In this study, a paleoseismic trench with limited age constraints that was previously excavated in 1990 across the central Garlock Fault near Christmas Canyon, in Searles Valley, California, was reopened to take advantage of new advances in luminescence dating techniques to investigate potential temporal variability in earthquake recurrence on the Garlock fault and to analyze previously unexposed older earthquake evidence. The trench exposed interbedded alluvial sand and pebble-gravels, with well-sorted, rounded, lacustrine sand from the most recent highstand of pluvial Lake Searles present at the base of the trench. Preliminary findings suggest at least 10 surface rupturing earthquake events occurred during the 10 k.y. time period exposed in the trench. To provide age constraints on the paleo-surface-rupturing events from the new trench, 54 luminescence samples were collected and the single-grain luminescence dating technique post- - was employed. The ages indicated that 7 events have occurred in the past ~7.2 ka, with at least 3 additional events in the more poorly stratified deeper section of the trench. This suggests a recurrence interval of ~1000 years. Event pattern seen at this trench did not exactly replicate the same pattern at other paleoseismic sites along the Garlock Fault. The most recent event seen at this trench occured within the same time period as the most recent events seen at the other paleoseismic sites on the central Garlock Fault.

Mit der Einsicht in den Aufbruch und Realisierung des Logos beschäftigt sich diese Arbeit mit der Architektonik im Anfang der Philosophie bei den Griechen und ihrer Erfüllung in den poietischen und praktischen Wissenschaften des Aristoteles.

Mylonitic rocks of the Shoo Fly Complex form a region of epidote-amphibolite grade quartzose and granitoid gneiss, subordinate schist and calcareous rocks, and rare amphibolite in the foothills of the Sierra Nevada range in central California. The Shoo Fly has endured a complicated Phanerozoic structural development involving seven superposed deformations at variable crustal depths. The first four of these (D1-D4) involved tight to isoclinal folding and shearing under medium grade metamorphic conditions. The last three (D5-D7) are marked by open folding and retrograde metamorphism of older fabric elements. The Shoo Fly is in ductile fault contact with east-dipping argillite, chert, and marble of the Calaveras Complex. The Calaveras-Shoo Fly thrust formed during D3 and is a 1-2 km wide syn-metamorphic ductile shear zone. Recognition of D3 overprinting of older Dl+D2 fabrics along the thrust zone indicates that upper plate Shoo Fly rocks record an earlier and more complex structural history than the lower plate Calaveras rocks. Paleozoic gneissic granitoids, an important lithologic component of the Shoo Fly, were intruded as a series of plutons ranging from calc-alkaline gabbro to granitoid (predominate) to syenite. They truncated the early S1 foliation in the Shoo Fly and were folded during regional D2 and D3 events when they were penetratively deformed into augen gneiss, blastomylonite, and ultramylonite. The Sonora dike swarm occurs as an areally extensive (> 1500 km2) subvertical consanguineous suite of andesite, lamprophyre, and basalt dikes that trend east-west across the Calaveras and Shoo Fly Complexes. The metamorphic complexes form the basement to a middle Jurassic calc-alkaline plutonic arc (Jawbone granitoid sequence). A middle Jurassic K-Ar age on the dikes (157-159 m.y.) together with the data of this report indicate that they are petrogenetically related to the Jawbone granitoid sequence and that the dikes probably formed during subduction beneath a continental arc. The dikes provide an important structural marker in the Shoo Fly and Calaveras Complexes. Intrusion of the dike swarm was sensitive to a structural anisotropy in the basement complexes. Since they intruded east-west along a spaced regional schistosity developed during folding of the Calaveras-Shoo Fly thrust, thrusting and subsequent folding were clearly pre-middle Jurassic events. Available geochronologic data sets middle Ordovician to late Devonian intrusive ages for the gneissic granitoids, establishing a pre-late Devonian depositional age for the Shoo Fly. D1 and intrusion of the orthogneiss protoliths may have been precursors of the Late Devonian to Early Mississippian Antler orogeny or, alternatively, may have occurred significantly earlier than the Antler orogeny. Based on cross-cutting relations, D2 formed during the Antler orogeny, D3 and possibly D4 during the Sonoma orogeny, and D5 and D6 during the Nevadan orogeny.

The Snoqualmie pass area lies about 50 mi (80 km) east of Seattle, Washington, along the crest of the Cascade Range. Five stratified units, forming a composite section over 22,000 ft (6700 m) thick, are recognized in the area. They were deformed and later intruded by granodiorite and quartz monzonite porphyry of the Snoqualmie batholith (middle Miocene). The oldest unit, the Denny Formation (Permian), 7000 ft (2100 m) thick, consists of interstratified basalt, andesite and dacite volcanic rocks and limestone and chert beds. This formation is unconformably overlain by a thick conformable sequence of early Tertiary strata which are subdivided, from oldest to youngest, into the Guye Formation, Mount Catherine Tuff, and Naches Formations (Paleocene to early Oligocene). The Guye Formation, 6500 ft (1980 m) thick, consists of carbonaceous mudstone, quartzofeldspathic siltstone and sandstone, and chert conglomerate. The Mount Catherine Tuff, 900 ft (274 m) thick, consists of interstratified dacitic and rhyolitic crystal-vitric welded tuff. The Naches Formation, more than 6000 ft (1830 m) thick, is composed of carbonaceous mudstone and quartzofeldspathic siltstone and sandstone with interstratified andesitic lava and pyroclastic rock. The Denny Mountain Formation, informally named, 1800 ft (550 m) thick,(Oligocene or early Miocene) overlies the Guye Formation along a major angular unconformity. This unit consists of interstratified dacitic and andesitic tuff, volcanic breccia, and intercalated andesitic lava. The rocks of all stratified formations except the Denny Mountain Formation were deformed at different times before emplacement of the Snoqualmie batholith. During batholithic emplacement, four stages of deformation are recognized: (1) development of an anticline in the Guye, Mount Catherine Tuff, and Naches Formations, (2) break-up of this anticline and downfaulting of limbs with displacements up to 2 mi (3.2 km), (3) uplift of blocks of the Denny Formation and juxtaposition of these with younger formational units, and (4) uplift of additional blocks of the Denny Formation along trends that cut obliquely across stratigraphic contacts and previous structural trends. Intrusion of the Snoqualmie granodiorite and quartz monzonite porphyry into limestone beds of the Denny Formation has formed local deposits of skarn containing principally magnetite and lesser amounts of chalcopyrite.

