Reference Work Entry

Encyclopedia of Natural Hazards

Part of the series Encyclopedia of Earth Sciences Series pp 906-906


Seismic Gap

  • John F. CassidyAffiliated withGeological Survey of Canada, Natural Resources Canada Email author 


Earthquake forecasting; Seismic potential


Seismic Gap. A segment of an active plate boundary that, relative to rest of the boundary, has not recently ruptured and is considered to be more likely to produce an Earthquake in the future.

The seismic gap theory (for a summary of early work in this field see McCann et al., 1979) states that a segment of a plate boundary that has not ruptured recently has the greatest chance of rupturing in the future (relative to other segments that have experienced large earthquakes). This is based on the recognition that tectonic plates move relative to one another at an approximately constant speed and the assumption that the slip of plate boundary faults occurs primarily during major (magnitude 7 or greater) earthquakes. There are clear applications of this method to the estimation of earthquake hazards and to “earthquake forecasting” (e.g., McCann et al., 1979). However, there are questions about the applicability of t ...

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