Papers by Boyko Ranguelov
Seismic Deformations in the Archaeological Sites of Varna, Bulgaria
Izvestiya-physics of The Solid Earth, Feb 1, 2022
Abstract —The ruins of Odessos are located on the territory of Varna, Bulgaria. Archaeoseismologi... more Abstract —The ruins of Odessos are located on the territory of Varna, Bulgaria. Archaeoseismological studies carried out at the archaeological sites of ancient Odessos revealed some significant damage and destruction in the ancient building constructions. These are numerous breaks, tilts, protrusions and turns of wall parts, longitudinal asymmetric deformation of the above-entrance arch, lateral in plan bending of the extended wall, outward knock-out of the stone blocks and intensive cracking. We attributed traces of subsequent shoddy repairs, which sometimes involved using single expensive stone blocks taken out of the ruins, as circumstantial evidence of strong earthquakes that had occurred here. Interestingly, medieval builders already knew about the possibility of strong earthquakes in the region and put wooden longitudinal beams in the walls to absorb vertical seismic vibrations. The degree of destruction and damage in medieval buildings built on loose fill soils increased due to subsidence. Archaeological research established 6 periods of construction in ancient Odessos: Using this periodization, we calculated the age of past seismic events: (1) around the 1st century A.D.—the destruction of the Late Hellenistic fortress wall; (2) the early 5th century—the early 6th century (a cluster of at least 3 strong earthquakes, judging also by deformations in the Bishop’s Basilica of Odessos (Minchev et al., 2020)): dismantling of the fortress wall, discontinued use of both thermae. The gate of Odessos remains in operation after repairs. There is low quality construction of houses. Accumulation of tile debris; (3) the destruction of the Orthodox church in the 1444 earthquake. We were able to determine the average direction of the maximum aggregate seismic movements that destroyed the large and small thermae, as well as the excavated segment of the fortress wall and the Odessos gate complex. They propagated along the WNW-ESE axis, most likely from the Shabla-Kaliakra seismogenic zone. The deformations of the 13th-century Orthodox church were caused by seismic vibrations that propagated in the submeridional direction from one of the seismically active faults south or north of Varna, although they may have been affected by ground subsidence. Thus, as a result of the studies, we were able to detect traces of yet unknown strong earthquakes, to determine their age and direction to the ancient epicentral zones. The intensity of seismic vibrations during all these earthquakes was I l = VIII—IX MSK-64. The data obtained can be used to improve the seismic hazard assessment of Varna and NE Bulgaria.
Tsunami research in Bulgaria: recent developments, gaps and further directions
<p>Tsunamis are severe natural hazards, causing significant human casualtie... more <p>Tsunamis are severe natural hazards, causing significant human casualties and material damage to infrastructure, especially in the coastal zone. Research shows that tsunami danger exists for any water basin. The Black Sea is an inland sea, surrounded and crossed by several active faults whose geodynamic characteristics indicate that they can generate a tsunami. Moreover, the Black Sea is also prone to landslide-generated tsunamis and meteotsunamis. Until five decades ago, the existence of a tsunami threat in the Black Sea was ignored until the appearance of books that mention events described by ancient chroniclers interpreting information about tsunami-related phenomena in historical documents.</p><p>This work reviews and systematizes the main achievements in the field of tsunami research in Bulgaria from the initial voluntary enthusiastic research, initiated through the FP4-ENV 2C funded project "Genesis and impact of the tsunami on the European coasts" (GITEC-TWO, 1996-1998; https://cordis.europa.eu/project/id/ENV4960297) up to the present days. The small number of tsunami events observed in the western Black Sea basin limits our knowledge of the tsunamigenic potential of the Black Sea. The main problems, omissions and challenges are related to establishing the characteristics of tsunami sources, such as kinematic parameters of active faults and their geometry, coastal and underwater landslides and special weather conditions inducing meteotsunamis. This review presents the actions, studies, and observations on the western Black Sea coast, the first steps in building a tsunami warning system and other related activities. Based on the collected information, we identify the research gaps according to the AGITHAR priority matrix (Behrens et al., 2021) and highlight the emerging research areas in the Black Sea basin. The possibility of proposing a framework for assessing multi-hazard and multi-risk due to the cascade effect of different hazards along the Bulgarian coast in the context of the Sendai Framework for Disaster Risk Reduction is also outlined.