Structure of the Suasselkä postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

Afonin, Nikita; Kozlovskaya, Elena; Kukkonen, Ilmo; Dafne,

doi:10.5194/se-8-531-2017

Cited by 8 publications

(6 citation statements)

References 37 publications

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“…However, special analysis of the continuous data would be necessary in order to extract the diffuse wavefield from the data. For this purpose, the SNRS algorithm described earlier in Afonin et al (2019) can be used. The technique is based on the global optimization algorithm, in which the optimized objective function is a signal-to-noise ratio of an EGF, retrieved at each iteration.…”

Section: Experiments Descriptionmentioning

confidence: 99%

Near-surface structure of the Sodankylä area in Finland, obtained by passive seismic interferometry

et al. 2021

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Abstract. Controlled-source seismic exploration surveys are not always possible in nature-protected areas. As an alternative, the application of passive seismic techniques in such areas can be proposed. In our study, we show results of passive seismic interferometry application for mapping the uppermost crust in the area of active mineral exploration in northern Finland. We utilize continuous seismic data acquired by the Sercel Unite wireless multichannel recording system along several profiles during XSoDEx (eXperiment of SOdankylä Deep Exploration) multidisciplinary geophysical project. The objective of XSoDEx was to obtain a structural image of the upper crust in the Sodankylä area of northern Finland in order to achieve a better understanding of the mineral system at depth. The key experiment of the project was a high-resolution seismic reflection experiment. In addition, continuous passive seismic data were acquired in parallel with reflection seismic data acquisition. Due to this, the length of passive data suitable for noise cross-correlation was limited from several hours to a couple of days. Analysis of the passive data demonstrated that dominating sources of ambient noise are non-stationary and have different origins across the XSoDEx study area. As the long data registration period and isotropic azimuthal distribution of noise sources are two major conditions for empirical Green function (EGF) extraction under the diffuse field approximation assumption, it was not possible to apply the conventional techniques of passive seismic interferometry. To find the way to obtain EGFs, we used numerical modelling in order to investigate properties of seismic noise originating from sources with different characteristics and propagating inside synthetic heterogeneous Earth models representing real geological conditions in the XSoDEx study area. The modelling demonstrated that scattering of ballistic waves on irregular shape heterogeneities, such as massive sulfides or mafic intrusions, could produce a diffused wavefield composed mainly of scattered surface waves. In our study, we show that this scattered wavefield can be used to retrieve reliable EGFs from short-term and non-stationary data using special techniques. One of the possible solutions is application of “signal-to-noise ratio stacking” (SNRS). The EGFs calculated for the XSoDEx profiles were inverted, in order to obtain S-wave velocity models down to the depth of 300 m. The obtained velocity models agree well with geological data and complement the results of reflection seismic data interpretation.

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Section: Experiments Descriptionmentioning

confidence: 99%

Near-surface structure of the Sodankylä area in Finland, obtained by passive seismic interferometry

et al. 2021

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“…Shapiro and Campillo, 2004;Roux et al, 2005;Ruigrok et al, 2011;Draganov et al, 2009;Poli et al, 2012;Tibuleac et al,. 2012;Wang et al, 2015;Taylor et al, 2016;Afonin et al, 2017;Oren and Nowack, 2016;Romero et al, 2018). In addition to ambient seismic noise interferometry, the coda wave interferometry was proposed (Campillo et al, 2003;Snieder et al, 2002;Snieder, 2006).…”

Section: Introductionmentioning

confidence: 99%

Near surface structure of Sodankylä area in Finland, obtained by advanced method of passive seismic interferometry

