Seismic Evidence for an Earthquake Nucleation Phase

Near-source observations show that earthquakes initiate with a distinctive seismic nucleation phase that is characterized by a low rate of moment release relative to the rest of the event. This phase was observed for the 30 earthquakes having moment magnitudes 2.6 to 8.1, and the size and duration o...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1995-05, Vol.268 (5212), p.851-855
Main Authors: Ellsworth, W. L., Beroza, G. C.
Format: Article
Language:English
Subjects:
Boundary layer separation
Cubes
Earth
Earth sciences
Earth, ocean, space
Earthquakes
Earthquakes, seismology
Exact sciences and technology
Exhibits
Internal geophysics
Kinetics
Motion
Musical intervals
Nucleation
Observation
Observations
P waves
Personality
Seismographs
Seismology
Wave velocity
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Description
Summary:Near-source observations show that earthquakes initiate with a distinctive seismic nucleation phase that is characterized by a low rate of moment release relative to the rest of the event. This phase was observed for the 30 earthquakes having moment magnitudes 2.6 to 8.1, and the size and duration of this phase scale with the eventual size of the earthquake. During the nucleation phase, moment release was irregular and appears to have been confined to a limited region of the fault. It was characteristically followed by quadratic growth in the moment rate as rupture began to propagate away from the nucleation zone. These observations suggest that the nucleation process exerts a strong influence on the size of the eventual earthquake.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.268.5212.851