COMPLEX MONITORING AND ALERT SYSTEM FOR SEISMOTECTONIC PHENOMENA VICTORIN-EMILIAN TOADER, IREN-ADELINA MOLDOVAN, CONSTANTIN IONESCU National Institute for Earth Physics, RO-077125 Magurele, Romania, E-mail:
[email protected] Received August 30, 2014
The paper describes a complex multidisciplinary monitoring system designed for Vrancea seismic area (bending area of Carpathians Mountains). This includes hardware (stations with sensors, acquisition and communication equipment) and software for data processing in real time. The result of this work is the growth of an alert service through: perfecting risk evaluation, seismic and climate forecast, informing the decision factors regarding the impact minimization of natural disasters and the education of the population. The information from database will help the scientists to develop the system and to improve their knowledge for other applications. A monitoring network involves a multidisciplinary activity that highlights the interdependence of environmental factors (air, earth) and their balance under normal conditions. Weather or seismic events represent the point of maximum imbalance. Electromagnetic, infrasound, seismoacoustic at high frequencies, air ionization and solar radiation monitoring, in correlation with global and local environmental factors (including seismic zones), is a new approach for atmospheric study in our area. Figure 1 describes a global structure of system. Data are acquired from ground (National Institute for Earth Physics – NIEP seismic stations) and satellites. Key words: earthquake forecast, electromagnetic and infrasonic monitoring, acoustic emission, micro cracking, fracture, multidisciplinary analysis, air ionization and solar radiation monitoring.
1. INTRODUCTION
A new project released in 2013 (Multidisciplinary complex system for monitoring clouds, aerosols and solar radiation in correlation with Vrancea seismic activity, a grant of the Romanian National Authority for Scientific Research) have started to monitor and analyze atmospheric aerosols, ions, clouds and solar radiation in relationship with environmental conditions (temperature, humidity, atmospheric pressure, wind speed and direction, variations of the telluric currents, variations of the local magnetic field and infrasound, variations of the atmospheric electrostatic field, variations in the earth crust with inclinometers, electromagnetic and seismic activity, animal behavior). Figure 1 describes the monitoring station general structure. Rom. Journ. Phys., Vol. 60, Nos. 7–8, P. 1225–1233, Bucharest, 2015
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Many examples indicate a relationship between earthquakes and aerosols density or clouds formations and sky color. Solar radiation and earthquakes means energy that affects the telluric field, the radio waves propagation and generally the ionosphere. The EarthCare (ESA’s cloud, aerosol and radiation mission) will complete the data obtained by ground monitoring system from the project. Atmospheric layers behave like “lenses” with variable properties because they depend on atmospheric phenomena and solar radiation. Air ionization and solar-earth radiation monitoring, in correlation with global and local environmental factors (including seismic zones), is a new approach for atmospheric study in our area.
Fig. 1 – General structure of a complex monitoring station and data processing.
The cumulative seismic energy evolution is a method of evaluation a feature magnitude [1, 2]. The software used was presented at EGU-2013-3880 session [3]. Acoustic emission monitoring at high frequencies is a new approach for tectonic stress analysis. Transient waves with small amplitudes and high frequencies [4, 5] are heard by dogs that start barking. Animals react to rapid changes in the environment.
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2. NETWORK STATIONS AND SEISMIC ENERGY
We present a general structure of monitoring network in Fig. 2.
Fig. 2 – NIEP seismotectonic monitoring phenomena network.
The most important is the position of stations from epicentral areas (Fig. 3). Vrancea generates important intermediate depth earthquakes in two main points: Nereju and Gura Teghii. Odobesti (ODB) is a reference station because is out from the seismic area. Monitoring stations involved in this research are: • BISR – Bisoca • LOPR – Lopatari • NEHR – Nehoiu • MLR – Muntele Rosu • COVR – Covasna • PLOR1 – Plostina 1 • PLOR7 – Plostina 7 • VRI – Vrancioaia • ODB – Odobesti
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The seismicity and the cumulative energy evolution are presented in the picture 3. Two successive earthquakes in a short time interval (5.5R, 2013/10/06 and 4.9R, 13/10/15) are the cause of ‘jump’ of energy. The seismic cumulative energy is calculated with formulas (Richter 1958, Båth 1983,Tselentis 1997) [1, 2]. The software used was presented at EGU-2013-3880 session [3]. lg(E) = 11.8 + 1.5 * Ms Ms = –2.14 + 1.43 * Ml – 0.018 * Ml
(1) 2
(2)
E = Energy expressed 1Erg = 1E + 18; Ml = Local magnitude [R]; Ms = Surface magnitude. We calculate E2 – E0 and E1 – E0 (‘Mag (R) E2-E0’, ‘Mag (R) E1-E0’, Fig. 3): lg(E0) = 11.8 + 1.5 * Ms0,
(3)
lg(E1) = 11.8 + 1.5 * Ms1,
(4)
lg(E2) = 11.8 + 1.5 * Ms2.
