A study of the seismic structure of upper oceanic crust using wide-angle reflections
Rohr, Kristin Marie Michener
MetadataShow full item record
LocationWestern North Atlantic Ocean
The lateral homogeneity of oceanic crust on the scale of a seismic experiment is a condition that most methods of seismic interpretation depend on. Whether this condition is in fact true is largely unknown and only recently have efforts been made to test this hypothesis. This thesis is part of that effort and is focussed on determining with as much resolution as possible the seismic structure of upper oceanic crust, i.e. Layer 1 and the uppermost part of Layer 2. This portion of the crust is of interest, because of the effect of the sediment-basement interface on the transmission and conversion of seismic energy, also because of the possibility of detecting lateral heterogeneities in upper Layer 2 caused by faulting, hydrothermal circulation etc. The data employed are a set of wide-angle reflections from oceanic crust 130 m.y. old in the western North Atlantic Ocean southwest of Bermuda. First, the sedimentary structure is determined by stacking the data along hyperbolae and interpreting the stacking velocities and two-way normal incidence travel-times for interval velocities. This method has not been applied to deep sea marine data before; it gives a more detailed velocity structure of the sediments than does a traditional study of the basement reflections' travel-times. Second, the same data are mapped into tau-p space in order to measure the velocity gradient in oceanic basement; unfortunately the scatter in the tau-p picks caused by the topography of the basement reflector combine with the properties of the tau-sum inversion to make such a measurement impossible. Third, the amplitudes of the basement reflections observed on three seismic lines are modelled by synthetic seismograms; each can be matched by velocity-depth models which contain a transition zone between the sediments and the basement. The different thicknesses of this transition zone near the three receivers is an indication that the top few hundred meters of Layer 2 are laterally heterogeneous on a scale of 3 to 8 km.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution January 1983
Showing items related by title, author, creator and subject.
Understanding the ocean carbon and sulfur cycles in the context of a variable ocean : a study of anthropogenic carbon storage and dimethylsulfide production in the Atlantic Ocean Levine, Naomi M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-02)Anthropogenic activity is rapidly changing the global climate through the emission of carbon dioxide. Ocean carbon and sulfur cycles have the potential to impact global climate directly and through feedback loops. Numerical ...
Oceanic lithosphere magnetization : marine magnetic investigations of crustal accretion and tectonic processes in mid-ocean ridge environments Williams, Clare M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-09)The origin of symmetric alternating magnetic polarity stripes on the seafloor is investigated in two marine environments; along the ridge axis of the fast spreading East Pacific Rise (EPR) (9º 25’-9º 55’N) and at Kane ...
A study of ocean wave statistical properties using nonlinear, directional, phase-resolved ocean wave-field simulations Henry, Legena Albertha (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-02)In the present work, we study the statistics of wavefields obtained from non-linear phase-resolved simulations. The numerical model used to generate the waves models wave-wave interactions based on the fully non-linear ...