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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 an east-we
Authors
Eugene A. Shinn, Barbara H. Lidz, Charles W. Holmes

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 graben fi
Authors
Anne M. Tréhu, 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, B. Milkereit, A. Green, Deborah R. Hutchinson

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 been coded in
Authors
James N. Murdock, Scott E. Halbert

Documented historical landslide dams from around the world

This data compilation consists of dBase IV1 data files of the location, date, triggering mechanism, kind, size, failure time and mechanism, breach dimensions, subsequent controls, materials, and references for 463 historical landslide dams and associated natural reservoirs that have been recorded throughout the World. The data base presented in this report is a compilation of information on the ch
Authors
John E. Costa, Robert L. Schuster

Volcanologic investigations in the Commonwealth of the Northern Mariana Islands, September-October 1990

U.S. Geological Survey volcanologists examined the ten volcanoes in the active Mariana Arc north of Saipan in May 1992, at the request of the Governor and the Disaster Control Office of the Commonwealth of the Northern Mariana Islands (CNMI). A shallow earthquake swarm on Anatahan in March-April 1990 and reports of possible new fuming on Agrigan in August 1990 had prompted the evacuation of all CN
Authors
Richard B. Moore, R. Y. Koyanagi, M. K. Sako, F. A. Trusdell, George Kojima, R. L. Ellorda, S. K. Zane

Low intensity of the geomagnetic field in early Jurassic time

From a large collection of Jurassic continental tholeiites cropping out in Europe and Africa, we selected 90 samples for paleointensity determinations. The samples were carefully selected to avoid any secondary magnetizations, especially viscous magnetization. Use of the Thellier method reveals that magnetic property changes due to heating begin often at quite low temperatures but fortunately with
Authors
M. Perrin, M. Prevot, E. A. Mankinen

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 settings and
Authors
R. T. Holcomb, R. C. Searle

Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, December 1991

No abstract available.
Authors
John B. Townshend, Richard V. O'Connell, Carol Ann Varner

Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, September 1991

No abstract available.
Authors
John B. Townshend, Richard V. O'Connell, Carol Ann Varner