Imaging and monitoring of subsurface structures using reflection retrieves from seismic interferometry

Geoscience & EngineeringCivil Engineering and Geoscience

Grip mikrofonen?

Listening to 210 recordings of Grieg’s opus 5 no. 3 from 1899–2005, I have selected a small section of the song (bars 10–16), and analysed the singer’s choice of expressions of intensity or intimacy. Intensity is defined as a quality where the potentiality of the expression is linked with general, congeneric elements (signs, symbols, gestures). Intimacy is defined as a quality where the actuality of the expression is linked with the performer and the moment of performance. From 1926 a new kind of singer emerged: the gramophone artist using the microphone as his/her main expression tool resulting in intimacy, mostly by performing regular text rhythms in an irregular way (parlando). The concert hall singer did not change his/her style of singing, taking advantage of the studio until the beginning of 1950s. The tendency of tidying up performances towards more literary correct performances is documented in these recordings up to 1975. Then the intimacy of parlando again becomes the main expression in this section

Interferometric identification of surface-related multiples

The theory of seismic interferometry redicts that crosscorrelations of recorded seismic res onses at two receivers yield an estimate of the interreceiver seismic res onse. The interferometric rocess a lied to surface-reflection data involves the summation, over sources, of crosscorrelated traces, and it allows retrieval of an estimate of the interreceiver reflection res onse. In articular, the crosscorrelations of the data with surfacerelated multi les in the data roduce the retrieval of seudo hysical reflections (virtual events with the same kinematics as hysical reflections in the original data). Thus, retrieved seudo hysical reflections can rovide feedback information about the surface multi les. From this ers ective, we have develo ed a data-driven interferometric method to detect and redict the arrival times of surface-related multi les in recorded reflection data using the retrieval of virtual data as diagnosis. The identification of the surface multi les is based on the estimation of source ositions in the stationary- hase regions of the retrieved seudo hysical reflections, thus not necessarily requiring sources and receivers on the same grid. We have evaluated the method of interferometric identification with a two-layer acoustic exam le and tested it on a more com lex synthetic data set. The results determined that we are able to identify the rominent surface multi les in a large range of the reflection data. Although missing near offsets roved to cause major roblems in multi le- rediction schemes based on convolutions and inversions, missing near offsets does not im ede our method from identifying surface multi les. Such interferometric diagnosis could be used to control the effectiveness of conventional multi le-removal schemes, such as ada tive subtraction of multi les redicted by convolution of the data.Applied Geophysics and Petrophysic

Surface-waves suppression using seismic interferometry for imaging and monitoring of the Groningen subsurface

High-resolution seismic reflections are essential for imaging and monitoring applications using data-driven methods such as seismic interferometry (SI) and Marchenko redatuming. For seismic land surveys using sources and receivers at the surface, the surface waves are the dominant noises that mask the reflections. We use SI to suppress surface waves from the reflection dataset. SI is a technique that allows the retrieval of new seismic responses at one receiver from a virtual source at the position of another receiver using, e.g., cross-correlation or convolution. We processed a two-dimensional seismic reflection dataset acquired along a line in Scheemda, located in the Groningen province of the Netherlands. The sources are placed with a spacing of 2 m, and 601 receivers are placed every 1 m. We implemented some pre-processing steps, including source signature deconvolution and filtering. Then, we applied SI by cross-correlation by turning receivers into virtual sources to estimate the dominant surface waves. Afterwards, we performed adaptive subtraction with different filter parameters for the matching filter to minimise the difference between the surface waves in the original data and the result of SI. Comparing the retrieved results from SI with the original data in the time domain and the frequency-wavenumber domain shows that at least some parts of surface waves are suppressed from the dataset, which can help to better visualise reflections for future studies in imaging and monitoring the subsurface.Applied Geophysics and Petrophysic

Identification and elimination of surface-related multiples using seismic interferometry with active sources

Geoscience & EngineeringCivil Engineering and Geoscience

Body-wave passive seismic interferometry revisited: mining exploration using the body waves of local microearthquakes

