Velocities,elastic moduli and weathering-age relations for pacific layer 2 basalts |
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| Authors: | Nikolas I Christensen Matthew H Salisbury |
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| Institution: | Department of Geological Sciences and Graduate Program in Geophysics, University of Washington, Seattle, Washington 98195,USA;Department of Geological Sciences, University of Washington, Seattle, Washington 98195,USA |
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| Abstract: | Compressional (Vp) and shear (Vs) wave velocities have been measured to 10 kb in 32 cores of basalt from 14 Pacific sites of the Deep Sea Drilling Project. Both VpandVs show wide ranges (3.70to6.38km/sec forVpand1.77to3.40km/sec forVsat0.5kb) which are linearly related to density and sea floor age, confirming earlier findings by Christensen and Salisbury of decreasing velocity with progressive submarine weathering based on studies of basalts from five sites in the Atlantic. Combined Pacific and Atlantic data give rates of decreasing velocity of ?1.89and?1.35km/sec per100my forVpandVs respectively. New analyses of oceanic seismic refraction data indicate a decrease in layer 2 velocities with age similar to that observed in the laboratory, suggesting that weathering penetrates to several hundred meters in many regions and is largely responsible for the extreme range and variability of layer 2 refraction velocities. |
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