Regularity of velocity averages

1997 ◽  
pp. 29-49
Author(s):  
M Mokhtar-Kharroubi
Keyword(s):  
Velocity Averages

scholarly journals Net Budget and Flow of South Cascade Glacier, Washington

1965 ◽  
Vol 5 (41) ◽  
pp. 547-566 ◽  
Author(s):  
Mark F. Meier ◽  
W. V. Tangborn
Keyword(s):  
Steady State ◽  
Surface Elevation ◽  
Elevation Change ◽  
Glacier Surface ◽  
Surface Elevation Change ◽  
Long Valley ◽  
Valley Glacier ◽  
Ice Velocity ◽  
The Mean ◽  
Velocity Averages

AbstractIce velocity, net mass budget and surface elevation change data were collected over the length and width of a small (3.4 km. long) valley glacier from 1957 to 1964. Ice velocities range up to about 20 m./yr.; three prominent velocity maxima along the length of the glacier correspond to maxima in surface slope. Net mass budgets averaged over the glacier surface range between − 3.3 m. of water equivalent (1957–58) and +1.2 m. (1963–64). Except for the year 1960–61, curves of net budget versus altitude are parallel. During the period 1958–61 the glacier became thinner at a rate averaging 0.93 m./yr. The net budget and thinning data are internally consistent. Relations between emergence velocity, net budget and surface elevation change are examined at four specific points on the glacier surface and as functions of distance along the length of the glacier. Emergence velocity averages about −0.5 m. in the upper part of the glacier and about +1.0 m. in the lower part. Ice discharge and ice thickness are also calculated as functions of distance. The discharge reaches a peak of 8.8 × 105m.3of ice per year 2.2 km. from the head of the glacier. The mean thickness of the glacier is about 83 m. A steady-state distribution of net budget is used to calculate a steady-state discharge, which is 2.2 times larger than the present discharge.

Compactness of Velocity Averages

2002 ◽  
Vol 51 (2) ◽  
pp. 0-0 ◽  
Author(s):  
Manuel Portilheiro
Keyword(s):  
Velocity Averages

HOMOGENIZATION OF BOUNDARY VALUE PROBLEMS AND SPECTRAL PROBLEMS FOR NEUTRON TRANSPORT IN LOCALLY PERIODIC MEDIA

2004 ◽  
Vol 14 (01) ◽  
pp. 47-78 ◽  
Author(s):  
MUSTAPHA MOKHTAR-KHARROUBI
Keyword(s):  
Strong Convergence ◽  
Boundary Value Problems ◽  
Neutron Transport ◽  
Boundary Value ◽  
Periodic Media ◽  
Spectral Problems ◽  
Convergence Results ◽  
Smoothing Effects ◽  
Neutron Transport Equations ◽  
Velocity Averages

This paper deals with boundary value problems and spectral problems for neutron transport equations involving locally periodic (in space) collision frequencies and collision operators. We show strong convergence results to the solution of homogenized problems when the period goes to zero. The mathematical analysis relies mainly on smoothing effects of velocity averages.

Velocity Averages

1977 ◽  
Vol 50 (5) ◽  
pp. 257-258 ◽  
Author(s):  
Gerald T. Cargo
Keyword(s):  
Velocity Averages

NORMAL‐MOVEOUT AND VELOCITY RELATIONS FOR FLAT AND DIPPING BEDS AND FOR LONG OFFSETS

Geophysics ◽  
1969 ◽  
Vol 34 (2) ◽  
pp. 180-195 ◽  
Author(s):  
Robert J. S. Brown
Keyword(s):  
Random Noise ◽  
Seismic Energy ◽  
Long Offset ◽  
Dominant Period ◽  
Exploration Seismology ◽  
Time Average ◽  
The Difference ◽  
Zero Offset ◽  
Velocity Averages ◽  
Velocity Average

Accurate relations between NMO and velocity are needed in modern exploration seismology, especially in long‐offset CDP work, where accurate NMO corrections must be made for stacking, and where several types of velocity averages may be computed with accuracy from NMO data. The velocity average associated with NMO is the time‐rms velocity [Formula: see text]. Even for long offsets the straight‐ray computation using [Formula: see text] is usually adequate, but a closer approximation for horizontal reflectors is obtained by reducing the NMO calculated from [Formula: see text] or reducing the value of [Formula: see text] calculated from NMO by the factor [Formula: see text], where σ is the rms deviation of the velocity from its mean, T is zero‐offset traveltime, and ΔT the NMO. The difference between time‐average and time‐rms velocities is often several percent. For the velocity function [Formula: see text] and for reflectors of arbitrary dip and strike, the NMO is shown to be [Formula: see text] where X is offset, α is emergence angle, and ψ is the angle between the offset direction and the reflector dip direction. The terms that contain angles can be used as a correction ΔΔT to the NMO value computed as if the seismic energy were reflected from a horizontal reflector, even for offset greater than those for which an NMO expression quadratic in offset is accurate. A further approximation gives [Formula: see text], where δT is dip moveout over a spread of length L, and [Formula: see text] is the angle between the receiver line and the dip direction, differing from ψ only if there is substantial perpendicular offset of the source point. An expression for the degradation of the stacked signals in CDP stacks because of NMO errors is given. It is shown that the criterion that the signal‐to‐random‐noise ratio could not be improved by dropping the longest‐offset trace(s) requires that the NMO error be not much larger than one‐quarter of a dominant period.

Velocity Averages

1977 ◽  
Vol 50 (5) ◽  
pp. 257 ◽  
Author(s):  
Gerald T. Cargo
Keyword(s):  
Velocity Averages

scholarly journals L p regularity of velocity averages

1991 ◽  
Vol 8 (3-4) ◽  
pp. 271-287 ◽  
Author(s):  
R.J. Diperna ◽  
P.L. Lions ◽  
Y. Meyer
Keyword(s):  
Velocity Averages

scholarly journals Net Budget and Flow of South Cascade Glacier, Washington

1965 ◽  
Vol 5 (41) ◽  
pp. 547-566 ◽  
Author(s):  
Mark F. Meier ◽  
W. V. Tangborn
Keyword(s):  
Steady State ◽  
Surface Elevation ◽  
Elevation Change ◽  
Glacier Surface ◽  
Surface Elevation Change ◽  
Long Valley ◽  
Valley Glacier ◽  
Ice Velocity ◽  
The Mean ◽  
Velocity Averages

AbstractIce velocity, net mass budget and surface elevation change data were collected over the length and width of a small (3.4 km. long) valley glacier from 1957 to 1964. Ice velocities range up to about 20 m./yr.; three prominent velocity maxima along the length of the glacier correspond to maxima in surface slope. Net mass budgets averaged over the glacier surface range between − 3.3 m. of water equivalent (1957–58) and +1.2 m. (1963–64). Except for the year 1960–61, curves of net budget versus altitude are parallel. During the period 1958–61 the glacier became thinner at a rate averaging 0.93 m./yr. The net budget and thinning data are internally consistent. Relations between emergence velocity, net budget and surface elevation change are examined at four specific points on the glacier surface and as functions of distance along the length of the glacier. Emergence velocity averages about −0.5 m. in the upper part of the glacier and about +1.0 m. in the lower part. Ice discharge and ice thickness are also calculated as functions of distance. The discharge reaches a peak of 8.8 × 105 m.3 of ice per year 2.2 km. from the head of the glacier. The mean thickness of the glacier is about 83 m. A steady-state distribution of net budget is used to calculate a steady-state discharge, which is 2.2 times larger than the present discharge.

Sign in / Sign up

Export Citation Format

Share Document