Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2005. / Includes bibliographical references (p. 117-128). / The relatively simple tectonic environment of mid-ocean ridge transform fault (RTF) seismicity provides a unique opportunity for investigation of earthquake and faulting processes. We develop a scaling model that is complete in that all the seismic parameters are related to the RTF tectonic parameters. Laboratory work on the frictional stability of olivine aggregates shows that the depth extent of oceanic faulting is thermally controlled and limited by the 600⁰C isotherm. Slip on RTFs is primarily aseismic, only 15% of the tectonic offset is accommodated by earthquakes. Despite extensive fault areas, few large earthquakes occur on RTFs, and few aftershocks follow the large events. Standard models of seismicity, in which all earthquakes result from the same seismic triggering process, do not describe RTF earthquakes. Instead, large earthquakes appear to be preceded by an extended fault preparation process marked by abundant foreshocks within 1 hour and 15 km of the main- shocks. In our experiments normal force vibrations, such as seismic radiation from nearby earthquakes, can weaken and potentially destabilize steadily creeping faults. / (cont.) Integrating the rheology, geology, and seismicity of RTFs, we develop a synoptic model to better understand the spatial distribution of fault strength and stability and provide insight into slip accommodation on RTFs. / by Margaret S. Boettcher. / Ph.D.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography: leaves 51-58. / by Jeremy D. Duschenes. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982. / Microfiche copy available in Archives and Science / Vita. / Bibliography: leaves 312-321. / by Anne Martine Tréhu. / Ph.D.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Vita. / Bibliography: leaves 158-162. / by David V. Fitterman. / Ph.D.

Thin-skinned models of deformation are currently accepted for the southern Appalachians. The mechanics of this type of deformation are not well understood. The Saltville thrust, a major overthrust in the southern Appalachians, was investigated with respect to deformation mechanics. Thrust termination occurs in the overturned, northwest facing Sinking Creek anticline, at the juncture between the southern and central Appalachians . The primary regional displacement transfer mechanism at the thrust terminus is the transition from faulting to folding. Mesoscopic fabrics show variations in deformation intensity across the anticline, with high strains on the northwest limb, and low strains on the upright southeast limb. Strain accommodation on the overturned limb was by folding, faulting, and cleavage development. Knox Dolomite in the core of the anticline is upward facing and unfolded. Strain patterns and facing data indicate that shear thrusting at depth caused passive regional folding. Subsequent movement caused the thrust to act as a break thrust and cut previously folded strata. Cataclasis is the primary bulk deformation mechanism along the thrust surface. Cataclastic fabrics in dolomites range from protocataclasites to ultracataclasites, and reflect changes in frictional grinding. Foliated cataclasites are described. Fault-rock fabrics indicate that thrust-sheet emplacement occurred through seismic failure, facilitated by transient, abnormally high pore pressures, and aseismic failure accomplished within a layer of cataclastically flowing gouge. Thin fault zones and rapid decreases in deformation intensity away from the fault surface indicate rapid sliding, and a lack of frictional grinding. / M.S.

The Fries fault zone south of Riner, Virginia is marked by a ductile, greenschist-facies thrust that places Middle Proterozoic gneiss over deformed Late Proterozoic(?)—Early Paleozoic rocks of the western Blue Ridge province. This work presents an analysis of the field relationships and finite strain patterns within the fault zone, and further relates these features to an interpretation of its structural framework. A geologic map of the fault zone is provided, in addition to more detailed lithologic descriptions within the text. Noteworthy aspects of the field geology include: (1) the discovery of a reasonable protolith to the mylonitic Little River Gneiss, which could previously only be inferred; and (2) the recognition of a varied lithologic assemblage that is considered to be correlative with the Pilot Gneiss, which is exposed along strike within the Brush Creek anticlinorium. Kinematic analysis of tectonic fabrics within the Little River Gneiss, Pilot Gneiss, and Chilhowee Group suggest that the fault zone developed in response to southeast—northwest shortening, accommodated by general noncoaxial flow, which produced a top-to-the-northwest sense of shear at all scales of observation. However, it is evident that the original stratigraphic anisotropy within the Chilhowee Group effectively partitioned the coaxial and noncoaxial components of strain. Additional finite strain analyses within the Chilhowee Group, including the correlation of R_f/Ø data with quartz c-axis fabrics, indicate that there is considerable variation in the geometry of finite strain along the fault zone. Whereas flattening strains appear to predominate, it is evident that domains of constructional strain and plane strain are localized near the nose of the Brush Creek anticlinorium. These data are considered to support an interpretation in which the Pilot Gneiss and Chilhowee Group were metamorphosed and folded into a doubly-plunging antiform during the Taconic orogeny (ca. 480-435 Ma), and that progressive shortening of the Laurentian continental margin during this interval caused the Little River Gneiss to be uplifted along the Fries fault. The present structural framework of the Fries fault zone south of Riner, Virginia is thus considered to represent a northwest-vergent fold composed of Late Proterozoic—early Paleozoic strata, which is transected by the base of the Little River Gneiss. / Master of Science

