37,460 research outputs found

    Crustal structure of the Borderland-Continent Transition Zone of southern California adjacent to Los Angeles

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    We use data from the onshore-offshore component of Los Angeles Region Seismic Experiment (LARSE) to model the broad-scale features of the midcrust to upper mantle beneath a north-south transect that spans the continental borderland in the Los Angeles, California, region. We have developed an analysis method for wide-angle seismic data that consists primarily of refractions, lacks near-offset recordings, and contains wide gaps in coverage. Although the data restrict the analysis to the modeling of broad-scale structure, the technique allows one to explore the limits of the data and determine the resolving power of the data set. The resulting composite velocity model constrains the crustal thickness and location and width of the continent-Borderland transition zone. We find that the mid to lower crust layer velocities of the Inner Borderland are slightly lower than the corresponding layers in the average southern California crust model, while the upper mantle velocity is significantly higher. The data require the Moho to deepen significantly to the north. We constrain the transition zone to initiate between the offshore slope and the southwest Los Angeles Basin. If the Inner Borderland crust is 22 km thick, then the transition zone is constrained to initiate within a 2 km wide region beneath the southwest Los Angeles Basin, and have a width of 20–25 km. The strong, coherent, and continuous Pn phase suggests the Moho is coherent and laterally continuous beneath the Inner Borderland and transition zone. The Inner California Borderland seems to be modified and thickened oceanic crust, with the oceanic upper mantle intact beneath it

    Borderland Identity

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    Chinese Americans and the Borderland Experience on Golden Mountain: The Development of a Chinese American Identity in the Woman Warrior: Memoirs of a Girlhood Among Ghosts

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    In The Woman Warrior: Memoirs of a Girlhood Among Ghosts, Maxine Hong Kingston tells the story of her immigrant family and their efforts to rise above their working-class status in America, which optimistic Chinese regard as the Golden Mountain. The Hongs\u27 experience is not unlike that of other immigrants who come to America to escape hardship in their homeland and hope to live the American Dream. The road to American success has numerous obstacles, and immigrants encounter many conflicts on their journey. One conflict relates to their cultural identities. Gloria AnzaldĂșa uses the word borderland to refer to the meeting of two cultures, and she defines the borderland as a place of contradictions. Hatred, anger and exploitation are the prominent features of this landscape (n.p.). While Anzaldua\u27s discussion focuses on the borderland encountered by Mexican Americans, she believes that many share this painful experience

    Chukchi Edges Project - Geophysical constraints on the history of the Amerasia Basin

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    The geological history of the Amerasia Basin is poorly understood, in part due to the lack of identified plate boundaries within it. These boundaries must exist to explain the basin history. Identification of these structures will make it possible to reconstruct the development of the basin, which will substantially improve our understanding of the surrounding continents. The Chukchi Borderland, a block of extended continental crust embedded in the Canada Basin, figures prominently in all tectonic models proposed for the opening of the Amerasia Basin. The Chukchi cannot be simply reconstructed back to any of the nearby continental shelves. It complicates any model for the Mesozoic opening of the Amerasia Basin. According to the commonly accepted model, the Canada Basin opened like a pair of scissors. This was accomplished by a counter-clockwise rotation of the North Alaskan-Chukchi micro-plate (Arctic Alaska Plate) by 66 degrees. The micro-plate collided with the Siberian margin. Most of the existing models for the development of the Amerasia Basin accept the basic pattern of scissors-like or, classically, the “windshield wiper” opening for the basin. This theory finds some support in the identification of a possible relict mid-ocean ridge axis in the central Canada Basin. Since the continental Chukchi Borderland creates a space problem for any simple opening model, the greatest differences between models revolve around how to accommodate that block. Fundamental differences among the proposed models include the paleo-location of the Chukchi Borderland as well as whether the Borderland is a single entity or is instead comprised of small terranes which behaved as independent microplates. A consequence of these models is the prediction that the Chukchi Borderland is distinct from the Chukchi Shelf. During the Chukchi Edges cruise on board the RV Marcus G. Langseth, we collected multi-channel seismic reflection, swath bathymetry, gravity, magnetics and sonobuoy refraction data across the transition from the Chukchi Shelf to the Borderland. These data will establish new constraints on the timing and distribution of deformation in the development of the Amerasia Basin and provide a test of the windshield wiper model of basin opening