</p><p><strong><em>Acknowledgements</em></strong><em>: The authors thank the Bulgarian National Science Fund for co-funding the research under the Contract КП-СЕ-КОСТ/8, 25.09.2020, which is carried out within the framework of COST Action 18109 “Accelerating Global science In Tsunami HAzard and Risk analysis” (AGITHAR; https://www.agithar.uni-hamburg.de/).</em></p><p> </p><p><strong>References:</strong></p><p>Behrens J, Løvholt F, Jalayer F, Lorito S, Salgado-Gálvez MA, Sørensen M, Abadie S, Aguirre-Ayerbe I, Aniel-Quiroga I, Babeyko A, Baiguera M, Basili R, Belliazzi S, Grezio A, Johnson K,Murphy S, Paris R, Rafliana I, De Risi R,Rossetto T, Selva J, Taroni M,Del Zoppo M, Armigliato A, Bures V, Cech P, Cecioni C, Christodoulides P, Davies G, Dias F, Bayraktar HB, González M, Gritsevich M, Guillas S, Harbitz CB, Kanoglu U, Macías J, Papadopoulos GA, Polet J, Romano F, Salamon A, Scala A, Stepinac M, Tappin DR, Thio HK, Tonini R, Triantafyllou I, Ulrich T, Varini E, Volpe M and Vyhmeister E (2021) Probabilistic Tsunami Hazard and Risk Analysis: A Review of Research Gaps. Front. Earth Sci. 9:628772. doi: 10.3389/feart.2021.628772</p><p><sup>* </sup>corresponding author</p>
A Stochastic Model for Prediction the Occurrence of Strong Earthquakes (M>7.0) in the Chile Seismogenic Area
On the basis of preliminary created stochastic model for earthquake prediction, new software is a... more On the basis of preliminary created stochastic model for earthquake prediction, new software is applied about the Chile coastal area. Data about strong earthquakes have been used for the model application. Strong effects of migration of the seismic sources have been discovered in N-S direction. Repeatability and predominant distances of the consecutive events are also result of these investigations. The physical meaning of such effects is dominated by the clear zone of subduction developed there. After the visualization the diagrams about the next expected strong seismic event are presented. The software could be useful to any other applications in the similar regions. The use of the earlier developed stochastic model is based on geometry considerations as well as the statistical distributions of the main parameters of any two consecutive seismic events: temporal and space positions and the magnitude differences. The obtained bi-modal distributions require the consideration of the most probable position of the next expected seismic event. The results obtained show the applicability of the suggested model. The last strong seismic event Mw8.8 occurred on 27 th February 2010 is considered as a starting point for the next expected strong earthquake in the area.
Tsunami investigations in the Black Sea (Bulgarian experience to the EU SCHEMA Project)
5th Congress of Balkan Geophysical Society, May 10, 2009
SCHEMA is the acronym of the Scenarios for Hazard-induced Emergencies Management Contract No: 030... more SCHEMA is the acronym of the Scenarios for Hazard-induced Emergencies Management Contract No: 030963 with EC of the PF6 Priorities (Space). Duration – 36 months, 12 Partners organizations from France, Portugal, England, Italy, Greece, Morocco, Turkey and Bulgaria The Project is constructed by several working packages - Lessons learn by the previous experience - 5 test site areas are under investigation - Morocco: Rabat region; Bulgaria : Varna region on Black sea – Balchik town is a representative sample; France : Mandelieu , Cote D’Azur; Portugal : Setubal; Italy : Catania, Sicily. The main task of the Project is to satisfy the end-users requirements about the possible prevention and protection actions to the population of the threaten test sites.
The survey presents the results of the distributed among the PECO countries and their experts a q... more The survey presents the results of the distributed among the PECO countries and their experts a questionnaire on the seismic risk mapping. This problem is considered as the common hazard in several PECO countries. The main aim of the questionnaire is to establish the state of the art of the risk mapping process on the earthquakes. The results after the processing procedure of the collected data are presented. They are illustrated by many tables and other information tools. They show very similar picture of the abilities of the different countries to map the seismic risk. The first part considers the seismic hazard data and hazard maps. The problem has several peculiarities in comparison with some other hazards also displayed in the same questionnaire: the vulnerability of the different structures to the earthquakes the vulnerability of population to the effects of the earthquakes the risk mapping as a combination of the hazard mapping and the vulnerable elements. Most of the countries are well prepared for these activities (i.e. base maps exist), but almost no one is using GIS technology for this mapping. The main aim of this survey is to make conclusions and some suggestions to the EC policy makers for the homogenization and legislation to be applied for all PECO countries. Most of the investigated countries mentioned that they would like to play positive role in such process. *PECO is the EC acronym of the new member states and the candidate countries for the EU.