A new interpretive slow-varying (long-wavelength) static estimation method is introduced to remove the effects of static anomalies caused by lateral variations in near-surface velocity. The application becomes critical where the wavelength of the variation of statics is larger than the maximum offset between source and receiver (spreadlength) used during data acquisition. The method used in this study utilizes the reflection and refraction arrival times from the shallowest reflector or refractor to determine the statics variations. The study include reprocessing of 12 seismic reflection data sets from the Savannah River Site area, near Aiken, South Carolina. The same data sets were also used to extract the refracted arrivals by the refraction stack processing. Application of the estimated slow-varying statics enhanced the S/N ratio, lateral continuity, and coherency for deep as well as shallow data and allowed to better determine the geometry of faults in the Coastal Plain sediments, which penetrate from the basement. Interpretation of the enhanced seismic reflection and generated seismic refraction sections helped to constrain the depth of upward penetration of the faults imaged in the seismic data. Refraction stack sections were used to obtain better definition of the delineation of the upward penetration of the faults at shallower depths. Despite the smoothing effect that is incorporated in the refraction stacks due to long refracted paths they exhibit clear-cut termination and offset on some of the lines in spatial zones where the Pen Branch fault can be projected in the shallow sediments. The seismic data indicate that the Coastal Plain sediments dip and thicken toward the southeast in the area. The basement top provides a high acoustic impedence contrast, and has a regional dip towards the southeast. The Pen Branch fault is one of the longest faults in the area, that acts as a basin bounding fault separating the Paleozoic crystalline basement from the Triassic basin fill. Other faults such as the Steel Creek and A TT A have also been discerned by the seismic data in the area. Small antithetic faults appear to join the Pen Branch and the A TT A fault. The offset of the Pen Branch fault (15 ms; 32 m) is relatively higher then the offsets observed for the ATTA (11.5 ms; 24.5 m) and Steel Creek (13 ms; 27.5 m) faults. The delineation of the upward depth of penetration of the Pen Branch fault is imaged best on lines 28 and 2EXP where the reflections at 0.18 to 0.2 s exhibit termination with amplitude changes, thereby suggesting the presence of the fault at that level. The offset associated with the A TT A fault can be traced up to 0.16 son line 27. The expression associated with the Steel Creek fault does not seem to go above 0.2 s. On the basis of the result from the interpretation of line 27, the upward depth of penetration of the A TT A fault in the Coastal Plain sediments reaches to a higher level then that of the Pen Branch fault. On the basis of the reflection and refraction data it is interpreted that the reactivation of the Pen Branch and the A TT A fault is as young as the age of the shallow reflector at 200 ms (top of Cretaceous?). / Master of Science

Includes copies of articles co-authored by author during the preparation of this thesis in back pocket. / Includes bibliographical references (leaves 113-124). / viii, 172 leaves : ill. (some col.), maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Focuses on the impact of change in the distribution of heat producing elements on lithospheric thermal regimes and on temperature dependent processes such as metamorphism, magmatism and deformation, with application to Proteozoic Australia (Mount Isa and Mount Painter inliers). / Thesis (Ph.D.)--Adelaide University, Dept. of Geology and Geophysics, 2001

The northeastern Rincon Mountains record a superposed history of low-angle normal-slip shear strain. Moderate- to low-angle faults, mapped previously as Laramide thrust faults, are recognized as normal faults of Tertiary age. Two faults are predominant: a younger-overolder ductile fault forms the base of a metasedimentary carapace, a ductile shear zone (decollement zone) of southwest vergent slip, and an older-over-younger (locally younger-over-older) fault named herein as the San Pedro basal detachment fault forms a brittle shear surface of west-southwest slip. The decollement zone is characterized by passive-slip folding, flexural-flow folding, boudinage, stretched pebbles, and low-angle ductile normal faults. Structural analysis reveals southwest- ergent simple shear strain with a component of superimposed pure shear strain (vertical flattening). The San Pedro basal etachment fault underlies a faulted, distended allochthon. The internal structure of the allochthon is characterized by an imbricate shingling of tilted fault blocks against west-dipping normal faults, suggesting emplacement from the east by an extensional and/or gravitional mechanism. Detachment faulting involved Late Oligocene sedimentary rocks yet cuts ∼26 m.y. old dikes. Mid-Miocene (?) faults form north-trending fault blocks which have rotated rocks of the metamorphic basement and the allochthon eastward. High-angle normal faults of the Basin and Range disturbance form an eastern fault margin across which the northeastern Rincon Mountains have been uplifted. The deformation recorded in the northeastern Rincon Mountains is interpreted to reflect mid-Tertiary crustal extension. Early structural elements define a ductile shear zone which is either truncated or overprinted by a subsequently thinner zone of brittle shear. The shear zone descends stratigraphically westward across the Rincon Mountains. Reconstructions of its mid-Tertiary configuration show the shear zone to be a surface of normal-slip. Displacement near the surface is by brittle shear, but is progressively replaced by ductile shear down-dip. Evolution of the surface superimposes the region of brittle shear against the region of ductile shear. Late Cenozoic block faulting has segmented, tilted, and exhumed the surface.

The Tualatin Valley is a well defined elliptical basin centered at Hillsboro, with a major axis trending roughly N65°W. The valley is bordered on the northeast by the Tualatin Mountains (Portland Hills) which are a faulted, northwest-trending asymmetrical anticline. Topographic and geophysical evidence have defined the Portland Hills fault, which occurs along the northeast side of the Tualatin Mountains. The possibility that a fault or fault zone occurs along the southwest side of the Tualatin Mountains was investigated in this study.