Source location using time‐reverse imaging

Abstract

A B S T R A C TWe present the chain of time-reverse modeling, image space wavefield decomposition and several imaging conditions as a migration-like algorithm called time-reverse imaging. The algorithm locates subsurface sources in passive seismic data and diffractors in active data. We use elastic propagators to capitalize on the full waveforms available in multicomponent data, although an acoustic example is presented as well.For the elastic case, we perform wavefield decomposition in the image domain with spatial derivatives to calculate P and S potentials. To locate sources, the time axis is collapsed by extracting the zero-lag of auto and cross-correlations to return images in physical space. The impulse response of the algorithm is very dependent on acquisition geometry and needs to be evaluated with point sources before processing field data. Band-limited data processed with these techniques image the radiation pattern of the source rather than just the location. We present several imaging conditions but we imagine others could be designed to investigate specific hypotheses concerning the nature of the source mechanism. We illustrate the flexible technique with synthetic 2D passive data examples and surface acquisition geometry specifically designed to investigate tremor type signals that are not easily identified or interpreted in the time domain.

Creating the Green's Response to a Virtual Source Inside a Medium Using Reflection Data with Internal Multiples

“…The method requires (1) the direct arriving wave front at the surface originated from a virtual source in the subsurface, and (2) the reflection impulse responses for all source and receiver positions at the surface. The direct arriving wave front can be obtained by modeling in a macro model, directly from the data by the CFP method (Berkhout, 1997) when the virtual source is located at an interface, from microseismic events (Artman et al, 2010), or from borehole check shots. A variant of the iterative scheme allows to decompose the reconstructed wavefield into downgoing and upgoing fields.…”

“…The iterative scheme requires the reflection response of the medium measured at the surface, complemented with independent information about the primary arrivals originated from the focusing location, to focus the acoustic wavefield inside the medium. The primary arrival wavefront can be estimated or measured in various ways: by forward modeling using a macro model, directly from the data by the Common Focusing Point method (CFP) (Thorbecke, 1997) when the virtual source is located at an interface, from microseismic events (Artman et al, 2010), or from borehole check shots. We denote the 2D spatial coordinates as x = (x, z).…”

Time reversal seismic source imaging using peak average power ratio (PAPR) parameter

“…The development of theoretical aspects of the method and its application in non-destructive testing were continued by Anderson et al (2009a, b) and Saenger et al (2011). The TRI technique in seismology has been used in source location and identification of source mechanisms (Gajewski and Tessmer 2005;Larmat et al 2006Larmat et al , 2010Kawakatsu and Montagner 2008;Steiner and Saenger 2010;Artman et al 2010;Debski 2015). In seismic exploration the TRI technique has been applied to wave field migration (Baysal et al 1983;McMechan 1983;Tarantola 1988;Fichtner et al 2006) and structure imaging in complex geological conditions like salt domes (Willis et al 2006).…”

A New Wave Equation Based Source Location Method with Full-waveform Inversion

“…However, they require picking the arrivals and rely on the high frequency asymptotic approximation of the wavefields, which will eventually lead to incorrect source locations with noisy data in complex areas. The other group of methods are based on solving the wave equation to focus the source, similar migration techniques, such as time reverse migration (Artman et al, 2010). These methods use the full wavefield to help locate the source.…”