SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Seismic wave Propagation and Imaging in Complex media: a European network Anne Sieminski Post-Doc Host Institution: Utrecht University Place of Origin: Strasbourg, France Appointment Time: August 2005 Project: Finite frequency sensitivity to anisotropy using adjoint methods Task Groups: TG Planetary Scale Cooperation: Caltech

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Finite frequency sensitivity of surface waves to anisotropy using adjoint methods Anne Sieminski 1, Qinya Liu 2, Jeannot Trampert 1 and Jeroen Tromp 2 (1) Utrecht University (2) Caltech Seismological Lab

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Introduction Surface wave tomography of mantle anisotropy is based on ray theory Finite frequency tomography has been tested to improve the imaging of the isotropic mantle How do finite frequency surface waves "sense" anisotropy ? Computational tool : Adjoint Spectral Element Method (ASEM) (Tromp et al., 2005)

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Introduction Outline : 1. Sensitivity computation with ASEM 2. Surface wave anisotropy 3. Sensitivity kernels

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Sensitivity computation (1) Tape et al. (2006) Sensitivity kernel : Construction : TT TT

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland In ray theory : (e.g. Larson et al., 1998 ; Montagner and Nataf, 1986) - Rayleigh waves - Love waves Surface wave anisotropy (2) vv hh transverse isotropy

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland In ray theory : (e.g. Larson et al., 1998 ; Montagner and Nataf, 1986) - Rayleigh waves - Love waves Surface wave anisotropy (2) azimuthal anisotropy

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland In depth, along the ray path : Sensitivity kernels (3) at mid-distance (mode 0 ; 100s < T < 180s ;  = 120º ) depth (km) KAKA KLKL KNKN s GPa -1 km -3

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Sensitivity kernels (3) Off the ray path : s GPa -1 km -3 Source radiation receiver at 150 km depth (mode 0 ; 100s < T < 180s ;  = 120º) KLKL Ray

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Love, 0 Rayleigh, 1 mm Rayleigh, 0 LL Sensitivity kernels (3) Off the ray path : s GPa -1 km -3 at 150 km depth (mode 0 ; 100s < T < 180s ;  = 120º) KLKL Ray Interpretation with Born scattering theory Rayleigh, 0

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Sensitivity kernels (3) Love-Rayleigh coupling effect : s GPa -1 km -3 at the surface (mode 0 ; 100s < T < 180s ;  = 120º) KNKN Ray Interpretation with Born scattering theory Rayleigh, 0 NN Love, 0 Rayleigh, 0

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Sensitivity kernels (3) Cross-branch coupling effect : s GPa -1 km -3 at the surface (mode 0 ; 100s < T < 180s ;  = 120º) KNKN Love Interpretation with Born scattering theory Love, 0 NN Love, 1

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland In Born scattering theory Sensitivity kernels (3) Gc Rayleigh, 0 at the surface (mode 0 ; 100s < T < 180s ;  = 120º) K Gc (cos 2  ) Ray s GPa -1 km -3 Path-dependency (azimuthal anisotropy) :

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Sensitivity kernels (3) Love-Rayleigh coupling and path-dependency : s GPa -1 km -3 at the surface (mode 0 ; 100s < T < 180s ;  = 120º) K Ec (cos 4  ) Ray

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Conclusion Surface wave sensitivity to anisotropy is controlled by : - significant mode coupling effects - strong path-dependency (azimuthal anisotropy) - source radiation  Most of the sensitivity kernels do not show a simple elliptical pattern  Consequences for tomography ?

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Construction of the adjoint source : The sensitivity may be calculated for any portion of the seismogram Sensitivity computation (+) "regular" displacement seismogram at the receiver adjoint source for traveltime information ( ) time (s)

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Sensitivity kernels (+) Isotropic kernels : s km -3 at the surface (mode 0 ; 100s < T < 180s ;  = 120º) K  /  Ray