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A medium term precursor to the Loma Prieta Earthquake?
Author(s) -
Gladwin M. T.,
Gwyther R. L.,
Higbie J. W.,
Hart R. G.
Publication year - 1991
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/91gl01846
Subject(s) - seismology , geology , borehole , geodetic datum , earthquake prediction , anomaly (physics) , shear (geology) , offset (computer science) , geodesy , petrology , geotechnical engineering , condensed matter physics , computer science , programming language , physics
The Loma Prieta earthquake ( M s =7.1, 17 October 1989) provided unique near field borehole tensor strain observations. The medium term data at the San Juan Bautista site showed a clear anomalous change in the fault parallel shear strain rate beginning about a year before the event. The anomaly ultimately reached 30% of the coseismic offset. The signal shows similarities with changes in strain rates reported from the geodetic record, suggesting a broad regional anomaly. The limited spacial sampling available prevents determination of a causal link useful for prediction between these data and the earthquake.