The geomagnetic field behavior inside Vrancea zone (Romania) in correlation with tectonic, atmospheric and solar activity

2021 ◽  
Author(s):  
Iren Adelina Moldovan ◽  
Andrei Mihai ◽  
Victorin Emilian Toader ◽  
Bogdan Dumitru Enescu ◽  
Cristian Ghita
Keyword(s):  
Weather Prediction ◽  
Low Frequency ◽  
Seismogenic Zone ◽  
Ratio Method ◽  
Daily Maximum ◽  
Vrancea Zone ◽  
Geomagnetic Data ◽  
Remote Station ◽  
Signal Processing Methods ◽  
Seismic Area

<p>The present study assesses two signal processing methods on geomagnetic data to detect precursory signals appearing before M>5.0 Vrancea, Romania earthquakes occurred between 2016 and 2021. Geomagnetic data are obtained from Muntele Rosu Seismological Observatory situated in one corner of Vrancea seismogenic zone – as primary station, and from Intermagnet Surlari National Geomagnetic Observatory of IGR, located about 150Km South-East to Vrancea zone as remote station respectively. The first method, the diurnal variation ratio method computes difference between daily maximum with minimum value before finding ratio of primary to remote station for each individual component. The second method, the polarization ratio analysis is performed on both stations data to compute the ratio of vertical to total horizontal component in ultra-low frequency range. Geomagnetic indices taken from NOAA/Space Weather Prediction Center are compared to separate the global variation from seismo-electromagnetic anomalies possibly presented in a seismic area like Vrancea zone and to ensure that any geomagnetic fluctuations are not caused by solar-terrestrial effect.</p><p>In the end, the paper aims to compare the results from both methods in term of reliability and effectiveness.</p><p>Acknowledgements. This work was funded by: PN19 08 01 01/2019 Multirisc Nucleu Project, by MCI , Phenomenal Project PN-III-P2-2.1-PED-2019-1693, 480PED/2020 and AFROS Project PN-III-P4-ID-PCE-2020-1361, PCE/2021 supported by UEFISCDI</p>

scholarly journals Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Tânia Pereira ◽  
Mariana Sequeira ◽  
Pedro Vaz ◽  
Ana Tomé ◽  
Helena C. Pereira ◽  
...  
Keyword(s):  
Low Frequency ◽  
Impedance Spectrum ◽  
Vibration Measurement ◽  
Vibration Velocity ◽  
Average Error ◽  
Laser Vibrometer ◽  
Optical Scheme ◽  
Doppler Signals ◽  
Mixing Techniques ◽  
Signal Processing Methods

Doppler self-mixing laser probing techniques are often used for vibration measurement with very high accuracy. A novel optoelectronic probe solution is proposed, based on off-the-shelf components, with a direct reflection optical scheme for contactless characterization of the target’s movement. This probe was tested with two test bench apparatus that enhance its precision performance, with a linear actuator at low frequency (35 µm, 5–60 Hz), and its dynamics, with disc shaped transducers for small amplitude and high frequency (0.6 µm, 100–2500 Hz). The results, obtained from well-established signal processing methods for self-mixing Doppler signals, allowed the evaluation of vibration velocity and amplitudes with an average error of less than 10%. The impedance spectrum of piezoelectric (PZ) disc target revealed a maximum of impedance (around 1 kHz) for minimal Doppler shift. A bidimensional scan over the PZ disc surface allowed the categorization of the vibration mode (0, 1) and explained its deflection directions. The feasibility of a laser vibrometer based on self-mixing principles and supported by tailored electronics able to accurately measure submicron displacements was, thus, successfully demonstrated.

scholarly journals Magnetic storm free ULF analysis in relation with earthquakes in Taiwan

2012 ◽  
Vol 12 (5) ◽  
pp. 1747-1754 ◽  
Author(s):  
S. Wen ◽  
C.-H. Chen ◽  
H.-Y. Yen ◽  
T.-K. Yeh ◽  
J.-Y. Liu ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Cross Correlation ◽  
Low Frequency ◽  
Magnetic Anomalies ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Geomagnetic Data ◽  
Before And After ◽  
The Cross ◽  
The Fourier Transform

