Anica Otilia Placinta

National Institute for Earth Physics · Laboratory of Seismological Research

Few high magnitude earthquakes were generated worldwide in the last three and a half years, some of which triggered tsunami waves. We took into account all the events during the interval January 2020 - June 2023. There was a total of 15 earthquakes (5 in 2020, 5 in 2021, 2 in 2022, 2 in 2023) which lead to moderate and/or small tsunami waves (above...

Ambient seismic noise has proven to be a particularly effective tool for subsurface imaging in the last decades, with applications ranging from near surface imaging, to crustal or upper mantle tomography. Fundamentally, it relies on the cross correlations of continuous recordings of ground motion data at pairs of seismic stations. Processing steps...

The Eastern-Europe region (EER), is a complex geotectonic area that captures part of the Alpine-Himalayan Orogen, the subduction of multiple NeoTethys Branches and part of the East European Craton. It is one of the most exciting geological areas in Europe due to a diversity of tectonic processes acting within it: extensional basin evolution, oceani...

The database contains macroseismic intensities obtained for two groups of earthquakes used for the calibration of the Bakun-Wentworth method of localization and estimation of the Mw magnitude using macroseismic data, respectively the group of earthquakes used to calibrate the attenuation relationship and the group of earthquakes used for its valida...

The Eastern European lithosphere is a natural laboratory to study continental formation and evolution through time, comprising Archean continental remnants, Proterozoic rifts and belts, and younger accreted terranes. We investigate the seismic structure of the East European Craton (EEC) crust and uppermost mantle, and the transition from Precambria...

The Vrancea seismic zone (VSZ), located in Romania, at the sharp bend of the southeast Carpathians, is an anomalous intraplate seismic nest releasing the largest strain in continental Europe. The last powerful earthquake in Vrancea occurred in 1977 causing significant damage to the densely populated cities in southeast Romania. The seismic infrastr...

We present a refined and the most complete catalogue of the focal mechanisms for the Intra-Carpathian region of Romania. It contains the high-quality solutions computed for 1217 earthquakes recorded between 1909 and 2018. Primary data gathered from the original seismograms and seismic bulletins have been used to compute the source parameters and fo...

1-D models for the quality factor along a few profiles crossing the Vrancea region and the adjacent extra-Carpathian zone have been recently developed, to reconstruct the ground motion generated by weak-to-moderate crustal earthquakes of Vrancea. The retrieved Q-structures reveal a consistent pattern of high attenuation at the bend of the Southeast...

The Catalogue is a compilation containing 1299 events (Mw≥3.0) that occurred between 08.01.1223 and 31.12.1989 within the Intra-Carpathians Region of Romania. It can be accessed and downloaded at: Mendeley Data, doi: 10.17632/p8rgkfhjbz.2 The focal parameters of imported earthquakes have been revised using all primary data collected from the ava...

Seismic velocity is the geophysical property that has a key role in characterizing dynamic processes and the state of the stress around the faults, providing valuable information regarding the change in the tectonic regime. The stress in the crust is an important indicator of the possible occurrence of a major earthquake, and the variation of seism...

The Black Sea is the largest European back-arc basin connected to the subduction and final closure of the Tethys ocean. Its origin and type of crust are widely debated, with contrasting views suggesting it is either a relic of Paleotethys or a rifted back-arc basin formed within the thick and cold Precambrian lithosphere. To investigate the structu...

The Black Sea is the largest European back-arc basin connected to the subduction and final closure of the Tethys ocean. Its origin and type of crust are widely debated, with contrasting views suggesting it is either a relic of Paleotethys or a rifted back-arc basin formed within the thick and cold Precambrian lithosphere. To investigate the structu...

Tectonic stresses in the lithosphere are the key to understanding geodynamic processes in general and seismogenesis in particular, being observed during their release by tectonic earthquakes. The relationships of the stress field with tectonics and the structure of the upper lithosphere are complex and controlled by both regional and local factors....

Modelling the causal relationship between the stress field specific to a complex geological environment as structure and composition and how it reacts and manifests itself through specific, observable and measurable deformations (fracturing and propagation of fractures, seismic faults, seismicity), is the key to understanding seismogenic processes...

The paper presents a seismotectonic model of the Southern Carpathians obtained from the analysis of the seismicity-stress field-geology and tectonics relationship. The seismicity model is based on a revised earthquake catalogue. The distribution of b-values in the 3D space facilitated the identification of stressed areas and asperities with reactiv...

Romanian seismicity is mainly confined to the Eastern Carpathians Arc bend (ECAB), where strong subcrustal earthquakes (magnitude up to 7.9) are generated in a narrow lithospheric body descending into the mantle. The seismic activity in the overlying crust is spread over a larger area, located mostly toward the outer side of the ECAB. It is signifi...

