Structure of the crust and upper mantle in the ALPS from the phase velocity of Rayleigh waves

Abstract The phase velocity method has been applied to the problem of the determination of the crust and upper mantle under the western Alpine crest and in the Alpine foreland to the north. An extensive data processing package has been designed so that Fourier analysis is applied to the determination of phase velocities, rather than the more usual peak-and-trough method. Effects of contamination by multipath interference, manifested in beats, can be minimized. Advantage is made of apparent azimuthal variations in phase velocity to yield a further refinement in the method whereby the tripartite results are assigned to discrete lines in the network rather than to the area swept out by the wave front. The results show that a well-developed low-velocity channel for S is found throughout the region with a velocity of S in the channel of 4.2 km/sec. The top of the channel is at about 80 km depth. A new analysis of P -wave data shows a likely horizon for reflections at 220 km; this is taken to be the depth of the lower boundary to the channel. The mean P -wave velocity in the lower crust is at least as high as 6.7 km/sec. The crustal and upper mantle structure vary significantly over relatively short distances. The Mohorovicic discontinuity is deepest under the crest of the Alps and shoals to the north and west; a well developed root has been found.

[1]  K. Kaminuma.  The Crust and Upper Mantle Structure in Japan. : Part 2. Crustal structure in Japan from the phase velocity of Rayleigh waves , 1966 .

[2]  O. Nuttli,et al.  Travel-time curves for a low-velocity channel in the upper mantle , 1964 .

[3]  I. Lehmann.  On the velocity of P in the upper mantle , 1964 .

[4]  L. Knopoff,et al.  Observations of multiple seismic events , 1964 .

[5]  I. Lehmann.  On the travel times of P as determined from nuclear explosions , 1964 .

[6]  I. Lehmann.  THE TRAVEL TIMES OF THE LONGITUDINAL WAVES OF THE LOGAN AND BLANCA ATOMIC EXPLOSIONS AND THEIR VELOCITIES IN THE UPPER MANTLE. , 1962 .

[7]  D. L. Anderson,et al.  Computation of surface wave dispersion for multilayered anisotropic media , 1962 .

[8]  I. Lehmann.  S and the Structure of the Upper Mantle , 1961 .

[9]  H. Jeffreys.  Small Corrections in the Theory of Surface Waves , 1961 .

[10]  Frank Press,et al.  A fast, convenient program for computation of surface-wave dispersion curves in multilayered media , 1961 .

[11]  F. Birch.  The velocity of compressional waves in rocks to 10 kilobars: 1. , 1960 .

[12]  F. Press.  Crustal structure in the California‐Nevada region , 1960 .

[13]  G. Sutton,et al.  A crustal section across the Puerto Rico trench , 1959 .

[14]  G. Woollard.  Crustal structure from gravity and seismic measurements , 1959 .

[15]  F. Press,et al.  DETERMINATION OF CRUSTAL STRUCTURE FROM PHASE VELOCITY OF RAYLEIGH WAVES: PART III: THE UNITED STATES , 1959 .

[16]  D. Carder,et al.  Seismic wave travel times from nuclear explosions , 1958 .

[17]  E. R. Niblett,et al.  Terrestrial Heat Flow in the Swiss Alps , 1956 .

[18]  J. W. Bruyn.  ISOGAM MAPS OF EUROPE AND NORTH AFRICA , 1955 .

[19]  C. G. Dahm.  Velocities of P and S waves calculated from the observed travel times of the Long Beach earthquake , 1936 .

[20]  S. K. Runcorn,et al.  Interpretation theory in applied geophysics , 1965 .

[21]  J. W. Berg,et al.  Discontinuities in the earth's upper mantle as indicated by reflected seismic energy , 1961 .

[22]  I. Lehmann.  Velocities of longitudinal waves in the upper part of the earth's mantle , 1959 .

[23]  L. Knopoff.  Green's function for eigenvalue problems and the inversion of Love wave dispersion data , 1937 .