Geodinamika i Tektonofizika, 2010
This paper presents research results of the study which aim is to reveal and quantitatively descr... more This paper presents research results of the study which aim is to reveal and quantitatively describe fractal properties of the European-Mediterranean seismotectonic model applied for seismic hazard assessment of the region under study. Several seismotectonic provinces are defined, and their nonlinear properties are calculated using both linear elements (boundaries of seismogenic units) and surface areas of the seismogenic units. The research is conducted on the basis of only formal relationships, not with data on real fault structures or other seismogenic elements, as the relationships have been accepted for seismic hazard calculations by the team of SESAME Project (Project Leader M. Jimenec) and published by Jimenec et al. [2001]. Special attention is paid to the Balkan seismotectonic model in order to develop a common seismotectonic model which uses data from the seismic hazard map for a period of 475 years (according the EUROCODE8), that was published in . All the calculations considered only the seismogenic units located in the earth crust, but not deeper seismogenic layers. It is concluded that most of the seismogenic provinces are similar in their fractal properties, which varied in a narrow range, except for the Adriatic one. The formal approach does not permit to explain these peculiarities.
Classifications, Management and Aerospace Methods for Natural Hazards Studies
5th Congress of Balkan Geophysical Society, May 1, 2009
The last year s world hazardous events (tsunamis, earthquakes, hurricanes, floods, etc.), generat... more The last year s world hazardous events (tsunamis, earthquakes, hurricanes, floods, etc.), generated a lot of discussions about the effectiveness of the space research technologies. The introduction of the high technologies in the everyday practice, fast communication systems and recent hardware and software, allows considering that early warning systems can play an important role in the population protection and safety. The concept of the destructive potential is introduced and several classifications about the different natural hazards and their possible negative influences are constructed.
THE SEISMOGENIC POTENTIAL OF THE SUBDUCTION ZONES - THE TWO GREAT EARTHQUAKES: CHILE (Mw8.8, 2010) AND SUMATRA (Mw9.1, 2004) - INDICATORS ABOUT SUDDEN PLATE MOVEMENTS
The comparative analysis about the two strong earthquakes near continental plate boundaries - Ind... more The comparative analysis about the two strong earthquakes near continental plate boundaries - Indian and Sunda plates (Sumatra Island-Indonesia) and South America and Nazca plates (Chile coast) is made concerning their seismogenic potential. In the frame of the recent geotectonics, epicenter and hypocenter positions, depths of the seismic events, rupture process and the other parameters considered the explanation about the plate movements is outlined. The first giant earthquake (Mw9.1) generated a huge transatlantic tsunami, which kills more than 200 000 people in many countries around the Indian Ocean, thus appeared one of the greatest catastrophes during the mankind history. The second one (Mw8.8), located to the Chilean east coast produced a very small tsunami (which is absolutely unusual for such size of magnitude), but brought large destructions and more than 1000 deaths on the coastal cities. To know the potential of the subduction seismic zones to produce huge earthquakes able to move suddenly continental plates or parts of them appears of essential importance in view of the recent geodynamics. The geodesy data and information is of primary importance to asses the limitations due to the underwater sources of the earthquakes. The huge areas and volumes of earth's crust destruction delineated by a sequence of the very powerful and numerous aftershocks can help to understand the destructive processes - their size and generic potential.
Tsunami Risk Mapping in Coastal Zones of Low Tsunami Hazard: The Case of the Balchik Town, Bulgarian Coast, Black Sea
AGUFM, Dec 1, 2009
ABSTRACT The Black Sea is characterized by low seismicity and low tsunami hazard. However, in the... more ABSTRACT The Black Sea is characterized by low seismicity and low tsunami hazard. However, in the coastal zone of Balchik, located about 20 km to the north of Varna, Bulgaria, a few strong earthquakes associated with damaging tsunami waves have been reported historically: AD544 or 545 and 1901. In addition, Varna and Balchik, is a highly tourist destination. Therefore, the town of Balchik, has been selected as one of the test-sites of the EU tsunami research project SCHEMA. One of the major components in that research project as regards the test-site of Balchik is the production of tsunami risk maps. Our contribution is outlined as follows. We compile an updated and revised earthquake and tsunami catalogue for the Black Sea and select the large event of AD545 to produce an extreme tsunami scenario on the basis of two independent approaches. The first is based only on tsunami descriptions contained in historical documentary sources and on findings of possible tsunami effects in the archaeological site of Cibele temple. The second is based on inundation results coming from numerical simulation of a tsunamigenic source which is only hypothetical given that we have no precise information about the focal parameters of the causative earthquake of 545. Finally we adopted an extreme wave of 3-5 m in height. Maps illustrating a number of attributes, such as tsunami inundation, local topography, land use/land cover, importance of facilities etc. have been used to characterize and map the expected tsunami impact in scale 1:5000 which is practically applicable. The tsunami impact scenario includes three different items: damage potential, vulnerability of population, risk of life. This is a contribution of the EU Research Project "SCHEMA", contract n. 030963, FP6.