We present the study of the earthquakes sequence from 25 June to 6 July 2020 occurred in the western South Carpathians. The main shock had Io= VMSK, Mw= 4.1, occurred at h= 16 km, was preceded by a foreshock (Mw= 3.2) and has 16 after-shocks (Mw= 1.6–4.1) concentrated in the depth range 14–21 km. The focal mechanisms are characterized by strike-sli...

The paper represents a multidisciplinary investigation of the relation between seismicity, active stress field and geological structure for the West of Romania. The study is based on revised and updated catalogues of earthquakes (3572 events) and focal mechanisms (89 solutions). The large spatio-temporal variations of the stress tensor parameters,...

The seismic hazard studies of the last 30 years have been largely carried out taking into account the needs of the construction engineers, by linking the specific quantities of soil movement with the physical parameters determined instrumentally, namely, with the maximum values of soil acceleration. At present, interest in the results of hazard stu...

Romania is one of the most seismic-prone countries in Europe due to the periodically occurrence of strong intermediate-depth earthquakes in Vrancea seismogenic zone. The Vrancea area is located beneath the South-Eastern Carpathian Arc bend, at the contact between the East - European plate and the Intra-Alpine and Moesian sub-plates. An intense seis...

The purpose of the present study is to elaborate a new model of the macroseismic intensity attenuation using all observed intensities data for the crustal earthquakes in Romania and then, based on this relationship, to calibrate the Bakun-Wentworth method, one of the modern methods most used to estimate the parameters of the historical earthquakes...

In the present paper, a relationship between geomagnetic anomalies recorded at one magnetometer located inside Vrancea seismogenic zone and the occurrence of intermediate earthquakes is examined. To better distinguish the regional anomalies from global geomagnetic storms, the datasets were correlated with the geomagnetic indices taken from NOAA/Spa...

We present a study of the strongest historical earthquakes (Mw > 5.0) occurred in West Romania between 1900 and 1980 conducted to review and homogenize the Romanian Earthquakes and Focal Mechanisms Catalogues on instrumental data basis. New hypocenters relocation, moment magnitudes, Mw and focal mechanisms solutions are obtained on historical instr...

Intra-Carpathian Region of Romania experienced strong earthquakes as it is mentioned in the national and international databases, e.g. November 26, 1829 (Ms = 6.4), October 10, 1834 (Ms = 6.3), January 26, 1916 (Ms = 6.4), July 12, 1991 (Mw = 5.7). The paper focuses on calibration and validation of MEEP method (Macroseismic Estimation of Earthquake...

The Vrancea seismic nest, located at the South-Eastern Carpathians Arc bend, in Romania, is a well-confined cluster of seismicity at intermediate depth (60 – 180 km). During the last 100 years four major shocks were recorded in the lithosphere body descending almost vertically beneath the Vrancea region: 10 November 1940 (Mw 7.7, depth 150 km), 4 M...

The Vrancea seismogenic area, located at the South-Eastern Carpathians in Romania, is generating extreme destructive subcrustal earthquakes in Europe. The largest events generated in the last ten years in the Vrancea subcrustal domain occurred on May 14, 2005 (01:53, 45.64°N, 26.53°E, h=149 km, Mw = 5.5), April 25, 2009 (17:18, 45.68°N, 26.62°E, h=...

The seismic activity in the Eastern Carpathians area is poorly recorded (a few hundreds of small-to-moderate earthquakes in the Romanian catalogue over the last century). The installation in 2002 of the high-performance Bucovina (BURAR) array in the Eastern Carpathians area contributed to a significant growth of the capacity to monitor local seismi...

In this study we have used the most reliable and homogeneous seismic datasets at the European scale, covering historical and modern instrumental seismicity until present days for the Eastern part of Romania and the Black Sea Area for computing the statistical parameters of seimogenic sources and assessing the probabilistic hazard in the South Easte...

The Vrancea seismic nest is a distinctive case of unusually clustered seismicity at intermediate depths. The source scaling properties are essential elements to understand and model the tectonic processes responsible for generating earthquakes in such a confined lithospheric volume. The purpose of the present paper is to investigate the scaling law...

The crustal seismicity in Romania is concentrated in front of the Carpathians Arc bend (Vrancea region) and at the contact between the extra-Carpathian platform regions and Carpathians orogen. The region investigated in this paper is characterizing the contact of the western side of the South Carpathians with the Tisza-Dacia region. In this area, t...

The main goal of this paper is rating the dams from the Western part of Romania into seismic risk classes. Dam owners and regulators must ensure that dams are safely operated and present no risk to the public in case of an earthquake. While most dams close to Vrancea seismic region have been evaluated and analyzed for seismic loads, dams located in...

The paper brings together, in the same frame, the solar activity, the seismicity and the geomagnetic field behavior. Using statistical approaches, we try to find a degree of correlation between the three phenomena. On one part, the solar activity influences the geomagnetic field, giving rise to two types of variations: regular and irregular variati...

