scholarly journals Assessment of a claimed ultra-low frequency electromagnetic (ULFEM) earthquake precursor

2021 ◽  
Author(s):  
Can Wang ◽  
Lilianna Christman ◽  
Simon Klemperer ◽  
Jonathan Glen ◽  
Darcy McPhee ◽  
...  
Keyword(s):  
Low Frequency ◽  
Temporal Distribution ◽  
Statistical Test ◽  
Earthquake Precursor ◽  
Magnetic Data ◽  
Detection Thresholds ◽  
Earthquake Hypocenter ◽  
Counting Algorithms ◽  
The Many ◽  
Cultural Noise

Anomalous ultra-low frequency electromagnetic (ULFEM) pulses occurring before the M5.4 2007 and M4.0 2010 Alum Rock earthquakes have been claimed to increase in number days to weeks prior to each earthquake. We re-examine the previously reported ultra-low frequency (ULF: 0.01-10 Hz) magnetic data recorded at a QuakeFinder site located 9 km from the earthquake hypocenter, as well as data from a nearby Stanford-USGS site located 42 km from the hypocenter, to analyze the characteristics of the pulses and assess their origin. Using pulse definitions and pulse-counting algorithms analogous to those previously reported, we corroborate the increase in pulse counts before the 2007 Alum Rock earthquake at the QuakeFinder station, but we note that the number of pulses depends greatly on chosen temporal and amplitude detection thresholds. These thresholds are necessarily arbitrary because we lack a clear physical model or basis for their selection. We do not see the same increase in pulse counts before the 2010 Alum Rock earthquake at the QuakeFinder or Stanford-USGS station. In addition, when comparing specific pulses in the QuakeFinder data and Stanford-USGS data, we find that the majority of pulses do not match temporally, indicating the pulses are not from solar-driven ionospheric/magnetospheric disturbances or from atmospheric lightning, and lack a common origin. Notably, however, our assessment of the temporal distribution of pulse counts throughout the day shows pulse counts increase during peak human activity hours, strongly suggesting these pulses result from local cultural noise and are not tectonic in origin. The many unknowns about the character and even existence of precursory earthquake pulses means that otherwise standard numerical and statistical test cannot be applied. Yet here we show that exhaustive investigation of many different aspects of ULFEM signals can be used to properly characterize their origin.

scholarly journals ANALISIS ANOMALI SINYAL ULTRA LOW FREQUENCY BERDASARKAN DATA PENGUKURAN GEOMAGNETIK SEBAGAI INDIKATOR PREKURSOR GEMPABUMI WILAYAH LAMPUNG TAHUN 2016

2020 ◽  
Vol 4 (2) ◽  
pp. 86-101
Author(s):  
Ulfa Wahyuningsih ◽  
Syamsurijal Rasimeng ◽  
Karyanto Karyanto
Keyword(s):  
Measurement Data ◽  
Low Frequency ◽  
Earthquake Precursor ◽  
Earthquake Precursors ◽  
Magnetic Data ◽  
Short Term ◽  
Horizontal Polarization ◽  
The Fourier Transform ◽  
Geomagnetic Anomaly

Regional research had been done to analysis anomalies signal of ultra low frequency based on measurement data as an indicator of the geomagnetic earthquake precursor of lampung in 2016. To achieve purpose of the study conducted by the following steps: (i) Calculation of the total magnetic field of data; (ii) Daily Trend Analysis; (iii) the Fourier transform of the data Geomagnetic Anomaly; (iv) Localization Frequency ULF; (v) Calculation of Ratio Vertical-Horizontal (Polarization Ratio Z / H); (vi) Correction magnetic storms or Disturbance Strom Time (DST); (vii) the identification of earthquake precursors; (viii) Determination of OnsetTime, leadtime,and the direction of precursors. The results of the analysis of ten earthquakes with a magnitude above 5 MW have precursors between 11 to 30 days before an earthquake. Nine out of ten earthquakes studied had an earthquake precursors and precursors that do not have, this is because the distance is too far from the station Magdas in Liwa, West Lampung. Thus it can be seen that the precursor using the magnetic data can be used to make short-term predictions.

