S.H.W. Hassing | TU Delft Repository

Adaptation of Iterative Supervirtual Interferometry for Enhancing Higher Modes From Surface Waves

Journal article (2026) - Sverre Hassing, Deyan Draganov, Eric Verschuur

For geotechnical applications, surface-wave methods are one of the most important techniques for gathering information about the strength of the near surface, but these methods are sensitive to noise. Often only the fundamental mode is considered, but higher modes can also provide more information on deeper parts of the subsurface. We investigate the use of iterative supervirtual interferometry (SVI) to increase the signal-to-noise ratio and to extract more information about the higher modes. A big advantage is that the method results in data in the same domain as the original data, such that similar multichannel analysis of surface waves–based procedures can be used afterwards. SVI utilises seismic interferometry to extract the extra information in consecutive folds. Generally, the strongest event in the data is boosted the most. Although surface waves are usually the strongest, they consist of sub-events (the modes) with different amplitudes. Previously, iterative SVI has been applied to further boost the result of SVI. For surface waves, this would further diminish the presence of weaker modes. Instead, we subtract the results of SVI from the original data and use the remainder as input for the next iteration, which gives potential for highlighting different modes. We apply our methodology to three different datasets to show different properties of the iterative SVI. When the level of random noise is high, further iterations retrieve mostly the dominant event and no extra information on different modes is gained. When the level of noise is relatively low, we show that higher modes can be found in a wider frequency band in the results of each separate iteration. In both cases, the combination of all iterations provides a more complete description of the surface waves. The presence of strong random noise or spikes in the data can have negative effects on the methodology in the form of spurious events originating from the spikes. ...

For geotechnical applications, surface-wave methods are one of the most important techniques for gathering information about the strength of the near surface, but these methods are sensitive to noise. Often only the fundamental mode is considered, but higher modes can also provide more information on deeper parts of the subsurface. We investigate the use of iterative supervirtual interferometry (SVI) to increase the signal-to-noise ratio and to extract more information about the higher modes. A big advantage is that the method results in data in the same domain as the original data, such that similar multichannel analysis of surface waves–based procedures can be used afterwards. SVI utilises seismic interferometry to extract the extra information in consecutive folds. Generally, the strongest event in the data is boosted the most. Although surface waves are usually the strongest, they consist of sub-events (the modes) with different amplitudes. Previously, iterative SVI has been applied to further boost the result of SVI. For surface waves, this would further diminish the presence of weaker modes. Instead, we subtract the results of SVI from the original data and use the remainder as input for the next iteration, which gives potential for highlighting different modes. We apply our methodology to three different datasets to show different properties of the iterative SVI. When the level of random noise is high, further iterations retrieve mostly the dominant event and no extra information on different modes is gained. When the level of noise is relatively low, we show that higher modes can be found in a wider frequency band in the results of each separate iteration. In both cases, the combination of all iterations provides a more complete description of the surface waves. The presence of strong random noise or spikes in the data can have negative effects on the methodology in the form of spurious events originating from the spikes.

Imaging CO₂ reinjection into basalts at the CarbFix2 reinjection reservoir (Hellisheiði, Iceland) with body-wave seismic interferometry

Journal article (2024) - S. H.W. Hassing, Deyan Draganov, Martijn Janssen, Auke Barnhoorn, K. H.A.A. Wolf, Jens van den Berg, Marc Friebel, Gijs van Otten, Flavio Poletto, More authors...

As part of the Synergetic Utilisation of CO (Formula presented.) storage Coupled with geothermal EnErgy Deployment project, investigating CO (Formula presented.) reinjection with different seismic methods, both passive and active seismic surveys have been conducted at the geothermal power plant at Hellisheiði, Iceland. During the 2021 survey, two geophone lines recorded noise for a week. We process the passive-source data with seismic interferometry to image the subsurface structure around the CarbFix2 reinjection reservoir. To improve image quality, we perform an illumination analysis to select only noise panels dominated by body-wave energy. The results show that most noise panels are dominated by air-wave energy arriving from the direction of the power plant. We use panels with a near-vertical incidence to create a zero-offset image and a larger selection of body-wave-dominated panels to create virtual common-shot gathers. We process the gathers with a simple reflection seismology processing workflow to obtain stacked images. The zero-offset images show a relatively lower signal-to-noise ratio and only horizontal reflectors. The stacked images show slightly dipping reflectors and possibly lateral amplitude variations around the expected injection region. This could indicate a region of interest for future research into the reinjection reservoir. ...

Surface-Wave Supervirtual Seismic Interferometry

The Ugly, the Bad, and the Good

Conference paper (2024) - S. Hassing, D. Draganov, E. Verschuur

We apply supervirtual interferometry to boost the surface-wave content of two different seismic surveys. The method uses seismic interferometric principles to exploit data redundancy in multi-fold surveys. The effect on the first survey is generally positive, where the signal-to-noise ratio is improved and the relative amplitude of other events, like direct waves or reflections, is decreased. The second survey shows that the effects are not always positive. For some shots, the quality of the dispersion curve decreases and for some a higher mode becomes more dominant. This can be caused when assumptions made for seismic interferometry by corrrelation are not complied with, primarily heterogeneities in the medium and attenuation. As such, the effect of applying supervirtual interferometry could be used as an indication for local heterogeneities. ...

Imaging the CarbFix2 Reinjection Reservoir at Hellisheiði, Iceland, with Body-wave Seismic Interferometry

Conference paper (2022) - S. Hassing, D. Draganov, A. Barnhoorn, M. Janssen

In July 2021, passive seismic data has been recorded on a network of geophones at the CarbFix2 injection site at Hellisheiði, Iceland. This data is processed using seismic interferometry to get an image of the injection reservoir. The data is split up into noise panels. Panels dominated by body-wave energy are selected using an illumination analysis. In panels where the dominant event has a (near) vertical incidence, each trace is autocorrelated to get a zero-offset section. In panels where the dominant event is recognized as a body-wave event, all the traces are crosscorrelated, obtaining virtual common-shot gathers. This is processed with a reflection-seismology workflow to obtain a stacked section. Comparing the two final sections shows that similar reflectors are imaged. The zero-offset section shows a higher frequency content, while the stacked section shows more continuous reflectors. Comparison with a local geological model shows that the results are plausible, but that a better interpretation has to wait for more results of the same survey to be processed. ...