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A seismically active section of the Southwest Indian Ridge
Author(s) -
Wald David J.,
Wallace Terry C.
Publication year - 1986
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/gl013i010p01003
Subject(s) - seismology , ridge , geology , induced seismicity , seismic moment , slip (aerodynamics) , inversion (geology) , transform fault , section (typography) , paleontology , tectonics , fault (geology) , physics , thermodynamics , advertising , business
The section of the Southwest Indian Ocean Ridge west of the Prince Edward Fracture zone has a large ridge axis offset and a complicated ridge‐transform morphology. We have determined the source mechanisms of transform earthquakes along this portion of the ridge from an inversion of long‐period P and SH waveforms. The seismicity is characterized by anomalous faulting mechanisms, source complexity and an unexpectedly large seismic moment release. Several earthquakes with dip‐slip components of faulting have been recognized on the central section of the Andrew Bain and 32° E transforms suggesting geometrical complexity along the transform. This region has experienced a Mw = 8.0 transform earthquake in 1942, yet we observe a seismic slip rate during the last 20 years that is still comparable to the predicted spreading rate (1.6 cm/yr). The calculated slip rate over a period of 60 years is three times greater than the expected rate of spreading.