ORIGINAL RESEARCH PAPER Seafloor elastic parameters estimation based on AVO inversion Yangting Liu 1 • Xuewei Liu 1 Received: 8 January 2015 / Accepted: 24 July 2015 / Published online: 30 July 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract Seafloor elastic parameters play an important role in many fields as diverse as marine construction, seabed resources exploration and seafloor acoustics. In order to estimate seafloor elastic parameters, we perform AVO inversion with seafloor reflected seismic data. As a particular reflection interface, the seafloor reflector does not support S-waves and the elastic parameters change dramatically across it. Conventional approximations to the Zoeppritz equations are not applicable for the seafloor situation. In this paper, we perform AVO inversion with the exact Zoeppritz equations through an unconstrained optimization method. Our synthetic study proves that the inversion method does not show strong dependence on the initial model for both unconsolidated and semi-consoli- dated seabed situations. The inversion uncertainty of the elastic parameters increases with the noise level, and decreases with the incidence angle range. Finally, we perform inversion of data from the South China Sea, and obtain satisfactory results, which are in good agreement with previous research. Keywords Seafloor AVO inversion Elastic parameters Optimization method The South China Sea Introduction Seabed elastic parameters play an important role in many fields as diverse as marine construction, seabed resources exploration and seafloor acoustics. Significant research work based on different wave fields has been previously carried out. Riedel and Theilen (2001) and Riedel et al. (2003) conducted AVO investigations of shallow marine sediments, and inverted AVO data to provide estimates and uncertain- ties of the viscoelastic physical parameters using a Bayesian approach. By exploiting the dispersive properties of Scholte waves, Klein et al. (2005) investigated the potential to reveal the elastic parameters of the shallow seabed subsurface and Wilken et al. (2009) inferred the shear-wave velocity structure. The features of converted waves in a shallow marine environment were studied by Allouche et al. (2011). Weemstra et al. (2013) used ambient seismic noise to con- strain subsurface attenuation by seismic interferometry. In geoacoustic inversion, there is also significant work that is based on the acoustic field rather than the seismic wave field (e.g., Dosso and Holland 2006; Dettmer et al. 2007, 2011; Dettmer and Dosso 2008). In this paper, we estimate the seabed elastic parameters by AVO response of reflected seismic data. AVO inversion is an effective method to estimate lithology parameters. Classical AVO inversion is based on approximations to the Zoeppritz (1919) equations. Most approximations are based on the weak property contrast assumptions or that the properties across the interface obey certain laws (e.g., Bortfeld 1961; Aki and Richards 1980; Shuey 1985; Vedanti and Sen 2009; Alemie and Sacchi 2011; Zhu and McMe- chan 2012). However, the properties across the seafloor interface vary dramatically. Furthermore, no S-wave gen- erates from the seafloor interface when the incident P-wave travels through seawater. Therefore, the assumption of those & Yangting Liu [email protected]Xuewei Liu [email protected]1 School of Geophysics and Information Technology, China University of Geosciences (Beijing), No. 29 Xueyuan Road, Haidian District, Beijing 100083, China 123 Mar Geophys Res (2015) 36:335–342 DOI 10.1007/s11001-015-9260-1
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Seafloor elastic parameters estimation based on AVO inversion...AVO theory is based on the Zoeppritz (1919) equations, which express the reflection and transmission coefficients
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ORIGINAL RESEARCH PAPER
Seafloor elastic parameters estimation based on AVO inversion
Yangting Liu1 • Xuewei Liu1
Received: 8 January 2015 / Accepted: 24 July 2015 / Published online: 30 July 2015
� Springer Science+Business Media Dordrecht 2015
Abstract Seafloor elastic parameters play an important
role in many fields as diverse as marine construction,
seabed resources exploration and seafloor acoustics. In
order to estimate seafloor elastic parameters, we perform
AVO inversion with seafloor reflected seismic data. As a
particular reflection interface, the seafloor reflector does
not support S-waves and the elastic parameters change
dramatically across it. Conventional approximations to the
Zoeppritz equations are not applicable for the seafloor
situation. In this paper, we perform AVO inversion with
the exact Zoeppritz equations through an unconstrained
optimization method. Our synthetic study proves that the
inversion method does not show strong dependence on the
initial model for both unconsolidated and semi-consoli-
dated seabed situations. The inversion uncertainty of the
elastic parameters increases with the noise level, and
decreases with the incidence angle range. Finally, we
perform inversion of data from the South China Sea, and
obtain satisfactory results, which are in good agreement
with previous research.
Keywords Seafloor � AVO inversion � Elasticparameters � Optimization method � The South China Sea
Introduction
Seabed elastic parameters play an important role in many
fields as diverse as marine construction, seabed resources
exploration and seafloor acoustics. Significant research work
based on different wave fields has been previously carried
out. Riedel and Theilen (2001) and Riedel et al. (2003)
conducted AVO investigations of shallow marine sediments,
and inverted AVO data to provide estimates and uncertain-
ties of the viscoelastic physical parameters using a Bayesian
approach. By exploiting the dispersive properties of Scholte
waves, Klein et al. (2005) investigated the potential to reveal
the elastic parameters of the shallow seabed subsurface and
Wilken et al. (2009) inferred the shear-wave velocity
structure. The features of converted waves in a shallow
marine environment were studied by Allouche et al. (2011).
Weemstra et al. (2013) used ambient seismic noise to con-
strain subsurface attenuation by seismic interferometry. In
geoacoustic inversion, there is also significant work that is
based on the acoustic field rather than the seismic wave field
(e.g., Dosso and Holland 2006; Dettmer et al. 2007, 2011;
Dettmer and Dosso 2008).
In this paper, we estimate the seabed elastic parameters
by AVO response of reflected seismic data. AVO inversion
is an effective method to estimate lithology parameters.
Classical AVO inversion is based on approximations to the
Zoeppritz (1919) equations. Most approximations are based
on the weak property contrast assumptions or that the
properties across the interface obey certain laws (e.g.,
Bortfeld 1961; Aki and Richards 1980; Shuey 1985; Vedanti
and Sen 2009; Alemie and Sacchi 2011; Zhu and McMe-
chan 2012). However, the properties across the seafloor
interface vary dramatically. Furthermore, no S-wave gen-
erates from the seafloor interface when the incident P-wave
travels through seawater. Therefore, the assumption of those