    Poverty in the Texas borderland and lower Mississippi Delta: A comparative analysis of differences by family type

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    We provide a comparative analysis of county-level poverty in the two poorest regions of the United States - the Texas Borderland and the Lower Mississippi Delta - with a special focus on differences by family type. Our results reveal important regional variation in both the prevalence of poverty and the composition of the poor population across major family types. Using OLS regression models of family type-specific poverty we demonstrate three key findings: 1) There are no significant regional differences in poverty levels by family type between the Borderland and the Delta, net of important structural factors that characterize the regions; 2) with the exception of the employment rate, the structural factors associated with poverty among married couple and single female-headed families are quite different; and 3) paradoxically, areas in the Borderland with high in-migration are especially likely to suffer from high married-couple family poverty. Our results suggest the need for regionally targeted and demographically tailored anti-poverty policies.family structure, Mississippi Delta, persistent poverty, poverty, regional poverty, Texas Borderland

    Morphometric evidences for regional variation in potential of neural plasticity

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    The neural plasticity showing the ability of nervous system to change its structure and function is a well-documented fact. However regional variation within a CNS structure to undergo plastic changes has been shown by limited studies. Along medial-lateral sequences of parasagittal sections, the molecular layer thickness of primary fissure borderlands in rat cerebellar left hemisphere was studied to assess the regional difference in plasticibility. Despite the homogeneity of cerebellar histology, this study showed that there is a significant interlobular difference between ML thicknesses of Prf borderlands. In addition, it revealed that the thickness alters in a significant trend within each borderland. The quantitative heterogeneity of cerebellar architecture such as variation of cortical thickness may provide some evidences to show that different regions of a homogenous cortex, even two adjacent borderlands and areas within them, can have different potentials for plasticity. © 2006 Sociedad Chilena de Anatomía

    Polish Interstate Relations with Ukraine, Belarus and Lithuania After 1990 in the Context of the Situation of National Minorities

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    When we compare the contemporary ethnic structure and national policy of Poland and its eastern neighbours, we can see clear asymmetry in both quantitative and legal-institutional aspects. There is currently a markedly smaller population of Ukrainians, Belarusians and Lithuanians living in Poland than the Polish population in the territories of our eastern neighbours. At the same time, the national minorities in Poland enjoy wider rights and better conditions to operate than Poles living in Ukraine, Belarus and Lithuania. Additional complicating factor in bilateral relations between national minority and the home state is different political status of Lithuania, Belarus and Ukraine and different processes of transformation the consequence of which is differentiated state of political relations of Poland with its eastern neighbours. Lithuania, like Poland, is a member of EU, Ukraine, outside the structures of European integration, pursued a variable foreign policy, depending on the ruling options and the economic situation, and Belarus, because of internal policy which is unacceptable in the EU countries, is located on the political periphery of Europe

    Sea Beam Survey of an Active Strike-Slip Fault: The San Clemente Fault in the California Continental Borderland

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    The San Clemente fault, located in the California Continental Borderland, is an active, northwest trending, right-lateral, wrench fault. Sea Beam data are used to map the major tectonic landforms associated with active submarine faulting in detail unavailable using conventional echo-sounding or seismic reflection data. In the area between North San Clemente Basin and Fortymile Bank, the major late Cenozoic faults are delineated by alignments of numerous tectonic landforms, including scarps, linear trenches, benches, and sags. Character and spatial patterns of these landforms are consistent with dextral wrench faulting, although vertical offsets may be substantial locally. The main trace of the San Clemente fault cuts a straight path directly across the rugged topography of the region, evidence of a steeply dipping fault surface. Basins or sags located at each right step in the en echelon pattern of faults are manifestations of pull-apart basin development in a right-slip fault zone. Seismic reflection profiles show offset reflectors and a graben in late Quaternary turbidites of the Navy Fan, where the fault zone follows a more northerly trend. Modern tectonic activity along the San Clemente fault zone is demonstrated by numerous earthquakes with epicenters located along the fault\u27s trend. The average strike of the San Clemente fault is parallel to the predicted Pacific-North American relative plate motion vector at this location. Therefore we conclude that the San Clemente fault zone is a part of the broad Pacific-North American transform plate boundary and that the southern California region may be considered as a broad shear zone
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