High-frequency seismic noise as a function of depth

1991 ◽  
Vol 81 (4) ◽  
pp. 1101-1114
Author(s):  
Jerry A. Carter ◽  
Noel Barstow ◽  
Paul W. Pomeroy ◽  
Eric P. Chael ◽  
Patrick J. Leahy
Keyword(s):  
New York ◽  
High Frequency ◽  
Seismic Noise ◽  
Low Frequency ◽  
Time Variability ◽  
Orthogonal Components ◽  
The Difference ◽  
Frequency Coherence ◽  
Cultural Noise ◽  
Natural Wind

Abstract Evidence is presented supporting the view that high-frequency seismic noise decreases with increased depth. Noise amplitudes are higher near the free surface where surface-wave noise, cultural noise, and natural (wind-induced) noise predominate. Data were gathered at a hard-rock site in the northwestern Adirondack lowlands of northern New York. Between 15- and 40-Hz noise levels at this site are more than 10 dB less at 945-m depth than they are at the surface, and from 40 to 100 Hz the difference is more than 20 dB. In addition, time variability of the spectra is shown to be greater at the surface than at either 335- or 945-m depths. Part of the difference between the surface and subsurface noise variability may be related to wind-induced noise. Coherency measurements between orthogonal components of motion show high-frequency seismic noise is more highly organized at the surface than it is at depth. Coherency measurements between the same component of motion at different vertical offsets show a strong low-frequency coherence at least up to 945-m vertical offsets. As the vertical offset decreases, the frequency band of high coherence increases.

DC and AC Measurements of Magnetite Nanoparticulates and Implications for Nonlinear Response

2008 ◽  
Vol 1138 ◽  
Author(s):  
Silvia Liong ◽  
Ricky Lamar Moore
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Polymer Composites ◽  
Magnetic Measurements ◽  
Bulk Material ◽  
Low Frequency ◽  
Anisotropy Field ◽  
Coaxial Line ◽  
Magnetic Data ◽  
Order Of Magnitude

AbstractThis paper discusses preparation, characterization and measurement of linear DC and AC magnetic properties of magnetite (Fe3O4) nanoparticles (size ranges of 7-50 nm and 5 microns) and polymer composites of those particulates. Selected data and analysis are taken from the PhD thesis of Liong [1]. The goal of this research is to obtain magnetic data, specifically magnetization, anisotropy and coercivity as functions of particle size. These will be used as inputs to non linear magnetic simulations and in planning for future nonlinear magnetic measurements. Magnetite nanoparticles were synthesized by chemical coprecipitation, a method that allowed for the production of samples in gram quantities. Vibrating sample magnetometry was used to measure the room-temperature DC magnetization and coercivity of the particulates. Coaxial line impedance measurements were used to measure low frequency and dispersive AC permeability of Fe3O4–polymer composites from 1 Megahertz to 10 Gigahertz. AC data are applied to infer particulate magnetic susceptibility and anisotropy field change with particle size. Particle size was calculated from XTD data and supported by TEM images.Measured DC saturation magnetization and coercivity decreased with particle dimension while anisotropy was calculated to increase. Magnetization data are consistent with models that calculate nanoparticle magnetization as a volumetric average of a spherical bulk material core and a passive outer shell. The shell thickness was calculated at 0.84 nm, very near one lattice constant of bulk Fe3O4, 0.8394 nm. Composites containing particulate volume fractions less than 20% were fabricated. Effective media theory was applied to measured AC composite permeability to extract particle magnetic properties and thereby anisotropy field, which increased by an order of magnitude from the bulk. Permeability decreased with particulate size.

scholarly journals Effects of Self-Generated Noise on Quiet Threshold by Transducer Type in School-Age Children and Adults

2020 ◽  
Vol 63 (6) ◽  
pp. 2027-2033
Author(s):  
Heather L. Porter ◽  
Lori J. Leibold ◽  
Emily Buss
Keyword(s):  
Low Frequency ◽  
Sound Field ◽  
School Age Children ◽  
School Age ◽  
Noise Levels ◽  
Detection Thresholds ◽  
Frequency Detection ◽  
Mild Hearing Loss ◽  
Insert Earphones ◽  
Transducer Type

Purpose Low-frequency detection thresholds in quiet vary across transducers. This experiment tested the hypothesis that transducer effects are larger in young children than adults, due to higher levels of self-generated noise in children. Method Listeners were normal-hearing 4.6- to 11.7-year-olds and adults. Warble-tone detection was measured at 125, 250, 500, and 1000 Hz with a sound-field speaker, insert earphones, and supra-aural headphones. Probe microphone recordings measured self-generated noise levels. Results Thresholds were similar across ages for speaker measurements. Transducer effects were larger for children than adults, with mean child–adult threshold differences at 125 Hz of 3.4 dB (insert earphones) and 6.6 dB (supra-aural headphones). Age effects on threshold were broadly consistent with noise levels measured in the ear canal. Conclusions Self-generated noise appears to elevate children's low-frequency thresholds measured with occluding transducers. These effects could be particularly relevant to the diagnosis of minimal and mild hearing loss in children.

