Extensive new trackline coverage of the Chile Trench between 23°S and 34°S, including more than 60 bathymetric and seismic reflection profiles across the trench axis, allows a much more detailed study of the tectonics and sedimentation of this feature than previously possible. Sediment distribution along the axis shows a remarkable...
The Nanga Parbat-Haramosh massif (NPHM) is a north-south trending
structural and topographic high, which interrupts the east-west trend
of the Himalaya in northern Pakistan. Previously, the massif was
thought to be bounded by the Main Mantle thrust (MMT), a north-dipping
thrust along which the Kohistan-Ladakh arc was thrust south over...
The collision of the Indian subcontinent with Asia beginning 40 million years ago
produced the Himalayan orogenic belt, the largest continental collision belt active today. The foreland fold-and-thrust belt in northern Pakistan consists of the Salt Range-Potwar Plateau area. In this region the distance from the Main Boundary Thrust(MBT) to...
Gravity data along a N-S profile from Kohistan to the Punjab plain of Pakistan
have been incorporated into recent interpretation of the gross structure of the foreland
fold and thrust belt of the Himalaya. In northern Pakistan large deviations from Airy
Isostatic equilibrium are observed. An excess of mass characterizes...
Surface-geology, oil-well, seismic-reflection, and magnetostratigraphic data are
integrated to evaluate structural style and shortening rate at the Himalayan front (Sub-Himalaya) of northwest India. The Sub-Himalaya, between the Main Boundary thrust
and the Himalayan Frontal fault, is the actively deforming front of the Himalaya. At
certain locations, the Himalayan Frontal fault...
The geology of Oregon has become a jigsaw puzzle of moving parts set on a foundation of changing conditions as the crust and mantle undergo successively different manners of deformation through time. As more megahypotheses arise from increasingly sophisticated views of plate tectonics and from more detailed analyses of synoptic...
The plate tectonic history of Oregon is but one piece of a worldwide jigsaw puzzle encompassing much of geologic time. With the splitting of Pangaea in Mesozoic times, Oregon has occupied the leading edge of the North American Plate as it has impinged upon the ancestral oceanic East Pacific Plate....
High seismic activity occurs along the Caribbean and the North
American Plate boundary beneath the eastern part of Hispaniola. A
large number of intermediate to deep earthquakes are clustered between
the Puerto Rico Trench to the north and the Muertos Trench to the
south suggesting the possibility of concurrent subduction...
At collisional mountain ranges the tectonic history of crustal shortening and
subsequent post-collisional erosion is preserved in the form of the presently observed
gravity anomalies. In this study, models of erosion and isostatic rebound at various stages
of collision illustrate the evolution of crustal structure, topography, and resulting gravity
anomalies....
Elliptical borehole enlargements or "breakouts" caused by systematic spalling of a
borehole wall due to regional maximum horizontal stresses were identified in 18 wells
drilled in the Coast Range and Willamette Valley of western Oregon. The breakouts
generally indicate a NNW to NNE orientation of maximum horizontal compression
(oH[subscript max])...
Two examples of Pacific rim plate boundary deformation are presented. In the first
part of the thesis crustal models are derived for the northwestern part of the Vizcaino
block in California using marine seismic and gravity data collected by the Mendocino
Triple Junction Seismic Experiment. A northwest-southeast trending kink in...
This thesis presents elastic finite difference simulations of two dimensional wavefield propagation for line-9, recorded during the 1993 part of the multi-institutional, multi-year Mendocino Triple Junction (MTJ) Seismic Experiment. Line-9 is a high-resolution, large-aperture seismic profile oriented in north-south direction, extending from the subduction regime north of the MTJ to...
Anomaly timescales for the last 90 million years, derived from
marine magnetic profiles and published prior to mid-1979, are summarized,
illustrated for comparison, and critically reviewed. A revised timescale
is constructed using calibration points which fix the ages of anomalies
2.3', 5.5, 24, and 29. An equation is presented for...
During the Cenozoic, tectonics in the Cuyama basin of the southeastern Salinian block changed from extension to strike-slip faulting to compression and rotation. During the Oligocene-early Miocene, the Cuyama basin was adjacent to the southern Mojave region and part of that extensional tectonic regime. Many present-day reverse faults have an...
Plate boundaries are commonly regions of complex, diffuse deformation with
the motion across the boundary accommodated by numerous structural systems, rather
than being narrow, discrete zones of deformation. One such boundary occurs where
the North American plate makes contact with Juan de Fuca, Gorda, and Pacific plates
along the west...