Abstract. Despite early optimism, pre-earthquake anomalous phenomena can be determined by using enhanced amplitude at the ultra-low-frequency range from geomagnetic data via the Fourier transform. In reality, accuracy of the enhanced amplitude in relation to earthquakes (deduced from time-varied geomagnetic data) would be damaged by magnetic storms and/or other unwanted influences resulting from solar activity and/or variations in the ionosphere, respectively. We substitute values of the cross correlation between amplitudes, summarized from the earthquake-related (0.1–0.01 Hz) and the comparable (0.01–0.001 Hz) frequency bands, for isolated amplitude enhancements as indexes of determination associated with seismo-magnetic anomalies to mitigate disturbance caused by magnetic storms. A station located about 300 km away from the others is also taken into account to further examine whether changes of the cross correlation values are caused by seismo-magnetic anomalies limited within local regions or not. Analytical results show that the values suddenly decrease near epicenters a few days before and after 67% (= 6/9) of earthquakes (M > = 5) in Taiwan between September 2010 and March 2011. Seismo-magnetic signals determined by using the values of cross correlation methods partially improve results yielded from the Fourier transform alone and provide advantageous information of earthquake locations.

scholarly journals Analisis Big Data Geomagnetik Dengan Metode Diferensiasi Sebagai Prekursor Gempa Lombok Tahun 2018

2021 ◽  
pp. 155-167
Author(s):  
Dwi Ratnasari ◽  
Helmy Amalia Ariesta ◽  
Teti Zubaidah ◽  
Bulkis Kanata ◽  
Made Sutha Yadnya ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Big Data ◽  
Low Frequency ◽  
Big Data Analysis ◽  
Disaster Mitigation ◽  
Geomagnetic Observatory ◽  
Geomagnetic Data ◽  
The Difference ◽  
Large Earthquakes ◽  
Geomagnetic Anomaly

Lombok is an area with the highest geomagnetic anomaly in Indonesia (Zubaidah et al., 2014). From the end of July to the end of August 2018, Lombok experienced a series of fairly large earthquakes. Identification of geomagnetic signals, especially in the Ultra Low Frequency (ULF) spectrum, can be used as earthquake precursors (Saroso, 2010). Intermagnet IAGA (International Aeronomy Geomagnetic Association) is a network of international geomagnetic observatory stations that have large world geomagnetic data. Big data analysis is very important because very large information is needed in disaster mitigation. This study uses geomagnetic data per second for 24 hours from 28 August to 30 November 2018 taken from Kakadu (KDU) Australia and Nurul Bayan Station (NRB) Lombok. The analytical method used is Differentiation by calculating the F value (total magnetic field) for KDU and NRB, then look for the difference and analyze the pattern. The results found that there was an anomaly phenomenon of the Earth's magnetic field in Nurul Bayan Lombok which was detected for 17 days during October 2018.  

Non-Linear Vibro-Acoustic Wave Modulations - Analysis of Different Types of Low-Frequency Excitation

2013 ◽  
Vol 569-570 ◽  
pp. 924-931 ◽  
Author(s):  
Andrzej Klepka ◽  
Wieslaw Jerzy Staszewski ◽  
Kajetan Dziedziech ◽  
Francesco Aymerich
Keyword(s):  
Signal Processing ◽  
Testing Machine ◽  
Low Frequency ◽  
Different Types ◽  
Non Linear ◽  
High Frequency Excitation ◽  
Reinforced Plate ◽  
Frequency Excitation ◽  
Acoustic Modulation ◽  
Signal Processing Methods

Signal processing method based on wavelet transform used in non-linear acoustic test is presented in the paper. The method is applied for sidebands identification in response signal acquired during vibro-acoustic modulation test of impacted carbon fiber reinforced plate (CFRP). The plate was impacted with known energy using drop-weight testing machine. The modulation effect in investigated specimen results from the interaction of low and high frequency excitation with damage. The paper investigates different than mono-harmonic low-frequency excitation usually used in non-linear acoustics tests. Application of aperiodic low-frequency excitation signal allows to omit the modal test, where natural frequency of the structure are estimated. However, this requires the use of dedicated signal processing methods.

