The "Rides Prerifaines" of northern Morocco represent an unusual type of inversion that inverts only the sedimentary fill of a complex Triassic-lower Jurassic half-graben system, without significantly involving the underlying basement. Frontal and lateral ramp anticlines form over underlying Triassic-lower Jurassic east-west and southwest-northeast trending extensional faults. The Upper Miocene-Pliocene deformation of the Rides Prerifaines follows the emplacement of the large accretionary wedge of the Nappe Prerifaine deformation which occurred earlier i.e., during the Tortonian-Messinian interval. Significant structures that underlie the Neogene Guercif basin are Upper Cretaceous-Eocene basement-involved partial inversions of Jurassic half-grabens. The overlying Neogene Guercif basin begins with some Tortonian transtensional normal faulting that is followed by late Neogene compression. The overall northward thickening of the Neogene Guercif, Saiss and Rharb foredeep is typical for the flexural loading by the Prerifaine accretionary wedge and the overlying Neogene basin fill.

Finite Element modeling of thrust faulting shows that the faults will propagate upward at very low angles from the leading edge of a regional horizontal decollement surface located at various depths in a homogeneous block of crustal material. The angles are consistent with Mode II crack propagation in Linear Elastic Fracture Mechanics and the relationship of stress trajectory and failure in the classic theory of shear fracture. Shallow faults will propagate at a steeper angle than deeper ones. The coefficient of friction does not affect the fault angle, though it probably affects the likelihood of Mode II deformation.

The Maldive Ridge is a volcanic lineament overlain by locally 3.3 km of mostly shallow-water carbonate sediments. The Maldive basement appears on seismic profiles as a volcanic plateau generated during two distinct eruptive phases separated by an episode of tectonic deformation. This deformation created a series of en-echelon pull-apart structures along the ridge acoustic basement and can be related to intraplate compression following the initial stages of the India-Asia collision. The deformation possibly triggered the extrusion of the basaltic flows overlying the acoustic basement and constituting the lithologic basement of the Maldive carbonate system. Widespread neritic carbonate sedimentation was initiated during the Eocene when the broad and relatively flat volcanic substrate started sinking below sea level. In spite of the lava flow extrusion, the initial depressions corresponding to the structural pull-apart basins remained as deep internal seaways surrounded by reefal margins until the late Oligocene. The Eocene-Early Oligocene depositional signature remained essentially aggradational and corresponds to a first transgressive cycle associated with a second-order sea-level rise. In the mid-Oligocene, a pronounced sea-level fall matching the development of a major ice sheet in Antarctica restricted the sedimentation to the internal basins. During the following transgression, the neritic carbonate system temporarily kept up with the sea-level rise, but was finally drowned near the Oligocene-Miocene boundary. In the early Miocene, pelagic ooze deposition covered the Paleogene neritic system and transformed the central troughs into one single deep basin, the paleo-Inner Sea. During the Neogene, following the establishment of a reef framework near the present location of the platform edge, systematic progradations of carbonate bank margins toward the central Inner Sea basin correspond to a long-term sea-level fall associated with a second-order regressive cycle. Segmentation of the prograding complex into individual carbonate banks occurred through local channeling and drowning events. Finally, the late Pliocene-Pleistocene depositional signature is mainly aggradational and corresponds to a regional modification from flat-topped carbonate banks to atoll physiographies. The onset of high-frequency eustatic and climatic changes following the initiation of Northern Hemisphere glaciation explains this evolution.

Approximately 3000 km of high and intermediate resolution seismic data and 117 sediment cores were examined to reconstruct the late Cenozoic glacial history of Bransfield Basin, Antarctica. The complexity of a glacial setting requires seismic data with vertical resolutions of 20-30 m to adequately image the depositional environments. This study demonstrates the utility of higher resolution seismic records to develop a complete understanding of the complicated nature of glacial environments. Lower resolution data, while appropriate for studying larger-scale features, lack necessary detail and can lead to over-simplified models. Investigation of the seismic facies resulted in characterization and mapping of glacial sub-environments leading to the construction of a subpolar depositional model for glacial-interglacial cycles. In addition, these results help constrain Pleistocene climatic conditions. As seismic facies analysis indicates no significant meltwater activity, it is suggested that temperate deglacial-interglacial conditions did not exist in Bransfield Basin during the time interval studied (Pleistocene? to present). Another outcome of this study was a 13,000-14,000 yr BP minimum age for the end of the last significant glacial period with $>$800 m of ice grounded in $>$600 m of water. Examination of the data and application of the depositional model led to identification of key sites for shallow and deep drilling to further resolve questions of timing and paleoclimate.

The identification of the source signature is a major calibration problem in reflection seismology. Conventional approaches to this problem involve statistical methods, direct measurement of the source, or the location of a clean reflection in the seismic section. As an alternative, we investigate the possibility of recovering the source and velocity from the data by means of nonlinear least squares. We model the earth as a linearly acoustic layered fluid. The problem of recovering the source and velocity then becomes that of identifying a boundary term and a velocity coefficient in an initial-boundary-value problem for the one-dimensional wave operator. We examine two formulations of the source-velocity identification problem in terms of nonlinear least squares. The first of these is output least squares, which in recent years has received attention as a method for velocity inversion. One question which heretofore has gone unanswered is that of the differentiability of the impulse response forward map, which relates the sound velocity and the seismogram in the case that the source is an impulse $\delta(t)$. The resolution of this issue is our first major result. We prove that the forward map will be differentiable at a velocity $c$ provided $c$ has three derivatives in $L\sp2$. Moreover, this result is optimal. Using this regularity theorem and a result due to Bube, Lailly, Sacks, Santosa, and Symes, we then prove a local uniqueness result for the output least squares source-velocity identification problem. We assume that the source is quasi-impulsive; i.e., the source $f$ has the form $f = \delta + h$, where $h \in L\sp2$. We show that locally the source and velocity are uniquely determined by boundary measurements. Recent research has shown that for a number of reasons, the output least squares approach is unsuitable for numerical computation. Moreover, realistic source models and seismograms are band-limited, so that results concerning quasi-impulsive sources have no immediate practical consequences. Thus, we will also examine the source-velocity problem in the setting of coherency optimization, an alternative to output least squares proposed by Symes. We will present a result which indicates that we should be able to stably recover band-limited components of the source and velocity.