Afonin

Kozlovskaya

Heinonen

et al. 2020

Preprint

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Abstract. Controlled-source seismic exploration surveys are not always possible in nature-protected areas. As an alternative, application of passive seismic techniques in such areas can be proposed. In our study, we show results of passive seismic interferometry application for mapping the uppermost crust in the area of active mineral exploration in Northern Finland. We are utilizing continuous seismic data acquired by Sercel Unite Wireless multichannel recording system along several profiles during XSoDEx (eXperiment of SOdankylä Deep Exploration) project. The objective of the project was to obtain a structural image of the upper crust in the Sodankylä area of Northern Finland in order to achieve a better understanding of the mineral system at depth. The key experiment of the project was a high-resolution seismic reflection experiment, and continuous passive seismic data was acquired in parallel with reflection seismic data acquisition. Due to this, the length of passive data suitable for noise cross-correlation was limited to several hours. In addition, analysis of the passive data demonstrated that dominating sources of ambient noise are non-stationary and have different origin across the XSoDEx study area. As the long data registration period and isotropic azimuthal distribution of noise sources are two major conditions for diffuse wavefield necessary for Empirical Green's Functions (EGFs) extraction, the conventional techniques of passive seismic interferometry was not possible to apply. To find the way to obtain EGFs, we used numerical modelling to investigate the properties of seismic noise originating from sources with different characteristics and propagating inside synthetic heterogeneous Earth models that models real geological conditions in the XSodEx study area. The modelling demonstrated that scattering of ballistic waves on irregular shape heterogeneities, such as massive sulphides or mafic intrusions, could produce diffused wavefield composed mainly of scattered surface waves. This scattered wavefield can be used to retrieve reliable Empirical Green Functions (EGFs) from short-term and non-stationary data, using a special technique called signal-to-noise ratio stacking (SNRS). The EGFs calculated for the XSoDEx profiles were inverted in order to obtain S-wave velocity models down to the depth of 300 meters. The obtained velocity models agree well with geological data and complement the results of reflection seismic data interpretation.

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“…For this, we develop a new method of improving the quality of empirical Green's function (EGFs) evaluated from high-frequency industrial, anthropogenic or natural seismic noise. We partly use algorithms described in Shapiro et al (2005), Campillo (2006), Bensen et al (2007), Groos et al (2012), Poli et al (2012aPoli et al ( , b, 2013, and Afonin et al (2017) for ambient noise preprocessing and implement a new algorithm of stacking crosscorrelation functions in the time domain.…”

Section: Introductionmentioning

confidence: 99%

“…One group of algorithms tries to improve the quality of the resulting EGFs using the evaluation of cross-correlation functions according to certain criteria prior to stacking them. For example, in the methods described in Baig et al (2009), a denoising procedure, based on S transform, is applied to cross-correlation functions before their stacking. In the "time-frequency domain phaseweighted stacking" method, which may use either S transform (Schimmel et al, 2011) or wavelet transform (Ventosa et al, 2017), phases of signals are analysed prior stacking them.…”

Section: Introductionmentioning

confidence: 99%

Improving the quality of empirical Green's functions, obtained by cross-correlation of high-frequency ambient seismic noise

et al. 2019

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Abstract. Studying the uppermost structure of the subsurface is a necessary part of solving many practical problems (exploration of minerals, groundwater studies, geoengineering, etc.). The practical application of active seismic methods for these purposes is not always possible for different reasons, such as logistical difficulties, high cost of work, and a high level of seismic and acoustic noise. That is why developing and improving passive seismic methods is one of the important problems in applied geophysics. In our study, we describe a way of improving the quality of empirical Green's functions (EGFs), evaluated from high-frequency ambient seismic noise, by using the advanced technique of cross-correlation function stacking in the time domain (in this paper we use term “high-frequency” for frequencies higher than 1 Hz). The technique is based on the global optimization algorithm, in which the optimized objective function is a signal-to-noise ratio of an EGF, retrieved at each iteration. In comparison to existing techniques, based, for example, on weight stacking of cross-correlation functions, our technique makes it possible to significantly increase the signal-to-noise ratio and, therefore, the quality of the EGFs. The technique has been tested with the field data acquired in an area with a high level of industrial noise (Pyhäsalmi Mine, Finland) and in an area with a low level of anthropogenic noise (Kuusamo Greenstone Belt, Finland). The results show that the proposed technique can be used for the extraction of EGFs from high-frequency seismic noise in practical problems of mapping of the shallow subsurface, both in areas with high and low levels of high-frequency seismic noise.

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Structure of the Suasselkä postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

Cited by 8 publications

References 37 publications

Near-surface structure of the Sodankylä area in Finland, obtained by passive seismic interferometry

Near-surface structure of the Sodankylä area in Finland, obtained by passive seismic interferometry

Near surface structure of Sodankylä area in Finland, obtained by advanced method of passive seismic interferometry

Improving the quality of empirical Green's functions, obtained by cross-correlation of high-frequency ambient seismic noise

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