Permanent, seasonal, and episodic seismic sources around Vatnajökull, Iceland from the analyses of correlograms

2021 ◽  
Author(s):  
Sylvain Nowé ◽  
Thomas Lecocq ◽  
Corentin Caudron ◽  
Kristín Jónsdóttir ◽  
Frank Pattyn
Keyword(s):  
Seismic Noise ◽  
Cross Correlation ◽  
Seismic Interferometry ◽  
Seismic Sources ◽  
Monitoring Method ◽  
West Part ◽  
Location Methods ◽  
Seismic Background ◽  
The Impact ◽  
Propagation Velocities

<p>This study aims at characterizing different seismic sources in the region of the Vatnajökull glacier using seismic interferometry. Vatnajökull is the largest Icelandic icecap, covering 4active volcanic systems. The seismic context is therefore very complex with glacial and volcanic events occurring simultaneously and a classification between the two can become cumbersome. </p><p>We used seismic interferometry or cross-correlation of seismic noise on seismic data from 2011 to 2019). Being based on continuous records, this passive monitoring method is not relying on earthquakes to locate seismic sources. We computed the cross-correlation functions between every pair of seismic stations using MSNoise for different frequency bands, from 0.5 to 8 Hz. The first step towards the location of seismic sources was to calculate the propagation velocities for each frequency range. The total range of velocities is between 1.39 km/s and 3.92 km/s. Then, we used two different location methods based on the calculated propagation velocities. The first method is based on hyperbole’s geometry and provides the location of seismic sources as the intersection between several hyperboles, while the second one, the Ballmer’s method (Ballmer et al. 2013), is based on the calculation of theoretical differential times and provides location probabilities for the seismic sources. We located and characterized persistent oceanic seismic noise located along the southern shoreline of Iceland potentially associated with waves activity and geometry of the shore, as well as a seasonal glacial tremor around outlet glaciers in the west part of the Vatnajökull icecap, potentially linked to glacial processes inside the glacier or in the glacial rivers. The uncertainty of a few kilometers is observed. Some limitations exist for these methods. For example, The Ballmer’s method (Ballmer et al. 2013) is reliable for seismic sources inside the seismic network but can only give an azimuthal direction for seismic sources located outside of it. When using hyperboles, slightly different propagation velocities between pairs of stations can affect the precision of the intersection. Therefore, the association of the two methods is important to diminish the impact of these limitations. </p><p>These results provide a better understanding of the seismic background of this region and will be compared and validated with other localization methods in the future.</p>

scholarly journals Permanent, seasonal, and episodic seismic sources around Vatnajökull, Iceland, from the analysis of correlograms

Volcanica ◽  
2021 ◽  
pp. 135-147
Author(s):  
Sylvain Nowé ◽  
Thomas Lecocq ◽  
Corentin Caudron ◽  
Kristín Jónsdóttir ◽  
Frank Pattyn
Keyword(s):  
Seismic Data ◽  
Seismic Noise ◽  
Search Method ◽  
Seismic Interferometry ◽  
Seismic Sources ◽  
Grid Search ◽  
Noise Sources ◽  
Grid Search Method ◽  
Volcanic Events ◽  
Propagation Velocities

In this study, we locate and characterise the main seismic noise sources in the region of the Vatnajökull icecap (Iceland). Vatnajökull is the largest Icelandic icecap, covering several active volcanoes. The seismic context is very complex, with glacial and volcanic events occurring simultaneously and the classification between the two can become cumbersome. Using seismic interferometry on continuous seismic data (2011–2019), we calculate the propagation velocities and locate the main seismic sources by using hyperbolic geometry and a grid-search method. We identify and characterise permanent oceanic sources, seasonal glacial-related sources, and episodic volcanic sources. These results give a better understanding of the background seismic noise sources in this region and could allow the identification of seismic sources associated with potentially threatening events in real-time.

scholarly journals Adaptive seismic noise reduction using Wiener filter

2019 ◽  
Vol 8 (1) ◽  
pp. 12-20
Author(s):  
Sesar Prabu Dwi Sriyanto
Keyword(s):  
Seismic Noise ◽  
Cross Correlation ◽  
Seismic Station ◽  
Wiener Filter ◽  
Dominant Frequency ◽  
Observation System ◽  
Before And After ◽  
Filter Process ◽  
The Cross ◽  
The Impact

