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Compression directions north of the San Fernando Valley determined from borehole breakouts
Author(s) -
Kerkela Stacy,
Stock Joann M.
Publication year - 1996
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 - 10.1029/96gl03054
Subject(s) - geology , seismology , borehole , aftershock , thrust fault , compression (physics) , upper crust , stress field , fault (geology) , tectonics , geotechnical engineering , materials science , physics , finite element method , composite material , thermodynamics
Borehole breakouts in 4 nearly vertical oil wells, and several other deviated holes, in the San Fernando Valley and Santa Susana Mountains suggest a maximum horizontal compressive stress direction (S H ) of N49°W. These wells provide information about the stress field from 1974 to 1983 in the uppermost crust (<3 km depth) near the aftershock zones of the January 1994 Northridge earthquake and the February 1971 Sylmar earthquake. This direction of S H is anomalous with respect to the N to NNE directions of S H seen in other regional data, but is consistent with the structural complexity of this zone, including local changes in strike of major thrust fault zones and the presence of lateral ramps in both the Santa Susana and San Fernando faults.