Finite difference seismic modeling of axial magma chambers

Swift, Stephen A.; Dougherty, Martin E.; Stephen, Ralph A.

doi:10.1029/gl017i012p02105

Cited by 11 publications

(5 citation statements)

References 25 publications

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“…Previous studies [Burnett et al, 1988;Swift et al, 1990] have demonstrated the feasibility of applying numerical techniques to model seismic propagation across mid-ocean ridges. In this chapter we apply a two-dimensional full-waveform finitedifference technique to address the reliability of the Q tomography method.…”

Section: Introductionmentioning

confidence: 99%

The seismic attenuation structure of the East Pacific Rise

Wilcock¹

1992

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Studies of seismic propagation through oceanic crust have contributed enormously to our understanding of the generation and evolution of oceanic crust. However, such work has largely been confined to the seismic velocity structure. In this thesis we present results from a study of seismic attenuation using a data set collected for three-dimensional tomographic imaging of a fast-spreading ridge. The experiment location at 9 0 30'N on the East Pacific Rise is the site of a strong mid-crustal seismic reflector which has been inferred to be the roof of a small axial magma chamber at about 1.6 km depth.A spectral method is used to estimate t*, a measure of the integrated attenuation along a wave path. Such a method assumes that the dominant frequency-dependent component of propagation is intrinsic attenuation. A logarithmic parameterization is then used to invert t* measurements for Q-I structure assuming that the velocity structure is given from earlier studies. To evaluate the method of Q tomography a full-waveform finitedifference technique which does not include attenuation is used to calculate solutions for seismic propagation through a two-dimensional velocity model. The results show a complex pattern of seismic propagation in the vicinity of the axial magma chamber. The first arrival always passes above the magma chamber. However, for paths of significant length that cross the rise axis the amplitude of this arrival is very small, and the first phase with significant amplitude is a diffraction below the magma chamber. High-amplitude Moho turning and PP arrivals may also be important secondary arrivals. Synthetic inversions show the importance of selecting time windows for power spectral estimation which are dominated by a single phase and of using wave paths which closely corresponds to that of the selected phase.A comparison of the finite difference solutions and the predictions of the a twodimensional, exact ray-tracing algorithm with record sections obtained during the tomography experiment significantly improves our understanding of seismic propagation across the East Pacific Rise. The results enable an objective choice of the position and length of the time window for t* estimation. Moreover, additional constraints are incorporated into an approximate three-dimensional ray-tracing algorithm used in the inversion so that the wave paths more closely correspond to those of the desired phase. The full data set to be inverted comprises about 3500 t* estimates and includes crustal paths which do not cross the rise axis, diffractions above and below the axial magma chamber, and Moho-turning phases. Wave paths for the Moho-turning phases cross the rise axis at a wide range of lower crustal depths.The Q-1 models resulting from two-dimensional and three-dimensional tomographic inversions show that the attenuation of seismic waves on the East Pacific Rise is dominated by two regions of low Q; one in the upper 1 km of crust, and one at depths greater than about 2 km below the rise axis. While the data do not ...

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Section: Introductionmentioning

confidence: 99%

The seismic attenuation structure of the East Pacific Rise

Wilcock¹

1992

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“…The seismic response characteristic of submarine sand waves induced hair-like reflection configuration is computed numerically by solving the two-dimensional acoustic wave equation with the finite-difference method (Madariaga, 1976;Frankel and Clayton, 1984;Frankel and Clayton, 1986). This numerical wave simulator models the high-order wave phenomena associated with complex velocity and density structures (Kelly et al, 1976;Swift et al, 1990). Reverse-time migration has been applied to synthetic seismic shot records of the submarine sand waves induced hair-like reflection configuration model to obtain seismic oceanography numerical simulation sections reflecting the characteristic of the water column and similar to the field seismic reflection section (Baysal et al, 1983 Based on fluid dynamics numerical simulation results, a mathematical model (acoustic velocity and density) that can be used for seismic oceanography numerical simulation is established using the seawater state equation and the acoustic velocity empirical equation (Figures 3A, B).…”

Section: Seismic Oceanography Mathematical Model and Numerical Simula...mentioning

confidence: 99%

Research on the fluid dynamics interaction between submarine sand waves and seawater by seismic oceanography

Han

Chen

et al. 2023

Front. Mar. Sci.

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IntroductionThe seafloor is an important interface between the lithosphere and the hydrosphere, where processes related to circulation and energy exchange happen along with various marine processes widely developed in the water column near the seafloor. These processes are still not yet completely understood as there are constraints of submarine detection technology and the interdisciplinary nature of these complex environments. Seismic reflection data have been a preferable tool to study and image these processes due to their characteristics in terms of spatial resolution. In seismic reflection data, submarine sand waves show hair-like reflection configurations with low continuity and wearing-hair style, appearing with an angle with the seafloor. Investigation of the relationship between the characteristics of submarine sand waves induced hair-like reflection configuration and hydrodynamics is crucial for understanding hair-like reflection configuration generation and spatiotemporal evolution. MethodsThis study combines fluid dynamics numerical simulation and seismic oceanography to discuss the seismic response characteristics and formation mechanisms of the hair-like reflection configuration. First, we create a seawater time-variant fluid-dynamical model followed by the numerical simulation of seismic oceanography data. This procedure results in seismic oceanography numerical simulation sections with hair-like reflection configurations for different constant flow conditions forced on the boundary. Optimal matching method is then applied to interpret field seismic reflection sections given the results obtained with the numerical experiments. Results and discussionAs consequence, the fluid dynamic explanation for the formation mechanism of the hair-like reflection configuration due to differences in seawater thermohaline is proposed. The study provides additional comprehension and further insights into the dynamic process of submarine sand waves induced hair-like reflection configuration using the seismic oceanography method.

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“…Finite difference methods have the ability to model high-order wave phenomena associated with complex velocity structures (Swift et al 1990). These models provide not only accurate seismograms with which observed data can be compared, but also a methodology to explore structures beyond the limits of seismic resolution.…”

Section: Seismic Modelingmentioning

confidence: 99%

Toe-of-slope of a Cretaceous carbonate platform in outcrop, seismic model and offshore seismic data (Apulia, Italy)

Gartner

Morsilli

Schlager

et al. 2002

International Journal of Earth Sciences

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Synthetic seismic models of outcrops in the Early Cretaceous slope of a carbonate platform on the Gargano Promontory (southern Italy) were compared to an offshore seismic section south of the Promontory. Outcrops of the same age on the promontory have the same sequence stratigraphic characteristics as their offshore equivalent, and are the only areas where the transition from platform to basin of Early Cretaceous is exposed on land. Two adjacent outcrop areas were combined into one seismic-scale lithologic model with the aid of photo mosaics, measured sections, and biostratigraphic data. Velocity, density, and porosity measurements on spot samples were used to construct the impedance model. Seismic models were generated by vertical incidence and finite difference programs. The results indicate that the reflections in the seismic model are controlled by the impedance contrast between low porous intervals rich in debris from the platform and highly porous intervals of pelagic lime mudstone, nearly devoid of debris. Finite difference seismic display showed best resemblance with the real seismic data, especially by mapping a drowning unconformity

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Finite difference seismic modeling of axial magma chambers

Cited by 11 publications

References 25 publications

The seismic attenuation structure of the East Pacific Rise

The seismic attenuation structure of the East Pacific Rise

Research on the fluid dynamics interaction between submarine sand waves and seawater by seismic oceanography

Toe-of-slope of a Cretaceous carbonate platform in outcrop, seismic model and offshore seismic data (Apulia, Italy)

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