Microearthquake evidence for extension across the Kane transform fault

Journal Article · Mon Sep 10 00:00:00 EDT 1990 · Journal of Geophysical Research; (USA)

DOI:https://doi.org/10.1029/JB095iB10p15439· OSTI ID:6055883

Wilcock, W S.D. ^[1]; Purdy, G M ^[2]; Solomon, S C ^[3]

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1. MIT/WHOI Joint Program in Oceanography, Cambridge, MA (USA)
2. Woods Hole Oceanographic Institution, MA (USA)
3. Massachusetts Institute of Technology, Cambridge (USA)

The Kane is a slow slipping (25 mm/yr), large-offset (150 km) transform delineated by a pronounced transform valley. The experiment site lies in the eastern half of the transform, 40 km west of the eastern ridge-transform intersection, in a region of marked transform-parallel topography. Hypocentral parameters were determined for 86 earthquakes. To the southeast activity may be associated with the inside corner of the ridge transform intersection, while to the north about 20 events occurred in 7-m.y.-old crust in a region of ridge-parallel bathymetry. Six focal mechanisms were obtained from P wave first motions for events within the transform valley. The best constrained solutions, for four earthquakes within the network, show normal faulting on fault planes subparallel to the trend of the transform. All the mechanisms indicate a tension axis perpendicular to the trend of the transform. These results together with a significant historical record of large earthquakes near the experiment site lead the authors to conclude that the principal transform displacement zone was inactive during the experiment and that the activity they recorded is the result of extension in the adjacent lithosphere. The observed focal mechanisms and the inference that the axis of least compressive stress is approximately perpendicular to the transform provide direct evidence that the transform fault is mechanically weak relative to the surrounding lithosphere. Potential sources of extension across the transform include thermal stress in the young oceanic lithosphere, topographic loading, a small component of plate divergence normal to the transform, and northward motion of the asthenosphere relative to the surface plate.

• OSTI ID: 6055883
• Journal Information: Journal of Geophysical Research; (USA), Vol. 95:B10; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC FAULTS
TECTONICS
OCEANIC CRUST
PLATE TECTONICS
ROCK MECHANICS
BATHYMETRY
DEPTH
GEOLOGIC STRUCTURES
HYPOCENTERS
MICROEARTHQUAKES
OCEANOGRAPHY
SEISMIC ARRAYS
SEISMIC DETECTION
SEISMIC P WAVES
STRESSES
TOPOGRAPHY
DETECTION
DIMENSIONS
EARTH CRUST
EARTHQUAKES
GEOLOGIC FRACTURES
MEASURING INSTRUMENTS
MECHANICS
SEISMIC EVENTS
SEISMIC WAVES
580000* - Geosciences