@conference {Tejero2014,
	title = {{Comparison of objective functionals in seismic full waveform inversion}},
	booktitle = {76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014},
	year = {2014},
	pages = {2819{\textendash}2823},
	publisher = {EAGE Publishing BV},
	organization = {EAGE Publishing BV},
	abstract = {The FWI method is a powerful tool that allows one to obtain high-resolution information from the subsurface. However, the method is highly non-linear as in the convergence to the solution it might get trapped in local-minima. Among other techniques, it becomes crucial a suitable choice of the objective function. We have selected five objective functions to perform a comparative study under a common 2Dacoustic FWI scheme: the L2-nom, cross-correlation travel time (CCTT), non-integration-method (NIM), envelope and phase objective functions. We test with a 2D-canonical model the susceptibility of the functions to the initial model perturbations. To complete de study with a more realistic synthetic example we test the functions with the Marmousi model. The L2-norm and phase objective functions give the highest resolution images and the CCTT, NIM and envelope objective functions lead to smooth models. However in realistic initial conditions, L2 and phase misfits fail in recovering the velocity model in contrast to the CCTT, NIM and envelope functions that maintain a more consistent behavior.},
	isbn = {9781632666949},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84907396478\&partnerID=tZOtx3y1},
	author = {Tejero, C. E Jimenez and Dagnino, D. and Sallar{\`e}s, V. and Ranero, C.}
}
@article {Dagnino2014,
	title = {{Scale- and parameter-adaptive model-based gradient pre-conditioner for elastic full-waveform inversion}},
	journal = {Geophysical Journal International},
	volume = {198},
	number = {2},
	year = {2014},
	month = {jun},
	pages = {1130{\textendash}1142},
	publisher = {Oxford University Press},
	abstract = {We present a scale- and parameter-adaptive method to pre-condition the gradient of the parameters to be inverted in time-domain 2-D elastic full-waveform inversion (FWI). The proposed technique, which relies on a change of variables of the model parameters, allows to balance the value of the gradient of the Lam{\'e} parameters and density throughout the model in each step of the multiscale inversion. The main difference compared to existing gradient pre-conditioners is that the variables are automatically selected based on a least squares minimization criteria of the gradient weight, which corresponds to the product of the gradient by a power of the parameter to be inverted. Based on numerical tests made with (1) a modified version of the Marmousi-2 model, and (2) a high-velocity and density local anomaly model, we illustrate that the value of the power helps to balance the gradient throughout the model. In addition, we show that a particular value exists for each parameter that optimizes the inversion results in terms of accuracy and efficiency. For the two models, the optimal power is \~{}2.0-2.5 and and \~{}1.5 for the first and second Lam{\'e} parameters, respectively; and between 3 and 6, depending on the inverted frequency, for density. These power values provide the fastest and most accurate inversion results for the three parameters in the framework of multiscale and multishooting FWI using three different optimization schemes. {\textcopyright} The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.},
	keywords = {Computational seismology, Inverse theory, Numerical approximations and analysis, Seismic tomography},
	issn = {0956-540X},
	doi = {10.1093/gji/ggu175},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84903949166\&partnerID=tZOtx3y1},
	author = {Dagnino, D. and Sallar{\`e}s, V. and Ranero, C. R.}
}
