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DTSTAMP:20210916T132454Z
LOCATION:Louis Favre
DTSTART;TZID=Europe/Stockholm:20210709T140000
DTEND;TZID=Europe/Stockholm:20210709T143000
UID:submissions.pasc-conference.org_PASC21_sess134_msa375@linklings.com
SUMMARY:Finite-Frequency Sensitivity of Waves probing Global Deep Earth St
ructure using Spectral-Element and Adjoint Methods
DESCRIPTION:Minisymposium\n\nFinite-Frequency Sensitivity of Waves probing
Global Deep Earth Structure using Spectral-Element and Adjoint Methods\n\
nKoroni\n\nUsing spectral-element and adjoint methods, this study investig
ates the sensitivity of seismic waves to structural and boundary parameter
s of the earth. Understanding wave propagation effects on many body wave s
eismic phases travelling through the earth is important for improving 3-D
mantle models. This study focusses on analysing the finite-frequency conte
nt of traveltimes of phases which in theory interact with global discontin
uities and specifically the core-mantle boundary, which separates the soli
d mantle from fluid outer core. Using adjoint methods, we obtain Frechet d
erivatives of selected time windows and illustrate the computed adjoint se
nsitivity of traveltimes to structural parameters, i.e. compressional and
shear wave-speed,and to the surface of the global boundaries. The main res
ults show wave interference for measurements in narrow time windows reveal
ing complicated wave propagation effects, which are not predicted by commo
n infinite frequency theory. Additionally, we observe strong trade-off bet
ween boundary and structural parameters at the core-mantle boundary. For t
he seismic phases that are considered in this study, that in theory are mo
stly sensitive to boundary structure, we see that structural parameters ha
ve actually an important non-linear impact on travel-times. This tradeoff
necessitates incorporating finite-frrequency Frechet derivatives in invers
ions for boundaries and structure. The main conclusion is that the finite-
frequency nature of the wavesÂ leads to complex kernels. These kernel
s however are important for understanding seismic observables, such as tra
veltimes, and should be considered in an iterative full-waveform inversion
scheme using spectral-element modelling and adjoint methods for better re
solution and simultaneous inversion of structural and boundary interface p
arameters.\n\nDomain: CS and Math, Physics, Solid Earth Dynamics
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