In:
Solid Earth, Copernicus GmbH, Vol. 10, No. 6 ( 2019-11-04), p. 1857-1876
Abstract:
Abstract. We present the implementation of Thomsen's weak
anisotropy approximation for vertical transverse isotropy (VTI) media within TOMO3D, our code for 2-D and
3-D joint refraction and reflection travel-time tomographic inversion. In
addition to the inversion of seismic P-wave velocity and reflector depth,
the code can now retrieve models of Thomsen's parameters (δ and
ε). Here, we test this new implementation following four
different strategies on a canonical synthetic experiment in ideal conditions
with the purpose of estimating the maximum capabilities and potential weak
points of our modeling tool and strategies. First, we study the sensitivity
of travel times to the presence of a 25 % anomaly in each of the
parameters. Next, we invert for two combinations of parameters (v, δ, ε and v, δ, v⊥), following two inversion strategies,
simultaneous and sequential, and compare the results to study their
performance and discuss their advantages and disadvantages. Simultaneous
inversion is the preferred strategy and the parameter combination (v, δ, ε)
produces the best overall results. The only advantage of
the parameter combination (v, δ, v⊥) is a better recovery of the
magnitude of v. In each case, we derive the fourth parameter from the equation
relating ε, v⊥ and v. Recovery of v, ε and
v⊥ is satisfactory, whereas δ proves to be impossible to
recover even in the most favorable scenario. However, this does not hinder
the recovery of the other parameters, and we show that it is still possible
to obtain a rough approximation of the δ distribution in the medium by
sampling a reasonable range of homogeneous initial δ models and
averaging the final δ models that are satisfactory in terms of data
fit.
Type of Medium:
Online Resource
ISSN:
1869-9529
DOI:
10.5194/se-10-1857-2019
DOI:
10.5194/se-10-1857-2019-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2545676-3
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