| Abstract: | Similar precursory phenomena have been observed before earthquakes in the United States, the Soviet Union, Japan, and China. Two quite different physical models are used to explain these phenomena. According to a model developed by US seismologists, the so-called dilatancy diffusion model, the earthquake occurs near maximum stress, following a period of dilatant crack expansion. Diffusion of water in and out of the dilatant volume is required to explain the recovery of seismic velocity before the earthquake. According to a model developed by Soviet scientists growth of cracks is also involved but diffusion of water in and out of the focal region is not required. With this model, the earthquake is assumed to occur during a period of falling stress and recovery of velocity here is due to crack closure as stress relaxes. In general, the dilatancy diffusion model gives a peaked precursor form, whereas the dry model gives a bay form, in which recovery is well under way before the earthquake. A number of field observations should help to distinguish between the two models: study of post-earthquake recovery, time variation of stress and pore pressure in the focal region, the occurrence of pre-existing faults, and any changes in direction of precursory phenomena during the anomalous period. ?? 1975 Birkha??user Verlag. |
| Genre: | Article |
| ProdID: | 70001234 |
| Citation Author: | Mjachkin, V. I.; Brace, W. F.; Sobolev, G. A.; Dieterich, J. H. |
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| Citation End Page: | 181 |
| Citation Issue: | 1 |
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| Citation Language: | English |
| Citation Larger Work Title: | Pure and Applied Geophysics PAGEOPH |
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| Citation Publisher: | Birkha??user-Verlag |
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| Citation Search Results Text: | Two models for earthquake forerunners; 1975; Article; Journal; Pure and Applied Geophysics PAGEOPH; Mjachkin, V. I.; Brace, W. F.; Sobolev, G. A.; Dieterich, J. H. |
| Citation Start Page: | 169 |
| Citation Volume: | 113 |
| Citation Year: | 1975 |
| Type: | citation/reference |
| Text: | Two models for earthquake forerunners; 1975; Article; Journal; Pure and Applied Geophysics PAGEOPH; Mjachkin, V. I.; Brace, W. F.; Sobolev, G. A.; Dieterich, J. H. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1007/BF01592908 |
| Date Other: | Tue, 28 Sep 2010 23:09 -0500 |
| Publisher: | Birkha??user-Verlag |
