The Canadian Rockies and the neighboring Alberta Basin mark the transition from the old North American continental lithosphere (east) to young accreted "terranes" (west). Geologic, seismic, and magnetic data in this region have suggested complex crustal domains, conductive anomalies, and major seismic velocity gradients in the mantle. However, the nature of the boundaries between the basement domains and their vertical extents remains controversial due to the lack of exposed geology and limited seismic and electromagnetic receivers. Since 2006, the seismic data coverage and depth sensitivity have received a major boost from the establishment of the Canadian Rockies and Alberta Network (nicknamed CRANE), the first semi-permanent broadband seismic array in Alberta. The availability of the array data provides vital constraints on the regional micro-earthquakes and crust/mantle seismic structures. Among the broad range of ongoing efforts, this study highlights promising results from the analyses of P-to-S wave receiver functions, shear wave splitting amplitudes/directions, and ambient seismic noise. Our preliminary receiver-function stacks show that the base of the crust gradually shallows from approximately 60 km beneath the Rockies near the Canadian-U.S. border to 37-40 km beneath central Alberta; the latter range is consistent with earlier findings from active-source experiments. Converted waves from "littered" crust and/ or lithosphere have also been detected at a number of stations in the depth range of 80-130 km. Complexities in the lithosphere are further evidenced by our regional shear wave splitting measurements. We infer a strong east-west change of mantle flow pattern, consistent with present-day plate motion. The spatial distribution of the SKS fast orientations highlights the contrasting crust/mantle structures and histories between the Rockies and adjacent domains. Dynamic effects associated with a migrating continental root east of the province may be important. Finally, our preliminary inversions using ambient seismic noise indicate more than 0.8 km/s in peak-to-peak group velocity variations throughout the crust. The upper crust beneath the Alberta Basin is dominated by low Rayleigh-wave group velocities. A lower-than-expected correlation between seismic velocities and tectonic domain boundaries suggests significant tectonic overprinting in the southern Western Canada Sedimentary Basin. Overall, the broadband seismic data from CRANE could play a key role in uncovering the mysteries of the crust and mantle beneath the transition region between cratons and terranes.

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[1] This study combines migration and forward source modeling techniques to examine the existence and location of persistent seismic noise near southern Italy. Our results demonstrate that noise source modeling is both feasible and recommended in validating the ''ambient source'' assumption prior to noise-based velocity analyses. Persistent noise sources near the Gargano promontory and the Tyrrhenian Sea coast are strongly suggested by the observed cross-correlations. The presence of a single point source or a cluster of point sources could both produce coherent Rayleigh wave energy in southern Italy. While the nature of the noise sources is still uncertain, baroclinic estimates and dynamic topography models favor an explanation that encompasses atmosphere-ocean coupling and heightened wave interaction off the Adriatic coast. Our records indicate that these noise sources can maintain their average location for up to 7 months despite seasonal and, possibly, daily variations.

In this study we utilize over 5000 SS waveforms to investigate the high‐resolution mantle reflectivity structure down to 1200 km beneath the South American convergent margin. Our results indicate that the dynamics of the Nazca subduction are more complex than previously suggested. The 410‐ and 660‐km seismic discontinuities beneath the Pacific Ocean and Amazonian Shield exhibit limited lateral depth variations, but their depths vary substantially in the vicinity of the subducting Nazca plate. The reflection amplitude of the 410‐km discontinuity is greatly diminished in a ∼1300‐km wide region in the back‐arc of the subducting plate, which is likely associated with a compositional heterogeneity on top of the upper mantle transition zone. The underlying 660‐km discontinuity is strongly depressed, showing localized depth and amplitude variations both within and to the east of the Wadati‐Benioff zone. The width of this anomalous zone (∼1000 km) far exceeds that of the high‐velocity slab structure and suggesting significant slab deformation within the transition zone. The shape of the 660‐km discontinuity and the presence of lower mantle reflectivity imply both stagnation and penetration are possible as the descending Nazca slab impinges upon the base of the upper mantle.