GENERAL INFORMATION

DISS-ID	ROISS005
Name	Capidava-Ovidiu known also as Falia Palazu, Falia Ianca-Palazu
Compilers	Diaconescu M. ^1
Contributors	Diaconescu M.^1, Craiu A.^1, Constantinescu E.G.^1, Banu D.M.^1
IT	Jianu O. ^1
Graphics	Constantinescu E.G. ^1
Affiliation(s)	^1 National Institute for Earth Physics, 12 Calugareni str., Magurele, Romania
Created	2024

PARAMETRIC INFORMATION, after [3, 5]

Location	Contact line between Central Dobrogea and South Dobrogea
Total length (km)	580	LD	Inferred from regional tectonic considerations [5]
Wide (km)	6	OD	Inferred from earthquakes distribution [5]
Minimum depth (km)	1	OD	Inferred from earthquakes distribution [5]
Maximum depth (km)	33	OD	Inferred from earthquakes distribution[5]
Strike (degree)	200	OD	Based on fault plane solutions, earthquake no.37, table 2 in [5]
Dip(degree)	75	OD	Based on fault plane solutions, earthquake no.37, table 2 in [5]
Rake(degree)	23	OD	Based on fault plane solutions, earthquake no.37, table 2 in [5]
Slip rate (mm/year)	-		Unknown
Max magnitude(Mw)	4.5 Mb 27.04.1986	OD	Derived from maximum magnitude of associated individual source(s)

COMENTARY

The Capidava-Ovidiu Fault (also known as the Palazu Fault or the Ianca-Palazu Fault) is a dextral strike slip crustal fault, oriented NW - SE, which separates, within the Moesic Platform, two compartments with special basements and sedimentary covers: the northern compartment (Dobrogea Central) and the southern (South Dobrogea). In the precontinental area, initially, it has a NW-SE orientation, then the direction changes to the east, coming into contact with the North-Dobrogean Orogen [8].

The Capidava-Ovidiu Fault, along with other crustal faults of Dobrogea (Peceneaga-Camena, Intramoesică), played a major role during the opening of the Black Sea and the formation of the Carpathians, from the Cretaceous to the Neogene. Including the strong east-concave shape of the Southern Carpathians, it is supposed to be the result of the sliding in the W-NW direction of the Moesian plate on the Dobrogea faults, including the Capidava-Ovidiu Fault, displacement due to the opening of the western Black Sea basin during the Cretaceous [1 , 9, 15, 17]. Activity along this fault ceased with the opening of the western Black Sea Basin [6].

It is part of the system of subcrustal, pre-Jurassic fractures, characteristic of Southern Dobrogea, oriented NW-SE, with a regional character, which extend from the west to the Black Sea shelf and which produced vertical bumps and horizontal translations to the NE: the Fault Capidava - Ovidiu (or Ianca - Palazu), Smirna - Agigea Fault (or North Agigea), Brăgăreasa - Eforie Fault and Lipia - Mangalia Fault [13, 18]. This fault system is driven to the NW in the Vrancea tectonic movements, representing areas where the outbreaks are located [8]. The Capidava-Ovidiu fault, of Baikalian age, is a deep dislocation that crosses the Conrad discontinuity [2, 5, 14] and which caused the dextral horizontal movement of the blocks it separates [10, 11, 18].
The Capidava-Ovidiu Fault has as its western extremity the intersection with the Trotușului Fault, and to the east it extends to the Black Sea platform. The Capidava-Ovidiu Fault is cut off by the Constanța Fault, a transversal fault, parallel to the Black Sea shore, which is superimposed on the "Voiteşti Flexure", a fact that led to the uplift and southward displacement of the eastern compartment [16] and intercepts the Fierbinti fault between the localities of Călăreți and Belciugatele [11].

The Capidava-Ovidiu Fault is an active fault, characterized by a significant but moderate seismic activity, the area between the Intramoesic and Capidava-Ovidiu Faults being characterized by numerous earthquakes, but of low magnitudes Mw = 2.0 ÷ 3.0, with the foci clustered along the direction of the fault (some events being suspected to be explosions in existing quarries in the area). Only a few earthquakes with magnitude Mw ≥ 3.0 were recorded in this area, with epicenters in Tomşani, Urziceni, Baba Ana, Căzănești, Rădulești (eg: the earthquake of January 4, 1960, with Mw=5.4 from Căzănești).

