Heeding the waveform inversion nonlinearity by unwrapping the model and data

Alkhalifah, Tariq Ali; Choi, Yun Seok

Heeding the waveform inversion nonlinearity by unwrapping the model and data

Type

Conference Paper

Authors

Alkhalifah, Tariq Ali

Choi, Yun Seok

KAUST Department

Earth Science and Engineering Program
Environmental Science and Engineering Program
Physical Science and Engineering (PSE) Division
Seismic Wave Analysis Group

Online Publication Date

2014-12-03

Print Publication Date

2012-06-04

Date

2014-12-03

Abstract

Unlike traveltime inversion, waveform inversion provides relatively higher-resolution inverted models. This feature, however, comes at the cost of introducing complex nonlinearity to the inversion operator complicating the convergence process. We use unwrapped-phase-based objective functions to reduce such nonlinearity in a domain in which the high-frequency component is given by the traveltime inversion. Such information is packaged in a frequency-dependent attribute (or traveltime) that can be easily manipulated at different frequencies. It unwraps the phase of the wavefield yielding far less nonlinearity in the objective function than those experienced with the conventional misfit objective function, and yet it still holds most of the critical waveform information in its frequency dependency. However, it suffers from nonlinearity introduced by the model (or reflectivity), as events interact with each other (something like cross talk). This stems from the sinusoidal nature of the band-limited reflectivity model. Unwrapping the phase for such a model can mitigate this nonlinearity as well. Specifically, a simple modification to the inverted domain (or model), can reduce the effect of the model-induced nonlinearity and, thus, make the inversion more convergent. Simple examples are used to highlight such features.

Citation

Alkhalifah, T., & Choi, Y. (2012). Heeding the Waveform Inversion Nonlinearity by Unwrapping the Model and Data. 74th EAGE Conference and Exhibition Incorporating EUROPEC 2012. doi:10.3997/2214-4609.20148331