Download or read book New Insights Into North America Pacific Plate Boundary Deformation from Lake Tahoe Salton Sea and Southern Baja California written by Daniel Stephen Brothers and published by . This book was released on 2009 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Five studies along the Pacific- North America (PA-NA) plate boundary offer new insights into continental margin processes, the development of the PA-NA tectonic margin and regional earthquake hazards. This research is based on the collection and analysis of several new marine geophysical and geological datasets. Two studies used seismic CHIRP surveys and sediment coring in Fallen Leaf Lake (FLL) and Lake Tahoe to constrain tectonic and geomorphic processes in the lakes, but also the slip-rate and earthquake history along the West Tahoe-Dollar Point Fault. CHIRP profiles image vertically offset and folded strata that record deformation associated with the most recent event (MRE). Radiocarbon dating of organic material extracted from piston cores constrain the age of the MRE to be between 4.1-4.5 k.y. B.P. Offset of Tioga aged glacial deposits yield a slip rate of 0.4-0.8 mm/yr. An ancillary study in FLL determined that submerged, in situ pine trees that date to between 900-1250 AD are related to a medieval megadrought in the Lake Tahoe Basin. The timing and severity of this event match medieval megadroughts observed in the western United States and in Europe. CHIRP profiles acquired in the Salton Sea, California provide new insights into the processes that control pull-apart basin development and earthquake hazards along the southernmost San Andreas Fault. Differential subsidence (>10 mm/yr) in the southern sea suggests the existence of northwest-dipping basin-bounding faults near the southern shoreline. In contrast to previous models, the rapid subsidence and fault architecture observed in the southern part of the sea are consistent with experimental models for pull-apart basins. Geophysical surveys imaged more than 15 ~N15°E oriented faults, some of which have produced up to 10 events in the last 2-3 kyr. Potentially 2 of the last 5 events on the southern San Andreas Fault (SAF) were synchronous with rupture on offshore faults, but it appears that ruptures on three offshore faults are synchronous with Colorado River diversions into the basin. The final study was used coincident wide-angle seismic refraction and multichannel seismic reflection surveys that spanned the width of the of the southern Baja California (BC) Peninsula. The data provide insight into the spatial and temporal evolution of the BC microplate capture by the Pacific Plate. Seismic reflection profiles constrain the upper crustal structure and deformation history along fault zone on the western Baja margin and in the Gulf of California. Stratal divergence in two transtensional basins along the Magdalena Shelf records the onset of extension across the Tosco-Abreojos and Santa Margarita faults. We define an upper bound of 12 Ma on the age of the pre-rift sediments and an age of ~8 Ma for the onset of extension. Tomographic imaging reveals a very heterogeneous upper crust and a narrow, high velocity zone that extends ~40 km east of the paleotrench and is interpreted to be remnant oceanic crust.
Download or read book New Insights Into Strain Accumulation and Release in the Central and Northern Walker Lane Pacific North American Plate Boundary California and Nevada USA written by Jayne Margret Bormann and published by . This book was released on 2013 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Walker Lane is a 100 km-wide distributed zone of complex transtensional faulting that flanks the eastern margin of the Sierra Nevada. Up to 25% of the total Pacific-North American relative right-lateral plate boundary deformation is accommodated east of the Sierra Nevada, primarily in the Walker Lane. The results of three studies in the Central and Northern Walker Lane offer new insights into how constantly accumulating plate boundary shear strain is released on faults in the Walker Lane and regional earthquake hazards. This research is based on the collection and analysis of new of geologic and geodetic datasets. Two studies are located in the Central Walker Lane, where plate boundary deformation is accommodated on northwest trending right-lateral faults, east-northeast trending left-lateral faults, and north trending normal faults. In this region, a prominent set of left-stepping, en-echelon, normal fault-bounded basins between Walker Lake and Lake Tahoe fill a gap in Walker Lane strike slip faults. Determining how these basins accommodate shear strain is a primary goal of this research. Paleoseismic and neotectonic observations from the Wassuk Range fault zone in the Walker Lake basin record evidence for at least 3 Holocene surface rupturing earthquakes and Holocene/late Pleistocene vertical slip rates between 0.4-0.7 mm/yr on the normal fault, but record no evidence of right-lateral slip along the rangefront fault. A complementary study presents new GPS velocity data that measures present-day deformation across the Central Walker Lane and infers fault slip and block rotation rates using an elastic block model. The model results show a clear partitioning between distinct zones of strain accommodation characterized by (1) right-lateral translation of blocks on northwest trending faults, (2) left-lateral slip and clockwise block rotations between east and northeast trending faults, and (3) right-lateral oblique normal slip with minor clockwise block rotations on north trending faults. Block model results show that a component of right-lateral slip in the normal-fault bounded basins is required to adequately fit the GPS data. New GPS data from the Northern Walker Lane constrains present-day slip rates on the Mohawk Valley, Grizzly Valley, and Honey Lake fault zones. Block model results predict right-lateral slip rates of 2.2 ± 0.2 mm/yr for the Mohawk Valley fault and 1.1 ± 0.4 mm/yr for the Honey Lake fault. The GPS data do not require slip on the Grizzly Valley fault, although right-lateral slip rates up to 1.2 mm/yr are allowed without increasing the block model misfit. The present-day distribution of slip between the Honey Lake and Mohawk Valley faults is opposite that predicted by latest Quaternary and Holocene geologic slip rate estimates. A temporally variable Wallace-type strain release model that includes 104-year timescale variations in fault slip rate could reconcile both datasets.
