Marine vibrators and the Doppler effect

Geophysics ◽  
1988 ◽  
Vol 53 (11) ◽  
pp. 1388-1398 ◽  
Author(s):  
William H. Dragoset
Keyword(s):  
Gulf Of Mexico ◽  
Doppler Effect ◽  
Synthetic Data ◽  
Simple Relationship ◽  
Phase Dispersion ◽  
Air Gun ◽  
Before And After ◽  
Doppler Factor ◽  
The Doppler Effect ◽  
Marine Seismic

Marine seismic data acquired with a moving vibrator suffer phase dispersion caused by Doppler shifting of the source sweep function. The dispersion for a particular reflection event depends upon frequency, the type of sweep function, and the Doppler factor associated with that event. Synthetic vibrator data show that, at typical ship speeds, the Doppler factors for steeply dipping events are big enough to cause phase dispersion as large as several hundred degrees. If unaccounted for, such dispersive effects could make a moving marine vibrator unacceptable for imaging steep dips. In a constant‐offset section, the Doppler factor for a reflection event is the product of ship speed and the event’s time dip. That key, simple relationship allows a two‐dimensional f-k filter to remove the phase dispersion caused by the Doppler effect. Comparisons of both synthetic data and Gulf of Mexico field data, before and after application of the phase‐correcting filter, show that the filter improves steep‐dip imaging in marine vibrator data. For the Gulf of Mexico line, steep dips are imaged just as well in the phase‐corrected vibrator data as in air‐gun data.

scholarly journals Doppler estimation and compensation method for underwater target active detection based on communication signal

2021 ◽  
Vol 39 (5) ◽  
pp. 962-970
Author(s):  
Jun LU ◽  
Qunfei ZHANG ◽  
Wentao SHI ◽  
Lingling ZHANG
Keyword(s):  
Doppler Effect ◽  
Compensation Method ◽  
Single Frequency ◽  
Frequency Signal ◽  
Communication Signals ◽  
Estimation Performance ◽  
Communication Signal ◽  
Doppler Factor ◽  
The Doppler Effect ◽  
Signal Segment

The integration of underwater detection and communication uses communication signals to detect a target actively, but the Doppler effect deteriorates the parameter estimation performance of the integrated system. To eliminate the influence of the Doppler effect, a joint Doppler estimation and compensation method based on spectrum zooming and correction is proposed. Firstly, the synchronization signal is used to obtain the signal receiving delay and intercept the single-frequency signal segment in the received signal. Then, the discrete Fourier transform is used to find the frequency that corresponds to the maximum amplitude of the single-frequency signal segment. Finally, the frequency spectrum is refined and corrected within the range near the frequency. The Doppler factor is estimated and the received signal is compensated by the Doppler estimation value. The simulation results show that the proposed method improves Doppler factor estimation accuracy, increases the cross-correlation processing gain and improves DOA (direction of arrival) estimation performance, thus being robust to different Doppler effects.

The music of marine seismic: A marine vibrator system based on folded surfaces

2020 ◽  
Vol 39 (4) ◽  
pp. 254-263
Author(s):  
Okwudili C. Orji ◽  
Mattias Oscarsson-Nagel ◽  
Walter Söllner ◽  
Endrias G. Asgedom ◽  
Øystein Trætten ◽  
...  
Keyword(s):  
Seismic Data ◽  
Frequency Tuning ◽  
Synthetic Data ◽  
Harmonic Distortion ◽  
Low Frequency ◽  
Source Control ◽  
Environmental Friendliness ◽  
Air Gun ◽  
Frequency Module ◽  
Marine Seismic

