Why monitor the seismic activity
Monitoring the seismicity on Romanian territory is one of the important objectives of NIEP, aimed mainly to detect and locate in the shortest time all seismic events (earthquakes, explosions) occurred. This information is quickly transmitted to inform the authorities, inspectorates for emergency situations,mass-media and the wide public.In case of strong earthquakes, an earthquake alert is issued for institutions with decision making roles.
Seismic Monitoring Network
Romanian Seismic Network
The main purpose of RSN is to monitor the seismic activity (natural and anthropogenic) on the Romanian territory and to provide high quality seismic data for seismic source studies, internal structure of the Earth investigation, microzonation and seismic hazard assessment, as well as seismic data exchange with International seismic data centers. RSN consists of real-time digital seismic stations that continuously record ground motion (125) and off-line triggering stations (16). The recorded data by RSN are sent to National Data Center where they are processed and analyzed by operators 24 /7.
The information about earthquakes recorded in Romania is listed on the NIEP’s website and refers to: date and origin time of the earthquake, location (latitude, longitude and depth) and magnitude (ML – local magnitude). The recorded data also contribute to build national and international seismic bulletins.
In case of surface earthquakes with magnitude greater than 3 and intermediate earthquakes with magnitude greater than 3.5, the data recorded by RSN are used to produce ground motion distribution maps used by the authorities for post-event rapid response(ShakeMaps, intensity maps).
RSN is composed of:
Real time short period network
Real time broadband network
The development of the real time broadband network started in the fall of 2001, when a new monitoring system was installed at Muntele Rosu (Cheia) in cooperation with JICA (Japan Inernational Cooperation Agency). Currently, the network includes 62 seismic stations equipped with the following broadband velocity sensors: Guralp CMG40T (24), CMG3ESP (5),CMG3T (1), KS2000 (18), KS54000 (1), Streckaisen STS2 (11), and Metrozet PBB (2). The network is designed to monitor small and moderate local earthquakes, as well as regional and teleseismic events.
Real time accelerometer network
The development of the Romanian strong motion network was initiated during the Romanian-German cooperation between NIEP and the Institute of Geophysics, University of Karlsruhe. Between 1995 and 1997, 36 triggered K2 digital accelerometers were installed on the Romanian territory as well as in Bucharest. At present, the network consist of 102 seismic stations equipped with acceleration sensors (Episensor) and is designed to monitor strong local earthquakes.
Accelerometer network in Bucharest and surroundings
The permanent GPS network stations
The development of Romanian high resolution GNSS / GPS (Global Navigation Satellite System / Global Positioning System) networks designed for monitoring crustal movements, started in 2001 when the first permanent station was installed in Lacauti. The network was set up within a Strategic Partnership between: the National Research Institute for Earth Physics (NIEP), Faculty of Geology and Geophysics, University of Bucharest (FGG), Technical University of Delft, Utrecht University, Netherlands Research Center for Integrated Earth Sciences (ISES) and Topgeocart company.
Stations making up the permanent network of NIEP at present are shown in the table above.
GPS permanent stations
GPS network have mixed equipment, the majority being manufactured by Leica, GRX 1200 GG Pro, GRX 1200 + GNSS and GR10 Professional type receivers and the models of antennas used are LEIAT 504, LEIAT 504 GG and LEIAT10. The network also contain a Leica GX 1230 mobile station with an AX 1230 1203 + GNSS antenna. Three new installed stations are equipped with instruments manufactured by Septentrio, AsteRx2HDC receivers and PolaNt-x MF antennas. Real time data transmission is provided by STS (Special Telecommunications Service), GPRS modems and several other communication suppliers.
Ground displacement at high frequencies of about 20 Hz, caused by Vrancea earthquakes, constitute important recordings to investigate coseismic contributions at frequencies higher than 1 Hz with GPS. Having this in mind and aiming to undertake advance research, 11 permanent GPS stations are also equipped with accelerometers.
The acquisition, analysis and processing
Data acquisition is done in real time, in RAW DATA and RINEX format, using Leica GNSS Spider and Septentrio Rx software and Spider QC software for data quality check.
Regarding data postprocessing, an agreement has been made, between NIEP and Jet Propulsion Laboratory (“JPL”), an operating division of the California Institute of Technology, concerning a license to use the software GIPSY OASIS NPO – GPS Positioning infer Orbit System Analysis and Simulation Software. This software will be used in the National Seismic Network Department for monitor crustal deformation using satellite data on Romania’s territory. This is the main software used to check data availability and integrity, during the entire stations lifespan, as well as for computing time series and displacement vectors. For data analysis we also use LGO software (Leica Geo Office), GLAB (developed by ESA – European Space Agency) and RTKLIB (Open Source Package).
