Abstract:
This thesis consists of three papers applying the techniques of
time series analysis to geophysical data. Surface wave dispersion
along the Walvis Ridge, South Atlantic Ocean, is obtained by bandpass
filtering the recorded seismogram in the frequency domain. The group
velocity is anomalously low in the period range of 15-50 s, and formal
inversion of the data indicates both crustal thickening to 12.5 km
and low shear velocity (4.25-4.35 km/s) to depths of 40-50 km. The
electromagnetic induction fields at a deep ocean site northeast of
Hawaii were used to determine the electrical conductivity of the earth
to 400 km depth. Singular value decomposition of the data matrix
indicates three degrees of freedom, suggesting source field complications
and a two dimensional conductive structure. Inversion of one of the
principal terms in the response function shows an abrupt rise in
electrical conductivity to 0.05 mho/m near 160 km with no resolvable
decrease below this. A model study suggests that moving source fields
influence the induction appreciably in the other principal response
tunction. A set of piston cores from the northeast Atlantic Ocean are
used to construct paleomagnetic time series covering the interval 25-127 kybp. Stratigraphic control is provided by counts of planktonic
toraminifera, and empirical orthogonal function analysis shows a
significant decrease in sedimentation rate at the interglaciai/glacial
transition. The sediments are magnetically stable and reliable relative
paleointensity measurements could be obtained. Spectral analysis of
the directions reveals a predominant 10 ky periodicity and no dominant
looping direction.