The nature of the basement underneath the Monagas foothills and the Serrania del Interior of the Eastern Venezuela Basin is unknown. It could consist of crystalline Precambrian, Paleozoic sedimentary rocks and/or Jurassic rocks deposited in half grabens. Alternative structural interpretations across the Monagas foothills range from basement-involved to non-basement-involved decollement tectonics. These hypotheses imply varying amounts of shortening along the Serrania to Foreland transect ranging from 15 to 115 km oblique component of the El Pilar fault. The foreland-verging thrust system appears to be "in sequence". In the Monagas foothills earlier decollements at the base of the Miocene are responsible for the formation of a complex accretionary wedge. The deeper structures of the Monagas foothills involve the Mesozoic which was thrusted following the emplacement of the Carapita accretionary wedge. Apparent "out of sequence" are due to the interference of late deeper structures with the earlier structures of the accretionary wedge.

An automatic geostatistical method of analyzing spatial characteristics of topography is presented. Anisotropy in spatial continuity is modeled by estimating the range of the directional semivariograms. Spatial characteristics of topography are defined by orientation of the semi-major axis, length of the semi-major axis and length of the semi-minor axis of the anisotropy model ellipse. Orientation of the ellipse gives the average orientation of the linear features. Aspect ratio of the ellipse estimates the degree of lineation of features. Area of the ellipse determines the roughness of the topography. The automatic geostatistical topography characterization method was applied to land topography from Western US and sea-floor topography from the Ross sea, Antarctica. The method was able to characterize the spatial patterns of topography from Western US. The method was used to separate highly lineated regions on the Antarctic sea floor from areas with less prominent or no lineations.

We use a thin viscous sheet model to interpret the observed shortening along a seismic reflection profile collected on the Phedre cruise (on the deforming oceanic lithosphere in the central Indian Ocean). We determine the 95% confidence region of the 1/e fall-off distance of strain rate to be between 7.1° and 20.4°, the vertically averaged power-law exponent to be between 1.6 and 18.5, and the ratio of the strength of the upper lithosphere to the lower lithosphere to be between 1 and 5.5. We calculate a simplified strength envelope of a two layered oceanic lithosphere based on the lower lithosphere deforming in accordance with the Dorn equation. This model estimates a range of between 0.2 and 20 TN m-1 for the strength of the oceanic lithosphere. The ratio of the strength of the upper lithosphere with respect to the lower lithosphere ranges between 8.6 and 13.98.

Sequences are recognized throughout the geologic record. The Angolan margin provides an excellent opportunity to examine the factors that control the deposition and preservation of sediments in sequences, as well as the factors that create the erosion or non-deposition along sequence boundaries. The Angolan sequences can be compared to global sequence charts and used to investigate the effects of local events versus global events on the area's sequences. Using seismic sequence stratigraphic principles, a 2D regional seismic data set covering three basins offshore Angola, the Lower Congo, Kwanza, and Benguela Basins, was interpreted. Sequences and their unconformities were correlated within each basin as well as between basins. Major sequences could be interpreted throughout and between the three basins with a high degree of confidence. Additional sequences within these major sequences were interpreted within a basin, but could not be correlated to the adjacent basin with a high degree of confidence. Detailed interpretation of the sequence stratigraphic significance of each reflector was performed on three profiles, one for each basin. Chronostratigraphic charts were constructed using the detailed interpretation of the profiles. Within the interpreted sequence stratigraphic framework, the timing and mechanics of the formation of salt structures was examined. The Angolan basins contain a variety of salt tectonic features. The reflectors of strata adjacent to the salt features were used to determine the timing and mechanics of the salt structure formation. This study accomplished several objectives. The tectonic evolution of the Angolan margin was reviewed. This study established a sequence stratigraphic framework for Angola. The process of deposition and preservation of sediments as depositional sequences was examined. The sequences were compared with the global sequence charts as well as with eustatic, tectonic, and oceanic circulation events. The formation of the sequence bounding unconformities was examined. Within the sequences, the interaction of sedimentation and salt movement was described.

The lower Cretaceous King Lear Formation (KLF) is a gently east-dipping succession of alluvial conglomerates and sandstones that were deposited in a small intra-arc basin. Supracrustal strata of Cretaceous age from within the western U.S. magmatic arc are extremely rare, so the KLF offers an opportunity to obtain paleoenvironmental information about the Cretaceous arc. A new division of the KLF into three members based on clast provenance provides a framework for understanding deposition in the King Lear Basin and thus is essential for paleoenvironmental studies on this portion of the arc. New structural observations and a shallow reflection seismic profile suggest that the KLF was deposited in a half-graben and never experienced compressive deformation. This conclusion means that compressive deformation both in the Jackson Mountains and also in the crustal-scale Luning-Fencemaker Fold and Thrust Belt must have been complete prior to the Early Cretaceous.