sense do not grow as fast as computational possi This book contains selections from Volumes bilities. I-V of the series "Computational Seismology," which Moreover, for some strange reason, comput was initiated a few years ago by the Academy of ers usually create a spirit of haste, though they are Sciences of the USSR. Volume V was still in prepa intended to provide time for meditation. In com ration when the translation was begun, and the trans puterizing seismology, therefore, one must first lations of papers from it were made from manu generalize the methods and then make them more scripts. Most of the authors are members of the rigorous mathematically. All relevant data must Department of Computational Geophysics of the In be processed jointly. Insofar as is possible, a priori stitute of Physics of the Earth, Moscow. hypotheses should be avoided. Particular attention The series is dedicated to theoretical and must be given to exact formulation of the problem, computational aspects of the analysis of seismolog to questions of uniqueness and stability, to the con ical data. The present state of this field is typical fidence limits of the results, etc. This general ap of our times. The rapidly increasing flow of infor proach is required in solving the main problems of mation is already too vast to be processed or even modern seismology, which are by definition general comprehended in a traditional way. This has forced problems. This approach has other advantages."

Surface waves form the longest and strongest portion of a seismic record excited by explosions and shallow earthquakes. Traversing areas with diverse geologic structures, they 'absorb' information on the properties of these areas which is best retlected in dispersion, the dependence of velocity on frequency. The other prop erties of these waves - polarization, frequency content, attenuation, azimuthal variation of the amplitude and phase - arc also controlled by the medium between the source and the recording station; some of these are affected by the properties of the source itself and by the conditions around it. In recent years surface wave seismology has become an indispensable part of seismological practice. The maximum amplitude in the surface wave train of virtually every earthquake or major explosion is being measured and used by all national and international seismological surveys in the determination of the most important energy parameter of a seismic source, namely, the magnitude M, . The relationship between M, and the body wave magnitude fI1t, is routinely employed in identification of underground nuclear explosions. Surface waves of hundreds of earthquakes recorded every year are being analysed to estimate the seismic moment tensor of earthquake sources, to determine the periods of free oscillations of the Earth, to construct regional dispersion curves from which in turn the crustal and upper mantle structure in various areas is derived, and to evaluate the dissipative parameters of the mantle material."