STUDIES OF THE EFFECT OF DEPTH OF FOCUS ON SEISMIC PULSES: ESTIMATION PROCEDURE FOR FOCAL-DEPTH DETERMINATION OF SEISMIC DISTURBANCES

Summary Least-squares adjustments of observations of waves of the P groups at central and southern California stations are used to obtain the speeds of various waves. Only observations made to tenths of a second are used. It is assumed that the waves have a common velocity for all earthquakes. But the time intercepts of the travel-time curves are allowed to be different for different shocks. The speed of P̄ is found to be 5.61 km/sec.±0.05. The speed for S̄ (founded on fewer data) is 3.26 km/sec. ± 0.09. There are slight differences in the epicenters located by the use of P̄ and S̄ which may or may not be significant. It is suggested that P̄ and S̄ may be released from different foci. The speed of Pn, the wave in the top of the mantle, is 8.02 km/sec. ± 0.05. Intermediate P waves of speeds 6.72 km/sec. ± 0.02 and 7.24 km/sec. ± 0.04 are observed. Only the former has a time intercept which allows a consistent computation of structure when considered a layer wave. For the Berkeley earthquake of March 8, 1937, the accurate determination of depth of focus was possible. This enabled a determination of layering of the earth's crust. The result was about 9 km. of granite over 23 km. of a medium of speed 6.72 km/sec. Underneath these two layers is the mantle of speed 8.02 km/sec. The data from other shocks centering south of Berkeley would not fit this structure, but an assumption of the thickening of the granite southerly brought all into agreement. The earthquakes discussed show a lag of Pn as it passes under the Sierra Nevada. This has been observed before. A reconsideration of the Pn data of the Nevada earthquake of December 20, 1932, together with the data mentioned above, leads to the conclusion that the root of the mountain mass projects into the mantle beneath the surface layers by an amount between 6 and 41 km.

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Experimental evaluation of the light sword lens performance with a variable pupil size

Photonics Letters of Poland ◽

10.4302/plp.v10i2.814 ◽

2018 ◽

Vol 10 (2) ◽

pp. 36 ◽

Cited By ~ 1

Author(s):

Walter Torres-Sepúlveda ◽

Alejandro Mira-Agudelo ◽

John Fredy Barrera ◽

Andrzej Kolodziejczyk

Keyword(s):

New York ◽

Experimental Study ◽

Pupil Size ◽

Focal Depth ◽

Optical Element ◽

Depth Of Focus ◽

Variable Diameter ◽

Diffraction Structure ◽

Do So

This paper presents an experimental study designed to test the performance of the light sword lens (LSL) with different pupil sizes. To do so, Snellen optotype images obtained by a monofocal lens either with or without an LSL, were compared. Images were obtained for three different pupil sizes at several target vergences. The correlation coefficient and through-focus curves were obtained and compared. The experimental results show differences in the contrast and the depth of focus with different pupil sizes using the monofocal lens without an LSL. In contrast, when using the monofocal lens in combination with the LSL, the quality of the images is similar for all pupils and target vergences used, with slight differences only in halos and contrast. Full Text: PDF ReferencesG. Mikula, Z. Jaroszewicz, A. Kolodziejczyk, K. Petelczyc, M. Sypek, G. P. Agrawal, "Imaging with extended focal depth by means of lenses with radial and angular modulation", Opt Express 15, 9184, (2007). CrossRef A. Kolodziejczyk, S. Bará, Z. Jaroszewicz, M. Sypek, "The Light Sword Optical Element—a New Diffraction Structure with Extended Depth of Focus", J. Mod Opt. 37, 1283, (1990). CrossRef K. Petelczyc et al, "Presbyopia compensation with a light sword optical element of a variable diameter", Photonics Lett. Pol. 1, 55 (2009). DirectLink A. Mira-Agudelo et al, "Compensation of Presbyopia With the Light Sword Lens", Invest Ophthalmol Vis Sci 57, 6871, (2016). CrossRef R.A. Fisher, Statistical Methods for Research Workers (New York, Hafner, 13th Ed., 1958) CrossRef

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