As the global need for mineral resources is constantly rising and the exploitable concentrations of these resources tend to become increasingly complex to explore and exploit, the mining industry is in a constant quest for innovative and cost‐effective exploration solutions. In this context, and in the framework of the Smart Exploration action, an integrated passive seismic survey was launched in the Gerolekas bauxite mining site in Central Greece. A passive seismic network, consisting of 129 three‐component short‐period stations was installed and operated continuously for 4 months. The acquired data permitted detection of approximately 1000 microearthquakes of very small magnitude (duration magnitude ranging between –1.5 and 2.0), located within or at a very close distance from the study area. We use this microseismicity as input for the application of passive seismic interferometry for reflection retrieval, using the body waves (P‐ and S‐wave coda) of the located microearthquakes. We retrieve by autocorrelation zero‐offset virtual reflection responses, per component, below each of the recording stations. We process the acquired results using reflection processing techniques to obtain zero‐offset time and depth sections, both for P‐ and for S‐waves. In the context of the present work, we evaluate one of the acquired depth sections, using an existing seismic line passing through the Gerolekas passive seismic network, and we perform forward modelling to assess the quality and value of the acquired results. We confirm that passive seismic reflected‐wave interferometry could constitute a cost‐effective and environmentally friendly innovative exploration alternative, especially in cases of difficult exploration settings.Applied Geophysics and Petrophysic

Monitoring tidal water-column changes in ports using distributed acoustic sensing

We show results of of using distributed acoustic sensing (DAS) for continuous relative water-column changes monitoring by relating the oscillating frequencies to measurements of a nearby tidal-station. The oscillations have a great qualitative agreement with the tidal-station, having a period of 12 hours and 25 minutes. No calibration is required to measure the tides and the relative difference in water height, though calibration would allow measuring the absolute water height at any location. Because we used two poles with different exposure lengths to air, at different depths and only 38 m apart, we can interpret he spectral oscillations are a result of constructive interference in our poles, likely generated by the wind. DAS could be a very attractive alternative for tidal monitoring in shallow marine environments, ports and waterways. DAS could potentially resolve spatial resolution problems with tidal monitoring, which is currently cost-prohibited, at a relatively low expense by wrapping a fibre around a pre-existing structure such as a docking pole. Furthermore, DAS can be used remotely and continuously, allowing for better model calibrations or local tidal fluctuation monitoring. This monitoring system could help determine if ships have enough water clearance to dock and, in turn, increase the occupation rate.Applied Geophysics and PetrophysicsRivers, Ports, Waterways and Dredging Engineerin

Imaging a landfill with seismics

Poster presentation at the Geoscience Research Meeting, Delft, 7-2-2013Geoscience & EngineeringCivil Engineering and Geoscience

The potential of imaging subsurface heterogeneities by local, natural earthquakes

We have developed a new imaging technique of subsurface heterogeneities that uses Sp-waves from natural earthquakes. This technique can be used as a first screening tool in frontier exploration areas before conventional active exploration. Analyzing Sp-waves from 28 earthquakes (Mj 2.0 to 4.2) recorded by two permanent seismic stations, we built an image of the distributions of velocity discontinuities in southeastern offshore Hokkaido, Japan, where intraplate earthquakes in the Pacific plate frequently occur. Our results indicated the presence of three horizontally continuous, distinct discontinuities corresponding to geologic boundaries estimated in a previous study.We also derived the frequency-dependent quality factor Q for P- and S-waves and use it as a method of characterizing physical properties of subsurface structure. The waveform traces with coherent Sp-phases in the southern part of the study area generally show a constant QS?QP ratio, and the waveform traces with randomly distributed phases in the northern part show a large variation of the QS?QP ratio (including several high values).Geoscience & EngineeringCivil Engineering and Geoscience

Monitoring changes inside subsurface layers using non-physical reflections retrieved from seismic interferometry

Seismic interferometry (SI) is a principle for retrieving responses between two receivers using cross-correlation. After the retrieval, one of the receivers acts as a virtual seismic source whose response is retrieved at the second receiver. Correct response retrieval relies on assumptions, among other, of a lossless medium being illuminated homogeneously by sufficiently densely spaced sources (passive or active). When these assumptions are not met, non-physical reflections might appear in the results of SI due to insufficient destructive interference. These non-physical reflections are caused by internal reflections inside subsurface layers. However, the non-physical reflections could be used for monitoring changes in the subsurface layers that generate them. We investigate utilization of non-physical reflections for monitoring velocity changes for purposes of the DeepNL programme. We simulate reflection experiments using an acoustic finite-difference modelling for a horizontally layered model and for a subsurface with inclined layers. We perform SI by autocorrelation and by cross-correlation. Comparing retrieved results with the directly modelled results, we confirm previous results that for a layered subsurface the retrieved ghost reflections can be used for multiple offsets. For inclined layers, zero-offset ghost reflections can be retrieved for the different receiver locations. Both types of non-physical reflections are sensitive to velocity change and thickness of the layer that cause them to appear in the SI results, so they can be used for monitoring purposes of the subsurface.Accepted Author ManuscriptApplied Geophysics and Petrophysic