Magnetotelluric and bioseismic studies performed by the network
It is well known that there are interconnections between the tectonic activity and the abnormal changes of geophysical, geochemical and hydrologic parameters that characterize the lithosphere. These transformations may reflect certain changes that occur in stress state at a crustal and sub-crustal level and may indicate the fact that a critical level of stress has been reached. Consequently, various geoscientific methods are trying to monitor the tectonic activity in order to identify areas and phases of critical stress, based on precursor phenomena associated with earthquakes.
The geophysics network for magnetotelluric and bioseismic studies experienced in 1996 and until now an exponential development, funded entirely from national and international research projects.
In 2005-2006 the first infrasound monitoring system IOANE was realized and installed at Plostina, the infrasound being associated with a wide range of events. Monitoring infrasonic sound waves propagated through the atmosphere has grown a large development during the Cold War as a tactic for surveillance of land in order to identify possible sources of certain acoustic waves, such as classical and nuclear explosions, missile launches of various types, heavy combat machinery movements, helicopters and airplanes. Although the range of application is currently similar, it is now directed mainly towards monitoring nuclear tests, but has also spread to other natural phenomena such as earthquakes, forming northern lights, detecting meteors crossing the atmosphere, tracking tornadoes and other similar subjects.
An overview of PLOR3 location of the Observatory Plostina and some of the equipment involved in monitoring: system acquisition, MBAZEL2007 microbarometer, triaxial fluxgate magnetometer MAG-03MS. The electric field monitor EFM-100 is installed in PLOR4 location, near the WS-3600 weather station.
Since July 2006, we designed and developed a comprehensive monitoring system that provides acoustic, electric, magnetic, electromagnetic and forecast information. This system is intended to search hidden correlations that may exist between variations in these fields and the preparation process of strong intermediate earthquakes in the area of Vrancea. Starting with 2008, the magnetotelluric and bioseismic studies department of INFP uses a real-time geomagnetic, electric and infrasonic monitoring network called MEMFIS – Multiple Electromagnetic Field and Infrasound Monitoring Network, which has been improved in 2009 by installing the receiver VLF / LF its antennas at Dobrogea Seismological Observatory.
MEMFIS Network – The Multiple Electromagnetic Field and Infrasound Monitoring Network (Table 1 / Fig. 1) is equipped with 4 fluxgate magnetometers (Bartington), with seismic sensors, 3 MBAZEL2007 infrasonic monitoring stations, an electrometer to measure the vertical component of the electric atmospheric field (Boltek EFM100) and a weather station La Crosse WS-3600Geophysical Observatories network of MEMFIS
Seismo-acoustic network of Plostina
It is an array composed of 6 elements: IPH2, IPH3, IPH4, IPH5, IPH6 and IPH7.
The core includes sensors for measuring electric field and weather conditions.
The data is recorded in real time and stored in the ROM NDC data center in Magurele.
DR. RADU CORNELIUS-VRÎNCIOAIA SEISMOLOGICAL OBSERVATORY
Vrincioaia Seismological Observatory is located in the NE part of the Vrancea epicentral area, aimed to provide data for seismic warning system for industrial and civilian objectives, and for
National Seismic Network. It was founded in 1942, following the massive earthquake on 10 November 1940 (magnitude M = 7.4). Equipped with Mainka seismograph type modified by romanian seismologist – Demetrescu, has stopped work in 1944 because of the war. In the period from 1952 to 1956 it worked sporadically.
It was reopened in 1964 by the seismologist Cornelius Radu in a very modest space, when in addition to Mainka seismograph type was installed the VEGIK seismograph type (russian fotocamera).
After the earthquake of March 4, 1977 (magnitude M = 7.2) station equipment has been completed with the following systems: seismograph Kirn (SKM); seismograph DD-1; SM-3 seismograph; seismometer S-13; Acelerograf SMA-1.
In October 1980, the station is updated with the S13 seismograph type and became the main station from seismic network, telemetering seismic data to Bucharest.
During 1986 – 1989, due to the work of modernizing thorugh the construction of a new building and new recorders, Seismological Observatory Vrincioaia becomes one of NIEP reference stations.
PLOSTINA SEISMOLOGICAL OBSERVATORY
Plostina Seismological Observatory is located 8 km North of Dr. Radu Cornelius Seismological Observatory of Vrincioaia, both are forming a scientific research center intended to monitor seismic activity on the territory of Romania, to measure the precursor distinct parameters with regard to the correlation with the seismic activity and to provide data for the warning systems of industrial and civilian objectives. The seismo-acustic array deployment started in 2007, when four seismic elements (PLOR1, PLOR2, PLOR3 and PLOR4) were installed. In 2009, two more seismic sites (PLOR 5 and PLOR6) were added, and the infrasound array deployment was initiated, by placing of three infrasonic instruments (IPH4, IPH5 and IPH6), collocated with the corresponding seismic locations. In 2010, another seismo-acoustic element (PLOR 7 and IPH7) was added and during 2012, sites 2 and 3 where equipped with infrasound sensors. Plostina seismo-acoustic array is currently distributed over an area of 3.5 km2 81 , inter-element distance varies between 450 and 2,450m. Presently, at Plostina, NIEP operates an integrated system which includes advanced technologies such as: seismic and infrasound arrays, strongmotion sensors,magnetic field and electric field monitoring, soil temperature measuring, and a weather station. The main applications of this system are: monitoring of the local microseismic activity, acoustic measurement (infrasound monitoring of explosions, mine and quarry blasts, volcanic eruptions, earthquakes, aircraft etc.), observation of the magnetic field variation in correlation with solar activity, observation of the variation of telluric currents.
