Fault scarp statistics at the Galapagos spreading centre from Deep Tow data |
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| Authors: | Mitchell Neil C Searle Roger C |
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| Institution: | (1) Department of Earth Sciences, University of Oxford, Park Road, Oxford, OX1 3PR, UK;(2) Department of Geological Sciences, University of Durham, UK (Phone: UK |
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| Abstract: | Much of the relief of the abyssal hills covering the ocean basins is believed to originate from faulting of oceanic crust at mid-ocean ridges. The timescale over which faults grow is controversial, however, with some authors arguing that faults continue to grow in places for 0.5 m.y. or more based on increasing relief of fault scarps with distance from ridge axes. We examine Deep Tow profiler records of the Galapagos Spreading Centre, in which basement reflections allow scarp relief to be measured beneath the sediment cover, and find that relief does not increase but decreases systematically to 40 km off-axis (1.5 Ma seafloor). Since reversal of fault offsets is unlikely in this tectonic setting, we interpret this result as indicating that variations in fault statistics could reflect temporal variations in the tectonic or volcanic state of the ridge crest, not necessarily progressive fault growth with age as previously assumed. Resolving the issue of fault longevity will therefore require independent data on the timing of fault growth and distribution of present growth activity. We suggest some possible alternative indicators of fault longevity and discuss more generally the implications of volcanic flows to studies of faulting at ridges. |
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| Keywords: | Mid-ocean ridge tectonics volcanic flows seismicity slope stability |
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