The Portland Hills fault forms a strong northwest trending lineament along the east side of the Tualatin Mountains. An en echelon lineament follows North Scappoose Creek, Alder Creek, and the Clatskanie River along the same trend, through Columbia County, Oregon. The possibility that this lineament follows a fault or fault zone was investigated in this study. Geophysical methods were used, with seismic refraction, magnetic and gravity lines run perpendicular to the lineament. The seismic refraction models indicate the near surface basalt is broken in many places, with 15 - 30 meters (50 - 100 feet) vertical displacement, down to the west, at Bunker Hill along the Alder Creek fault. Gravity models required a faulted zone approximately two kilometers wide across the lineament. The proposed fault zone is more clearly defined in the south, becoming more diffuse and branching in the northern part of the study area. The Bouguer gravity values from this study distort the -40 milligal contour farther to the northwest than is shown on the Complete Bouguer Gravity Anomaly Map of Oregon {Berg and Thiruvathukal, 1967b). The existence of sharp topographic features and the geophysical evidence indicate fault activity along the zone.

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In this thesis, I analyze seismic signals collected during two passive-source broadband seismic deployments that instrumented tectonic boundaries with opposing plate motion—the heavily sedimented forearc of the obliquely convergent Indo-Burman subduction zone and the Malawi rift of the divergent East African rift system—as part of the BIMA and SEGMeNT experiments. These two settings provide unprecedented opportunities to broaden the extent of our understanding of tectonic processes and linkages between atmosphere-to-solid earth seismic coupling, respectively. The Indo-Burman forearc represents an extreme endmember system for sedimentary accretion underneath Earth’s largest delta, while the Malawi rift contains one of the widest and deepest freshwater bodies and one of the first to be instrumented by a seismic array from lake bottom to lake shore. Collectively, this work represents a diverse set of seismic observations that improve our understanding of environmental and tectonic systems across a range of scales, from oblique convergence under heavy sedimentation to energy transfer between the atmosphere and the solid earth. Using the BIMA dataset, we investigate the seismic shear-velocity structure across the extensive sediment blanket, crust, and uppermost mantle of the Indo-Burman forearc margin to robustly constrain subsurface structure and lithology. We construct a comprehensive three- dimensional survey of seismic shear velocity across the region using a joint-inversion of surface- and scattered-wave constraints that explicitly parameterizes key boundary layers. We extract measurements of Rayleigh-wave phase velocities from (1) interstation Rayleigh wavefields produced from the cross-correlation and spectral waveform fitting of ambient seismic noise between 12-25 s period and (2) intra-array Rayleigh-wave phase variations form regional and teleseismic earthquakes propagating across the array between 20-80 s period, in order to constrain absolute shear velocities throughout the model. To constrain the depths to and amplitudes of significant velocity interfaces, we also develop a generalized-Radon-transform migration image across the array and incorporate the resulting scattered-wave measurements into the joint inversion. Together, these measurements complement each other’s individual limitations and allow for a comprehensive modeling analysis. Overall, the Bengal basin appears markedly slower than other heavily sedimented basins observed globally. East-west dispersion variations highlight a deepening slow structure to the east, which suggests a basin geometry primarily controlled by a down-dipping slab interface as opposed to central basin loading. Scattered-wave imaging captures three important interfaces in the velocity architecture underlying the region. Within the joint-inversion modeling, we observe two model classes that emblemize the evolution of consolidation and stress state within the uppermost sediments and metasediments along a predominantly northeast-southwest trend. We interpret variations in deeper seismic structure under two proposed scenarios: (1) a Moho at ~21-26 km underlying a package of metasediments and a thin oceanic crust, with a slow mantle lithosphere that may contain retained melt from the onset of India-Antarctica seafloor spreading; or (2) a Moho at ~50-59 km underlying a package of metasediments and a thick slug of mafic material, which may correspond to significant underplating from the Kerguelen hotspot at the time of creation of the subducting crust. These findings improve our understanding of sediment evolution and tectonic architecture across the Indo-Burman forearc margin. Using the amphibious SEGMeNT data at Lake Malawi, we explore variations in the spectral character of lake-generated microseisms to investigate the dominant parameters controlling seismic coupling between water and the solid earth. We document clear evidence for two spectral peaks in the lake microseism band, and relate variations in spectral behavior as a function of recording depth and proximity to steep lake-floor slopes and shorelines to suggest that these spectral bands may correspond to single- and double-frequency generation processes, akin to primary and secondary ocean microseisms. Some observations are otherwise complex and inconsistent with traditional microseism theory, indicating that signals may alternatively reflect interactions between differing source regions within separate basins of the lake under exclusively double-frequency generation processes, an ambiguity that might have been resolved with the availability of colocated wind and wave-state data sets. This dissertation work highlights the value of array-based seismic deployments and the incorporation of complementary data types for exploring the detailed structure and evolution of systems, especially in high-noise settings.