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1
Content available Badania geochemiczno-mineralogiczne i geofizyczne (VLF) w poszukiwaniach złóż złota typu żyłowego w dawnym Okręgu Rudnym Klecza-Radomice w Górach Kaczawskich
Mikulski Stanisław Z., Ostrowski Szymon
Przegląd Geologiczny
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2023
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Vol. 71, nr 4
219--223
EN
The abandoned Klecza–Radomice gold mining area in the Kaczawskie Mountains is prospective for new occurrences of vein-type gold deposits. Research of sulphide ore samples from old mining wastes confirmed a rich gold abundance in this area. Chemical bulk-rock analyses proved a high content of gold (up to 60 ppm Au) and a common occurrence of microscopic gold (mainly electrum). The application of geophysical VLF surveys showed a number of linear anomalies indicating the possibility of the emergence of new ore veins between the areas of former mining exploitation. This area is very promising for gold prospecting and should be the subject of further geophysical research using the induced polarization method (IP), and verified by shallow prospecting drillings. Execution of this type of comprehensive exploration and research work would open a completely new stage of prospecting for primary gold deposits in the Sudetes.
2
Badanie pola elektrycznego dojrzałej chmury burzowej przy pomocy długich anten napowietrznych
Miś Tomasz Aleksander
Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne
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2022
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nr 4
351--354
PL
Referat porusza kwestię wyznaczania wartości natężenia pola elektrycznego wewnątrz dojrzałej chmury typu Nimbostratus (ciepły front burzowy) przy pomocy danych doświadczalnych zebranych w trakcie balonowego lotu testowego napowietrznej długiej anteny liniowej. Na podstawie zarejestrowanych sygnałów i założonego modelu teoretycznego różnicowania ładunków elektrycznych na antenie wewnątrz chmury wyznaczono wartości pola elektrycznego zewnętrznego, generującego proces ładowania i powstawania wyładowań koronowych na przewodzie antenowym. Uzyskane dane porównano z danymi doświadczalnymi z lat poprzednich dla chmur burzowych typu Nimbostratus, ukazując nowe zastosowanie długich napowietrznych anten liniowych w bezpośrednim badaniu niebezpiecznych procesów zachodzących w atmosferze Ziemi.
EN
The paper describes an attempt to define the electric fields strength inside a mature Nimbostratus cloud (warm storm front) using experimental data collected during the flight of a long linear airborne antenna. Basing on the registered signals and a theoretical model of electrical interactions between the antenna and the cloud’s interior the values of the external electric field strength have been calculated – the field that allows the build-up of the electric charge of the antenna and the excitation of corona. The calculations have been compared with experimental data on the electric field strength in Nimbostratus clouds, showing a new use of long airborne antennas in direct research on dangerous processes in the Earth’s atmosphere.
3
Content available remote Earthquake prediction assessment using VLF radio signal sounding and space-based ULF emission observation
Mahmoudian Alireza, Safari Mohsen, Rezapour Mehdi
Acta Geophysica
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2022
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Vol. 70, no 3
1269--1284
EN
The present paper aims at earthquake prediction assessment in Iran using VLF radio signal sounding and space-based ULF emission observation. VLF subionospheric data using the Denizkoy transmitter in Turkey at 26.7 kHz and a receiving station in Tehran are incorporated. Three earthquake events during 2019 located at different distances to the signal propagation path are used in this study. The short-term variations in the VLF signal for the 5 days averaged amplitude, as well as the deviation of the VLF signal against the 30 days averaged signal to monitor the alternation in the trend, are employed in this study to perform earthquake prediction assessment using VLF radio signal sounding. Several characteristic parameters of the VLF signal such fall-time, minimum 1 and minimum 2 throughout the day are used. A threshold over the standard deviation of the signal is used to determine the signal anomaly. The signal anomalies associated with three selected events and the correlation of prediction with the distance are discussed. A decision-making procedure for the detection of EQ-related anomalies based on the assessment of the proposed approach is introduced. The ULF emissions recorded by the China Seismo-Electromagnetic Satellite (CSES) are provided and associated with the two analyzed earthquakes using the VLF data due to lack of time coverage for the third case. The space-based detected ULF signals are presented and discussed. The proximity of the detected ULF emission with respect to the earthquake epicenter is discussed.
4
Quality Management of Transmission Power Cables for Safe and Reliable Grid Operation
Gulski Edward, Jongen Rogier, Parciak Jarosław
Wiadomości Elektrotechniczne
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2020
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R. 88, nr 9
4--9
EN
Taking under consideration, that reliable transmission of energy is fundamental to proper operation of national power grid, quality control is essential for newly installed and in-service cable connections. It is known that routine tests (insulation coordination) completely check the quality of a power cable and accessories at the manufacturer. Nevertheless, the risk of problems with the delivery and installation of accessories can affect the quality of a newly installed power cable circuit. Based on international experience gathered on various power grids over the past 20 years, this article focuses on the use of non-destructive testing for after-installation - and diagnostic tests of all types of transmission cables. This document discusses in particular various actual aspects of testing new connections as well as the condition assessment of service aged HV power cables.
