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a trench ditched on the surface of an ełastic half-space (136], and by corrugations (grooves and ridges) tor an arbltrary angle of incidence [137] has been considered. The Born approximation has been used in selsmic scattering problems [138]. Scattering of ełastic waves from a fluid-filled cavlty [139] by an induslon embedded in an infinite homogeneous medium [140] and by a three-dimensional non-homogeneity In a half-space [141] has been studied.

The scattering of obliqueły incident P and SV waves by an infinite rigid elliptic cylinder [142] and of piane harmonie SH. P. SV, and Rayleigh waves by several inclusions of arbitrary shape [143] has been investigated. Multiple scattering from cracks in two-dimensional plane-strain conditions [144] has been discussed. as have scattering of SH waves by subsurface circular cavities and thin slits [14] and scattering of waves through a crust and upper mantle with random lateral and vertical nonhomogeneities [146].

Early precursors to PP' have been reinterpreted as waves scattered on an underside refłection at the core-mantle boundary [147]. The scattering and attenuation of shear waves in the lithosphere have also been studied [148].

Attenuation of waves due to multiple scattering from inclusions [149], in a random anisotropic two-phase medium [150], and in a materiał containłng cracks

[151]    has been discussed. as has attenuation of Love and Rayleigh waves across the Atlantic ocean

[152] . Expressions for attenuation by means of a

stochastic perturbation technique [153] using random wave propagation theory. an intensity attenuation equation [ 154], and an attenuation coefficient for a Rayleigh wave propagating along a corrugated surface of crystals of cubic and hexagonal sym.-netries [155] have been derived. The specific dissipation factor    of rocks containing smali

amounts of volatile materiał has been determined [156], as has the Q value using amplitudes of first P arrivals recorded at many stations [157],

Mantle creep and attenuation. viscoelastic behavior of rock. and body waves have been discussed [158]. The structure of the mantle beneath the East Euro-pean platform [ 159] has been analyzed Thermody-namic properties of the Earth's lower mantle [160]. rheological properties of the upper mantle [161], and seismic discontinuities in the mantle [162] have been studied. lnvestigations of the Earth's interior that require the application of high-pressure research have been considered [163]. A model to explain the generation of earthquake lights has been proposed [164]. The occurrence of double seismic płanes beneath some island ares has been explained [165] in terms of an unbending of the descending lithosphere; the temperaturę at double seismic zones in the descending lithosphere was estimated. Variations in the stress field of the Earth's crust due to lateral variation in thickness and in temperaturo [166] have been analyzed. A basie nonhomogeneity of the upper mantle [167] and mantle vełocity distribution [168] have been considered. Compressional and shear wave velocities have been measured [169] in a cubic anvil apparatus up to 700°C at 6 kbar in igneous and metamorphic rocks typical of the crust and mantle. The equation of State has been applied to high-pressure and high-temperature States of geophysically relevant substances [170] and to the Barth's lower mantle [171].

Problems of seismological instrumentation have been discussed [172]. A device capable of automatically recording a number of bursts of acoustic emission from rocks has been developed [173]. The basie design of a handy. compact, maintenance-free seismo-graph [174] has been described. A practical algo-rithm for the detection of S-wave arrivals has been considered [175]. A laser interferometer has been developed to study the displacements and oscilla-tions of the Earth's crust [176], as has an acoustic interferometrie technique to measure ultrasonic velocity and attenuation in rock melts (177].

A method for rapid retrieval of earthquake-source parameters from long-period surface waves has been described [178]. An instrument to study changes of frequency. temperaturę, and pressure has been considered [179]. Down-hole logging methods as applied to uranipm exploration have been described [180]. The soil gas Rn value has been measured [181] in various ways: by two types of alpha-particle track detectors, by emanometry. and by counting alpha activity on Rn decay-product collectors.

A variable R = Kf/K_s has been defined [182] in strain softening earthquake models. that will measure the degree of earthquake instability (Kf = stiffnessof the fault zonę. K_s = stiffness of the elastic surroundings);

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