The project is aimed at providing new or refined constraints on models of evolution and composition of the continental crust, by simultaneously measuring crustal thickness, Poisson's ratio which can be uniquely determined by the ratio between P and S-wave velocities, and crustal P-wave velocities beneath about 200 broadband seismic stations distributed all over the continents. About 80,000 source-normalized broadband seismograms will be visually checked and used for the proposed study. A set of computer codes that the PIs developed to search for the optimal combination of the three parameters beneath a station will be used for the study, and the bootstrap procedure will be used to estimate the errors of the measurements. The existence of dipping Moho beneath each of the stations will be examined. Another part of the project is for the collection of a set of published tectonic history and petrological data obtained from lower crustal xenoliths or terrains related to the composition and evolution of the lower crust inthe vicinity of each of the stations. Those geological data will be used for the interpretation of the seismological results.
Expected results from the proposed work will be used by geochemists, mineral physicists, and geodynamicists to address a broad range of important questions regarding the formation and evolution of early crust and mantle. Thus this study should have an impact that is beyond the seismological community.
