Bisztricsány, E

Kiss, Z

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MSPHRSION OF SF RFACB-W AVES CROSS!XO A R KAS OF Y A R U H S( H FSTA!. T H )( h \ HSSbyE. B 1 S X T E 1 C 8 Á X Y - X .  K I S S((ir(.]'i.vsi<a! Institute of Lorárul Eötvös l'n iw rs ity )<Hc<<ivcd:31. V i l i .  1963)( rustal thickness has been computed for Eurasian paths with interpreta- tioti of the dispersion Rayleigh waves generated by carthcpiakes. The para­meters of the eart If quakes in question are listed in Table 1.Die data have been recorded with Kirnos type seismographs in Budapest.The wave-path are shown in Fig. !- 'Die group-velocity curves have been constructed in the usuai way. The arrivai times of the different periods were corrigated by a phase-shift curve, computed from the constants of the instru­ment. The group-velocity-period functions of different earthquakes did not differ substantially from each other, thus identical theoretical group-velocitv curves could be used for the interpretation (Fig. 2.)The comparison of observed group velocity data with theoretical curves gave a crustalthickness of 35 km.Tahlv !.No. DataOrigin time Ocographic coordinates of earthquake Kmh m "1. 4. ! .  1962 "4 35 42,6 33.9- X ¡3 3 .2 ' E 8970<? 7. .6. 1962 17 39 36.3 4 5 ,3 ' X 146.7 ' E 85063. 2". s. 1 962 16 26 63 3 8 .3 ' X  142 ,4 ' E 89404. 22. 1". 1962 16 23 32.9 49.8" X  13 5 ,8 ' E 84203. 11. 11. 1962 11 31 44,3 3 5 .8 ' X 113,1" E 60461 f Bisztricsany B. — Kiss z.F.\r. 2. Recorded data and th e o re tic ! curves o f the dispersion of Ravh-igh waves for Eurasian wave paths. D ata taken from Tab!e 1 are symbolized as foiiows:C for shock 1,E for shook 2,V for shock 3, e  for shock 4. for shock o.The theoretics) curves are those by R . Stoneiey (2), the dashed )ine refers to //. = 24. i f .  = 12 H = 36 km. The fu)! tine refers to a crusta) ttuckness o f 34 kmDispersion of Surface-waves i lCo?:cÍM3?'OHThe wave-paths of the utilized earthquakes cross the East-Siberian area in a depth of 2 -3 0 0 0  km. A greater crustal thickness was to be expected but we found only a continental crust of 35 km thickness. Our two earlier papers are worth to be mentioned from this point of view.a A v e r a g e  crustal thickness was computed for Eurasian paths using dispersion Love-waves of two South-C'hina earthquakes in 1960 (4).The recording station was Budapest. A crustal thickness of 33 km was obtained, in spite of the fact that 30 percent of the wave-paths crossed high- mountain areas, where E. F . Savarensky using the same principle found a value of 55 km.In 1962. E.Bisztricsány computed crustal thickness from the Ravleigh- wave generated by an earthquake in the West Indies. In that case, crustal thickness was found to be equal to that under the oceans though 16 to 20 per­cent of the wave-path crossed a continent (Europe) where crustal thickness had been found to be 35 km.The above considerations reveal th at the real average crustal thickness is not always reflected by the surface-wave dispersion of waves crossing regions of different crustal structure. Surface-wave dispersion needs, then, further theoretical examination.L IT E R A T U RL S a v a r e n s k y ,  E . F . : On the determination o f group and phase velocities from obser­vations. B all. /sv. Acad. <Sci. l.S'-S'B 6?ropAy#. Bcr. No. I f .  1919.2. S t o n e l e y ,  R . : Rayleigh-w aves in a medium with the surface layers. .VonlA. Not. /toy- A sir. Boc. GeopAys. Suppl. 7. No. 2. 1955.3. B  i s z t  r i c s á n y, E . -  K  i s s. Z .: A com putation of average crustal thickness from Lovewave dispersion, for an Eurasian wave path. Ana. b lu e. Bci. Badapesliacasis, CeoL I I I .  1960. 15 -  17. . ,4 .  S a  v a r e n s k y, E . F .  -  S  i k h a r n 1 i d z e. D. I . : D eterm inatton of the thtekness of the E arth 's  crust from Love-wave dispersion observations. BaM. /-e. A. <S. f  B BB . G eoL III- 1959. 6 2 0 - 6 2 2 .5. B i s z t r i c s á n y  E . : Dispersion o f Ravleigh-waves along a  mainly A tlantic path. Geo/, purn e apph 54. 1963. 84 — 86.

Dispersion of surface-waves crossing areas of various crustat thicknes

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Dispersion of surface-waves crossing areas of various crustat thicknes

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