Abstract
We present a review of the influence of various parameters of the sources of major oceanic earthquakes on the amplitude of tsunamis at transoceanic distances. We base our computations on the normal mode formalism, applied to realistic Earth models, but interpret our principal results in the simpler framework of Haskell theory in the case of a water layer over a Poisson half-space. Our results show that source depth and focal geometry play only a limited role in controlling the amplitude of the tsunami; their combined influence reaches at most 1 order of magnitude down to a depth of 150 km into the hard rock. More important are the effects of directivity due to rupture propagation along the fault, which for large earthquakes can result in a ten-fold decrease in tsunami amplitude by destructive interference, and the possibility of enhanced tsunami excitation in material with weaker elastic properties, such as sedimentary layers. Modelling of the so-called ‘tsunami earthquakes’ suggests that an event for which 10% of the moment release takes place in sediments generates a tsunami 10 times larger than its seismic moment would suggest. We also investigate the properties of non-double couple sources and find that their relative excitation of tsunamis and Rayleigh waves is in general comparable to that of regular seismic sources. In particular, landslides involving weak sediments could result in very large tsunamis. Finally, we emphasize that the final amplitude at a receiving shore can be strongly affected by focusing and defocusing effects, due to variations in bathymetry along the path of the tsunami.
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References
Abe, K.: 1973, Tsunami and mechanism of great earthquakes, Phys. Earth Planet. Inter. 7, 143–153.
Abe, K.: 1979, Size of great earthquakes of 1837–1974 inferred from tsunami data, J. Geophys. Res. 84, 1561–1568.
Abe, K.: 1983, A new scale of tsunami magnitude, M t, in K. Iida and T. Iwasaki (eds), Tsunamis — Their Science and Engineering, Terrapub, Tokyo, pp. 91–101.
Aki, K. and Richards, P. G.: 1980, Quantitative Seismology, W. H. Freeman, San Francisco.
Ben-Menahem, A. and Singh, S. J.: 1981, Seismic Waves and Sources, Springer, New York, 1981.
Ben-Menahem, A. and Rosenman, M.: 1972, Amplitude patterns of tsunami waves from submarine earthquakes, J. Geophys. Res. 77, 3097–3128.
Comer, R. P.: 1980, Tsunami height and earthquake magnitude: theoretical basis of an empirical relation, Geophys. Res. Lett. 7, 445–448.
Comer, R. P.: 1982, Tsunami generation: validity of decoupling the ocean from the solid Earth, Eos, Trans. Amer. Geophys. Un. 63, 376 [abstract].
Eissler, H. K. and Kanamori, H.: 1987, A single-force model for the 1975 Kalapana, Hawaii, earthquake, J. Geophys. Res. 92, 4827–4836.
Fukao, Y.: 1979, Tsunami earthquakes and subduction processes near deep-sea trenches, J. Geophys. Res. 84, 2303–2314.
Geller, R. J.: 1976, Scaling relations for earthquake source parameters and magnitudes, Bull. Seismol. Soc. Amer. 66, 1501–1523.
Gilbert, F.: 1970, Excitation of the normal modes of the Earth by earthquake sources, Geophys. J. Res. Astr. Soc. 22, 223–226.
Gilbert, F. and Dziewonski, A. M.: 1975, An application of normal mode theory to the retrieval of structural parameters and source mechanisms from seismic spectra, Phil. Trans. Roy. Soc. London 278A, 187–269.
Harkrider, D. G. and Press, F.: 1967, The Krakatoa air-sea waves: an example of pulse propagation in coupled systems, Geophys. J. Roy. Astr. Soc. 13, 139–159.
Hwang, L.-S. and Lin, A.: 1970, Experimental investigation of wave run-up under the influence of local geometry, in W. Adams (ed.), Tsunamis in the Pacific Ocean, East-West Center Press, Honolulu, pp. 407–426.
Iida, K., Suzuki, T., Inagaki, K., and Hasegawa, K.: 1983, Finite element method for tsunami wave propagation in the Tokai district, in K. Iida and T. Iwasaki (eds.), Tsunamis: Their Science and Engineering, Terrapub, Tokyo, 1983, pp. 293–301.
Kanamori, H.: 1970, The Alaska earthquake of 1964: Radiation of long-period surface waves and source mechanism, J. Geophys. Res. 75, 5029–5040.
Kanamori, H.: 1972, Mechanism of tsunami earthquakes, Phys. Earth Planet. Inter. 6, 346–359.
Kanamori, H.: 1985, Non-double couple seismic source, Proc. XXIIIrd Gen. Assemb. Intl. Assoc. Seismol. Phys. Earth Inter., Tokyo, 1985, p. 425, [abstract].
