Deriving 3D Q Models from Surface Seismic Data Using Attenuated Traveltime Tomography

摘要

Estimation of the intrinsic attenuation of the Earth, conveniently described by the quality factor Q, is of great importance in seismic processing and rock physics interpretation. However, deriving a Q Earth model from seismic data is quite challenging, as anelastic and elastic attenuation effects on propagated waves can be difficult to dissociate. In this paper, we propose to derive 3D Q Earth models from prestack surface data by applying an inversion of the attenuated traveltimes of selected seismic events (first arrivals, reflections). Attenuated traveltime is defined as the traveltime of the propagated signal weighted by its effective-Q factor. This factor is obtained from a preliminary effective-Q mapping based on a suitable amplitude analysis and assumed to provide "intrinsic enough" effective-Q estimates.An estimate of the velocity is only required for a kinematic ray tracing during the inversion. This technique can be applied, for instance, to first-arrival events.Afirst-arrival tomography is implemented to derive both a near-surface velocity model (traveltime inversion) and a near-surface Q model (attenuated traveltime inversion). This approach is illustrated here on a synthetic dataset. Reflection attenuated traveltime tomography can be considered in a similar manner.