TECTONICS/Earthquakes 329 geographical, geological, theoretical, and mathematical studies of seismicity An example is a study by Lya Tuliani in Russia, which addressed problems of geodynamics and seismology, tectonosphere layering, and lithostructure in seismically active regions in order to develop risk estimates The procedure involved mathematical data processing It was claimed that this study allowed highly accurate prediction of the coordinates of high-risk sites This statistical, mathematical, and office-based approach contrasts with research in the USA (which involves actually drilling down to earthquake foci on faults), research into the Boothiel lineament, the site of the New Madrid earthquakes (which has revealed sand boils caused by the earthquake), and excavations in the alluvium of the rice paddies west of Beijing, China (where the actual earthquake fault of a seventeenth century event has been exposed cutting the clayey alluvium in open pits) Research has been carried out into much older earthquakes in Iran, based on the dislocation of qanats (horizontal wells) All these approaches and many more are invaluable, but the problem of predicting earthquakes is extremely complex and may never be completely solved Volcanic Earthquakes There can be a connection between major tectonic earthquakes and volcanic eruptions In Chile in 1960, a major earthquake triggered the eruptions of several volcanoes, and in Sicily there is a record of Etna erupting a day or two before a major tectonic earthquake However, the swarms of small seisms that usually precede volcanic eruptions (though there may be no such prelude) pose little threat to life and property They do, however, provide valuable warnings of forthcoming eruption, and arrays of instruments are mounted on dangerous volcanoes for this purpose Man-Made Earthquakes Small seismic disturbances can be triggered by human activity In the USA, the Boulder Dam and Lake Mead are constructed in a region that is highly strained; many small shocks have been correlated with changes in water depth In Colorado, the injection of liquid wastes down boreholes has also been shown to trigger small seisms Moonquakes and Seisms on Other Planets Very small earthquakes occur on the largely quiescent Moon when it undergoes maximum tidal stresses resulting from the attraction of the Earth and Sun Similar stresses must operate on the Earth and cause minor seisms, but the effect is of no importance in such a dynamic body Moonquakes and artificial seisms produced on the surfaces of other extraterrestrial bodies – Mars, Venus, and Mercury – can provide a valuable insight into their internal make up A fascinating project would be to site an instrument from an unmanned spacecraft on Io, Jupiter’s volcanically active satellite, to obtain detail of its interior configuration – Io must be seismically active See Also Earth: Mantle; Crust Earth Structure and Origins Engineering Geology: Aspects of Earthquakes; Natural and Anthropogenic Geohazards; Liquefaction Plate Tectonics Tectonics: Faults Further Reading Bolt BA (1999) Earthquakes New York: Freeman Bommer JJ and Ambraseys NN (1989) The Spitak, Armenia, USSR earthquake of December 1988: a summary engin eering geology report Earthquake Engineering and Struc tural Dynamics 18: 921 925 Chen Y, Tsoi KL, Chen F, et al (1988) The Great Tangshan Earthquake of 1976 Oxford: Pergamon Degg MR (1992) Some implications of the 1985 Maxican earthquake for hazard assessment In: McCall GJH, Laming DJC, and Scott SC (eds.) Geohazards Natural and Man Made, pp 93 114 London: Chapman and Hall Degg MR (1995) Earthquakes, volcanoes and tsunamis: tectonic hazards in the built environment of southern Europe Built Environment 21: 94 113 Degg MR (1998) Hazard mitigation in the urban environ ment In: Maund JG and Eddleston M (eds.) Geohazards in Engineering Geology, pp 329 337 Engineering Geology Special Publication 15 London: Geological Society Esper P and Tachibana E (1998) The Kobe earthquake In: Maund JG and Eddleston M (eds.) Geohazards in Engin eering Geology, pp 105 116 Engineering Geology Special Publication 15 London: Geological Society Everingham I (1968) Preliminary report on the 14th Octo ber 1968 earthquake at Meckering, Western Australia Record 1968/142 Canberra: Bureau of Mineral Re sources, Geology and Geophysics Keller GR (2000) Seismic properties of rocks In: Hancock PL and Skinner BJ (eds.) The Oxford Companion to the Earth Oxford: Oxford University Press McCall GJH (1996) Natural hazards In: McCall GJH, de Mulder EFJ, and Marker BR (eds.) Urban Geoscience, pp 81 125 Rotterdam: Balkema McCall GJH (2000) The great Colchester earthquake of 1884 revisited Geoscientist 10: McCall GJH (2004) Remembering Bam Geoscientist 14: