Experimental study of the features of VLF, MF, HF and VHF electromagnetic radiation accompanying rock fracture

Qian, Shu‐Qing; Ren, Ke-Xin; Lu, Zhuo

doi:10.1007/bf02650980

Cited by 18 publications

(13 citation statements)

References 8 publications

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“…Laboratory experiments by Qian et al (1996Qian et al ( , 2003 and Hao et al (2003) presented that electromagnetic signals are always recorded when rock samples are subjected to dynamic stresses. Shorter-period electromagnetic pulses appearing at the last stage of the experiment may be induced by instantaneous electric current of accumulated charges during the stress accelerating.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan MS 8.0 earthquake

Tan

Cao

2016

Solid Earth

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Abstract. A three-layer (Earth-air-ionosphere) physical model, as well as a two-layer (Earth-air) model, is employed in this paper to investigate the ionospheric effect on the wave fields for a finite length dipole current source co-located at a hypocenter depth and along the main fault of an earthquake when the distance between the epicenter and an observing station is up to 1000 km or even more. The results show that all electrical fields are free of ionospheric effects for different frequencies in a relative short range, e.g., ∼ 300 km for f = 1 Hz, implying the ionospheric influence on electromagnetic fields can be neglected within this range, which becomes smaller as the frequency increases. However, the ionosphere can give a constructive interference to the waves passing through and make them decay slowly when an observation is out of this range; moreover, the ionospheric effect can be up to 1-2 orders of magnitude of the electrical fields. For a ground-based observable 1.3 mV m −1 electric signal at f = 1 Hz 1440 km away from the Wenchuan M S 8.0 earthquake, the expected seismo-telluric current magnitude for the Earth-air-ionosphere model is of 5.0 × 10 7 A, 1 magnitude smaller than the current value of 3.7 × 10 8 A obtained by the Earth-air model free of ionospheric effects. This indicates that the ionosphere facilitates the electromagnetic wave propagation, as if the detectability of the system were improved effectively and it is easier to record a signal even for stations located at distances beyond their detectability thresholds. Furthermore, the radiating patterns of the electrical field components |E x | and |E y | are complementary to each other, although any two-dimensional (2-D) power distribution of these components shows strong power areas as well as weak ones, which is advantageous to register a signal if the observing system is designed to measure both of them instead of only one.

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Section: Introductionmentioning

confidence: 99%

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan MS 8.0 earthquake

Tan

Cao

2016

Solid Earth

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“…Laboratory rock fracturing experiments show that electromagnetic radiation is produced during the fracture process, and the frequency ranges from very high frequencies to ultra-low frequencies. The long period radiation signals appear before short period signals [Qian et al, 1998], and these long periodic signals may lead to pre-, co-, and after-seismic correlation coefficient anomalies. In actual observations, many strong earthquakes have recorded electromagnetic radiation signals [Karakelian et al, 2002] during the microcracks and expansion of rocks in the late stage of earthquakes.…”

Section: Discussionmentioning

confidence: 99%

Investigation of the characteristics of geoelectric filed earthquake precursors: a case study of the Pingliang observation station, China

Zhang-hui

Zhan

Fan

et al. 2019

Annals of Geophysics

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An increasing number of earthquake precursors have been observed by geoelectromagnetic stations; however, the statistical characteristics of the earthquake and geoelectric field (GEF) are not well known. Based on the sliding correlation method (SCM) and its validity test, we analyzed 125 months of continuous data from the Pingliang (PL) GEF station in China. Two factors, seismic energy and epicentral distance (D), were used to select the earthquake events. When the lower limit of the magnitude energy is set as 10 6 J/km 2 , the number of earthquake events in area A (D < 200 km) is 36, and the number of seismic events in area B (200 km ≤ D < 365 km) is 34.In the analysis of the calculated results, the mean value of 1000 times random test SCM calculation is taken as the anomaly standard. In addition, it is found that the anomalies occurring north-south, and north-east of PL station are the most significant in area A, and the anomalies are concentrated approximately 8-26 days before the earthquakes. There is no obvious correlation east-west of PL station in area A, and there is no similar abnormal phenomenon in area B. The reasons and probably mechanism of the investigation results are analyzed and discussed in combination with the fault belt features of the study area, numerical simulation, and laboratory rock fracturing experiments. The uniqueness of the results is verified by reducing the energy standard of a single earthquake. This investigation supports the statistical point of view of the microcosmic interpretation of GEF abnormalities, provides significant suggestions for the selection of electrode-layout orientations used for GEF observations and also provides a reference for the gathering of the seismic precursor information.

