingle crystals and bicrystals of water ice have been adiabatically pressurized to produce, and clearly illustrate, two types of internal melt figures: (1) dendritic figures that grow from nucleation imperfections on the specimen’s surface, or from air bubbles at grain boundaries, into the ice as pressure is elevated; and (2) compression melt fractures, flat liquid-filled disks, that nucleate at imperfections in the crystal and grow with the application of pressure eventually to sprout dendritic fingers at the periphery. The transparency of the ice permitted visualization of the growth and behavior of the figures, and this could be an important tool in understanding the role of phase transformations in deep-focus earthquakes. Correlation between figure size and pressure is noted for the first time.

Sharpening Deep Focus

1980 ◽  
Vol 34 (2) ◽  
pp. 62-64
Author(s):  
Joe Heumann ◽  
Charles H. Harpole
Keyword(s):  
Deep Focus

On the generation of deep focus earthquakes in subduction zones

1999 ◽  
Vol 12 (5) ◽  
pp. 573-583 ◽  
Author(s):  
Jie-Yuan Ning ◽  
Shao-Xian Zang
Keyword(s):  
Subduction Zones ◽  
Deep Focus

A method of obtaining P and S travel-time curves within a “Stripped Earth”*

1952 ◽  
Vol 42 (4) ◽  
pp. 313-314
Author(s):  
V. C. Stechschulte
Keyword(s):  
Travel Time ◽  
Depth Distribution ◽  
Epicentral Distance ◽  
Travel Times ◽  
Depth Of Focus ◽  
Distance Curve ◽  
Simple Method ◽  
Time Distance ◽  
Deep Focus

Abstract A simple method is outlined for obtaining from a time-distance curve of a deep-focus earthquake a table of travel times within an earth “stripped” to the depth h, the depth of focus. The method depends on the fact that such a curve for a deep-focus earthquake has a point of inflection and therefore has the same slope at two different values of epicentral distance. The Herglotz-Wiechert method may then be applied to these travel times to obtain a velocity-depth distribution.

Two-parameter scaling of source spectra: Love waves from deep-focus Bonin Islands earthquakes

1977 ◽  
Vol 67 (2) ◽  
pp. 285-300
Author(s):  
R. James Brown
Keyword(s):  
Body Wave ◽  
Scaling Law ◽  
Spectral Ratio ◽  
Love Waves ◽  
Corner Frequency ◽  
Spectral Ratios ◽  
Bonin Islands ◽  
Deep Focus ◽  
Two Parameter ◽  
Fault Length

Abstract Starting with the one-parameter scaling law of Aki, a two-parameter expression is developed to model the source factor of the far-field spectrum from a dislocation fault source for both ω−2 and ω−3 high-frequency asymptotic types. Aki's assumption of similarity is relaxed in two respects: it is neither here assumed that wD0 ∞ L2 (L = fault length, w = fault width, D0 = average dislocation) nor that kT = v kL (kT−1 = correlation time, kL−1 = correlation length, v = velocity of rupture propagation), the latter being equivalent to allowing for Brune's fractional stress drop. From this two-parameter model a four-parameter model of spectral ratio is obtained and fitted to observed spectral ratios by computer optimization of the four parameters. Observed spectral ratios have been determined from the Love waves recorded at NORSAR from six deep-focus Bonin Islands earthquakes using a common-path method. From the optimal values of the four parameters, values are determined for corner frequency (f ≈ 0.2 Hz for m 6.0; f ≈ 0.3 Hz for m = 5.3; m = PDE body-wave magnitude), relative fault length, relative seismic moment (and magnitudes), and p, the slope of the corner-frequency locus. Values found for p are all greater than 3 and such p, in combination with an ω−3 scaling law, can yield a reasonable m:M relation, i.e., with no ceiling imposed on m. A slightly better fit is obtained by starting with an ω−3 model than with ω−2.

The Hindu Kush earthquake of March 4, 1949 as recorded in Europe

1964 ◽  
Vol 54 (6A) ◽  
pp. 1915-1925 ◽  
Author(s):  
I. Lehmann
Keyword(s):  
Amplitude Ratio ◽  
Epicentral Distance ◽  
Focal Region ◽  
Travel Times ◽  
Period Range ◽  
Characteristic Appearance ◽  
Hindu Kush ◽  
The Difference ◽  
Deep Focus ◽  
The Many

abstract The European records from distances 36°-50° of the deep Hindu Kush earthquake of March 4, 1949 were studied. The many clearly recorded deep-focus reflections lend to the records a characteristic appearance which is repeated in many other shocks from the same focal region. The ratios of the amplitudes of these phases vary somewhat from one shock to another. In the shock here considered sP and sPP are exceptionally large at most stations; in the Italian stations they are not so large, while pP is a clear phase. pP is not very well defined at most other stations. Most of the 1949 records were from the old type long-period instruments having their highest magnification for periods from about 5 sec to 12 sec. Present day instruments of quite short or of very long proper period while admirable for many purposes do not record waves in this period range very well and therefore do not produce a satisfactory picture of the forerunners of earthquakes. The difference between the records obtained on different instruments is illustrated. It is shown in examples that the amplitude ratio PP:P may differ strongly at the same epicentral distance and also that pP may vary greatly with azimuth. The deficiency of station readings is noted. Travel times and their residuals are tabulated and travel times plotted versus epicentral distances.

Regional strain release characteristics for Indian regions

1966 ◽  
Vol 56 (3) ◽  
pp. 749-754
Author(s):  
R. K. S. Chouhan
Keyword(s):  
Strain Accumulation ◽  
Single Cycle ◽  
Regional Strain ◽  
Indian Origin ◽  
Strain Release ◽  
Deep Focus ◽  
Shallow Focus

abstract The strain accumulation and release curves for shallow and deep focus earthquakes of Indian origin have been constructed for a span of sixty years, from 1905 to 1964. For shallow focus earthquakes, magnitudes 7.2 and above have been considered; for deep focus shocks, magnitudes 6.7 and above are used. Strain rebound characteristics yield a number of very interesting features; for example, the curve for shallow focus earthquakes shows two linear segments of strain accumulation. Deep focus shocks show a single cycle of strain accumulation. Comparison of these curves with similar curves from other regions given by Benioff are made.

Geologic and related effects of the Taltal earthquake, Chile, of December 28, 1966

1968 ◽  
Vol 58 (3) ◽  
pp. 851-859
Author(s):  
Richard W. Lemke ◽  
Ernest Dobrovolny ◽  
Leonardo Alvarez S. ◽  
Francisco Ortiz O.
Keyword(s):  
Ground Surface ◽  
Surface Effects ◽  
Fault Zones ◽  
Open Pit ◽  
Open Pit Mines ◽  
Deep Focus ◽  
The Town ◽  
Natural Slopes

abstract Surface effects of the Taltal earthquake were comparatively small, probably because of the deep focus, although the magnitude was 7 ¾. Small fractures broke the ground surface along fault zones in the vicinity of Taltal. Minor slumping occurred on a few steep natural slopes and in some cuts and fills along highways. There was minor damage at a few open pit mines. At Taltal, the town most affected by the earthquake, 250 buildings out of a total of 1,100 were heavily damaged.

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