Kanamori, H. and Cipar, J. J.: 1974, Focal process of the great Chilean earthquake, May 22, 1960, Phys. Earth Planet. Inter. 9, 138–136.
Kanamori, H. and Given, J. W.: 1982, Analysis of long-period seismic waves excited by the May 18, 1980 eruption of Mount St. Helens — A terrestrial monopole?, J. Geophys. Res. 87, 5422–5432.
Kanamori, H. and Stewart, G. S.: 1976, Mode of the strain release along the Gibbs Fracture Zone, Mid-Atlantic Ridge, Phys. Earth Planet. Inter. 11, 312–332.
Kanamori, H., Given, J. W., and Lay, T.: 1984, Analysis of seismic body waves excited by the Mount St. Helens eruption of May 18, 1980, J. Geophys. Res. 89, 1856–1866.
Kanamori, H., Ekström, G., Dziewonski, A. M., and Barker, J. S.: 1986, An anomalous seismic event near Tori-Shima, Japan: a possible magma injection event, Eos, Trans. Amer. Geophys. Un. 67, 1117 [abstract].
Kienle, J., Kowalik, Z., Murty, T. S.: 1987, Tsunamis generated by eruptions from Mount St. Augustine, Science 236, 1442–1447.
Lynnes, C. S. and Ruff, L. J.: 1985, Source process and tectonic implications of the great 1975 North Atlantic earthquake, Geophys. J. Roy. astr. Soc. 82, 497–510.
Okal, E. A.: 1978, A physical classification of the Earth's spheroidal modes, J. Phys. Earth 26, 75–103.
Okal, E. A.: 1982a, Mode-wave equivalence and other asymptotic problems in tsunami theory, Phys. Earth Planet. Inter. 30, 1–11.
Okal, E. A.: 1982b, Higher moment excitation of normal modes and surface waves, J. Phys. Earth 30, 1–31.
Okal, E. A. and Talandier, J.: 1987, M m: Theory of a variable-period mantle magnitude, Geophys. Res. Lett. 14, 836–839.
Raichlen, F., Lepelletier, T. G., and Tam, C. K.: 1983, The excitation of harbors by tsunamis, in K. Iida and T. Iwasaki (eds.), Tsunamis: Their Science and Engineering, Terrapub, Tokyo, pp. 359–385.
Satake, K.: 1988, Effects of bathymetry on tsunami propagation: Application of ray-tracing to tsunamis, Pure Appl. Geoph. 126, 27–36.
Shimazaki, K.: 1975, Nemuro-Oki earthquake of June 17, 1973: A lithospheric rebound at the upper half of the interface, Phys. Earth Planet. Inter. 9, 315–327.
Silver, P. G. and Jordan, T. H.: 1983, Total moment spectra of fourteen large earthquakes, J. Geophys. Res. 88, 3273–3293.
Sommerfeld, A.: 1964, Optics, Academic Press, New York.
Spudich, P. K. P. and Orcutt, J. A.: 1980, Petrology and porosity of an oceanic crustal site: results from waveform modeling of seismic refraction data, J. Geophys. Res. 85, 1409–1433.
Talandier, J. and Okal, E. A.: 1979, Human perception of T waves: the June 22, 1977 Tonga earthquake felt on Tahiti, Bull. Seismol. Soc. Amer. 69, 1475–1486.
Talandier, J., Reymond, D., and Okal, E. A.: 1987, M m: Use of a variable-period mantle magnitude for the rapid one-station estimation of teleseismic moments, Geophys. Res. Lett. 14, 840–843.
Ward, S. N.: 1980, Relationships of tsunami generation and an earthquake source, J. Phys. Earth 28, 441–474.
Ward, S. N.: 1981, On tsunami nucleation: I. A point source, J. Geophys. Res. 86, 7895–7900.
Ward, S. N.: 1982a, On tsunami nucleation: II. An instantaneous modulated line source, Phys. Earth Planet Inter. 27, 273–285.
Ward, S. N.: 1982b, Earthquake mechanism and tsunami generation: the Kurile Islands event of October 13, 1963, Bull. Seismol. Soc. Amer. 72, 759–777.
Woods, M. T. and Okal, E. A.: 1987, Effect of variable bathymetry on the amplitude of teleseismic tsunamis: a ray-tracing experiment, Geophys. Res. Lett. 14, 765–768.
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Okal, E.A. Seismic parameters controlling far-field tsunami amplitudes: A review. Nat Hazards 1, 67–96 (1988). https://doi.org/10.1007/BF00168222
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DOI: https://doi.org/10.1007/BF00168222