Marine vibrators have bespoke geophysical benefits that are yet to be harnessed because of robustness and efficiency issues. We have developed a new marine vibrator source technology that is efficient and stable. The source technology overcomes the historical problems of inefficiency and robustness by using folded surface technology and resonance frequency tuning. We show measured output examples that demonstrate that the folded surface concept combined with small displacements can provide the required output levels. Our source system consists of a low-frequency module covering 1–10 Hz and a high-frequency module covering 10–125 Hz. The source control system has shown high stability and precision and can handle harmonic distortion. With the aid of synthetic data examples, we demonstrate that seismic data acquired using marine vibrators in either intermittent or continuous mode can be processed. Finally, we demonstrate the environmental friendliness of the source in comparison to air gun-based sources.

scholarly journals Geolocators reveal migration routes, stopover sites, and nonbreeding dispersion in a population of Cerulean Warblers

2020 ◽  
Vol 7 (1) ◽  
pp. 19-26
Author(s):  
Clayton D Delancey ◽  
Kamal Islam ◽  
Gunnar R Kramer ◽  
Garrett J MacDonald ◽  
Alexander R Sharp ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Spring Migration ◽  
Autumn Migration ◽  
Migration Routes ◽  
Neotropical Migrant ◽  
Wood Warblers ◽  
Before And After ◽  
The Caribbean ◽  
Declining Species ◽  
Cerulean Warblers

AbstractCerulean Warblers (Setophaga cerulea) are among the fastest declining Nearctic-Neotropical migrant wood-warblers (Parulidae) in North America. Despite ongoing conservation efforts, little is known about their non-breeding distribution. In June 2016-2018, we deployed geolocators (n = 30) on adult male Cerulean Warblers in Indiana, USA, to track annual movements of individuals. Recovered geolocators (n = 4) showed that Cerulean Warblers occurred broadly throughout northern South America. Autumn migration lasted 44-71 days (n = 4), whereas spring migration lasted 37-41 days (n = 3). The average migration distance was 5268 km. During autumn migration, Cerulean Warblers made 1-4 stopovers (i.e., ≥2 days; n = 4) and 1-2 stopovers during spring migration (n = 3). When crossing the Gulf of Mexico during autumn migration, two birds stopped over after crossing, but not beforehand. Two others navigated through the Caribbean rather than crossing the Gulf of Mexico. During spring migration, one individual stopped after crossing, one individual stopped before crossing, and one individual stopped before and after crossing the Gulf of Mexico. No birds migrated through the Caribbean Islands during spring migration. These results represent novel information describing annual movements of individual Cerulean Warblers and will inform conservation efforts for this declining species.

ON THE THEORY OF THE DOPPLER EFFECT IN A MOVING MEDIUM

1998 ◽  
Vol 13 (01) ◽  
pp. 1-6 ◽  
Author(s):  
BRUNO BERTOTTI
Keyword(s):  
Solar Wind ◽  
Doppler Effect ◽  
Dispersive Medium ◽  
Time Derivative ◽  
Optical Path ◽  
Moving Medium ◽  
Perturbation Theorem ◽  
Hamiltonian Theory ◽  
The Doppler Effect ◽  
Definition Of

The increase in the accuracy of Doppler measurements in space requires a rigorous definition of the observed quantity when the propagation occurs in a moving, and possibly dispersive medium, like the solar wind. This is usually done in two divergent ways: in the phase viewpoint it is the time derivative of the correction to the optical path; in the ray viewpoint the signal is obtained form the deflection produced in the ray. They can be reconciled by using the time derivative of the optical path in the Lagrangian sense, i.e. differentiating from ray to ray. To rigorously derive this result an understanding, through relativistic Hamiltonian theory, of the delicate interplay between rays and phase is required; a general perturbation theorem which generalizes the concept of the Doppler effect as a Lagrangian derivative is proved. Relativistic retardation corrections O(v) are obtained, well within the expected sensitivity of Doppler experiments near solar conjunction.

The doppler effect

1976 ◽  
Vol 11 (1) ◽  
pp. 5-6
Author(s):  
Charles W Fox ◽  
E M Wray
Keyword(s):  
Doppler Effect ◽  
The Doppler Effect
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