Electromagnetic Monitoring of the Northern Tien Shan
Development of the Electromagnetic Monitoring Technology for Seismically Active Zones of the Northern Tien Shan in the Frequency Range from 0.1 Hz to 1 MHz
Tech Area / Field
- ENV-MIN/Monitoring and Instrumentation/Environment
8 Project completed
Senior Project Manager
Kirichenko V V
Kyrgyz National Technical University, Kyrgyzstan, Bishkek
- St Petersburg State University, Russia, St Petersburg
- KRISS - Korea Research Institute of Standards and Science, Korea, Taejeon\nDaegu University, Korea, Gyeongsan\nUniversity of Cologne / Institute of Geophysics and Meteorology, Germany, Köln\nUniversitat de Barcelona / Dept. Geodinamica i Geofisica, Spain, Barcelona\nUniversity of Athens / Solid Earth Physics Instiurte, Greece, Athens
Project summaryRocks electric resistivity (ρ) measurements and electromagnetic emission (EME) anomalies registrations are widely used for the geological medium stress-strain state and the earthquake prediction monitoring. These precursors effectiveness has been practically confirmed in various world seismically active regions. The experience of the different monitoring methods application has shown that electromagnetic earthquake precursors are the most sensitive indicators of the geological medium stress-strain state. It was found that the anomaly changes are usually observed in the periods from some months to some days, and EME anomalies – from several days to some hours before earthquakes. Electric resistivity and EME variations joint investigations allow us to obtain data for the intermediate- and short-term earthquake predictions.
Based on the analysis of various electromagnetic methods applications for the rocks stress-strain state monitoring we have chosen earlier the audio frequency range (1 – 800 Hz) as the perspective one for the ρ and EME variations monitoring. The high measurements accuracy (not more than 1 % for the measured parameter - apparent resistivity ρa, and 0.5 deg. for the impedance phase φz) reached last years in the audiomagnetotelluric (AMT) sounding method provides reliable data for the rocks stress-strain state monitoring. The AMT soundings method has a big enough investigation depth for the exclusion of seasonal and metrological factors influences. A strict and well developed theory of the method has been worked out for the primary field plane wave model and it ensures the authentic data interpretation. The AMT method is cheaper than controlled source electromagnetic sounding methods, and it is important for the observation networks creation in seismically hazardous regions.
Seismo-electromagnetic phenomena investigations in the audio frequency range were carried out by the current project executors at the Bishkek prediction test site during the ISTC project KR-583 in 2003-2007. The tensosensitive zones selection technique was developed to monitor the seismic activity during long time periods. The equipment modernizations and software tools were fulfilled considering the Bishkek test site geological and geophysical features and noise situation. Sites for the receiving equipment installation were chosen, the variations investigation technique was developed, various EME anomalies registration methods were tested and these parameters monitoring was carried out. Electromagnetic field behavior regularities in various frequency intervals of the audio frequency range 1 - 800 Hz have been investigated, frequency intervals in which the most reliable and informative data can be obtained were determined for the geological medium stress-strain state monitoring. Software tools for the variations data processing and EME anomalies monitoring for the parameters determination which describe the spectral content and measured electromagnetic field variations were developed.
Obtained data were used for the resistivity variations and EME anomalies regularities investigation in the audio frequency range at the Bishkek prediction test site. Thus the basic attention was paid to the apparent resistivity variations analysis connected to the Earth crust tidal deformations. For the first time at the Bishkek prediction test site ρa tidal variations were registered and the geological medium stress-strain state monitoring possibility was shown.
Seismo-electromagnetic phenomena investigations in the audio frequency range during the ISTC project KR-583 allow us to plan the following stages – the monitoring technology development and then stationary networks creation for the seismic activity monitoring in this region.
When developing the electromagnetic monitoring technology during the project the basic attention will be paid to regular monitoring observations in the tensosensitive zones which were chosen by the developed technique using tidal effects observations, to the development of data processing and data quick analysis software tools for resistivity variations monitoring data, and technique and data processing software tools improvement for the EME parameters registration.
The Bishkek prediction test site monitoring experience in the audio frequency range has shown that the observations in the extension frequency range by adding of the subaudio and radio frequency intervals with monitoring realization in the 0.1 Hz – 1 MHz frequency range is necessary for the informative value monitoring and reliability increasing at the intermediate- and short-term earthquake prediction. According to the radio wave fields classification the extended frequency range contains Ultra Low, Extremely Low, Very Low, Low and Middle Frequency (ULF-ELF-VLF-LF-MF) intervals.
