Nationwide and scientific-operational activities of NIGGG serving the state

The National Institute of Geophysics, Geodesy and Geography (NIGGG) at the Bulgarian Academy of Sciences (BAS) provides the Bulgarian state and society with scientific-operative and monitoring information, analyses and assessments in the field of seismology, geophysics, geodesy, and geography.

NIGGG operates and maintains unique national monitoring networks, observatories and centers for processing and analysis of results, such as the National Seismological Network, the Accelerometric Network for Registration and Evaluation of Earth Movements, the National Permanent GNSS (Global Navigation Satellite Systems) Network, the National Mareographic Network for Monitoring the Black Sea Level, the Chemical Weather Forecast System, the Ultraviolet Radiation Monitoring Network, the Paleomagnetic Laboratory, the “Panagyurishte” Geomagnetic Observatory, and the “Plana” Geodetic Observatory.

At the national level, the main users of the data and the analysis of results are: the Ministry of Interior; the Ministry of Regional Development and Public Works; the Ministry of Environment and Water; the Ministry of Defence; the Ministry of Foreign Affairs; the Ministry of Culture; the Ministry of Agriculture and Food; regional and municipal governments; the National Electricity Company, etc.

Through the National Operative Telemetric System for Seismological Information (NOTSSI), NIGGG provides reliable information about the earthquakes occurring in Bulgaria and the neighbouring countries, both for the public and for institutions related to the management of the seismic risk. NOTSSI is the only infrastructural telemetry system in Bulgaria, determining in real time the parameters of earthquakes in Bulgaria. The organized 24-hour duty ensures continuous registration and analysis of seismic signals, in order to send timely information about the seismic situation to the Ministry of Interior. Currently, NOTSSI consists of 33 digital seismic stations and 2 local networks with 8 digital seismic stations.

NIGGG is the coordinator of the National Data Center at the Ministry of Foreign Affairs with regard to the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

The Accelerometric Network for Registration and Evaluation of Strong Earth Movements. Through the national network of accelerometric stations, instrumental registration of seismic impacts is carried out in the form of accelerograms, which provide data and information about the nature of earthquake impacts in the area of each registration point. The information is collected in the Center for Processing and Analysis at NIGGG. Currently, the accelerometric network consists of 15 digital stations located throughout the country.

National Permanent GNSS Network. By processing and analysing the measurements made by the permanent GNSS network, monitoring of modern movements and tensions of the Earth’s crust is carried out, based on the obtained point velocities and seismic risk assessment. The number of permanent GNSS stations owned by NIGGG is 18.

National Mareographic Network. Together with the Geodesy, Cartography and Cadastre Agency of the Ministry of Interior, and the Institute of Oceanology at the Bulgarian Academy of Sciences, NIGGG maintains a national network of mareographic stations along the Bulgarian Black Sea coast – in Varna, Irakli, Burgas, and Ahtopol. The purpose of those stations is to carry out continuous measurements of the sea level.

Chemical Weather Forecast System. The system is designed to provide timely and reliable information and forecasts, meeting the needs of various users. The system uses three models and provides a forecast for the next three days on an hourly basis for the entire territory of the country, as well as the cities of Sofia, Plovdiv and Varna. The system also calculates the concentrations of ground-level ozone, nitrogen dioxide, sulphur dioxide, and fine dust particles. The obtained information is published online on the NIGGG website.

Global empirical total electron content (TEC) models based on CODE TEC data. The total electron content of the ionosphere is an important parameter for the propagation of radio waves in the ionosphere. A forecast of the critical frequencies in the ionosphere is calculated based on a model using archival data for the critical frequencies over Bulgaria, as well as the total electron content. The obtained results are published on the NIGGG website and provided to the Ministry of Defence, as well as other interested persons and institutions.

Ultraviolet Radiation Monitoring Network. NIGGG has three permanent measurement stations for biologically active ultraviolet radiation. A 24-hour forecast is compiled and published on the NIGGG website. Using the specially developed online calculator, users can check the permissible time of stay under the Sun’s rays, as well as the necessary safety measures.

Paleomagnetic Laboratory. It is the only one in Bulgaria equipped with modern specialized equipment for measuring and analysing the magnetic properties of rocks, sediments, soils and archaeological remains of baked clay. Through the laboratory activities, the database of archaeomagnetic determinations of the direction and intensity of the geomagnetic field in the historical past, important for the modelling of the geomagnetic field, is maintained and expanded.

“Panagyurishte” Geomagnetic Observatory. The operational activity at the “Panagyurishte” National Geomagnetic Observatory (GMO “Panagyurishte”) is related to continuous registration of the variations of the elements of the geomagnetic field, and periodic absolute measurements of their values. The variations are presented in a graphic form and are published in real time on the NIGGG website (www.geophys.bas.bg), as well as information about the local K-index, calculated using the data registered in the observatory.

Based on GMO “Panagyurishte” data, information about magnetic storms and other extreme events related to the solar activity is provided. Monthly forecasts of the state of the geomagnetic field are prepared and published.

The “Plana” National Geodetic Observatory of NIGGG. The observatory is equipped with unique astrometric and astronomical equipment, a GPS/GNSS receiver, a seismometer and accelerometer, and an automatic weather station. Measurements for monitoring solar radiation and the environment are made at the observatory.

NIGGG also carries out:

• monitoring of the behaviour of potentially toxic chemical elements in riparian geosystems. Database on the contents of heavy metals and metalloids in the soils of Bulgaria is maintained and developed, as well as a statistical model of the arsenic content in river and groundwater in representative points along the Ogosta River valley;
• speleo-microclimatic, radiological and socio-economic monitoring.