Imaging and suppressing near-receiver scattered surface waves

Abstract

When traveling through a complex overburden, upcoming seismic body waves can be disturbed by scattering from local heterogeneities. Currently, surface-consistent static and amplitude corrections correct for rapid variations in arrival times and amplitudes of a reflector, but these methods impose strong assumptions on the near-surface model. Observations on synthetic and laboratory experiments of near-surface scattering with densely sampled data suggest that removing noise from near-receiver scattering requires multichannel approaches rather than single-channel, near-surface corrections. In this paper we develop a wavefield-based imaging method to suppress surface waves scattered directly beneath the receivers. Using an integral-equation formulation, we account for near-surface heterogeneities by a surface impedance function. This impedance function is used to model scattered surface waves, excited by upcoming wavefronts. The final step in our algorithm is to subtract the scattered surface waves. We successfully apply this method to laboratory data of scattered surface waves, excited and monitored with a noncontacting acquisition system.

Imaging Near-surface Heterogeneities by Natural Migration of Back-scattered Surface Waves

“…For surface waves, the image m(x) in eq. (2) can be evaluated on the free surface to produce 2-D images which are projections of the scatterer's locations onto the free surface (Snieder 1986;Blonk & Herman 1994;Campman et al 2005). These projections are appropriate for scatterer's at shallow depths that are detectable by surface waves.…”

“…For many practical applications, the background velocity model is assumed to be a layered medium. This methodology has found a growing number of uses in earthquake, exploration and engineering seismology (Snieder 1986;Blonk et al 1995;Wijk 2003;Campman et al 2005;Riyanti 2005;Campman & Riyanti 2007;Kaslilar 2007).…”

“…The typical strategy is to (1) linearize the relation between the scattered data d and the model perturbation m (i.e. heterogeneities map) under the Born approximation d = Lm, and then (2) find the approximate solution by either an iterative optimization method (Riyanti 2005;Campman & Riyanti 2007;Kaslilar 2007) or by applying the adjoint (Snieder 1986;Blonk et al 1995;Campman et al 2005;Yu et al 2014) of the modeling operator L † to the scattered data d to get the migration image m mig = L † d. In all cases, the two key assumptions are that the velocity model (typically, just the smooth component of the surface wave velocity distribution) is known and the weak-scattering approximation is invoked. For many practical applications, the background velocity model is assumed to be a layered medium.…”

Ray-map migration of transmitted surface waves

“…To generate detailed images of fault zones, geophysicists proposed the migration of back-scattered surface waves (Snieder, 1986;Campman et al, 2004Campman et al, , 2005Brandsberg-Dahl et al, 2007;Sinha et al, 2009;Hanafy et al, 2014;Sloan et al, 2015;AlTheyab et al, 2016). The migration procedure can be either a reverse time migration method (Almuhaidib and Toksöz, 2015), a Kirchhoff-like migration (Hyslop and Stewart, 2014;Yu et al, 2014), or a seismic scanning tunneling macroscope method (AlTheyab et al, 2016).…”

Imaging of near-surface heterogeneities by scattered elastic waves

“…These methods have difficulties when dealing with large and high-contrast heterogeneities that violate the Born approximation. Campman et al (2005Campman et al ( , 2006 use an inverse scattering approach based on an integral-equation formulation to image the near-surface heterogeneities, but they assume that scattering takes place immediately under the receivers. Other methods, based on solving integral equations using the method of moments, can handle strong contrast and large heterogeneities and can take into account multiple scattering (Riyanti and Herman, 2005;Campman and Riyanti, 2007).…”