Download or read book New Constraints on Strain Partitioning Across Southern California s Diffuse Plate Boundary written by Boe Jay Derosier and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geologic observations provide an important lens to objectively view the natural world and contextualize the processes that have and continue to shape Earth's brittle crust. As a result, many geologic and geophysical tools have been developed. This dissertation uses high-resolution sub-bottom and multi-channel seismic data to observe sequence stratigraphic and morphologic signatures of deformation encoded into Southern California and its offshore component, the California Continental Borderland (CCB). Using geophysical tools, this dissertation first investigates the vertical displacement history of the Inner California Borderland (ICB) using marine terraces. By Imaging marine terraces with sub-bottom profilers offshore San Clemente and Santa Catalina Islands and contextualizing them with legacy on and offshore data, it is possible to extend our current Quaternary understanding of the vertical displacement history of the ICB through to the Middle Miocene. In addition, this model provides a framework for the formation of disputed marine terraces observed at depths deeper than the Last Glacial Maximum (LGM). Second, I conducted a seismic stratigraphic analysis of the Catalina Basin, one of the many basins that make up the ICB, to constrain the late Cenozoic evolution of the region and put into context basin-wide markers of historic relative sea level with regional geology. Third, this dissertation outlines the use of the Kongsberg SBP 29, recently installed on the R/V Sally Ride in June of 2021, to image and characterize active deformation within the Outer California Borderland (OCB). The OCB, a relatively under-surveyed region within the CCB, has not been widely recognized as accommodating active deformation. Interpretation of the high-resolution sub-bottom data is constrained by proximal Ocean Drilling Project cores. As a result, it is possible confidently report that the Ferrelo Fault has been active within the last 1,000 years, accommodating Pacific/North American relative strain. Lastly, the novel use of a sub-bottom profiler is employed, typically a marine and or lacustrine instrument, to image onshore deformation along an unlined section of the All-American Canal. This survey images deformation within the Imperial Valley, along the Imperial, Dixieland, and Michoacán Faults, in an area where anthropogenic activity has otherwise made direct observations of surface deformation difficult.
Download or read book Investigating Crustal Deformation Associated With The North America Pacific Plate Boundary In Southern California With GPS Geodesy written by Joshua C. Spinler and published by . This book was released on 2014 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Geophysical Approaches to Study Neotectonics and Associated Geohazards written by Jeffrey Andrew Dingler and published by . This book was released on 2007 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-resolution measurements of earthquake and submarine landslide geomorphology were collected in three different environments along the actively deforming Pacific - North American plate boundary. These four research projects use high-resolution imaging devices and 3D visualization to present new insights into past and future geohazards. Seismic CHIRP imaging with sub-meter accuracy, together with detailed multi-beam and LIDAR derived bathymetry were used to measure fault offset, earthquake derived colluvial wedges, wave-cut paleo-terraces, and other geomorphic subbottom features in the Lake Tahoe Basin. Analysis of these features provides revised and improved extension rates, as well as new information on Holocene faulting. Such an understanding of the deformation has helped place the Tahoe Basin into the larger context of Walker Lane tectonics. The combined east-west extension rate across Lake Tahoe Basin is 0.53 - 1.15 mm/yr. Empirical fault displacement length scaling relationships suggest the Incline Village Fault (IVF) may have ruptured in conjunction with either the Stateline - North Tahoe Fault (SNTF) to the southwest, or faults farther to the north. Assuming the IVF ruptures in concert with the SNTF with a vertical displacement of 3 m and a rupture length of ~35 km, it would generate a Mw 6.9 " 0.7 earthquake. High-resolution CHIRP data acquired in the northern Santa Barbara Basin, California provide new insights into the processes that control shallow submarine landslides. Rills formed on the slope by off shelf gravity flows appear to introduce sediment heterogeneity, which may inhibit the development of high pore pressure and thus, limit the occurrence and size of surficial failures. Furthermore, failures in this region are characterized by short run out distances indicative of low velocities and therefore pose little tsunamigenic hazard. Terrestrial laser scanner data acquired from Mecca Hills, California provides improved constraints on fault offsets and paleoearthquake magnitudes for the southern San Andreas Fault. A comprehensive 3D data set of 22 overlapping terrestrial laser scans allows quantitative geomorphology measurements at an unprecedented resolution along an ~250 m segment of the fault. Our measured slip rate of 15.6 " 1.9 mm/yr, based on 5.1 m of surface offset since the most recent earthquake (MRE), falls squarely in the middle of our calculated long-term Holocene slip rate of 14-20 mm/yr. Our measured rates approach those calculated by modern geodetic methods and suggest that discrepancies between geologic and geodetic rates may decrease with increased survey resolution. These slip rates combined with the long modern ~325 yr quiescent period, implies a future rupture would exhibit 5.3 - 7.0 m of coseismic offset at the surface.
