Petya Trifonova

Bulgarian Academy of Sciences | BAS · National Institute of Geophysics, Geodesy and Geography

Records of the magnetometers responding to the effects of big earthquakes were noticed more than a hundred years ago. Even then began to dispute what caused these effects: mechanical vibrations of instruments or electric or magnetic oscillations generated by the earthquakes. In Panagjurishte (PAG) observatory we have great opportunity to shed light...

During ground magnetic surveys are recorded signals from a wide variety of sources – from terrain, natural and man-made surface features, as well as instrumental, geological, and planetary sources. Such signals directly disturb the subsurface effects over the Earth’s surface causing errors in the measurements. External variations which are due to t...

Geomagnetic observatories placed all over the globe determine some parameters which show the geomagnetic activity as a signature of the response of the Earth magnetosphere and ionosphere to solar forcing. Indices might be local, which are calculated from data of a single geomagnetic observatory, or planetary, which characterize the planetary distur...

Present research analyses the human exposure at one of the most dangerous earthquake zones in Bulgaria-Blagoevgrad region and propose a detailed seismic scenario for the main city. Seismic hazard is modelled using GIS and overlaid with one square kilometer grid of population distribution in order to determine the population exposure in the region....

Investigations of hydraulically induced micro-seismicity are typically connected with magma injections, exploitation of geothermal fields and salt mines. Our study examines the seismicity and seismic sources in a peri-platform region with long salt production history. In addition, a very large site for extraction of aggregates and limestone is pres...

The NATIONAL GEOINFORMATION CENTER (NGIC) is a newly established scientific infrastructure for cooperation and integration of human resources, informational products and data from monitoring networks and observatories, their complex analysis and implementation into services to the community. It is part of the National road map for scientific infras...

This paper presents assessment of one of the main elements of the seismic risk – human exposure at the territory of Bulgaria. Seismic hazard in terms of Peak Ground Acceleration map is modelled using GIS and overlaid with a model of population distribution in order to extract a population exposure index (PEI). We use as indicator the population den...

Probabilistic seismic hazard assessment (PSHA) takes into account as much data as possible for defining the initial seismic source zone model. In response to this, an algo-rithm has been developed for integration of geological, geophysical and seismological data through a spatial index showing the presence or absence of a potential seismic source f...

Analysis of input data is a fundamental component of the seismic hazard assessment. The territory of Bulgaria, located in the seismically active region of the Balkans, gives us the opportunity to test new methods of integrating different types of data in order to refine our seismotectonic model. In recent years, a number of high-quality geological,...

The territory of Bulgaria represents a typical example of high seismic risk area in the eastern part of the Balkan Peninsula. Bulgaria contains important industrial areas that face considerable earthquake risk. Moreover, the seismicity of the neighboring countries, like Greece, Turkey, Serbia, FYROM and Romania (especially Vrancea-Romania intermedi...

The Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 epoch and its secular variation model prediction up to 2020.0 is produced and presented in this paper. The main field model is based on the well-known polynomial approximation in latitude and longitude of the geomagnetic field elements. The challenge in our modelling strategy was to upda...

Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic hazard and vulnerability to earthquakes are steadily increasing as urbanization and development occupy more areas that are prone to effects of strong earthquakes. The assessment of t...

Geological studies [1] suggest crustal interactions and interplay between various processes involved in the late Alpine history of the Eastern Rhodope Massif, namely the extensional tectonics, volcanic activity and ore formation. In this active geodynamic context complicated geological structures were formed including metamorphic domes, as well as...

Besides regional mapping of the Earth’s magnetic field, the main usage of repeat station data is for modeling the main field. To have a precise model two components need to be determined in order to obtain high accuracy data that contain reliable information about the internal field: 1) short-period external variations and 2) crustal biases. The re...

Introduction The present poster provides information about the observed trends of the geomagnetic field variations, calculated local geomagnetic indices and tendencies of the secular variations of the field according to data time series of PAG observatory for the present solar cycle-24. • Solar Terrestrial Interactions The solar cycle (or solar mag...

The Project “Black Sea Earthquake Safety Net(work)” ESNET has the intention to educate and raise awareness of seismic risk in the Black Sea Basin in four countries: Moldova, Romania, Bulgaria and Turkey. The project is financed through “The Black Sea Basin Joint Operational Programme”, an EU operational programmes under European Neighbourhood & Par...

Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban envi- ronment. Global seismic hazard and vulnerability to earthquakes are steadily increasing as urbanisation and development occupy more areas that are prone to effects of strong earthquakes. The assessment of...

Weakly magmatic passive margins record large amounts of extensional strain prior to breakup, but the role of magma intrusion and the along-strike variability of strain remain poorly understood. We re-evaluate existing onshore and offshore gravity, magnetic, seismic reflection, and well data from the Australo-Antarctic margins to probe the evolution...