Seismic noise disrupts the earthquake observation system due to the frequency and amplitude of seismic noise similar to the earthquake signal. The filter process is one of the methods that can be used to reduce seismic noise. In this study, the Wiener filter algorithm was designed with the Decision-Directed method for Apriori SNR estimation. This filter was chosen because it is adaptive, so it can adjust to environmental conditions without requiring manual parameter settings. The data used are earthquake signals that occur in the Palu area, Central Sulawesi, which are recorded on PKA29 temporary seismic station from February 3 to April 28, 2015. After each signal data has been filtered, then it is evaluated by calculating SNR differences before and after filtering, the signal's dominant frequency, and the cross-correlation of the signal before and after filtering. As a result, the Wiener filter is able to reduce the noise content in earthquake signals according to noisy frequencies before earthquake signals. The impact is that SNR has increased with an average of 8.056 dB. In addition, this filter is also able to maintain the shape of earthquake signals. This is indicated by the normalization value of the cross-correlation between signals before and after the filter which ranges from 0.703 to 1.00.

scholarly journals Seismic Interferometry by cross‐correlation and by multi‐dimensional deconvolution using ambient seismic noise

2009 ◽  
Author(s):  
Jan Thorbecke ◽  
Elmer Ruigrok ◽  
Deyan Draganov ◽  
Joost v.d. Neut ◽  
Jürg Hunziker ◽  
...  
Keyword(s):  
Seismic Noise ◽  
Cross Correlation ◽  
Seismic Interferometry ◽  
Ambient Seismic Noise

scholarly journals Imaging New Zealand's Crustal Structure Using Ambient Seismic Noise Recordings from Permanent and Temporary Instruments

2021 ◽  
Author(s):  
◽  
Yannik Behr
Keyword(s):  
Seismic Noise ◽  
Cross Correlation ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Ambient Seismic Noise ◽  
Uppermost Mantle ◽  
Noise Sources ◽  
Noise Field ◽  
Rayleigh And Love Waves ◽  
Noise Cross Correlation

<p>We use ambient seismic noise to image the crust and uppermost mantle, and to determine the spatiotemporal characteristics of the noise field itself, and examine the way in which those characteristics may influence imaging results. Surface wave information extracted from ambient seismic noise using cross-correlation methods significantly enhances our knowledge of the crustal and uppermost mantle shear-velocity structure of New Zealand. We assemble a large dataset of three-component broadband continuous seismic data from temporary and permanent seismic stations, increasing the achievable resolution of surface wave velocity maps in comparison to a previous study. Three-component data enables us to examine both Rayleigh and Love waves using noise cross-correlation functions. Employing a Monte Carlo inversion method, we invert Rayleigh and Love wave phase and group velocity dispersion curves separately for spatially averaged isotropic shear velocity models beneath the Northland Peninsula. The results yield first-order radial anisotropy estimates of 2% in the upper crust and up to 15% in the lower crust, and estimates of Moho depth and uppermost mantle velocity compatible with previous studies. We also construct a high-resolution, pseudo-3D image of the shear-velocity distribution in the crust and uppermost mantle beneath the central North Island using Rayleigh and Love waves. We document, for the first time, the lateral extent of low shear-velocity zones in the upper and mid-crust beneath the highly active Taupo Volcanic Zone, which have been reported previously based on spatially confined 1D shear-velocity profiles. Attributing these low shear-velocities to the presence of partial melt, we use an empirical relation to estimate an average percentage of partial melt of < 4:2% in the upper and middle crust. Analysis of the ambient seismic noise field in the North Island using plane wave beamforming and slant stacking indicates that higher mode Rayleigh waves can be detected, in addition to the fundamental mode. The azimuthal distributions of seismic noise sources inferred from beamforming are compatible with high near-coastal ocean wave heights in the period band of the secondary microseism (~7 s). Averaged over 130 days, the distribution of seismic noise sources is azimuthally homogeneous, indicating that the seismic noise field is well-suited to noise cross-correlation studies. This is underpinned by the good agreement of our results with those from previous studies. The effective homogeneity of the seismic noise field and the large dataset of noise cross-correlation functions we here compiled, provide the cornerstone for future studies of ambient seismic noise and crustal shear velocity structure in New Zealand.</p>

scholarly journals Importance and Impact of the Poultry Red Mite (Dermanyssus Gallinae) in Layer Farms - Analysis of Farmers’ Perception

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Miroslav Kjosevski ◽  
Danijela Horvatek Tomić ◽  
Aleksandar Dodovski
Keyword(s):  
Crude Oil ◽  
Pest Management ◽  
Descriptive Statistics ◽  
Dermanyssus Gallinae ◽  
Bayes Classifier ◽  
Poultry Red Mite ◽  
Monitoring Method ◽  
Poultry Farms ◽  
And Control ◽  
The Impact

