A morphometric and alignment analysis of volcanic seamounts to determine stress directions, northwestern Ross Sea, Antarctica

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2013-05

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The Ohio State University

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Abstract

Linear arrangements of monogenetic volcanic vents represent important sources for stress and strain data. These volcanic alignments form in platform volcanic fields due to separated eruptions along the trend of fissures fed by subsurface feeder dikes. Subsurface feeder dikes and their surface volcanic vents form alignments parallel to the maximum horizontal stress direction and perpendicular to the minimum horizontal stress in the upper crust, either due to formation of new, magmatically-induced cracks or by the exploitation of suitably oriented preexisting fractures. This research focuses on mapping volcanic vent alignments of a platform volcanic field on the Ross Sea floor in Antarctica. A new method for systematic mapping of vent alignments and elongate vents using multibeam bathymetry is developed. A morphometric analysis of each volcanic vent was completed to provide constraints for mapping the trend of the underlying fissure. Parameters including the measurement of the axial ratio of vent base shape, standard deviation of orthogonal distances from the best fit line connecting vents, standard angular deviation of the vent long axes from the trend of the best fit line, and the average distance between cones were used to test the reliability of each alignment. Mapped alignments have a dominant NE-SW trend, documenting a regional NW-SE orientation of the minimum horizontal stress. This stress direction is not compatible with the orientation of rift structures in the region, suggesting that this is a younger stress regime.

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stress, bathymetry, volcanic alignment, fissure

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