(5)
Fig. 3 – Recent seismic energy evolution for Vrancea area.
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The result is an evaluated energy with an equivalent M. Note that the date 2013/10/05 is a break from previous trends. Seismic information is from NIEP data base and EMSC [6, 7].
3. MONITORING STATION STRUCTURE
NIEP’ stations are mainly for seismic monitoring. Few of them (Fig. 2) include other kind of sensors: infrasound, meteorological, telluric – magnetic fields and GPS. The new project released in 2013 will extend the sensor area and the complexity of the MEMFIS Network [8, 9]. The new monitoring station will also include atmospheric aerosols, ions, clouds and solar radiation in relationship with environmental conditions as described in Fig. 1. An environmental monitoring (Fig. 1) needs more information about atmosphere and the relation with lithosphere. The ground measurements are complementary with EarthCare ESA’s mission results and validate them. There are equipment specialized for aerosols measurements (COM-3700 used in Japan for earthquake prediction) or sky radiometer. But this is not enough for understanding the complex phenomena. The EarthCare satellite will bring complementary information about clouds, aerosols and solar radiation from the top of atmosphere. SWARM ESA’s mission will provide magnetic information (NIEP has a magnetometer network). NOAA has a data service with information about X Ray, Electron-Proton Flux and magnetic information. EUMETSAT and the Meteorological National Administration will help up with their database about clouds and aerosols. The research put together all information for forecast the risk situations (storms, earthquakes, climate change).
4. ELECTROMAGNETIC, INFRASOUND, IONS, METEOROLOGICAL AND SEISMOACOUSTIC MONITORING
Figure 4 presents a global data analysis of multiple signals. The seismicity is present by ML and H (last two drawn). We use pairs of electrodes in the ground to measure the telluric field (Figs. 4 and 5). The variations are correlated with seismic activity. Period in which the telluric signal is limited corresponds with most important Vrancea seismic quiescence from 2004 to present. After this we got an energy ‘jump’ described in Fig. 3.
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Fig. 4 – Analysis software for precursor phenomena.
Fig. 5 – Telluric variation before and after the seismic quiescence.
Figure 5 presents more clearly the telluric variations from Fig. 4. A Chaparral infrasound network records earthquake and other signals from air (Fig. 6).
Fig. 6 – Infrasound record, earthquake 5.5R, 135 Km depth, Eforie station.
The tectonic stress generates ions in epicentral areas.
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Fig. 7 – Multidisciplinary monitoring Eforie station (ions, seismoacoustic, VLF receiver, air electric field and solar radiation).
Figure 7 shows a multidisciplinary monitoring structure. We record + and – ions, solar radiation, lightning and seismoacoustic waves. Ions variation in a thunderstorm period is in Fig. 8. The electric field and negative ions increase.
Fig. 8 – Ion variation in thunderstorm period.
The seismoacoustic monitoring records short signals followed by barks before earthquake with 4 – 5 hours (Fig. 9). The rocks' microcracks generate elastic waves under the tectonic stress. These waves have small amplitude and high
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frequency [6]. The next record has 20 Khz sample rate and the high pass filter is set at 5 Khz. Animals with a very good hearing ability react at these sounds.
Fig. 9 – Seismoacoustic signal in VRI station, 14/03/29, Ml = 4.9R, 135 Km depth.
5. CONCLUSIONS
A monitoring network involves a multidisciplinary activity that highlights the interdependence of environmental factors (air, earth) and their balance under normal conditions. Weather or seismic events represent the point of maximum imbalance. Electromagnetic, infrasound, seismoacoustic, air ionization and solar radiation monitoring, in correlation with global and local environmental factors (including seismic zones), is a new approach for atmospheric study in our area. The result of this project is the growth of the seismic alert service through: perfecting risk evaluation, seismic forecast, informing the decision factors regarding the impact minimization of natural disasters and the education of the population. NIEP has a seismic and tsunami early warning service (Figure 10) that inform the Romanian Government, the ISUs (Inspectorate for Emergency Situations in Romania and Bulgaria) and the Romanian Ministry of Defense. The analysis using cumulative energy indicates an increase of seismicity in Vrancea area. An earthquake cannot be precisely predicted but can be expected from the accumulation of energy which results in a release through one or more earthquakes.
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Fig. 10 – NIEP Information and Alert Center. Acknowledgements. This work was supported by a grant of the Romanian National Authority for Scientific Research, Programe for research – Space Technology and Avanced Research – STAR, project number 84/2013.
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