Download or read book Plate Boundary Deformation of the Pacific Plate written by Beate Leitner and published by . This book was released on 1999 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 the Moho is imaged and interpreted to have formed under compression by reactivation of preexisting thrust faults in the paleoaccretionary prism at the seaward margin of the Vizcaino block. The study suggests that the deformation resulted from mainly north-south compression between the Pacific-Juan de Fuca plates across the Mendocino transform fault and predates late Pliocene Pacific-North America plate convergence. In the second part, 195 earthquakes recorded during the duration of the Southern Alps Passive Seismic Experiment (SAPSE) are analysed. Precise earthquake locations and focal mechanisms provide unprecedented detail of the seismotectonics in the central South Island. The short term (6 month) SAPSE seismicity is compared with long term (8 years) seismicity recorded by the New Zealand National Seismic network and the Lake Pukaki network. The seismicity rate of the Alpine fault is low, but comparable to locked sections of the San Andreas fault, with large earthquakes expected. Changes of the depth of the seismogenic zone, generally uniform at about 10-12 km, occur only localised over distances smaller than 30 km, suggesting that thermal perturbations must be of similar scale. This implies that the thermal effects of the uplift of the Southern Alps do not change the seismogenic depth significantly and are not in accordance with most of the present thermal models. Both the Hope and Porters Pass fault zones are seismically active and deformation is accommodated near the fault zones and in the adjacent crust. North of Mt Cook, a triangular shaped region along the Alpine fault is characterised by absence of earthquakes. We interpret this as the result of the plate boundary shift from the Alpine fault to the Hope and Porters Pass fault zones. The study region shows distributed deformation in a 60-100 km wide zone on NNE-SSW trending thrust faults and strike-slip mechanisms on transfer faults.
Download or read book Diffuse Deformation Patterns Along the North American Plate Boundary Zone Offshore Western United States written by Jason D. Chaytor and published by . This book was released on 2006 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 coast of the United States, forming a wide zone of deformation which crosses the ocean-continent transition. Two offshore regions associated with this boundary zone, the Gorda plate and California Continental Borderland, have undergone significant deformation in order to accommodate the changing relative tectonic motion across the boundary. The Gorda plate, seaward of the Cascadia Subduction Zone is deforming as a modified, vertically-hinged flexural-slip buckle that utilizes, via-reactivation, the relict spreading-fabric faults and newly-formed leftlateral strike-slip faults that cut the original fabric. In this way, it appears that the Gorda plate, as the youngest and weakest plate in the system, absorbs the motion of the surrounding plates, essentially buffering the strain accumulation in other regions. In southern California, the plate boundary is dominated by the San Andreas transform system, but with deformation distributed over structures within a zone whose width west of the main San Andreas fault exceeds 300 km. While much of this deforming zone is onshore, a significant component is offshore within the California Borderland and Western Transverse Ranges provinces. Deformation related to the growth of the San Andreas fault system within the Borderland has been ongoing since the late Oligocene, resulting in a poly-deformed terrane of distributed deformation, reflecting the shift from subduction to a highly evolved transform system. Two areas within the Borderland illuminate aspects of the regions complex history: the intersection of the Santa Cruz-Catalina Ridge and northern Channel Islands platform which reflect the current transpressional tectonic regime, and Dall Bank within the Outer Borderland which contains evidence of earlier (Oligocene-Miocene) deformational phases.