Large and destructive intermediate-depth earthquakes in Vrancea have been generated about every century during the last millennium. Possible earthquake precursors, such as bio-location data obtained across crustal faults, and three component magnetic continuous recordings, have been used in the last decade in and around the Vrancea region. After-th...

Geomagnetic variations associated with earthquakes are widely accepted and several anomalous geomagnetic observations have been interpreted as a result of changing rock magnetic properties under varying tectonic stress (piezomagnetic effect). During the last 15 years of geomagnetic investigations conducted in Vrancea seismogenic zone, period coveri...

Study events belong to three seismogenic zones in the South Carpathians area: Ramnicu Sarat - 2 sequences on November 29, 2007 (main shock, 45.62oN, 27.22oE, h=19 km, M = 3.9) and December 6, 2009 (main shock, 45.39oN, 26.98oE, h=25 km, M = 4.2); Vrincioaia - one sequence on September 6, 2008 in (main shock, 45.80oN, 26.51oE, h=13 km, M = 4.4); Fag...

The paper presents the Romanian VLF/LF monitoring system consisting in a radio receiver - made by Elettronika S.R.L. (Italy) and provided by the Bari University - and the infrastructure that is necessary to record and transmit the collected data. This system is a part of the international initiative INFREP. Through this initiative, originated in It...

The main goal of this paper is rating the dams from the South-Western part of Romania (Danube, Olt, Jiu and Lotru rivers) into seismic risk classes. Dam owners and regulators must ensure that dams are safely operated and present no risk to the public in case of an earthquake. While most old or new dams in recognized seismic regions have been evalua...

The paper presents the Romanian VLF / LF monitoring system consisting in a radio receiver -made by Elettronika S.R.L. (Italy) and provided by the Bari University- and the infrastructure that is necessary to record and transmit the collected data. This system is a part of the international initiative INFREP. Through this initiative, originated in It...

p>The study presents a statistical cross-correlation between geomagnetic anomalies, earthquake occurrence and solar magnetic storms. The working data are from: (i) geomagnetic field records from Muntele Rosu (MLR) Observatory, and from Surlari (SUA) and/or Tihany (THY) INTERMAGNET Observatories; (ii) seismic data for the Vrancea source zone; and (i...

The paper is based on geomagnetic records made at Muntele Rosu Observatory (Romania), during the time interval from 1998 to date. The working data are represented by the geomagnetic field as recorded at Muntele Rosu Observatory and manual corrected emphasizing the missing data and by the seismic data, taken from the seismic bulletins of the Nationa...

The paper tries an association between an unexplained, slow evolving and significant amplitude geomagnetic anomaly and the Vrancea (Romania) October 2004 intermediate-depth earthquake of moderate-to-high magnitude (Mw=6.0) followed by few weaker earthquakes (Mw<3). The fact that previous studies of Vrancea seismogenic zone indicate that observable...

The main goal of this paper is the probabilistic assessment of the seismic hazard in the Moesian Platform due to intemediate-depth and crustal earthquakes and the rating of all dams from the zone into seismic risk classes. The second goal is to realise a scenario of loss estimates in the case of one of the largest dams from the Moesian Platform, th...

(Received September 5, 2006) Abstract. A small-aperture seismic array (BURAR) was installed in 2002 in the northern part

Attenuation specific from Vrancea intermediate-depth focus toward SE is revised at length in order to re-evaluate the seismic hazard at the nuclear power plant (NPP) Cernavoda. To this aim, we took into consideration all the strong motion data available for the region and test a large range of relationship types. Since the instrumental data are lim...

The systematic analysis of seismograms recorded on the Romanian territory using Vrancea intermediate-depth earthquakes shows a strong asymmetric pattern relative to the epicentral area: on one side, in the Transylvanian Basin and the Eastern Carpathians (approximately along the inner volcanic chain), the amplitudes are reduced by a factor of 20 on...

The seismic hazard assessment in dense-populated areas and the strategic objectives design are based on the study of seismicity of the seismogenic sources (which can have an effect at the site above a specified minimum level that is considered risky) and the attenuation between focus and site. The purpose of this paper is to provide a complete set...

The paper is adverted to a complex activity of research concerning the settlement of the seismic risk class in which each big dam, located in the North Eastern Part of Romania, is framed, to catalogue and pursuit their behavior in time by the meaning of ultramodern statistical and structural investigation of these buildings and of their sites, as w...

For the present study we selected 126 earthquakes of moderate magnitudes (3.2 ≤ M D ≤ 6.2) occurred in the time interval 1997–2005 in the Vrancea seismic region at intermediate depths (62 ≤ h ≤ 166 km). Two relative deconvolution techniques (spectral ratios and empirical Green's function) are applied to retrieve the source parameters. To this purpo...

ABSTARCT The main goal of this paper is rating all dams from Transylvania and the central part of Romania into seismic risk classes. Risk classes can be used to establish the necessity of detailed assessment of seismic safety of the dams and to establish the priorities of these evaluations. Methodology that is used in this paper offers an easy way...