Presently, in the era of Internet communication the preliminary time series (INTERMAGNET's reported data) acquired in geomagnetic observatories are available in near-real time, while the final absolute time series (definitive data) are disseminated with many months delay, being subject to many checks. This paper reports the quasi-definitive geomagn...

Deformations in the earth's upper layer can be mapped using a variety of methods and techniques. This paper examines the regional pattern of linear structures on the territory of Bulgaria using Bouguer gravity anomalies. The gravity data were analyzed using integrated gradient interpretation techniques, such as the Total Horizontal Gradient (THG) a...

According to the current archeological investigations Ada Tepe is the oldest gold mine in Europe with Late Bronze and Early Iron age. It is a typical low-sulfidation epithermal gold deposit and is hosted in Maastrichtian-Paleocene sedimentary rocks above a detachment fault contact with underlying Paleozoic metamorphic rocks. Ada Tepe (25o.39'E; 41o...

Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their socially and economically impact on the urban environment. Seismic hazard assessment for industrial objects is of a substantial importance, because it provides valuable information for seismic safety and disaster mitigation. The main objective of the s...

Seismicity exploration certainly requires comprehensive analysis of location, orientation and length distribution of fault and block systems with a variety of geophysical methods. In the present research capability of geomagnetic and gravity anomalous field data are used for revealing of buried structures inside the earth's upper layers. Interpreta...

The territory of Bulgaria represents a typical example of high seismic risk area in the eastern part of the Balkan Peninsula. Bulgaria contains important industrial areas that face considerable earthquake risk. Moreover, the seismicity of the neighboring countries, like Greece, Turkey, former Yugoslavia and Romania (especially Vrancea-Romania inter...

Probabilistic seismic hazard analysis (PSHA) considers a multitude of earthquake occurrences and ground motions, and produces an integrated description of seismic hazard, representing all events. The PSHA is able to quantify and account for the random uncertainties associated with estimation of the seismicity and the attenuation characteristics of...

The present study aims at demonstrating the capability of gravity and magnetic anomalous data for revealing deep structures in the Earth crust of Bulgaria. Interpretation of gravity and magnetic data is well known [ 1 ] and often applied [ 2, 3 ] to delineate various geological structures such as faults, flex-ures, thrusts, borders of dislocated bl...

Despite the presence of modern electronic devices aeronautics still needs of magnetic compasses as a primary direction indicators on small aircrafts and as very important back-up devices on larger airplanes. Airports infrastructure must include elements which allowed an aircraft check to be performed, and to calibrate or compensate onboard compasse...

The territory of Bulgaria represents a typical example of high seismic risk area. Over the centuries, Bulgaria has experienced strong earthquakes. The main purpose of this work is to compare the calculated and observed intensity values and to judge if they are meaningful and can be used to "validate" forecasting scenario. To make this, a test scena...

The paper presents the ionospheric and geomagnetic responses to the re-current geomagnetic activity with period of 9 days observed over Bulgaria. The period of time 1 October 2007 – 31 March 2009 is considered when the solar ac-tivity is very low. The 9-day waves are derived from the ionospheric parameter f o F 2 measured at Sofia ionosonde station...

Capability of combined gravity and seismological data analysis for more detailed resolution of structures and faults parameters

The basal depth of the magnetic layer (Curie point depths) of Bulgarian territory was calculated using interpretation of geomagnetic field observation and a map of the variations of this border was produced for the first time. The magnetic layer bottom thus obtained has normal (28-32km) values in the Moesian platform and central part of Bulgaria wh...

Regional set of dislocation in the Earth s crust is outlined using the magnitude of total horizontal gradient calculated from the new rectified Bouguer gravity grid of 1x1 km along the territory of Bulgaria. The constructed map of steep gradient anomalies serves as a basis in more detailed analysis and interpretation of faults, flexures, thrust and...

The basal depth of the magnetic layer (Curie point depths) of Bulgarian territory was calculated using geomagnetic field observation and the variations of this border were mapped for the first time. The adopted computational method transforms the spatial data into the frequency domain and provides a relationship between radially averaged power spec...

Weakly magmatic passive margins record large amounts of extensional strain prior to breakup, but the role of magma intrusion and the along-strike variability of strain remain poorly understood. We re-evaluate existing onshore and offshore gravity, magnetic, seismic reflection, and well data from the Australo-Antarctic margins to probe the evolution...

The evolution of the conjugate Australian – Antarctic margins has been loosely constrained by plate kinematic and widely spaced seismic reflection profiles. Gravity and magnetics data calibrated by seismic profiles and well data provide continuous coverage of the Otway margin, allowing us to evaluate current models of continental break up. We use m...