Global mapping of the 410 km upper mantle boundary using PP precursor waves



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Globally mapping the mineral phase discontinuities in the earth’s upper mantle will enable us to develop detailed 1D models of the upper mantle discontinuity at 410 km depth using underside reflections from PP precursor waves. The 520 km discontinuity has proven difficult to image with PP waves due to interference from sidelobes from reflections off of the underside of discontinuity boundaries at 410 km and 660 km depth. PP precursors cannot be used to map the 660 km discontinuity either since the reflection from this boundary does not appear consistently. We have stacked and binned 25 years-worth of seismic data collected between 1990 and 2015 from stations all over the globe available from the IRIS data management services (DMC). Using the stacked PP functions, we will assess the behavior of the 410 km discontinuity in regions where there are significant temperature anomalies based on the mapped depth of the 410 and amplitude of the pulses reflected from this discontinuity.



Upper mantle discontinuity, Transition zone