Global gravity wave detections at infrasound stations of the International Monitoring System

2020 ◽  
Author(s):  
Patrick Hupe ◽  
Lars Ceranna ◽  
Alexis Le Pichon
Keyword(s):  
Monitoring System ◽  
Deep Convection ◽  
Weather Prediction ◽  
Low Frequency ◽  
Correlation Method ◽  
International Monitoring System ◽  
Wind Noise ◽  
Global Gravity ◽  
International Monitoring ◽  
Energy And Momentum

<p>Atmospheric gravity waves (GWs) transport energy and momentum horizontally and vertically. The dissipation of GWs can modify the atmospheric circulation at different altitude layers. Knowledge about the occurrence of GWs is thus essential for Numerical Weather Prediction (NWP). However, uniform networks for global GW measurements are rare, and satellite observations generally allow to derive GW parameters in the middle and upper atmosphere only. The barometric sensors of the International Monitoring System (IMS) infrasound network can potentially fill this gap of global GW observations at the Earth’s surface. This infrasound network has been established for monitoring the atmosphere to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty.<br>Two alternative configurations of the Progressive Multi-Channel Correlation Method (PMCC) are discussed for deriving GW detections from the differential pressure data. These configurations focus on GW frequencies equivalent to periods of between 5 min and 150 min. This range covers sources of deep convection, particularly in the tropics, whereas at mid-latitudes, GWs are hard to distinguish from other low-frequency signals, e.g. coherent wind noise. Challenges and perspectives of using the IMS infrasound data for deriving ground-based GW parameters useful for NWP will be discussed.</p>

Correction of Low Frequency Component in Spectrum Analysis Based on Hilbert Transform

2013 ◽  
Vol 584 ◽  
pp. 154-158
Author(s):  
Jun Jie Wang ◽  
Zhi Jiang Xie ◽  
Ping Chen
Keyword(s):  
Hilbert Transform ◽  
Low Frequency ◽  
Frequency Component ◽  
Side Lobe ◽  
Spectral Lines ◽  
Frequency Resolution ◽  
Ratio Method ◽  
Frequency Correction ◽  
The Impact ◽  
Frequency Phase

Because of the serious interference coming from the negative frequency in low frequency correction, the traditional correction methods no longer work. This paper proposes an improved ratio method to correct the frequency, phase and amplitude of spectrum peak when the spectral line locates near the left end in spectrum. The Hilbert Transform is used to diminish the impact of interference of the mirror frequency. The barycenter of two spectral lines is used to obtain the correcting value. A new formula is developed when the frequency is less than the frequency resolution. One of the spectral lines is located in the main lobe and the other is in the first side lobe. Furthermore, the direct current has nearly no impact on this new method theoretically which is a key problem in low frequency correction. The simulation shows that the frequency, phase and amplitude of a theoretical low frequency can be corrected satisfactorily. The result of the correction improves a lot compared with the traditional method. However, this method could not correct the spectrum with multiple components of low frequency.

Benchmarking the Raw Model-Generated Background Forecast in Rapidly Updated Surface Temperature Analyses. Part II: Gridded Benchmark

2020 ◽  
Vol 148 (2) ◽  
pp. 701-717 ◽  
Author(s):  
Thomas M. Hamill ◽  
Michael Scheuerer
Keyword(s):  
High Resolution ◽  
Surface Temperature ◽  
Weather Prediction ◽  
Daily Maximum ◽  
Interpolation Procedure ◽  
Potential Applications ◽  
Validation Procedure ◽  
Background Forecast ◽  
Statistical Interpolation ◽  
Better Than

Abstract This is the second part of a series on benchmarking raw 1-h high-resolution numerical weather prediction surface-temperature forecasts from NOAA’s High-Resolution Rapid Refresh (HRRR) system. Such 1-h forecasts are commonly used to underpin the background for an hourly updated surface temperature analysis. The benchmark in this article was produced through a gridded statistical interpolation procedure using only surface observations and a diurnally, seasonally dependent gridded surface temperature climatology. The temporally varying climatologies were produced by synthesizing high-resolution monthly gridded climatologies of daily maximum and minimum temperatures over the contiguous United States with yearly and diurnally dependent estimates of the station-based climatologies of surface temperature. To produce a 1-h benchmark forecast, for a given hour of the day, say 0000 UTC, the gridded climatology was interpolated to station locations and then subtracted from the observations. These station anomalies were statistically interpolated to produce the 0000 UTC gridded anomaly. This anomaly pattern was continued for 1 h and added to the 0100 UTC gridded climatology to generate the 0100 UTC gridded benchmark forecast. The benchmark is thus a simple 1-h persistence of the analyzed deviations from the diurnally dependent climatology. Using a cross-validation procedure with July 2015 and August 2018 data, the gridded benchmark provided competitive, relatively unbiased 1-h surface temperature forecasts relative to the HRRR. Benchmark forecasts were lower in error and bias in 2015, but the HRRR system was highly competitive or better than the gridded benchmark in 2018. Implications of the benchmarking results are discussed, as well as potential applications of the simple benchmarking procedure to data assimilation.

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