Abstract Poultry red mite (PRM), Dermanyssus gallinae, causes egg drop production, anemia and can be a vector in transmitting diseases. The PRM control mainly focuses on usage of the conventional chemical biocides. The objective of this study was to analyze the farmers’ perception regarding the impact, management and control of PRM in Macedonian layer farms. The data were collected with direct on-site visits using a unified questionnaire. In total, 29 poultry farms (28% of farms in the country), all with conventional cages, were part of this study. The data were analyzed by descriptive statistics, inferential statistics and Naïve Bayes Classifier technique. In 30% of the poultry farms the farmers had observed that the flock was infested with PRM. In total, 32 different treatments against PRM were reported from the farmers, and three of them were non-biocide treatments. The most used biocides (17% of the farms) were crude oil, Formalin, Neopitroid® and disinfectants. The highest agreement regarding biocides application among the farms (38%) was before the production starts. Most of the farmers applied biocides routinely, before the infestation is evident (75%). The median costs for PRM treatment were 175€ per flock, higher in the infested farms 493±677€ compared to non - infested 100±71€, p<0.05. None of the Macedonian farmers included in the study was using monitoring method for PRM infestation, contributing to poor data records. This study highlights the need of developing unified strategy for PRM control included in the Integrated Pest Management in poultry layer farms.

Crosscorrelation migration of microseismic source locations with hybrid imaging condition

Geophysics ◽  
2021 ◽  
pp. 1-49
Author(s):  
Shaojiang Wu ◽  
Yibo Wang ◽  
Fei Xie ◽  
Xu Chang
Keyword(s):  
Cross Correlation ◽  
Hybrid Imaging ◽  
Hydraulic Fractures ◽  
Imaging Condition ◽  
Time Scanning ◽  
Comparison Results ◽  
Excitation Time ◽  
Seismic Location ◽  
Location Methods ◽  
Selection Of

Locating microseismic sources is critical to monitor the hydraulic fractures that occur during fluid extraction/injection in unconventional oil or gas exploration. Waveform-based seismic location methods can reliably and automatically image weak microseismic source locations without phase picking. Among them, the cross-correlation migration (CCM) method can avoid excitation time scanning by generating virtual gathers. We propose a CCM location method based on the hybrid imaging condition (HIC). There are four main steps in the implementation of this method: 1) selection of receivers with good azimuthal coverage; 2) generation of virtual gathers by correlating the reference receiver with the rest of the receivers; 3) summation of back-projections in the virtual gathers; and 4) multiplication of all summations. The CCM-HIC method was tested on synthetic and field datasets, and the results were compared with those obtained by conventional summation imaging condition (SIC) and multiplication imaging condition (MIC). The comparison results demonstrate that the CCM-HIC is sufficiently robust to obtain better stability and higher spatial resolution image of source location, despite the presence of strong noise.

scholarly journals Understanding the role of visual attention on wines’ purchase intention: an eye-tracking study

2019 ◽  
Vol 32 (2) ◽  
pp. 161-179
Author(s):  
Patrícia Monteiro ◽  
João Guerreiro ◽  
Sandra Maria Correia Loureiro
Keyword(s):  
Visual Attention ◽  
Eye Tracking ◽  
Purchase Intention ◽  
Purchase Intentions ◽  
Monitoring Method ◽  
Content Type ◽  
Quality Perceptions ◽  
Consumption Situation ◽  
The Impact

Purpose Wine bottles compete for consumers’ attention in the shelf during the decisive moment of choice. This study aims to explore the role that visual attention to wine labels has on the purchase decision and the mediating role of quality perceptions and desire on such purchase behaviours. Wine awards and consumption situation are used as moderators.. Design/methodology/approach The study was conducted in Portugal and 36 individuals participated in a 2 × 2 within subjects design (awarded/not awarded × self-consumption/social-consumption). For each scenario, individuals’ attention, perceptions of quality, desire and purchase intentions were recorded. Findings Data from eye-tracking shows that, during the purchase process, the amount of attention given to a bottle is determinant of individuals’ purchase intentions, a relationship that increases in significance for bottles with awards and for when consumers are buying wine for a consumption situation involving a social environment. In addition, both quality perceptions and desire are confirmed to positively influence wines’ purchase intentions. Originality/value By using an eye monitoring method, this paper brings new insights into the wine industry by highlighting the impact that wines’ labels and different consumption situations have on individuals’ attention and purchase intention. Wine producers and retailers may benefit from the insights provided by the current study to refine their communication strategies by either highlighting product characteristics and pictorial elements, as it is the case of the awards, or communicating about their products for different consumption situations.

Sign in / Sign up

Export Citation Format

Share Document