Topography of Upper Mantle Discontinuities Beneath Nazca Plate and Its Surrounding Area Reveals from SS Precursor and Its Tectonic Significance

MA Yuyan, GE Zengxi†

ACTA Scientiarum Naturalium Universitatis Pekinensis - - CONTENTS - MA Yuyan, GE Zengxi

School of Earth and Space Sciences, Peking University, Beijing 100871; † Corresponding author, E-mail: [email protected]

Abstract An upper mantle discontinuity topography map of southern Nazca Plate and western South America Plate (120°W‒60°W, 30°S‒5°N) was obtained by using common mid-point stacking in bins of 5 degree radius over ten thousand Usarray teleseismic records. The resolution was higher than that of previous studies because the records more densely sampled the region so that stacking bins were smaller. Discontinuity topography corresponding to high temperature anomalies in deep mantle was observed beneath Galapagos, Easter and San Felix hotspots. Other findings include a depression of 410 km discontinuity beneath Southern East Pacific Rise and depressions of both 410 km and 660 km discontinuities beneath the subduction zone. Key words upper mantle discontinuity; mantle transition zone; hotspot; slab; Southern East Pacific Rise

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