Encyclopedia of Natural Hazards

2013 Edition
| Editors: Peter T. Bobrowsky

Hypocenter

Reference work entry
DOI: https://doi.org/10.1007/978-1-4020-4399-4_181

Synonyms

Earthquake focus; Focal point

Definition

A point beneath the Earth’s surface where the vibrations of an earthquake originates and which corresponds to the location where the motion on a fault surface starts. The focal depth of earthquake hypocenters may vary from the surface down to nearly 700 km in subduction zones.

Discussion

Earthquake magnitude, and more precisely the Moment Magnitude, is function of the amount of slip and area of the fault surface that ruptures during an earthquake. For small earthquakes, such as magnitude 4 or less, or for earthquakes displayed on maps and cross-sections at a regional scale, the hypocenter is essentially a point with three coordinates (latitude, longitude, and focal depth). As the magnitude increases, the earthquake rupture is no longer a point but is rather a surface. In this latter case, the hypocenter is defined as the point where the rupture started.

The traditional method used to calculate the earthquake hypocenter is similar to...

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Bibliography

  1. Kissling, E., 1988. Geotomography with local earthquake data. Review of Geophysics, 26, 659–698.CrossRefGoogle Scholar
  2. Kulhánek, O., 2002. The structure and interpretation of seismograms. In Lee, W. H. K., Kanamori, H., Jennings, P. C., and Kisslinger, C. (eds.), International Handbook of Earthquake and Engineering Seismology. San Diego: Academic Press, Vol. 81A, pp. 333–348.CrossRefGoogle Scholar
  3. Musson, R. M. W., and Cecić, I., 2002. Macroseismology. In: Lee W. H. K., Kanamori, H., Jennings, P. C., and Kisslinger C. (eds.), International Handbook of Earthquake and Engineering Seismology. San Diego: Academic Press, Vol. 81A, pp. 807–825.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Natural Resources CanadaOttawaCanada