HR: 08:00h
AN: S31A-13    [Abstracts]
TI: High precision finite-differences time-domain direct modelling of wave equation for seismic oceanography experiments
AU: * Sallares, V
EM: vsallares@cmima.csic.es
AF: Marine Technology Unit, CMIMA-CSIC, Passeig Maritim Barceloneta, 37-49, Barcelona, 08003, Spain
AU: Kormann, J
EM: jkormann@hotmail.com
AF: Instituto de Acustica, CSIC., Serrano, 144, Madrid, 28006, Spain
AU: Cobo, P
EM: iacpc24@ia.cetef.csic.es
AF: Instituto de Acustica, CSIC., Serrano, 144, Madrid, 28006, Spain
AU: Biescas, B
EM: biescas@cmima.csic.es
AF: Marine Technology Unit, CMIMA-CSIC, Passeig Maritim Barceloneta, 37-49, Barcelona, 08003, Spain
AU: Carbonell, R
EM: rcarbo@ija.csic.es
AF: Institute of Earth Sciences "Jaume Almera", Sole i Sabaris, s/n, Barcelona, 08028, Spain
AB: Holbrook et al. (2003) demonstrated recently the possibility of visualizing fine structures in the water column, like thermohaline intrusion or internal waves, through seismic exploration experiments. Seismic exploration is becoming a popular technique for providing high-lateral resolution images of the explored area, in contrast with the classical oceanography probes, like XBT or XCDT. In this work we present a wave propagation model based upon a high order finite-differences time-domain (FDTD) scheme which includes special absorbing conditions in the boundaries. FDTD algorithms are known for presenting problems with reflections on the computational edges. Classical boundary conditions, like those of Engquist, provide reflection coefficients or the order of 10-2. However, reflection coefficients of fine structures in the water we are trying to model are about 10-4. Thus, the key point of the algorithm we present is in the implementation of Perfectly Matched Layer (PML) boundary conditions. These consist in zones with high absorption (therefore, very low reflection coefficient). The PML implemented in this scheme consists in a second order algorithm in the time domain, to take advantage of its stability and convergence properties. In this work we specify the propagation algorithm, and compare it results with the with Engquist and PML absorbing boundaries conditions. The PML condition affords reflection coefficients in the numerical edges lower than 10-4. Holbrook, W.S., Paramo, P., Pearse, S. and Schmitt, R.W., 2003. Thermohaline fine structure in an oceanographic front from seismic reflection profiling. Science, 301, 821-824.
DE: 0902 Computational methods: seismic
DE: 0935 Seismic methods (3025, 7294)
DE: 3025 Marine seismics (0935, 7294)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Joint Assembly