Towards a Better Understanding of Shallow Seismic Anomalies in the Dutch Offshore

2014 ◽  
Author(s):  
J.H. ten Veen ◽  
G. de Bruin ◽  
J.M. Verweij ◽  
T. Donders
Keyword(s):  
Shallow Seismic ◽  
Seismic Anomalies

Delineating paleochannels using shallow seismic reflection

1997 ◽  
Vol 16 (11) ◽  
pp. 1671-1674 ◽  
Author(s):  
Richard D. Miller ◽  
Jianghai Xia
Keyword(s):  
Seismic Reflection ◽  
Shallow Seismic

Improving surface‐wave group velocity measurements by energy reassignment

Geophysics ◽  
2003 ◽  
Vol 68 (2) ◽  
pp. 677-684 ◽  
Author(s):  
Helle A. Pedersen ◽  
Jérôme I. Mars ◽  
Pierre‐Olivier Amblard
Keyword(s):  
Surface Waves ◽  
Dispersion Curve ◽  
Group Velocity ◽  
Shear Wave ◽  
Group Velocity Dispersion ◽  
Seismic Survey ◽  
Earth Model ◽  
Velocity Measurements ◽  
Time Frequency ◽  
Shallow Seismic

Surface waves are increasingly used for shallow seismic surveys—in particular, in acoustic logging, environmental, and engineering applications. These waves are dispersive, and their dispersion curves are used to obtain shear velocity profiles with depth. The main obstacle to their more widespread use is the complexity of the associated data processing and interpretation of the results. Our objective is to show that energy reassignment in the time–frequency domain helps improve the precision of group velocity measurements of surface waves. To show this, full‐waveform seismograms with added white noise for a shallow flat‐layered earth model are analyzed by classic and reassigned multiple filter analysis (MFA). Classic MFA gives the expected smeared image of the group velocity dispersion curve, while the reassigned curve gives a very well‐constrained, narrow dispersion curve. Systematic errors from spectral fall‐off are largely corrected by the reassignment procedure. The subsequent inversion of the dispersion curve to obtain the shear‐wave velocity with depth is carried out through a procedure combining linearized inversion with a nonlinear Monte Carlo inversion. The diminished uncertainty obtained after reassignment introduces significantly better constraints on the earth model than by inverting the output of classic MFA. The reassignment is finally carried out on data from a shallow seismic survey in northern Belgium, with the aim of determining the shear‐wave velocities for seismic risk assessment. The reassignment is very stable in this case as well. The use of reassignment can make dispersion measurements highly automated, thereby facilitating the use of surface waves for shallow surveys.

Finite-frequency effects for imaging underground cavities

2021 ◽  
Author(s):  
Felix M. Schneider ◽  
Petr Kolínský ◽  
Götz Bokelmann
Keyword(s):  
Analytical Approach ◽  
Nuclear Test ◽  
Underground Cavity ◽  
Finite Frequency ◽  
Cavity Detection ◽  
Frequency Effects ◽  
The Past ◽  
Nuclear Tests ◽  
Seismic Anomalies ◽  
Test Ban

<p>We study finite-frequency effects that arise in cavity detection. The task comes along with the Onsite-Inspection part for the Comprehensive Nuclear Test Ban Treaty (CTBT), where the remnants of a potential nuclear test need to be identified. In such nuclear tests, there is preexisting knowledge about the depths at which nuclear tests may take place, and also about sizes that such cavities can attain. The task of cavity detection has consistently been a difficult one in the past, which is surprising, since a cavity represents one of the strongest seismic anomalies one can ever have in the subsurface. A conclusion of this study is that considering finite-frequency effects are rather promising for cavity detection, and that it is worthwhile to take them into account. We utilize an analytical approach for the forward problem of the a seismic wave interacting with a underground cavity in order to develop an inversion routine that finds and detects an underground cavity utilizing the transmitted wave-field.</p><p> </p>

Improving The Reliability of Velocity Analysis of Shallow Seismic Data

2021 ◽  
Author(s):  
A.G. Yaroslavtsev ◽  
M.V. Tarantin ◽  
T.V. Baibakova
Keyword(s):  
Seismic Data ◽  
Velocity Analysis ◽  
Shallow Seismic
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