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Crustal structure of accreted terranes in southern Alaska, Chugach Mountains and Copper River Basin, from seismic refraction results Crustal structure of accreted terranes in southern Alaska, Chugach Mountains and Copper River Basin, from seismic refraction results

Seismic refraction data were collected along a 320-km-long "transect' line in southern Alaska, crossing the Prince William, Chugach, Peninsular, and Wrangellia terranes, and along several shorter lines within individual terranes. Velocity structure in the upper crust (less than 9-km depth) differs among the four terranes. In contrast, layers in the middle crust (9- to 25-km depth) in...
Authors
G. S. Fuis, E. L. Ambos, Walter D. Mooney, N.I. Christensen, E. Geist

Is the extent of glaciation limited by marine gas-hydrates? Is the extent of glaciation limited by marine gas-hydrates?

Methane may have been released to the atmosphere during the Quaternary from Arctic shelf gas-hydrates as a result of thermal decomposition caused by climatic warming and rising sea-level; this release of methane (a greenhouse gas) may represent a positive feedback on global warming [Revelle, 1983; Kvenvolden, 1988a; Nisbet, 1990]. We consider the response to sea-level changes by the...
Authors
Charles K. Paull, William Ussler, William P. Dillon

High-energy carbonate-sand accumulation, the Quicksands, southwest Florida Keys High-energy carbonate-sand accumulation, the Quicksands, southwest Florida Keys

High-resolution seismic-reflection profiles of the Quicksands, located along a broad ridge on the platform shelf west of Key West, Florida, indicate a significant deposit of non-oolitic carbonate sand occurs in a belt 47 km long by 28 km wide. The surface of the belt is ornamented by large (5 m), migrating tidal bars, oriented in a north-south direction, on which sand waves, oriented in...
Authors
Eugene A. Shinn, Barbara H. Lidz, Charles W. Holmes

Large landslides from oceanic volcanoes Large landslides from oceanic volcanoes

Large landslides are ubiquitous around the submarine flanks of Hawaiian volcanoes, and GLORIA has also revealed large landslides offshore from Tristan da Cunha and El Hierro. On both of the latter islands, steep flanks formerly attributed to tilting or marine erosion have been reinterpreted as landslide headwalls mantled by younger lava flows. These landslides occur in a wide range of...
Authors
R. T. Holcomb, R. C. Searle

A C language implementation of the SRO (Murdock) detector/analyzer A C language implementation of the SRO (Murdock) detector/analyzer

A signal detector and analyzer algorithm was described by Murdock and Hutt in 1983. The algorithm emulates the performance of a human interpreter of seismograms. It estimates the signal onset, the direction of onset (positive or negative), the quality of these determinations, the period and amplitude of the signal, and the background noise at the time of the signal. The algorithm has...
Authors
James N. Murdock, Scott E. Halbert

Imaging the midcontinent rift beneath Lake Superior using large aperture seismic data Imaging the midcontinent rift beneath Lake Superior using large aperture seismic data

We present a detailed velocity model across the 1.1 billion year old Midcontinent Rift System (MRS) in central Lake Superior. The model was derived primarily from onshore-offshore large-aperture seismic and gravity data. High velocities obtained within a highly reflective half-graben that was imaged on coincident seismic reflection data demonstrate the dominantly mafic composition of the...
Authors
Anne M. Trehu, Patrick Morel-a-l’Huissier, R. Meyer, Z. Hajnal, J. Karl, R.F. Mereu, John L. Sexton, J. Shay, W. K. Chan, D. Epili, T. Jefferson, X. R. Shih, S. Wendling, Bernd Milkereit, A. Green, Deborah R. Hutchinson
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