DOBROGEA SEISMOLOGICAL OBSERVATORY
In 2008 a new modern Seismological Observatory was inaugurated at Eforie, as backup for the data acquisition and processing in Magurele and as monitoring center for Black Sea tsunamis. The observatory employers assure also the maintenance of other 10 seismic stations installed in the region. These stations are equipped with seismometers and accelerometers and the recorded data are transmitted in real time to NDC. Equipment to measure electromagnetic field and UV radiation is operating as well .
TIRGUSOR SEISMOLOGICAL OBSERVATORY
Tirgusor Seismological Observatory is part of the national seismic network, providing data about the local seismicity. The seismic station is equipped with both an acceleration sensor and a broadband velocity sensor. It also provides data for the GEOFON network operated by the University of Potsdam, Germany.
CHEIA – MUNTELE ROSU SEISMOLOGICAL OBSERVATORY
Since 1994, a high performance seismic system (Quanterra data logger, GPS timing broadband velocity sensors, three components andmore than 7 days buffer for the data storage) has been installed at theMunteleRosu (MLR) observatory , in the framework of the cooperation with the GEOFON Network (Germany). MLR station was included in the auxiliary seismic network of the International Monitoring System (IMS) coordinated by CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization). In order to ensure Romania’s technical participation to the CTBTO activities and to maintain the station at the operational standards required by the Treaty, since 1999, an important upgrade has been carried out both at the seismic station MLR and at the NDC, involving technical cooperation with the Government of Japan and technical assistance from the CTBT Organization . The data were continuously recorded and transmitted in real-time to the NDC in Magurele and IDC in Vienna.
BUCOVINA SEISMOLOGICAL OBSERVATORY
Since July, 2002, a new seismic monitoring system, Bucovina Seismic Array (BURAR), has been established in the Northern part of the country, in a joint effort of the Air Force Technical Applications Center (AFTAC), USA and NIEP. Data recorded by BURAR array are continuously transmitted in real time to the National Data Center of USA in Florida and to NDC, in Magurele. BURAR seismic array consists of 10 seismic stations located in boreholes and distributed over an area of 5 km2. Nine stations are equipped with short-period vertical sensors (GS-21) and one station is equipped with broad-band three-component sensor (KS 54000). In 2007 two new elements equipped with 3-C broad-band sensors were installed aiming to obtain the most convenient array combination of 3-C elements for the recording and identification of the secondary seismic phases, to optimize the array response, achieving a superior sensitivity and resolution of BURAR in S-type seismic signals identification.
BUZIAS SEISMOLOGICAL OBSERVATORY
Seismological Observatory Buzias, located in Timis county is part of the National Seismic Network, providing data on seismicity of Banloc area. Seismic station is equipped with a broadband sensor.
DEVA SEISMOLOGICAL OBSERVATORY
Oservatorul seismological Deva was founded in May 1971, the date on which it was made out the global seismic network for the study of world’s seismicity, being included in UNESCO seismic network. Currently it is part of the Romanian National Seismic Network, contributing in monitoring romanian seismicity (especially Hateg and Banat seismic areas). It is equipped with broadband and short-period sensors.
TIMISOARA SEISMOLOGICAL OBSERVATORY
Timisoara Seismological Observatory was founded by professor Ioan Curea, considered the pioneer of modern seismology in Romania. Ioan Curea revigorated the seismic monitoring in Banat and Ardeal by the foundation of two seismic stations in Cluj and Timisoara. In 1939 he founded the Seismic Station Cluj as a department of the University’s Astronomical Observatory. As professor at the University of Timisoara, Ioan Curea engineered two horizontal Mainka seismometers (m=540 kg). They were installed in November 1942 at the Astronomical Observatory of Timisoara and they have been used until 1944. After the war, in 1950, professor Ioan Curea reactivated the seismic station in a temporary room at the Polytechnic Institute, where it has been functioning until 1965.
Mihaela Popa, Mircea Radulian, Daniela Ghica, Cristian Neagoe and Eduard Nastase – Romanian Seismic Network Since 1980 to the Present – Nonlinear Mathematical Physics and Natural Hazards, Chapter 9, , Springer International Publishing, Switzerland, 2014