Prestack planewave migration of teleseismic P-to-S converted phases

This research presents a new prestack migration technique to image the Earth with forward scattered teleseismic P-to-S converted phases (receiver functions). The method builds on the pseudostation stacking technique presented by Neal and Pavlis [1999 and a planewave decomposition-based migration technique introduced by Treitel et al. [1982]. We apply this procedure to dozens of teleseismic earthquakes recorded by the Lodore array in northwestern Colorado, which was deployed to image the subsurface structure of the Cheyenne belt. The Cheyenne belt has been interpreted as the surface expression of a suture zone between the Archean-age Wyoming province and the Proterozoic-age Colorado Plateau. The end result of applying planewave migration to many events recorded by the Lodore array is that we obtain a high resolution image which suggests the presence of a major, lithospheric scale discontinuity between the Wyoming province and the Colorado Plateau. The imaged discontinuity extends to a depth of at least 90km, which is the maximum depth that we can image with the Lodore array. Additionally, we apply planewave migration to approximately one dozen teleseismic earthquakes recorded by a large array in the Tien Shan mountains (Asia) to image a major suture zone there. Based the two different datasets provided by the Lodore array and the Tien Shan array, we suggest that scars from continental sutures extend to depths greater than 200 km and remain as distinct features for hundreds of millions of years.; In a separate study, we analyze data from 35 three-component seismic recording instruments deployed in a 5 x 7 grid over a steep slope. The array was deployed to record to site response of the steep slope and recorded ten underwater explosions detonated in a lake which was adjacent to the slope. The explosions were approximately 800 meters from the array. We found that the slope crest had a local acceleration approximately twice that of the surrounding flat ground. Additionally, we observed a site resonance effect that was frequency dependent.