Direct Imaging of Crust and Upper Mantle Structure with Broadband Seismic Arrays

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Abstract for proposal EAR0106062 (PH # 34x)Title: Direct Imaging of Crust and Upper Mantle Structure with Broadband Seismic ArraysPI's: Gary L. Pavlis, Indiana University, Bloomington We have developed a new technology for direct imaging of P to S converted phases. It builds on imaging concepts used in the oil and gas industry to directly image backscattered (reflected) seismic waves, but we utilize forward scattered P to S conversions produced by distant earthquakes instead of backscattered waves generated by artificial sources. This allows us to directly manipulate raw recordings of distant earthquakes to produce an image of P to S scattering potential underneath a seismic array. The mathematical model used is a form of inverse scattering appropriate for this type of wave interaction. Applications of the technique to date have revealed the presence of previously unseen dipping boundaries that coincide with ancient suture zones within the continents. Existing applications of the technique have been limited to 2D slices. The proposed project would extend the capabilities of this technique to produce 3D images of P to S conversion structure beneath broadband arrays. The technique will be applied to data from the recently completed array experiment in the Tien Shan of central Asia to address fundamental issues about the relation of mantle and crustal processes in continent-continent collision zones. We also propose to apply this approach to new, dense broadband array data available in southern California. This may provide new insights on the nature of flow in the upper mantle connected with the San Andreas fault system.