We introduce a technique to compute exact anelastic sensitivity kernels in the time domain using parsimonious disk storage. The method is based on a reordering of the time loop of time-domain forward/adjoint wave propagation solvers combined with the use of a memory buffer. It avoids instabilities that occur when time-reversing dissipative wave propagation simulations. The total number of required time steps is unchanged compared to usual acoustic or elastic approaches. The cost is reduced by a factor of 4/3 compared to the case in which anelasticity is partially accounted for by accommodating the effects of physical dispersion. We validate our technique by performing a test in which we compare the K α sensitivity kernel to the exact kernel obtained by saving the entire forward calculation. This benchmark confirms that our approach is also exact. We illustrate the importance of including full attenuation in the calculation of sensitivity kernels by showing significant differences with physical-dispersion-only kernels. *** This manuscript is now published as a paper in the Geophysical JournalInternational, 2016. *** I IntroductionEfficient numerical methods for simulating the propagation of acoustic, elastic, or anelastic waves in the time domain are widely available, for instance based on finite-difference methods see e.g., 63 for a review, spectral-element methods e.g., 32;61;30;31 , or standard finiteelement methods e.g., 28 . Nowadays, these techniques are heavily used for imaging based on full waveform inversion (FWI) or adjoint tomography e.g., 59;44;60;63;20;41 . FWI involves fitting band-pass filtered versions of observed seismograms by minimizing least-squared differences between observed and synthetic seismograms. Adjoint tomography generalizes FWI by considering arbitrary measures of misfit, e.g., cross-correlation traveltimes, multi-taper phase and amplitude anomalies, or instantaneous phase measurements.In the context of imaging, it is useful to resort to the concept of sensitivity kernels e.g., 56;57;58;59;60;39;20;21 . Let s denote the forward displacement wavefield and s † the adjoint wavefield. In an isotropic Earth model, the kernels K κ and K µ represent Fréchet derivatives with respect to relative bulk and shear moduli perturbations, respectively. These kernels are given by e.g.,whereanddenote the traceless strain deviator and its adjoint, respectively, x is the position vector, and κ and µ are the bulk and shear moduli, respectively. Their expression remains valid for elastic perturbations superimposed on an anelastic Earth model 39 if the regular and adjoint wavefields are computed in that anelastic reference model. In practical applications, it is often useful to define compressional and shear wavespeed sensitivity kernels, namely 59;60andIn order to perform the convolution involved in the calculation of the kernels (1) and (2), simultaneous access to the forward wavefield s at time t and the adjoint wavefield s † at time T − t is required (or conversely, sinceconvolving two funct...

No abstract

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

No abstract