Influence of Tidal Forces on the Triggering of Seismic Events
- 312 Downloads
Tidal stresses are generated in any three-dimensional body influenced by an external inhomogeneous gravity field of rotating planets or moons. In this paper, as a special case, stresses caused within the solid Earth by the body tides are discussed from viewpoint of their influence on seismic activity. The earthquake triggering effects of the Moon and Sun are usually investigated by statistical comparison of tidal variations and temporal distribution of earthquake activity, or with the use of mathematical or experimental modelling of physical processes in earthquake prone structures. In this study, the magnitude of the lunisolar stress tensor in terms of its components along the latitude of the spherical surface of the Earth as well as inside the Earth (up to the core-mantle boundary) were calculated for the PREM (Dziewonski and Anderson in Phys Earth Planet Inter 25(4):297–356, 1981). Results of calculations prove that stress increases as a function of depth reaching a value around some kPa at the depth of 900–1500 km, well below the zone of deep earthquakes. At the depth of the overwhelming part of seismic energy accumulation (around 50 km) the stresses of lunisolar origin are only (0.0–1.0)·103 Pa. Despite the fact that these values are much smaller than the earthquake stress drops (1–30 MPa) (Kanamori in Annu Rev Earth Planet Sci 22:207–237, 1994) this does not exclude the possibility of an impact of tidal forces on outbreak of seismic events. Since the tidal potential and its derivatives are coordinate dependent and the zonal, tesseral and sectorial tides have different distributions from the surface down to the CMB, the lunisolar stress cannot influence the break-out of every seismological event in the same degree. The influencing lunisolar effect of the solid earth tides on earthquake occurrences is connected first of all with stress components acting parallel to the surface of the Earth. The influence of load tides is limited to the loaded area and its immediate vicinity.
KeywordsSpherical tidal stress tensor zonal, tesseral and sectorial tides oceanic tidal load
We thank our reviewers (Walter Zürn and an anonymous colleague) for their helpful comments. The research described in this paper was completed during research stay of P. Varga (01.03.2016–31.05.2016) supported by the Alexander Humboldt Foundation at the Department of Geodesy and Geoinformatics, Stuttgart University. P. Varga thanks Professor Nico Sneeuw for the excellent research conditions provided by him. Financial support from the Hungarian Scientific Research Found OTKA (Project K12508) is acknowledged.
- Cotton, L. A. (1922). Earthquake frequency with special reference to tidal stresses in the lithosphere. Bulletin of the Seismological Society of America, 12, 47–198.Google Scholar
- Davison, C. (1927). Founders of seismology. Cambridge: Cambridge University Press.Google Scholar
- Emter, D. (1997). Tidal triggering of earthquakes and volcanic events. In H. Wilhelm, W. Zürn, & H.-G. Wenzel (Eds.), Tidal phenomena (Vol. 66, pp. 293–309). Lecture Notes in Earth Sciences Heidelberg: Springer.Google Scholar
- Heaton, T. H. (1982). Tidal triggering of earthquakes. Bulletin of the Seismological Society of America, 72(6), 2181–2200.Google Scholar
- Molodensky, M. S. (1953). Elastic tides, free nutations and some questions concerning the inner structure of the Earth. Trudi Geofizitseskogo Instituta Akademii Nauk of the USSR, 19(146), 3–42.Google Scholar
- Perrey, A. (1875). Sur la fréquences des tremblements de terre relativement a l’age de la lune. Comptes Rendus hebdomadaires des séances de la Académie des Sciences, 81, 690–692.Google Scholar
- Pertzev, B. P. (1976). Influence of the oceanic tides. Physics of the Solid Earth, 1, 13–27.Google Scholar
- Schuster, A. (1911). Some problems of seismology. Bulletin of the Seismological Society of America, 1, 97–100.Google Scholar
- Varga, P., Rogozhin, E. A., Süle, B., & Andreeva, N. V. (2017). A study of energy released by great (M7) deep focus seismic events having regard to the May 24, 2013 Mw 8.3 earthquake the Sea of Okhotsk, Russia. Izvestiya, Physics of the Solid Earth, 53(5), 385–409.Google Scholar
- Young, D., & Zürn, W. (1979). Tidal triggering of earthquakes in the Swabian Jura? Journal of Geophysics, 45, 171–182.Google Scholar