5
Content available remote Precursors signatures of few major earthquakes in Italy using very low frequency signal of 45.9 kHz
Kandel Keshav Prasad, Khadka Balaram, Bhatta Karan, Ghimire Basu Dev
Acta Geophysica
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2019
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Vol. 67, no. 4
1253--1263
EN
On May 20 and May 29, 2012, earthquakes of magnitude MW 6.1 and 5.8, respectively, struck Emilia-Romagna of Italy. We present the results obtained from the US Navy VLF Transmitter’s NSY signal of 45.9 kHz transmitted from Niscemi, in the province of Sicily, Italy, and received at the Kiel Longwave Monitor, Germany, for 2012. We analyzed the terminator times, D-layer preparation and disappearance times and nighttime fuctuation parameters. We also analyzed trends, dispersion and nighttime fuctuation which gave us possible precursors to these earthquakes. Possible perturbations due to other factors were fltered. Moreover, the fndings of these two earthquakes were compared to Central Italy EQ on August 24, 2016, and Tuscany EQ on June 21, 2013. Therefore, this manuscript is the overall analysis of four earthquakes, out of which two were already published before. As our TRGCP path is North–South, the sunrise and sunset times in transmitter and receiver places match making a pathway for VLF/LF smoother and therefore hoping to obtain more natural data. We found many clear anomalies (as precursors) in terminator times 5 days to 16 days before the earthquakes. Moreover, using nighttime fuctuation method, we found clear anomalies 5–13 days prior to main earthquakes. This exactly correlates with the fndings of previous authors that ionospheric perturbations are seen from few days to few weeks before the seismic activity. In addition to this, we observed an unexpected decrease in dispersion on certain anomalies where it was supposed to increase, thereby not supporting our fnding to some extent. To resolve this problem, we devised a new parameter called dispersion nighttime (dispersion*). On analyzing, this parameter decreases signifcantly on days of nighttime anomalies, thereby supporting our precursors to much extent.
6
Content available remote On precursors to the Italy earthquake M.6.2 using VLF signal of NSY(45.9 kHz) received at Kiel Longwave Monitor
Kandel K. P., Khadka B., Bhatta K., Schnoor P. W., Ghimire B. D.
Acta Geophysica
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2017
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Vol. 65, no. 6
1269--1275
EN
On August 24, 2016, an earthquake of magnitude 6.2 struck Central Italy (42.706°N and 13.223°E) at 1:36 UT. We present the results obtained from the US Navy VLF Transmitter’s NSY signal of 45.9 kHz transmitted from Niscemi, in the province of Sicily, Italy and received at the Kiel Longwave Monitor, Germany for 2016. We analysed the terminator times and their individual differences. We also analysed trends, dispersion and night time fluctuation which gave us a possible precursor the Italy earthquake. We found ionospheric perturbations in these parameters on 14th, 19th and 22nd of August, few days prior. Moreover, we filtered the possible effects due to lightning, storms and auroras if any.
7
Content available remote Anomalous Variations of Ionosphere Associated with the Strong Earthquake at Pakistan-Iran Border at a Low Latitude Station Agra, India
Pundhir D., Singh B., Singh O. P., Gupta S. K.
Acta Geophysica
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2016
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Vol. 64, no. 3
796--809
EN
In this paper, we analyze the TEC data for April 2013 observed at Agra station, India (geogr. lat. 27.2° N, long. 78° E) to examine the effect of earthquake of magnitude M = 7.8 which occurred on 16 April 2013 at Pakistan–Iran border region. We process the TEC data using the σ statistical criterion to find out anomalous variation in TEC data. We also study the VLF propagation signal from NPM, Hawaii (21.42° N, 158° W), which is monitored at the same station (Agra station) in the light of this earthquake as well as solar flares. The nighttime fluctuation method is used to analyze the VLF data for the period of ±5 days from the day of earthquake (11-21 April 2013). The anomalous enhancements and depletions are found in TEC data on 1-9 days before the occurrence of event.
8
Content available remote A Study of Early/Slow VLF Perturbations Observed at Agra, India
Pandey U., Singh A. K., Singh O. P., Singh B., Saraswat K.
Acta Geophysica
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2016
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Vol. 64, no. 3
755--771
EN
We present here the results of sub-ionospheric VLF perturbations observed on NWC (19.8 kHz) transmitter signal propagating in the Earth-ionosphere waveguide, monitored at our low latitude station Agra. During the period of observation (June-December 2011), we found 89 cases of VLF perturbation, while only 73 cases showing early character associated with strong lightning discharges. Out of 73 events, 64 (~84%) of the early VLF perturbations are found to be early/slow in nature; the remaining 9 events are early/fast. The onset duration of these early/slow VLF perturbations is up to ~ 5 s. A total of 54 observed early events show amplitude change lying between ± 3.0 dB, and phase change ± 12 degree, respectively, and found to occur mainly during nighttime. One of the interesting results we found is that the events with larger recovery time lie far away from the VLF propagation path, while events with smaller duration of recovery are within the ± 50-100 km of signal path. The World Wide Lightning Location Network (WWLLN) data is analysed to find the location of causative lightning and temporal variation. The lightning discharge and associated processes that lead to early VLF events are discussed.
9
Content available remote Mapping with VLF tool - gold investigation case study that yielded unexpected structural minutiae
Ostrowski S.
Geologia Sudetica
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2014
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Vol. 42
68--68
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