Geological Society, London, Special Publications, 2006
Southwest Bulgaria is an intracontinental region between the Dinaro-Hellenic and Balkan mountain ... more Southwest Bulgaria is an intracontinental region between the Dinaro-Hellenic and Balkan mountain ranges that has experienced infrequent, but strong and destructive earthquakes. The general geometric and kinematic characteristics of the major faults, mainly the active ones, are investigated, as the seismic activity is insufficient to describe thoroughly the active crustal deformation associated with the faulting. The results suggest a major rupture zone with a length of more than 50 km. The east-west-striking Kochani-Kroupnik-Bansko 'rupture zone' was potentially associated with the large 1904 Kroupnik earthquakes, and has been found to transect the region joining the Kochani, Kroupnik and Bansko faults. In addition, a long-term slip rate ranging from 0.14 to 0.7 mm a -1 has been estimated for some large faults in the region using morphotectonic features. The most active faults are normal ones striking WNW-ESE to ENE-WSW, whereas the NNW-SSE-to NW-SEstriking faults tended to act as barriers to the growth of the former faults, as they do not exhibit much indication of recent reactivation. The stress regime determined is extensional with the least principal stress axis (s 3 ) subhorizontal and oriented north-south. The fact that the active faults show geometric and kinematic characteristics, as well as estimated long-term slip rates, similar to those of the active faults of central and eastern Macedonia and Thrace (Northern Greece) suggests that both of these regions share a single contemporary stress field.
Godišnik ... na Departament Prirodni nauki, Nov 19, 2021
Резюме: В тази разработка са представени обобщения на резултатите от целеви комплексни геофизични... more Резюме: В тази разработка са представени обобщения на резултатите от целеви комплексни геофизични изследвания на открити или предполагаеми древни археологически обекти, консултирани предварително със специалисти археолози от НАИМ-БАН. Приложеният комплекс от методи на плитката геофизика се оказва основно предимство за повишаване на ефективността на проучванията. Известно е, че методите на приложната геофизика боравят с т.н. обратни геофизични задачи, които нямат еднозначно решение. За да се намали тази нееднозначност, са използвани методи които взаимно се допълват и така улесняват интерпретацията на получените резултати.
Russian Journal of Earth Sciences, Nov 20, 2019
Over the past few decades Messenger spacecraft missions have provided to the scientific community... more Over the past few decades Messenger spacecraft missions have provided to the scientific community a huge amount of new data on the geology and physics of the planet closest to the Sun -Mercury. The collected data became the starting material for the building of the gravity field model of the Mercury -HgM008. Based on it, a very recent NASA scientific team has released a high-quality "free-air" gravity map for the topography of the small planet. This enables new analyzes and interpretations of Mercury's physics and geology. The present study presents the results of Mercury's free-air gravity field (FAG) and digital elevation model (DEM) analysis using the (multi)fractal approach. The obtained results shed new light on the natural processes that have taken place during the geological evolution of Mercury. The results confirmed clear differences between the two hemispheres of the planet. Within the northern hemisphere fractal dimensions of FAG and DEM have variations (𝑅 2 ) 0.908 and 0.942, while within the southern hemisphere 𝑅 2 of FAG and DEM have values 0.975 and 0.857. The results obtained determine the different intensity and density characteristics of space objects colliding with Mercury's two hemispheres, which necessitates additional interpretations.
