HR: 17:05h
AN: S44A-04    [Abstracts]
TI: Integrating Active and Passive Imaging of Deep Crustal Magma
AU: * Brown, L
EM: brown@geology.cornell.edu
AF: Institute for the Study of the Continents, 3120 Snee Hall Cornell University, Ithaca, NY 14853 United States
AB: The two crustal features which have been most commonly recognized from both active and passive seismic techniques are the Moho (universal) and mid-crustal magma bodies (local). The latter provide a particular test of relative resolution and sensitivity of these methodologies. Magma bodies have been inferred from unusually strong reflections recorded by controlled source surveys in both near-vertical reflection profiling and wide-angle mode, from anomalous reflections associated with local earthquake sources, from local tomographic inversions and from teleseismic receiver functions. The best known oif these features is the Socorro magma body in central New Mexico, first identified from unusual reflected shear phases on microearthquake seismograms. The Socorro sill was subsequently traced out by COCORP deep reflection profiling (P waves) and detected on receiver functions (S wave). Anomalous S phases from microearthquake sources have been used to detail presumptive magma bodies at several sites in Japan. Notably, microearthquake sources seem to overlie these postulated magma reflectors but at a distance of a few km, suggested a rheological aureole. Deep reflection profiling and receiver functions have led to recognition of anomalous mid-crustal bodies at a number of sites in the western U.S., and at various locales worldwide. Perhaps the best studied of these features from both active and passive methodologies are those in southern Tibet, where active and passive seismic results are supported by magnetotelluric and geothermal observations. The relative contributions of each method to developing the case for magma, or at least fluids, deep in the Tibetan crust provide a model for integration of these methods in crustal studies.
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
SC: Seismology [S]
MN: Fall Meeting 2005