Using of the subaudio 0.1–1 Hz frequency range natural electromagnetic fields for variations observations allows increasing the monitoring investigation depth. The monitoring frequency range extension up to 1 MHz is supposed for the more reliable registration of the section upper part influence. According to the investigations experience in various world regions (Greece, Japan etc.) the EME registration in the subaudio and radio frequency ranges in addition to the audio frequency range allows us to pide more confidently emission from rocks deformations and ones caused from outside sources (magnetospheric, ionospheric, storm, industrial etc.).
Using of the radio frequency range gives us the possibility of the ionospheric earthquake precursors investigation based on observations of the signals amplitude and phase parameters from remote radio transmitters (such investigations have been carried out in Japan, Italy and other countries). Additional data about the ionosphere state will be obtained using observations of natural electromagnetic field Schumann resonances in the audio frequency range.
The use of the ACF-4M equipment is supposed for subaudio 0.1 – 1 Hz frequency range electromagnetic fields observations, investigations with this equipment were carried out during the ISTC project KR-583. It is planned to use the radio magnetotelluric method RMT-F equipment for radio frequency range electromagnetic field observations, which will provide monitoring possibilities in the 1-1000 kHz frequency range after some modernization.
The region expanding of the developing monitoring technology application is supposed in consideration of its availability for the Northern Tien Shan seismically active zones including the Bishkek and Issyk Kul prediction test sites.
Thus the monitoring technology development includes the equipment modernization, measurement techniques, the software tools for data processing and interpretation development, which will ensure registration in the wide 0.1 Hz - 1 MHz frequency range such earthquake precursors as rocks electric resistivity changes and electromagnetic emission variations, and also will allow us to estimate possibilities of registration of ionospheric effects above earthquakes preparation zones.
The project main purpose is to develop the rocks stress-strain state electromagnetic monitoring technology in the wide 0.1 Hz - 1 MHz frequency range for the stationary monitoring networks subsequent creation in the Northern Tien Shan seismically active zones.
The following tasks will be solved to accomplish the main project purpose:
A1: The tensosensitive zones selection for experimental electromagnetic monitoring investigations carrying out at the Bishkek and Issyk Kul prediction test sites and for their subsequent use at the creation of the stationary monitoring networks.
А2: The RMT equipment with extended frequency range development for the electromagnetic monitoring realization and the EME anomalies and ionospheric disturbances investigation.А3: The rocks electric resistivity changes electromagnetic monitoring technology development in the 0.1 Hz - 1 MHz frequency range in seismically active zones.
А4: The electromagnetic emission monitoring technology development in the 0.1 Hz - 1 MHz frequency range in seismically active zones.
А5: The estimation of ionospheric earthquake precursors monitoring possibilities using signal from remote radio transmitters amplitude and phase parameters observations in the radio frequency range and using the natural electromagnetic field Schumann resonances registration in the audio frequency range.
А6: The realization of the pilot phase of electromagnetic monitoring technology application for the Northern Tien Shan seismically active zones in the 0.1 Hz - 1 MHz frequency range.
Earthquake preparation processes mathematical and field modeling methods based on tidal effects observations at the electric resistivity variations and EME anomalies monitoring, experimental investigations for the tensosensitive zones selection, electromagnetic monitoring equipment and technology testing will be used for the project tasks solution. The ACF-4M equipment modernization for high measurements accuracy providing in subaudio frequency range and RMT-F equipment modernization for the EME anomalies and ionospheric earthquake precursors registration are planned. The electromagnetic monitoring technology will include the tensosensitive zones selection technique for the earthquake precursors registration, the technique and software tools for the electric resistivity variations, impedance phase and EME anomalies study in the subaudio, audio and radio frequencies ranges, and software tools for data of monitoring network quick analysis and interpretation.
The project implementation will allow us to create the basis for the electromagnetic monitoring stationary operating networks creation in the Northern Tien Shan seismically active zones and also for the similar monitoring networks installation in other seismically hazardous areas.
At the project realization will be used:
- KSTU investigations results in geomagnetic phenomena and geophysical methods testing for earthquake prediction at the Bishkek prediction test site;
- SPbSU investigations results in natural and radio transmitters electromagnetic fields measurements for the seismic activity monitoring.
Works under the project will be carried out in a close contact with the foreign collaborators. Information interchange, joint planning and investigations at test and prediction sites implementation, tests of hardware-software complexes and the scientific seminars organization will be fulfilled.
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