HR: 08:35h
AN: S51C-03 INVITED     [Abstracts]
TI: Attenuation of Seismic Waves Along and Perpendicular to the Pacific Coast of Mexico: Does it Differ?
AU: * García, D
EM: danielg@fis.ucm.es
AF: Inst. de Geofísica, UNAM, Ciudad Universitaria Coyoacán 04510, Mexico DF, Mexico
AU: * García, D
EM: danielg@fis.ucm.es
AF: Dpto. Geofísica y Meteorología, UCM, Av. Ciudad Universitaria s/n, Madrid, 28040, Spain
AU: Singh, S K
EM: krishna@ollin.igeofcu.unam.mx
AF: Inst. de Geofísica, UNAM, Ciudad Universitaria Coyoacán 04510, Mexico DF, Mexico
AU: Herraiz, M
EM: mherraiz@fis.ucm.es
AF: Dpto. Geofísica y Meteorología, UCM, Av. Ciudad Universitaria s/n, Madrid, 28040, Spain
AU: Pacheco, J F
EM: javier@ollin.igeofcu.unam.mx
AF: Inst. de Geofísica, UNAM, Ciudad Universitaria Coyoacán 04510, Mexico DF, Mexico
AU: Ordaz, M
EM: mors@pumas.iingen.unam.mx
AF: Inst. de Ingeniería, UNAM, Ciudad Universitaria Coyoacán 04510, Mexico DF, Mexico
AB: Does the attenuation of seismic waves along the Pacific coast of Mexico and towards inland, along the dip direction of the subducted slab, differ? Several studies report different attenuation along these two trajectories. Others, however, have not found any difference. To resolve this issue, we analyze an extended dataset of nearly 450 strong-motion recordings from Mexican interplate earthquakes. Our data show that the Fourier amplitude spectra of the horizontal components of S-wave at inland sites are larger than those at coastal sites at similar distances. We explore and discard possible source and site effects. Hence, the observed differences seem to be a reflection of differences on the attenuation function, Γ(f,R) = e^{-π f R/β Q(f)}/G(R), where Q is the quality factor and G(R) is the geometrical spreading term. The strong trade-off between Q and G(R) hinders reliable estimation of Q. Numerical simulations suggest that Lg and SmS phases propagate very efficiently along the direction of the dipping slab, which could explain the observations. We propose new attenuation functions for both trajectories that may be useful in predicting future ground motions.
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7218 Lithosphere (1236)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Seismology [S]
MN: 2007 Joint Assembly