A deep source-receiver seismic refraction experiment was conducted
on the upper part of the Monterey Deep Sea Fan. The aim of this thesis is
to construct the velocity structure of the upper Monterey Fan and to examine
the lateral seismic velocity variations among the upper, middle and lower
fan subunits. Using primary waves and whispering gallery phases (the
multiply-reflected refraction waves), the sediment velocity structure was
modeled by the tau-zeta travel time inversion process. The changes in
velocity gradients with depth of the upper Monterey Fan are
morphologically similar to that found on both the Central Bengal Fan and
the Nicobar Fan, an abandoned lower fan of the Bengal Fan Complex. The
velocity gradient of the upper Monterey Fan at depth, 0.59 s⁻¹ is
significantly lower than both the middle Bengal Fan (0.68 s⁻¹) and the
Nicobar Fan (0.81 s⁻¹). The upper fan subunit, which is closer to its
sediment source, is characterized by higher porosities caused primarily by
a higher sedimentation rate than the lower fan subunits. Since seismic
velocity is inversely related to porosity, the upper fan subunit should have
lower velocity gradients and seismic velocities than the other fan subunits.
If porosity and velocity variations exist, then these variations can be used to
constrain various models of deep sea fan formation. No definite conclusion
can be drawn at this time due to a fault within 1 km of the Nicobar Fan site;
however, a systematic velocity variation pattern of deep sea fans is
revealed.
Some portions of the Monterey Fan data contain refracted waves
which have bottomed within the underlying acoustic basement structure.
The entire velocity structure was solved by both the general and the
"stripping" solving schemes. The results of basement structure show a
velocity ranging from 3.4 to 5.8 km/s indicating that the uppermost part may
be pre-existing continental rise sediments. / Graduation date: 1986
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29229 |
| Date | 10 January 1986 |
| Creators | Dwan, Shufa F. |
| Contributors | Jacobson, R. S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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