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“…Within the range of a few hundred meters, at the strain variation or turning points of part of the waveforms, the geoelectric fields have clear leaps and sudden jumps. After the eighties of last century, Guo et al (1999), Hao et al (2003), Qian et al (1996) also detected the phenomenon of leaps and sudden jumps of electromagnetic signals in rock fracture experiments, but the frequencies of the electromagnetic signals detected in these experiments are higher. The E curve of geoelectric field in Fig.…”

Section: Possibility Of Leaps and Sudden Jumps In Spontaneous Fieldmentioning

confidence: 99%

Features of Regional Variations of the Spontaneous Field

Tan

Jialiu

Liu

et al. 2014

Chinese J of Geophysics

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According to the classification principle of field sources, the geoelectric field E is composed of the spontaneous field ESP and telluric field ET. The ESP originates from the physical and chemical actions of underground media. Its change and stability have usually obvious characteristics of local sites. The ET originates from the space current system and tidal forces, and shows the nature of broad areas in diurnal variation waveforms and spectral characteristics. In respect of the microscopic mechanism of their formations, the ESP and ET can have partly same processes of mechanisms. In 2008-2013, in the vicinity of the north-south seismic zone in China mainland, the data of representative 13 geoelectric field observatories suggest that the ESP of most sites do not exhibit clear annual variation waveforms, and their stabilities depend on regions, sites, orientation, tectonic activities and other factors. In these areas, the variation of ESP showed some common phenomena like relatively steady rises and falls, rapid jumps, sudden jumps and so forth. In the vicinity of major fault and local areas, the trend turning points of big variations often show the features of temporal synchronization and quasi-synchronization. The data stability may be similar at the same period of time, while its variation forms are usually irrelevant for site factors. During the more steady phase of the ESP, the preferred orientation α of crack water seepage calculated by the application of spectral features of tidal geoelectric field tends to be in a relatively stable state; during extreme fluctuations of the ESP, the α often experiences significant changes. The α calculated on a daily basis according to the spectral characteristics of the tidal geoelectric field may reveal the daily variation information of fissures, crack water seepage, principal compressive stress of the site, which thus can help analyze the process of microscopic mechanism of macro changes of the ESP and ET.

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Experimental study of the features of VLF, MF, HF and VHF electromagnetic radiation accompanying rock fracture

Cited by 18 publications

References 8 publications

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan <i>M</i><sub><i>S</i></sub> 8.0 earthquake

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan <i>M</i><sub><i>S</i></sub> 8.0 earthquake

Investigation of the characteristics of geoelectric filed earthquake precursors: a case study of the Pingliang observation station, China

Features of Regional Variations of the Spontaneous Field

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Experimental study of the features of VLF, MF, HF and VHF electromagnetic radiation accompanying rock fracture

Cited by 18 publications

References 8 publications

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;S&lt;/i&gt;&lt;/sub&gt; 8.0 earthquake

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;S&lt;/i&gt;&lt;/sub&gt; 8.0 earthquake

Investigation of the characteristics of geoelectric filed earthquake precursors: a case study of the Pingliang observation station, China

Features of Regional Variations of the Spontaneous Field

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Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan <i>M</i><sub><i>S</i></sub> 8.0 earthquake

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan <i>M</i><sub><i>S</i></sub> 8.0 earthquake