HR: 0800h
AN: S41A-0236    [Abstracts]
TI: Converted phases migration using active and passive seismic data at the Campi Flegrei caldera
AU: * Blacic, T M
EM: lowvelocityzone@gmail.com
AF: Geosciences Azur, 250 rue Albert Einstein, Valbonne, 06560, France
AU: Latorre, D
AF: INGV, 605 Via di Vigna Murata, Rome, 00143, Italy
AU: Virieux, J
AF: Geosciences Azur, 250 rue Albert Einstein, Valbonne, 06560, France
AU: Vassalo, M
AF: RISSC, University of Naples 156 Via Coroglio, Naples, 80124, Italy
AU: Zollo, A
AF: RISSC, University of Naples 156 Via Coroglio, Naples, 80124, Italy
AB: We applied a type of depth migration for converted seismic phases to active and passive seismic data sets from the Campi Flegrei volcanic region in southern Italy. The converted phases analysis is based on the diffraction summation migration technique. Travel times to grid points in a volume are calculated in smooth P and S-velocity models from tomography and trace energy near the calculated converted phase time is stacked over multiple sources at one receiver. Weighting factors based on Snell's Law at an arbitrarily oriented local interface are applied to aid in focusing of trace energy. PP and PS reflection images from the active data set show features near 2-3 km in depth, which may be associated with an over-pressured gas volume suggested by tomographic investigations. Possible deeper features near 4 km depth may be related to the presence of the carbonate basement. A portion of the caldera rim near 1-2 km depth is imaged considering PP reflections. We found that the passive earthquake data set from the 1984 bradiseismic crisis was not well suited to the converted phases analysis due to the acquisition geometry, however, we can confirm some features found in our investigation of the active data using the earthquake traces and images from two selected stations.
DE: 0902 Computational methods: seismic
DE: 0935 Seismic methods (3025, 7294)
DE: 7299 General or miscellaneous
DE: 8440 Calderas
DE: 8494 Instruments and techniques
SC: Seismology [S]
MN: 2007 Fall Meeting