Low frequency passive seismic interferometry for land data

Introduction

Seismic interferometry aims to retrieve the Green's function between two receiver stations by correlating measurements of seismic responses at both stations, effectively turning one station into a virtual source (Claerbout, 1968; Wapenaar, 2004). Recently, a variety of applications have been developed for active seismic data, such as the virtual source method (Bakulin and Calvert, 2006), redatuming (Schuster et al., 2004; Schuster and Zhou, 2006), and imaging of multiples (Berkhout and Verschuur, 2006). Commonly, active seismic (controlled source) interferometry attempts to reconstruct the high-frequency ($> 10$ Hz) impulse response of the earth. Passive seismic interferometry has mainly focused on retrieving high-frequency virtual sources where acquiring data with real sources is undesirable. Thus far, results of passive seismic interferometry have been less than promising, partially due to directionality of the ambient seismic wavefield and poor sampling of the medium by passive seismic sources. Early attempts of Cole (1995), (Artman, 2007,2006) yielded less than satisfactory results; more recently, Dragonov et al. (2007) retrieved high-frequency reflection events from pre-selected body-wave events. Meanwhile, global seismologists have been successful using seismic interferometry to retrieve Green's functions at much lower frequency. More recently, the ambient seismic field at lower frequencies ($< 10$ ) Hz has been shown to contain sufficient coherent and omnidirectional seismic energy to yield low-frequency Green's functions containing direct arrivals in a marine environment. Dellinger (2008) pointed out that conventional arrays record useable energy at low frequencies, while Dellinger and Yu (2009), Landes et al. (2009) and Bussat and Kugler (2009) have reported on the use of low-frequency seismic energy recorded in marine environments to image shallow seafloor structures.

An ambient seismic field recorded above a field in Saudi Arabia has previously been studied using novel imaging methods to locate microseismic events (Fu and Luo, 2009) and seismic interferometery to retrieve high frequency events (Xiao et al., 2009). Here we show interferometric retrieval of the Rayleigh surface waves at low frequencies. These surface waves are further studied for potential reservoir monitoring and imaging capabilities. Data availability limits the study to a conventional microtremor dispersion-curve analysis technique (Aki, 1957), which assumes laterally invariant media. However, more generally the retrieved Green's function can be studied and imaged without implicit lateral invariant assumptions.

Low frequency passive seismic interferometry for land data