Lake Superior seismic experiment: Frequency spectra and absorption1

2013 ◽  
pp. 227-233 ◽  
Author(s):  
B. F. Howell
Keyword(s):  
Lake Superior ◽  
Frequency Spectra ◽  
Seismic Experiment

Maine seismic experiment: Frequency spectra of refraction arrivals and the nature of the Mohorovičić discontinuity

1964 ◽  
Vol 54 (1) ◽  
pp. 9-18
Author(s):  
Yosio Nakamura ◽  
Benjamin F. Howell
Keyword(s):  
Velocity Gradient ◽  
Gulf Of Maine ◽  
Statistical Tests ◽  
Fourier Integral ◽  
Frequency Content ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Seismic Experiment ◽  
Wave Forms ◽  
Mohorovičić Discontinuity

abstract Wave forms of first arrivals at various distances from explosions in the Gulf of Maine, 1961, were analyzed by Fourier integral analysis. Frequency spectra of the wave forms in the frequency range 2.6 to 25 cps were obtained. The frequency spectra of the refraction arrivals were compared with those of the direct arrivals. Statistical tests show that there is no clear dependence of the frequency content of the arrivals upon distance for either the direct or the refraction arrival, and that the two groups of arrivals definitely belong to two separate groups. Comparison with the results of a model experiment enables an estimate of the minimum possible velocity gradient at the Mohorovičić discontinuity to be made. On the assumption of a linear velocity transition at the boundary, the minimum possible velocity gradient is found to be 4 (km/sec)/km, or the maximum possible thickness of the transition layer to be 12 kilometers.

Lake Superior seismic experiment

1964 ◽  
Author(s):  
W.H. Jackson ◽  
B.L. Tibbetts
Keyword(s):  
Lake Superior ◽  
Seismic Experiment

Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

1983 ◽  
Vol 41 ◽  
pp. 462-463
Author(s):  
Richard L. Leino ◽  
Jon G. Anderson ◽  
J. Howard McCormick
Keyword(s):  
Confidence Interval ◽  
Chronic Exposure ◽  
Lake Superior ◽  
Pimephales Promelas ◽  
Chloride Cells ◽  
Fathead Minnows ◽  
Secondary Lamellae ◽  
Untreated Water ◽  
Water Ph ◽  
Flow Through

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.

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