Earthquake precursors

Journal Article · Wed Oct 01 04:00:00 EDT 1975 · Bull. Seismol. Soc. Am.; (United States)

OSTI ID:6586852

Rikitake, T

An analysis of existing earthquake precursor data leads to a conclusion that the precursors reported so far can be classified into three types, i.e., A/sub 1/, A/sub 2/ and B types. Most of type B precursors, observed in terms of anomalous tilts and strains or foreshocks, have no magnitude-dependent precursor time. Meanwhile the A/sub 2/-type precursors observed by means of geodetic work, changes in seismic-wave velocities and the like seem to have a precursor time which is closely correlated to the magnitude of coming earthquakes. A precursor of this type may possibly be interpreted by the current theory of dilatancy. The A/sub 1/-type precursors, observed mostly several hours prior to the main shock, may be caused by a creeplike failure before the main rupture of the earth's crust. Probabilities for an anomalous signal of various geophysical elements to be related to a forthcoming earthquake are estimated on the basis of the existing data of precursors. A feasible strategy for predicting a large earthquake as suggested by the present study would be as follows: First of all, the accumulation of crustal strain is monitored by means of geodetic work. The next task is to detect an A/sub 2/ signal which would arise from a highly strained crust sooner or later. If the spatial extent of the A/sub 2/-type precursor is known, it is possible to estimate roughly the magnitude as well as the occurrence time of the coming earthquake. Finally, detection of an A/sub 1/-type precursor, if it should occur, would provide a short-range forecast having a time span of hours.

• OSTI ID: 6586852
• Journal Information: Bull. Seismol. Soc. Am.; (United States), Journal Name: Bull. Seismol. Soc. Am.; (United States) Vol. 65:5; ISSN BSSAA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
ANISOTROPY
EARTHQUAKES
EUROPE
FORESHOCKS
PHASE VELOCITY
PRECURSOR
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC WAVES
TIME DEPENDENCE
USSR
VELOCITY