Download or read book Cycles of Rock and Water written by Kenneth A. Brown and published by Harper San Francisco. This book was released on 1994 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Role of Rift Obliquity in Formation of the Gulf of California written by Scott Edmund Kelsey Bennett and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Gulf of California illustrates how highly oblique rift geometries, where transform faults are kinematically linked to large-offset normal faults in adjacent pull-apart basins, enhance the ability of continental lithosphere to rupture and, ultimately, hasten the formation of new oceanic basins. The Gulf of California rift has accommodated oblique divergence of the Pacific and North America tectonic plates in northwestern Mexico since Miocene time. Due to its infancy, the rifted margins of the Gulf of California preserve a rare onshore record of early continental break-up processes from which to investigate the role of rift obliquity in strain localization. Using new high-precision paleomagnetic vectors from tectonically stable sites in north-central Baja California, I compile a paleomagnetic transect of Miocene ignimbrites across northern Baja California and Sonora that reveals the timing and distribution of dextral shear associated with inception of this oblique rift. I integrate detailed geologic mapping, basin analysis, and geochronology of pre-rift and syn-rift volcanic units to determine the timing of fault activity on Isla Tiburón, a proximal onshore exposure of the rifted North America margin, adjacent to the axis of the Gulf of California. The onset of strike-slip faulting on Isla Tiburón, ca. 8 - 7 Ma, was synchronous with the onset of transform faulting along a significant length of the nascent plate boundary within the rift. This tectonic transition coincides with a clockwise azimuthal shift in Pacific-North America relative motion that increased rift obliquity. I constrain the earliest marine conditions on southwest Isla Tiburón to ca. 6.4 - 6.0 Ma, coincident with a regional latest Miocene marine incursion in the northern proto-Gulf of California. This event likely flooded a narrow, incipient topographic depression along a ~650 km-long portion of the latest Miocene plate boundary and corresponds in time and space with formation of a newly-constrained ~50-100 kilometer-wide transtensional belt of focused strike-slip faulting, basin formation, and rotating crustal blocks. This proto-Gulf of California shear zone, embedded within the wider Mexican Basin and Range extensional province and connected to the San Andreas fault in southern California, hosted subsequent localization of the plate boundary and rupture of the continental lithosphere.
Download or read book Plate Boundary Zones written by Seth Stein and published by American Geophysical Union. This book was released on 2002-01-21 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume collects some recent studies on the motions, mechanics, and earthquakes that take place within plate boundary zones. Many of the studies reflect advances made possible by the development of space geodetic techniques. Among the topics of the 21 papers are tectonic processes in the Eurasian-African plate boundary zone, the structure of the Dead Sea basin, the January 2001 Bhuj earthquake in India, geological investigations of the Kamchatka region in Russia, and crustal shortening and extension in the central Andes. There is no index. Annotation copyrighted by Book News, Inc., Portland, OR.
Download or read book The Ocean Basins and Margins written by Alan E.M. Nairn and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 965 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Near bottom Studies of the East Pacific Rise Crest and Tectonics of the Mouth of the Gulf of California written by Roger Lee Larson and published by . This book was released on 1970 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bathymetric and magnetic measurements have been used to delineate the boundary between the North American and Pacific Plates in the vicinity of the mouth of the Gulf of California and indicate a spreading rate of 6 cm/yr. Magnetic anomalies, fracture zones and earthquake mechanisms indicate the validity of the rigid plate assumption for the interactions between the Pacific, American and Cocos plates. A survey with a near-bottom instrument over the East Pacific Rise crest shows lineated abyssal hills with no sediment cover at the rise crest itself. Magnetic field measurements made near the ocean floor show to a certain extent the history of the earth's magnetic field over the last 1.2 million years and show a reversal transition time of 1000 years and intensity fluctuations with periods ranging between 18000 and 50000 years. (Author).
Download or read book A Detailed Near bottom Geophysical Study of the Gorda Rise and Implications of Plate Tectonics for the Cenozoic Tectonic Evolution of Western North America written by Tanya Maria Atwater and published by . This book was released on 1972 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Plate Motions Recorded in Tectonostratigraphic Terranes of the Franciscan Complex and Evolution of the Mendocino Triple Junction Northwestern California written by Geological Survey (U.S.) and published by . This book was released on 1994 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Global Positioning System Measurements of Crustal Defomration Across the Pacific North American Plate Boundary in Southern California and Northern Baja Mexico written by Richard Anthony Bennett and published by . This book was released on 1996 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Plate Tectonic Evolution of the Gulf of California written by George Frederick Sharman and published by . This book was released on 1976 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pacific Slope Geology of Northern Baja California and Adjacent Alta California written by American Association of Petroleum Geologists. Pacific Section and published by . This book was released on 1970 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
