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Lithospheric Emissions as Earthquake Precursors

#1435


The Study of Electromagnetic Ultra-Low-Frequency Lithospheric Emissions (ULE) as Possible Precursor of Earthquakes

Tech Area / Field

  • ENV-SEM/Seismic Monitoring/Environment

Статус
3 Approved without Funding

Дата регистрации
24.12.1998

Ведущий институт
IZMIRAN, Russia, Moscow reg., Troitsk

Соавторы

  • Institute of Physical and Chemical Research (RIKEN), Japan, Saitama, Wako\nUniversity of Electro-Communications / Sugadaira Space Radio Observatory, Japan, Tokyo\nJAXA / Earth Observation Research Center (EORC), Japan, Tokyo

Краткое описание проекта

The study of seismo-electromagnetic effects in Ultra-low-frequency (ULF) range is a relatively new, but skyrocketing field of geophysics. A great interest to these investigations is mainly caused by possible application for the problem of earthquake (EQ) forecasting. From the point of view of geophysics, the ability of the crust areas under deformation to transform mechanical energy into electromagnetic waves is a possible contribution to the short- and medium-term EQ forecasting.

The results of experimental observations of electromagnetic ULF Lithospheric Emissions (ULE) are well known. The main features of ULE magnetic component are the following:


- the ULE always exist in any seismically active zone;
- the ULE appearance is the result of "electromagnetic breath" of the Earth crust;
- the ULE activity is associated with seismic activity and the ULE intensity is associated with nearby moderate to strong EQs;
- there are two different kinds of ULE spectra: wide-band noise-like one in frequency range 0.01-10 Hz and narrow-band quasisinusoidal one in frequency range 0.1-10 Hz;
- maximal intensity of ULE of both kind of spectra before some strong EQs (M~7) can reach values of 5-10 nT at epicentral zone and of 0.1-0.2 nT at the epicentral distances of 100-150 km;
- usually the ULE intensity begins to increase some months before the shock and can reach a maximum some hours before it;
- the ULE intensity decreases to background values in some weeks after the main shock.

The ULE of high intensity were observed before some large and moderate EQs in different seismically active zones of the Earth, suggesting that the ULE can be used as short- and medium-term precursor of the EQs.

As a whole, the ULE activity increasing probably is a result of redistribution of energy in the Earth's crust at different stages of the EQ's preparation. Measuring a whole spectrum of ULF electromagnetic fields by three-component ground-based gradient observation both of magnetic and electric (telluric) fields, we can exclude an influence of extraneous sources and extract an information on local properties of the Earth's crust in area of EQ's hearth zone. Difficulties of solving the EQ forecasting problem do not rule out the possibility of using the experimental results, in spite of absence of their theoretical explanation.

The goal of the suggested project is elaboration of methods for medium- and short-term earthquake (EQ) forecasting based on differential three-component ground-based magnetic measurements of electromagnetic Ultra-low-frequency Lithospheric Emissions (ULE) in frequency range from 10-2 to 10 Hz. The elaboration of methods for ULE separation both from background of geomagnetic pulsations and from ULF man-made magnetic background will be an important part of the project.

For the purposes of ULE magnetic field using as EQ precursor we propose:


- to develop and to produce a high-sensitive Digital Magneto-Variation Complex MVC-2DS intended for vector gradient measurements of ULF magnetic and electric (telluric current) fields (SPbF IZMIRAN, Russia);
- to carry out gradient three-component measurements of magnetic field of ULE in seismically active zone of Japan (SPbF IZMIRAN, Russia - Japanese collaborators);
- to elaborate methods for ULE separation both from background of geomagnetic pulsations and from ULF man-made magnetic background (SPbF IZMIRAN, Russia);
- to elaborate methods for medium- and short-term forecasting of moderate to large EQs and for location of their epicentres on the basis of ULE gradient magnetic and electric measurements (base length of about 1-5 km) in seismically active zone (SPbF IZMIRAN, Russia - Japanese collaborators).

Magnetic and telluric current measurements are planned to perform in seismically active zone of Japan by two sets of ground-based gradient installation (MVC-3EMP) spaced 30-100 km apart, each consisting of three MVC-2DS magnetometers arranged in a triangle and spaced 1-5 km apart. For ULE separation from ULF man-made magnetic background we should use at least one additional MVC-2DS magnetometer, located at the distance of about 5-10 km from each MVC-3EMP set.

The suggested Project fully complies with the aims of ISTC. The project contains development and producing instrumentation, field expedition for measurements, elaboration of methods for valid signal separation from background of noise and elaboration of methods for EQs forecasting. The proposed project will provide the job for highly skilled Russian scientists and engineers previously involved in military research.


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