Seismic Deformations in an Early Christian Monastery in the Area of Djanavara, Varna, Bulgaria. Part 2: Results of Investigations

Autor: O. V. Dimitrov, A. A. Strelnikov, V. Tenekedjiev, E. A. Rogozhin, B. Ranguelov, A. M. Korzhenkov, A. Minchev, A. N. Ovsyuchenko, A. S. Larkov
Rok vydání: 2021
Předmět:
Zdroj: Seismic Instruments. 57:472-489
ISSN: 1934-7871
0747-9239
DOI: 10.3103/s0747923921040071
Popis: We conducted archaeoseismological studies at the Djanavara Monastery Complex in 2019. It consists of early medieval buildings of different ages, the main of which was the church. The church and the atrium were first badly damaged and then destroyed. There were attempts to repair them, as evidenced by the laying of a doorway in the north wall of the atrium. The age of this seismic event may coincide with the destruction of the “second” Episcopal Basilica of Varna, also built in the second half of the 5th century CE. This earthquake took place several decades later. Judging by the kinematic indicators in the building structures, the source of seismic movements was apparently located north-northeast of the Episcopal Basilica of Varna and, accordingly, of the Djanavara Monastery Complex. In this direction, the largest seismotectonic node is located at the intersection of sublatitudinal faults with the Shabla-Kaliakra seismogenic zone. Subsequent renovation of the Djanavara Church and construction of poor-quality buildings around it took place after this seismic event. However, even in these, later, walls, we see traces of younger seismic deformations, evidenced by numerous buttress walls attached to the walls that survived the second earthquake. Judging by the buttress walls attached to the original meridional walls from the east and west, the seismic movements of the second earthquake propagated along the east–west axis. The third seismic event put an end to the activity of the monastery complex. It can be seen that the repaired low-quality walls were again deformed: the later masonry that covered the doorway moved outward, and there was also a joint deformation of the meridional wall and its buttress. The westward movement of the latest masonry testifies to the source of seismic oscillations of this time, located west of the Djanavara Complex. However, the meridional walls show clockwise rotation of their parts, while a perpendicular wall was rotated counterclockwise. Such a systematic deformation presupposes the location of the seismic source not strictly to the west of the monastery complex, but to the southwest, which coincides with the direction to the source, which we determined for the deformations in the episcopal basilica of Varna. Some researchers believe that the Djanavara Monastery Complex was destroyed and finally abandoned in 614–615 CE during the Avar–Slavic invasion. However, there are materials indicating that residents left ancient Odessos even before the attack, most likely due to a strong (third in our case) earthquake, during which the entire city was engulfed in fires and many buildings were destroyed. We were unable to accurately estimate the local seismic intensity for each of the three described ancient earthquakes, however, such significant deformations as systematic inclination and shifting of walls, as well as rotations of their parts around the vertical axis, indicate that the intensity of seismic oscillations during the studied earthquakes reached IL ≤ 9 on the MSK-64 scale. The intensity of seismic oscillations may have been enhanced by unfavorable soil conditions at the site of the construction of the Djanavara Monastery Complex.
Databáze: OpenAIRE
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