Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Efficient extended-search space full-waveform inversion with unknown
  source signatures   Full waveform inversion (FWI) requires an accurate estimation of source
signatures. Due to the coupling between the source signatures and the
subsurface model, small errors in the former can translate into large errors in
the latter. When direct methods are used to solve the forward problem,
classical frequency-domain FWI efficiently processes multiple sources for
source signature and wavefield estimations once a single Lower-Upper (LU)
decomposition of the wave-equation operator has been performed. However, this
efficient FWI formulation is based on the exact solution of the wave equation
and hence is highly sensitive to the inaccuracy of the velocity model due to
the cycle skipping pathology. Recent extended-space FWI variants tackle this
sensitivity issue through a relaxation of the wave equation combined with data
assimilation, allowing the wavefields to closely match the data from the first
inversion iteration. Then, the subsurface parameters are updated by minimizing
the wave-equation violations. When the wavefields and the source signatures are
jointly estimated with this approach, the extended wave equation operator
becomes source dependent, hence making direct methods ineffective. In this
paper, we propose a simple method to bypass this issue and estimate source
signatures efficiently during extended FWI. The proposed method replaces each
source with a blended source during each data-assimilated wavefield
reconstruction to make the extended wave equation operator source independent.
Besides computational efficiency, the additional degrees of freedom introduced
by spatially distributing the sources allows for a better signature estimation
at the physical location when the velocity model is rough. Numerical tests on
the Marmousi II and 2004 BP salt synthetic models confirm the efficiency and
the robustness of the proposed method.

31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th