[1] Intermittent seismic discontinuities near 250-300 km depth beneath South America and the Pacific basin are detected with high-resolution seismic array methods that use SS and PP precursors recorded at the High Lava Plains Seismic Experiment and the EarthScope Transportable Array. The transformation of coesite to stishovite in an eclogite-rich mantle composition produces a seismic discontinuity near 300 km depth; lateral changes in basalt fraction of the upper mantle will thus produce an intermittent seismic discontinuity. The sensitivity of the precursors to intermittent seismic structure is addressed using an axisymmetric finite difference model of wave propagation in the mantle. These numerical experiments find that the precursors are sensitive to structures ≥500 km in lateral extent and that the observations of this discontinuity are plausibly tied to lateral variations in basaltic composition of the upper mantle related to dynamics, such as plumes and subduction. Citation: Schmerr, N. C., B. M. Kelly, and M. S. Thorne (2013), Broadband array observations of the 300 km seismic discontinuity, Geophys. Res. Lett., 40, 841-846, doi:10.1002/ grl.50257.

The monitoring of a SAGD heavy oil reservoir is commonly executed through time-lapse 3D seismic surveying, focused on identifying areas of steam stimulation by tracking the movement of a steam front, and identifying areas of bypassed reserves. In this thesis, we processed and interpreted a 4D -3C seismic dataset, identified time-lapse amplitude anomalies and isochron time-delays associated with the injection of high volumes of steam into a McMurray Formation reservoir. Through processing, and the application of a novel calibration procedure, non-production related differences between the baseline and monitor seismic surveys were minimized. Production-related differences were analyzed through a variety of geophysical techniques, and were projected into a map display to delineate the spatial position of the reservoir steam zones. It was interpreted that the observed amplitude anomalies corresponded to steam injection, while concurrent time-delays represent reservoir heating above pre-injection ambient temperatures.

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