Wide-band extraction of mantle P waves from ambient noise

Abstract

Abstract The spatial correlation characteristics of ambient short-period (0.5 to 5 cps) noise at Ft. Sill, Oklahoma, and on the Cumberland Plateau in Tennessee were investigated on "permanent" arrays with 3-4 kilometer diameter. Dominant ambient noise at the two locations is spatially organized, and to first order may be treated as a combination of seismic propagating wave trains. At the Tennessee location noise energy above one cps is dominantly propagating with velocities from 3.5 to 4.5 km/sec, and must be carried in deeply trapped, high-order modes.Generalized multichannel filtering (Burg) can be used to preserve a large class of mantle P-wave signals, wideband, in a single output trace, while at the same time specifically rejecting ambient noise on the basis of its organization. Results of generalized multichannel filtering applied on-line at the nineteen-element array in Tennessee and applied off-line are discussed.