The Capidava-Ovidiu fault has very weak seismic activity on the central-Dobrogean segment, but the stresses are significantly amplified only on the Vrancean segment of the fault, which proves that only the internal processes in the paleo-subducted lithospheric block and in the process of detaching are the ones that influence the dynamics of the earth's crust, even if over time the fault has played a significant role in the evolution of the tectonics of Dobrogea. It is considered by some researchers that the northeastern sector of the Capidava-Ovidiu Fault stiffened later, during the Hercynian orogeny. [8]

In the area between the Capidava-Ovidiu and Peceneaga-Camena Faults, numerous historical earthquakes were identified (with 5 ≤ Mw ≤ 6 (in 1276, 1900, 1942, 1943, 1960, 1967), however, after the installation of the seismic network, it was recorded in this area only one earthquake with magnitude Mw=3.4 on June 12, 1990.

REFERENCES

[1] Airinei S., 1983, Rapports geodynamiques entre la microplaque moesienne et l’arc carpatho-balkanique sur le territoire de la Roumanie. Anu. Inst. Geol. Geofiz. 60, 7 –14

[2] Craiu A., Ghita C., Craiu M., Diaconescu M., Mihai M., Ardeleanu L., 2018, The source mechanism of the seismic events during the sequence of the moderate-size crustal earthquake of november 22, 2014 of Vrancea region (Romania), Annals of geophysics, 61, 6, SE666, 2018; doi: 10.4401/ag-7617

[3] Diaconescu M., Craiu A., Toma-Dănila D., Craiu G., Active faults from onshore and offshore of the Black Sea coast, 15th International Balkan Workshop on Applied Physics and Materials Science IBWAP 2-4 July 2015, Ovidius University of Constanta, Romania

[4] Diaconescu M., 2017, Sisteme de fracturi active crustale pe teritoriul Romaniei, Editura Granada

[5] Diaconescu M., Craiu A., Toma-Danila D., Craiu G.M., Ghita C., 2019, Main active faults from the eastern part of Romania (Dobrogea and Black Sea). Part I: Longitudinal faults system, Romanian Reports in Physics 71, 702

[6] Dinu C., Wong H.K., Ţambre, D., Maţenco L., 2005, Stratigraphic and structural characteristics of the Romanian Black Sea shelf. Tectonophysics 410, 1-4, 417-435

[7] Enescu D., 1992, Lithosphere structure in Romania: I. Lithosphere thickness and average velocities of seismic waves P and S. Comparison with other geophysical data. Rev. Roum. Phys. 37 (6), 623–639

[8] Juravle D.T., 2009, Geologia României, Volumul I, Geologia terenurilor Est-Carpatice (Platformele şi Orogenul Nord-Dobrogean), Ed. Stef Iasi

[9] Manetti P., Boccaletti M., Peccerillo A., 1988, The Black Sea: remnant of a marginal basin behind the Srednegorie–Pontides island arc system during the Upper Cretaceous– Eocene times. Boll. Geofis. Teor. Appl. 30, 39– 51

[10] Mirăuță O., 1969, Tectonica Proterozoicului superior din Dobrogea Centrala. An. Inst. Geol., 37, 7-36

[11] Mutihac V., 1990, Structura Geologică a Teritoriului României. Ed. Tehnica, Bucharest (in Romanian), 424 pp

[12] Oaie Gh., Seghedi A., Rădulescu V., 2016, Natural marine hazards in the Black Sea and the system of their monitoring and real-time warning, Geo-Eco-Marina 22/2016

[13] Paraschiv D., Dăneţ N., Popescu M., Dumitrescu V., 1983. The present stage of the pre-Jurassic deposits knowledge in South Dobrogea. An. Inst. Geol. Geoffiz., LIX, 30-37, Bucuresti

[14] Rădulescu D., Cornea I., Săndulescu M., Constantinescu P., Rădulescu Fl., Pompilian A., 1976, Structure de la crouˆte Terrestre en Roumanie. Essai d’interpretation des etudes seismiques profondes. Anu. Inst. Geol. Geofiz. L, 5 – 36

[15] Săndulescu M., 1980, Analyse geotectonique des chaines alpines situees autour de la Mer Noire occidentale. Ann. Inst. Geol. Geofiz. 56, 5– 54

[16] Săndulescu M., 1984, Geotectonica României (Geotectonics of Romania), Tectonica, Bucarest, 336 pp. (in Romanian)

[17] Săndulescu M., 1994, Overview on Romanian geology. In: Berza, T. (Ed.), Alcapa II Field Guidebook: Geological Evolution of the Alpine –Carpathian –Pannonian System. Rom. J. Tecton. Reg. Geol. 74, pp. 3 –15

[18] Visarion M., Săndulescu M., Stănică D., Veliciu S., 1988, Contributions a la connaissance de la structure profonde de la plateforme moesienne en Roumanie. Stud. Teh. Econ., Geofiz. 15, 211 – 222