Compilation of the seismic hazard maps in Bosnia and Herzegovina
Introduction
Bosnia and Herzegovina (BIH) is situated in the Western Balkans between latitudes 42° and 46° N, and longitudes 15° and 20° E. The seismic activity of this region has been documented for more than 2000 years. Large-scale earthquakes are rare in Bosnia and Herzegovina, however, if they are to strike, they would most probably cause far-reaching and costly damage and may lead to potentially hundreds or even thousands of casualties.
The effects of earthquakes, as well as active faults, cross national borders, so we describe the most important earthquakes also in neighboring regions. The most devastating earthquake of the ex-Yugoslavian region was the 1963 Skopje earthquake. The magnitude of the earthquake was 6.1 on the Richter scale and the intensity by Mercalli-Sieberg-Cancani scale (MSC) was of level IX. The total number of casualties was 13,000 and 4000 people were injured. Around 80.7% of all the buildings in Skopje were destroyed; more than 200,000 people became homeless (76%); and only 19.7% of buildings could be used [1]. It is interesting to note that the majority of the destroyed buildings were made of masonry and had load-bearing walls only in one direction [2]. Many hospitals, schools, and public institutions, representative of category I structures, were destroyed. The devastation was so large that financial, medical, and engineering support was offered by 78 countries. Only sixteen years later, a strong earthquake hit Monte Negro (magnitude 6.9 on the Richter scale). It was accompanied by several aftershocks with magnitudes up to 6.1. In the North-South direction, the maximum acceleration was 0.4 g. A very large area of ex-Yugoslavia was shaken by this earthquake and the intensity in BIH was reported as V by MSC. The number of casualties was much smaller than in Skopje and amounted to 101, while 100,000 people were left homeless. The most devastating earthquake which hit BIH was the 1969 Banja Luka earthquake, having a magnitude of 6.6 on Richter's scale and the MCS intensity in the range from VII to IX, as a result of soil characteristics [3]. After two months the same region was hit by a 5.4 magnitude earthquake. During these earthquakes, numerous buildings (schools, hospitals, etc.), cultural and heritage structures were destroyed or damaged. All these earthquakes are characterized by a shallow focal depth causing higher destruction.
Just after the Skopje earthquake, the temporary code for Construction in Seismic Regions (1964) was adopted in ex-Yugoslavia. Regardless of the high seismic activity of this region, severe earthquake actions were not taken into account during the structures’ design. It is believed that the catastrophic earthquakes (1963 Skopje earthquake and 1969 Banja Luka earthquake) were the impetus for drafting the new rules. However, the Technical Regulations for Design and Construction of Buildings in Seismic Regions were enforced [4] only in 1981. These regulations had much stricter conditions than the previous temporary codes. The rulebook for Technical Standards for Masonry Walls was made available only in 1991 [5], ten years after the adoption of the Technical Regulations for Design and Construction of Buildings in Seismic Regions, but it was never enforced. A large number of structures were built without any seismic regulations. Currently, BIH is using for some projects Eurocodes (even though these codes are not enforced) and Eurocode 8 – Design of structures for earthquake resistance - requires a map of the seismic hazard in Bosnia and Herzegovina, which did not exist in the required form. This paper presents the process of compiling the new hazard map of Bosnia and Herzegovina, which has become an integral part of the National Annex for Eurocode 8.
Section snippets
History of seismic hazard assessment in europe with Bosnia and Herzegovina
Within the last 15 years, several projects dealing with the seismic hazard assessment of Europe and the Mediterranean region were launched and finalized. The first global map of seismic hazard in the function of peak ground acceleration (PGA) was completed within the framework of the Global Seismic Hazard Assessment Program (GSHAP), which took place from 1992 to 1999 [6]. The first more detailed, unified seismic source model was created within the project “Seismotectonics and Seismic Hazard
Geological setting, tectonics and seismogeneric potential of Bosnia and Herzegovina
Bosnia and Herzegovina lies in the central part of the Dinaridic Mountain System. The geotectonic zones which have been identified are illustrated in Fig. 1 [18].
- a)
The Dinaridic carbonate platform is composed of the Upper Paleozoic sequence, the Late Permian to Norian sequence, and the Norian-Lutetian carbonate platform.
- b)
The Bosnian Flysch, reaching a total thickness of approximately 3 km, consists of two distinct subunits: the “Vranduk Subgroup” and “Ugar Subgroup”.
- c)
The Dinaride Ophiolite Zone
Approaches to seismic hazard assessment
Two main approaches can be used to estimate the seismic hazard: deterministic (DSHA) and probabilistic (PSHA). In recent years, procedures have been developed to simulate the ground motion using fault rupture modeling and seismic wave propagation, e.g. Refs. [39]. These procedures are used mainly for evaluating active regions, requiring enough instrumental data to construct these models. Each approach has its advantages and weaknesses. For example, the DSHA involves the assumption of a certain
Obtained results
All these input data were processed in open-source software for seismic hazard and risk assessment, the OpenQuake engine, Pagani et al. [85], and probabilistic hazard curves were calculated on a grid with 10 km spacing. The configuration files for the calculation are present in the electronic supplement (as an attached zip file).
The result of the seismic hazard calculation is a set of seismic hazard curves for percentiles 16%, 50%, 84%, as well as for the mean value for each grid point (Fig. 7
Conclusion
Bosnia and Herzegovina with its surrounding areas is an integral part of the Dinarides which are part of the Mediterranean orogenic system formed during the Mesozoic–Cenozoic age. Subduction in the Dinarides began in the Middle Jurassic that was followed by the abduction of ophiolites and the formation of ophiolitic mélange during the Upper Jurassic-Lower Cretaceous times. This was followed by a continental collision between the Adria and European derived continental units that started during
Author contributions
Naida Ademović: Conceptualization, Methodology, Validation, writing—original draft preparation, final writing—review and editing.
Vedad Demir: writing—original draft preparation, Software, Methodology.
Snježana Cvijić-Amulić: writing—original draft preparation, Validation.
Jiří Málek: writing—original draft preparation, Software, Methodology, final writing—review and editing.
Ivan Prachař: writing—original draft preparation, Software, Methodology.
Jiří Vackař: writing—original draft preparation,
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
The authors gratefully acknowledge the development cooperation project “Support of Capacities of the Institute for Standardization of Bosnia and Herzegovina in the Area of Implementation of EUROCODES“ No. CzDA-RO-BA-2014-3-15110 under the financial support of the Czech Republic whose main objective was to support the Institute for Standardization of Bosna and Herzegovina (BAS) in the area of implementation of European standards system for the design of building structures—Eurocodes. The project
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