The effect of the irregularities of the shape of the Earth's core-mantle boundary on the observed acceleration of gravity

Summary The disturbing gravitational effect of the irregularities of the shape of the coremantle boundary are studied at a point on the Earth's surface. The effect is computed for models of local and zonal distribution of the disturbing masses under the assumption that the total mass of the Earth remains constant. Formulae giving the disturbing gravitational effect as a function of the distribution of the disturbing masses and of the position of the point of observation on the Earth's surface are derived for the individual models. Numerical values of the disturbances have been calculate in all cases.     

Mean crustal velocity: a critical parameter for interpreting crustal structure and crustal growth

Mean crustal velocity is a critical parameter for genesis of continental crystalline crust because it is a function of mean crustal composition and therefore may be used to resolve continental crustal growth in space and time. Although the best values of mean crustal velocity are determined from wide-angle reflection measurements, most studied here necessarily come from vertical averages in crustal refraction determinations. The mode of 158 values of mean crustal velocity is 6.3 km/s, a velocity which corresponds to a mean crustal composition of granodiorite to felsic quartz diorite; Archean crust may be slightly more mafic. Mean crustal velocities range from 5.8 to 7.0 km/s. The lowest values invariably are found in thermally disturbed rift zones and the highest values correspond to velocities in gabbro. Velocities in island arcs may be as low as 6.0 km/s but are typically 6.5–6.9 km/s which corresponds to andesitic composition; estimates of island arc composition are andesitic. If values of mean crustal velocity are not biased, this observation suggests that continental crust did not grow simply by addition of island arc material. Possibilities are that crust formed from fusion of island arcs and was later changed to more felsic composition by addition of material from the mantle or that the late Archean episode of major crustal growth did not involve processes similar to younger island arcs. Some crustal blocks might be changed in composition and thickness by such processes as underplating, interthrusting, necking and sub-crustal erosion. Specially designed experiments are suggested to determine this parameter so critical for understanding genesis of continental crust.     

Geodynamic interpretation of the earthquake distribution in the kermadec subduction zone

Summary The morphology of the Wadati-Benioff zone in the Kermadec region, based on the distribution of 1100 earthquake foci, verified the existence of an intermediate aseismic gap and its relation to active andesitic volcanism, and the non-uniformity of subduction due to the hampering effect of the main structural features of the subducting Pacific plate. Two cycles of the recently active subduction in the Tonga-Kermadec island arc were found.     

Elastic properties of eclogite rocks from the Bohemian massif

Summary Compressional velocity anistropy has been studied in detail at atmospheric pressure for 78 specimens of 23 types of eclogite rocks from the Bohemian massif. For nine of these rock types, compressional and shear velocities were measured as a function of pressure to750 MPa at room temperature. The velocity anisotropy for both compressional and shear waves is less than4% at high pressure. The velocities increase with increasing garnet content and decrease with increasing symplectitization. The Moldanubian eclogites have significantly higher velocities, on the average, than the eclogites from the Kruné hory crystalline complex, although the densities of both groups are comparable.     

Morphology of the Wadati-Benioff zone,andesitic volcanism,and active fracture zones in Central America

Summary The morphology of the Wadati-Benioff zone in the region of Central America, based on the distribution of 1377 earthquake foci, verified the existence of an intermediate aseismic gap and its relation to active andesitic volcanism, and the non-uniformity of subduction due to the hampering effect of the main structural features of the subducting Cocos plate. Four deep seismically active fracture zones, genetically connected with the process of subduction, and three fracture zones manifesting the possible boundary between the Americas and Caribbean plates were identified in the continental wedge.     

On the universal character of particle transfer in a field of turbulence

Summary With the aid of elementary methods of the theory of dimensionality we approach the problem of existence of invariants in the process of mixing particles of a passive admixture in a field of turbulence.     

西太平洋副热带高压中期变化的数值试验 Ⅰ.青藏高原热源的作用

用一个全球谱模式作数值试验研究了１９７９年６月中旬一次西太平洋副热带高压西伸北进的中期天气过程中青藏高原热源的作用。结果表明：高原的热力作用主要表现在对副高北侧锋区的形成、锋区瓣强度以及与锋区对应的对流层中上层西风急流的强度有较大的影响,有高原热力作用时,锋眍和西风流的强度都强,反之则很弱;另外还发现青藏高原感热和潜热作用是相互依赖的,在一定的天气过程中,弧立起来讨论其各自的相对重要性不太合符实际     

NUMERICAL EXPERIMENT OF MEDIUM-RANGE CHANGE OF THE SUBTROPICAL HIGH Ⅰ. THE INFLUENCE OF THE HEATING SOURCE OVER TIBET PLATEAU

The medium-range change of the subtropical high of June 1979 and its influences of the heating sources over Tibet Plateau are studied by using a global circulation spectrum-model. The analyses of the simulation results show that the heating sources over Tibet Plateau play an important role in the process of frontogenesis. the intensity of frontal zone and the upper-tropospheric westerly jet associated with it. When there are heating sources over Tibet Plateau. both the frontal zone and westerly jet are stronger. There are very important mutual relations between the sensible heating and latent heating. After the sensible heating and latent heating are isolated.it departs much from reality that the significance of them are studied