Receiver-function studies in the Trans-Hudson Orogen, Saskatchewan

Teleseismic events were recorded on an array of three-component broadband a nd short-period seismographs in the Trans-Hudson Orogen over a period of al most 3 years. Receiver functions calculated from these data were used in a forward-modelling study to derive the local shear-wave velocity structure b eneath 20 stations. Station FFC (Flin Flon), located within the Flin Flon b elt, was one of two stations situated on bedrock and produced the highest q uality receiver functions. The FFC velocity model correlates well with an i nterpretation of nearby reflection data and features a distinct lower crust interpreted as Archean basement which cores the entire Reindeer Zone. Both radial and tangential receiver functions at FFC show strong evidence for a northeasterly dipping shallow boundary within rocks of the Flin Pion belt with a dip angle of 20 degrees. Total crustal thickness is 37 km. Eighteen stations are situated on Phanerozoic sedimentary cover ranging in thickness from 0.4 km to greater than 2 km. Receiver functions at these stations dis play prominent high-amplitude, low-frequency reverberations that obscure mo re subtle phases associated with deeper structure. Because of this, only th e gross crustal velocity structure can be constrained by modelling. Depth t o Moho, which is 40-43 km at most stations, is the most strongly constraine d feature. Stations with relatively thick crust within the Glennie domain s uggest a connection between two regions of thick crust previously inferred from reflection and refraction data. This crustal root, presumably associat ed with a structural culmination imaged by reflection data and cored by Arc hean basement, is confined to the southwestern Glennie domain. One-dimensio nal modelling results show that the reverberations can be explained by a th in layer (<0.7 km) at the top of the sediments with a very high Poisson's r atio (0.4-0.48). The degree to which later arrivals are affected by reverbe rations is directly related to the parameters of this uppermost layer. We p resent the results of synthetic studies that demonstrate the sensitivity of receiver functions to this type of feature.