scholarly journals One second vector and scalar magnetic measurements at low latitude observatory, CPL

2017 ◽  
Author(s):  
Phani Chandrasekhar Nelapatla ◽  
Sai Vijay Kumar Potharaju ◽  
Kusumita Arora ◽  
Chandra Shakhar Rao Kasuba ◽  
Leonid Rakhlin ◽  
...  
Keyword(s):  
Real Time ◽  
Magnetic Measurements ◽  
Low Frequency ◽  
Magnetic Data ◽  
Magnetic Observatory ◽  
Fluxgate Magnetometer ◽  
Main Concern ◽  
Low Latitude ◽  
Time Space ◽  
New Instrument

Abstract. There is increasing demand from the global geomagnetic community for the recording of 1 second vector and scalar magnetic datain lieu of the traditional of the 1 minute data, as the 1 second magnetic data would be more compatible with measurements made from low-earth orbiting satellites and the increased detectability threshold, would contribute to: (i) understanding the global scale ultra-low frequency (ULF) waves, sudden impulses and other processes in the ionosphere & magnetosphere: (ii) development of real-time space weather forecasts. The combination of ground and satellite data opens a new pathway in understanding many underlying physical processes in the lower-middle atmospheric dynamics, which has not been accurately understood so far. The International Real-time Magnetic ObservatoryNetwork (INTERMAGNET)observatories (IMO-s) have taken a lead in this direction and many IMO-s now produce both 1 minute and 1 second data. Being affordable, rugged, compact as well as having low power consumption, fluxgate magnetometers are the staple vector sensors of IMO-s.The increased order of noise in these sensors with increasing frequencies, is the main concern and work has been going on for the last decade towards development of suitable instruments (Courtillot and Chulliat, 2008; Korepanov et al. 2006, 2009; Pedersen and Merenyi, 2016 and references therein, Dobrodnyak, 2014; Logvinov, 2014) and techniques for the evaluation and elimination of noise from the data is also being pursued (Turbitt et al. 2013). At the new Magnetic Observatory of CSIR-NGRI in Choutuppal (CPL) campus, 1 second magnetic measurements commenced in the year 2016 using the newly developed Observatory grade 1 second fluxgate magnetometer, GEOMAG-02MO, from GEOMAGNET Ukraine and the Overhauser Proton Precession Magnetometer along with the data acquisition system, MAGREC-4B. The processes of commissioning of this setup in low-latitude conditions, with the aim to finally produce 1 second definitive data (the standards of which are still under discussion with INTERMAGNET) and the characteristics of the data from this new instrument are presented in this work.

scholarly journals Pengaruh Variasi Busi Terhadap Performa dan Emisi Gas Buang pada Sepeda Motor

Jurnal METTEK ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. 103
Author(s):  
Ardi Syahrifudin ◽  
Deri Teguh Santoso ◽  
Viktor Naubnome
Keyword(s):  
Statistical Analysis ◽  
Exhaust Emissions ◽  
Statistical Test ◽  
Improve Performance ◽  
Test Analysis ◽  
Spark Plug ◽  
The Many ◽  
One Way Anova