A Kinematical Model of the Seismic Early Warning System (SEWS)
Several models with illustrative pictures are presented covering different seismic possible expli... more Several models with illustrative pictures are presented covering different seismic possible explicit hazardous situations in Bulgaria: -Vrancea seismic source and distances model -Vrancea seismic source and differences in travel times P and S waves model -Pernik city source kinematics model - distances and travel times of the seismic waves The reliability of the models and obtained results strongly depends on several factors: -The exact positions of the seismogenic faults -The locations of the ground strong motion devices -The kinematics of the travel times of P and S waves -The triggering levels of the device sensitivities -The velocity of data transfer and the reliability of the communication links, etc. The legislation issues and the levels of the warnings need further development due to the sensitivity of the public to the “true and false” alarms. All described issues are under investigations in this paper.
Tsunami vulnerability modelling for the Bulgarian Black Sea Coast
Water Science and Technology, 1995
The problem of tsunami hazard assessment and water pollution appear during the last years in conn... more The problem of tsunami hazard assessment and water pollution appear during the last years in connection with the increased density of infrastructure and industrial facilities on the Black Sea coast. The paper deals with the main results of the tsunami vulnerability modelling in accordance with the internationally recognised methods and new data obtained during the last years. Data collection, new approaches for travel times and dynamic properties of the giant sea waves have been investigated in the previous research. Now the main tsunamigenic sources together with the most vulnerable areas are outlined on the Bulgarian part of the coast. Together with the tsunami energy distribution according to the new method of ray tracing and refraction, the results give the possibility to establish the concentration-dissipation areas, which are most important to the tsunami risk assessment.
Possible Sources of Nonseismic Tsunamis in the Baltic and Black seas
The tsunamigenic sources of nonseismic origin are investigated. The relevant sources for the Blac... more The tsunamigenic sources of nonseismic origin are investigated. The relevant sources for the Black Sea (except earthquakes) might be: - underwater slides - meteorological impact (sashes) - meteorites The relevant sources about tsunamis in the Baltic Sea might be: - meteorological impact (storm surges) - meteorites - fast ferries (anthropogenic impact) Many examples and modeling results are presented illustrating the above mentioned nonseismic tsunami sources with quantitative characteristics of the modeled waves.
New trends in earthquake prediction -A case study of AI performance, 2025
The short term earthquake prediction problem is considered not solved yet. The new trends on this... more The short term earthquake prediction problem is considered not solved yet. The new trends on this topic are related to the intrusion of the Artificial Intelligence (AI) with believes it can help significantly to the solution. The case study of an experiment in China during 2023 and published in BSSA (https://pubs.geoscienceworld.
Deleted Journal, May 7, 2024
This paper presents a comparative study for two couples of very strong seismic events-Bulgarian K... more This paper presents a comparative study for two couples of very strong seismic events-Bulgarian Kresna-Kroupnic seismic source activated during 4th April, 1904 (magnitudes 7.2 and 7.8) and those in Turkey 6th February 2023, Gaziantep and Kahramanmaraş seismic source (magnitudes 7.8 and 7.5) called "doublets". The comparison includes main geophysical and seismological parameters and some social and post events consequences and characteristics. The study reveals similarities in the power and huge differences in the consequences of these seismic events occurred in different geodynamic and environmental conditions. Other studies are considered related to strong seismic events and their consequences in other seismic active regions. Comparative tables are developed for easier and visual following of the similarities and differences, and detailed comparison and explanations are given in discussion to try to explain why these differences existed. Conclusions about the effects (social and practical issues) are derived and they could be useful in case of actual retrospective analysis for seismic zoning and for the future assessment of seismic hazard and risk.
Списание на Българското геологическо дружество, Nov 30, 2023
The most northeastern part of the territory of Bulgaria is characterized by high seismicity. In 2... more The most northeastern part of the territory of Bulgaria is characterized by high seismicity. In 2019, archeoseismological studies of traces of strong earthquakes were carried out in the oldest architectural monument in Europe -Durankulak. There are reports of earthquakes in these places in the Middle Ages and in Аntiquity, but the data on the location of their foci is unspecified. Therefore, a team of scientists from Bulgaria and Russia carried out special scientific research on the islands in Lake Durankulak. A large number of artifacts have been found on the Big Island. The ruins located there are very old and have fixed traces of seismic impacts that have occurred over a long period of time. As a result of paleoseismological and archaeoseismological studies, three major earthquakes have been identified. Most likely, the focus of the first is connected to the Intramysian fault, and the focus of the second and third to the Shabla-Kaliakra seismic zone. The first was between VIII and IX degree on the scale of MSK 64, the second between IX and X, the third also between VIII and IX degree on the same scale.
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Papers by Boyko Ranguelov