Performa sepeda motor dipengaruhi oleh banyak faktor, diantaranya adalah penggantian beberapa part pada sepeda motor. Salah satu bagian yang banyak untuk dimodifikasi adalah busi yang dipercaya dapat meningkatkan performa. Bahan bakar yang digunakan juga dapat mempengaruhi performa. Tujuan dari penelitian ini adalah untuk melihat pengaruh penggunaan variasi busi terhadap torsi, daya dan emisi gas buang. Metode yang digunakan adalah menggunakan analisis uji statistik one way anova untuk dapat melihat pengaruh dari variasi busi yang dilakukan. Dari hasil perhitungan softwere analisis statistik one way anova dapat disimpulkan bahwa variasi busi tidak berpengaruh secara signifikan terhadap torsi karena F value < F crit (0,031 < 5,143253). Variasi busi tidak berpengaruh secara signifikan terhadap daya karena F value < F crit (0,003 < 5,143253). Variasi busi tidak berpengaruh secara signifikan terhadap HC karena F value < F crit (3,48 < 5,143253). Variasi busi tidak berpengaruh secara signifikan terhadap CO karena F value < F crit (4,97 < 5,143253). Variasi busi tidak berpengaruh secara signifikan terhadap , karena F value < F crit (1,207 < 5,143253). Variasi busi berpengaruh secara signifikan terhadap , karena F value > F crit (5,528 > 5,143253). Motorcycle performance is influenced by many factors, including the replacement of several parts on a motorcycle. One of the many parts to modify is the spark plug which is believed to improve performance. The fuel used can also affect performance. The purpose of this study was to see the effect of using variations of spark plugs on torque, power and exhaust emissions. The method used is to use one way ANOVA statistical test analysis to be able to see the effect of the variation of the spark plugs performed. From the results of software calculations one way ANOVA statistical analysis, it can be concluded that the variation of spark plugs does not significantly influence torque because F value < F crit (0.031 < 5.143253). The variation of the spark plugs did not significantly influence the power because the F value < F crit (0.003 < 5.143253). Variation of spark plugs did not significantly influence HC because F value < F crit (3.48 < 5.143253). Spark plug variation does not significantly influence CO because F value <  F crit (4.97 < 5.143253). Spark plug variation does not significantly influence , because F value <  F crit (1.207 < 5.143253). Spark plug variations significantly influence , because F value > F crit (5,528 > 5,143253).

scholarly journals THE IMPACTS OF THE USE OF GADGETS ON THE DEVELOPMENT OF CHILDREN 3-6 YEARS OF AGE

2020 ◽  
Vol 6 (1) ◽  
pp. 34-38
Author(s):  
Enny fitriahadi Enny fitriahadi ◽  
Venaswari Hanna Tyastiti
Keyword(s):  
Statistical Test ◽  
P Value ◽  
Health Post ◽  
Spearman Rank ◽  
Adverse Impacts ◽  
The Many ◽  
The Impact

Gadgets can indeed distract someone with the fun they get from these gadgets. Children are also affected by the latest technology because of the many applications offered in the gadgets, for example smartphones, that can change their habits to be immersed in a fun program in the gadgets they hold. Therefore, this study aims to determine the magnitude of the impact that can be produced by the use of gadgets on children, especially those aged 3-6 years. This research was conducted in a health post for children with a total of 26 respondents from the parents of the children studied. The instrument used was a questionnaire and a prescreening developmental format with Spearman rank for the statistical test. The result showed that there was a relationship between the use of gadgets and the development of children with a p value of 0.000. Parents’ control over the use of gadgets among children is needed to protect children from addiction that gives adverse impacts.

Using Time-Periodicity for Inducing Energy Transfer Between Vibration Modes

2013 ◽  
Author(s):  
Fadi Dohnal ◽  
Aleš Tondl
Keyword(s):  
Energy Transfer ◽  
Degrees Of Freedom ◽  
Vibrational Energy ◽  
Low Frequency ◽  
Vibration Modes ◽  
Present Contribution ◽  
Multiple Degrees Of Freedom ◽  
Time Periodicity ◽  
The Many ◽  
And Control

Introducing time-periodicity in system parameters may lead, in general, to a dangerous and well-known parametric resonance. In contrast to such a resonance, a properly tuned time-periodicity is capable of transferring energy between vibration modes. Time-periodicity in combination with system damping is capable of efficiently extracting vibrational energy from the system and of amplifying the existing damping affecting transient vibrations. Operating the system at such a specific time-periodicity, the system is tuned at a parametric anti-resonance. The basic principle of this concept has been studied theoretically and was proven experimentally. The physical interpretation of this concept was proposed in “Damping by Parametric Stiffness Excitation: Resonance and Anti-Resonance”, Journal of Vibration and Control, 2008, for a multiple degrees of freedom system. The present contribution highlights those findings on a multiple degrees of freedom system. It is illustrated that a parametric anti-resonance is connected to inducing an energy transfer between two of the many vibration modes of the underlying system with constant coefficients. The induced energy transfer can be utilized to transfer the vibration energy from low frequency to high frequency or vice versa or, in case of system damping, to a more efficient dissipation of vibrational energy. The achievable energy dissipation is most significant if an energy transfer is induced between a lightly damped mode and a strongly damped mode.

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