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The purpose of this work consists in analyses of declustering catalogue and seismic sequence recorded in Vrancea crustal area . The moderate-size earthquake with local magnitude 5,7 which occurred on November 22, 2014 in Vrancea region, at 41 km depth, is the largest crustal event instrumentally recorded at the bending of the Eastern Carpathians. The crust seismicity in front of the Carpathian Arc spreads to the East, in a strip delimited by the Peceneaga-Camena fault, to the North and East, and to the South is lost to the Intramoesica fault. The crust seismicity does not exceed the magnitude of 5.6 (Mw) and it seems to have no relation to the seismic activity of the subduction lithosphere. Seismic activity is characterized by spatial and temporal clustering in the Râmnicu Sărat sub-zones through seismic sequences and swarms in the Vrâncioaia area. Using the first version of the software SEDA v.1 [1] we determined the Maximum Likelihood Estimation (MLE) ETAS model on an Vrancea area. The algorithm implemented in SEDAv1.0 is an innovative method based on Simulated Annealing. The Epidemic Type Aftershock Sequences (ETAS) model is the most popular stochastic model used to describe earthquake occurrence, to forecast earthquakes and to detect fluid/magma signals or induced seismicity. [ABSTRACT FROM AUTHOR]

The moderate-size earthquake with local magnitude 5,7 which occurred on November 22, 2014 in Vrancea region, at 41 km depth, is the largest crustal event instrumentally recorded at the bending of the Eastern Carpathians. Using the method developed by [2] termed the Hash method, (incorporated in Seisan software) we obtain the focal mechanisms for earthquakes that occurred in Vrancea region associated with the seismic sequence of November 22, 2014. We have examined the main shock and 29 aftershocks that occurred after 22 November 2014. P-wave arrivals and polarities are manually identified on the vertical component of each station. Polarities are marked as impulsive or emergent and the pick is given a quality rating (0-4). We then use the S/P amplitude ratios computed from three-component seismograms, to determine mechanisms-Hash [2]. We had also investigate the spatial variation in focal mechanism type (e.g. strike-slip, normal, or thrust) and inferred fault strike. Most of the mechanisms are normal faulting, with the nodal planes oriented SE - NW, in agreement with the tectonic characteristics of the zone. This crustal seismicity is related to the normal fault system associated to Peceneaga - Camena major fault, which separates the Focsani Basin, part of the Moesian Platform, from the North Dobrogea promontory. [ABSTRACT FROM AUTHOR]

A moderate-size earthquake with local magnitude 5.7 occurred on November 22, 2014, at 41 km depth, in Vrancea region. The event was followed by a burst of seismicity. The strongest aftershock (local magnitude 4.5) occurred on December 7, 2014, and a significant decrease of the activity was observed only after January 3, 2015. The occurrence of a 4.2 local magnitude earthquake on January 12, 2015 led to a new increase of the seismic activity, which lasted until around February 1, 2015. During the period November 22, 2014 - February 1, 2015, 271 events with local magnitude greater than 0.1 were localized in the mainshock epicentral area. This crustal seismicity is related to the normal fault system associated to Peceneaga - Camena major fault, which separates the Focsani Basin, part of the Moesian Platform, from the North Dobrogea promontory. We determine the focal mechanisms of the largest shocks of the sequence - 10 earthquakes with local magnitudes above 2.5, and one 2.5 magnitude event - for which at least 14 reliable P-wave polarity data have been available. The mechanism of the mainshock is a normal faulting with a dominant dip-slip component; both nodal planes are oriented SE-NW. The fault plane solutions of the strongest aftershocks (magnitudes above 4) are quite similar. A certain variability is observed among the weaker events, nevertheless, the normal faulting characterizes most the determined focal mechanisms. [ABSTRACT FROM AUTHOR]

The study area is located at the contact between the Apuseni Mountains (Western Carpathians) with Pannonian Depression-to the west and with Transylvanian Depression - to the east. The eastern limit is marked by the Eastern Carpathians. The current tectonic activity is manifested by an uplift of the Carpathian Orogeny in relation to neighboring units, particularly the Pannonian Depression. The main seismological active areas are on the edge of the Pannonian Basin and in contact with the basement of Apuseni Mountains and Eastern Carpathians. Historical data suggests two potential earthquake magnitudes Mw >6, one of magnitude 6.2 (Mw) and one with magnitude 6 (Mw). Generally, the characteristics earthquakes of the area have magnitude Mw=5.6. We expect that the horizontal components of the movement (generated by the uplift of the Carpathians) to produce a compressive stress, as shown by focal mechanism solutions. [ABSTRACT FROM AUTHOR]

In the present paper, we highlighted the two active seismogenetic zones, one to the north-east of Campulung city, and the other one along Ialomita River (west from Sinaia). Schematically we can say that the Southern Carpathians, between the Dambovita and Olt Valley, are represented by the Supragetic Nappe, which has been over thrust on the Getic nappe during Middle Cretaceous. The Moesian Platform represents a Precambrian block involved in the Epihercynian European Platforms and is composed by three different segments, bounded by the Intramoesian and Calimanesti-Tg. Jiu crustal faults, the Dobrudjean, the Valachian and Danubian domains respectively. The Eastern Carpathians represent the central part of the Outer Carpathians belt and stretch from North to the junction with the Southern Carpathians along Intramoesian Fault. In the studied areal we covered all these units mentioned above and the main faults which mark the areal are Intramoesian Fault (IF) and Calimanesti-Tirgu Jiu fault, also there are a number of the medium to high reverse angle faults, thrust faults and strike slip to transpressional fault zones having a NW-SE direction. More of the earthquakes are located around six major seismogentic areas, such as: Campulung city, Sinaia city, Ialomita River, Targului Valley, Arges Valley and a W to E seismological line in Fagaras mountains. [ABSTRACT FROM AUTHOR]

The seismicity of Romania is significantly affected by earthquakes produced by the Vrancea seismic source with intermediate depth events (3 shocks/century with magnitude Mw greater than 7.0). The seismic activity on the Romanian territory consists on both shallow and intermediate depth earthquakes. The crustal seismicity is moderate and more scattered in comparison with the intermediate depth one. The recent upgrade of the seismic network in Romania with high dynamic range accelerometers (114 real time seismic stations equipped with episensors) allows recording of moderate to large magnitude earthquakes at very close epicentral distances (less than 10-20 Km). A network for monitoring the strong motion that can occur in a given area records data that provide an excellent opportunity to study how source, path and site influence the ground motion, specifically that in the near-source area. Such data are essential for updating seismic hazard maps and consequently building codes and earthquake-resistant design. A fast seismic data analysis is essential to provide rapid and useful information to Authorities that have to take decisions immediately after a strong earthquake occurrence. Modern accelerometers are the only instruments that can provide nearsource high-quality data during a strong earthquake. The purpose of this work consists mainly in the estimation of moment magnitude Mw using the strong motion network of NIEP. A stable and automatic method developed by [1], has been implemented in real time data acquisition and processing system (ANTELOPE) to estimate in real time the seismic moment, the moment magnitude and the corner frequency of events recorded by accelerometers, using [2] method applied to S waves. The main goal is the independent estimation of seismic moment and corner frequency for all events recorded by the strong motion network. [ABSTRACT FROM AUTHOR]

The systematic studies of the focal mechanism solutions furnish fundamental data about some of the main factors that control the seismic phenomenon, e.g. stress field peculiarities and the types of faulting, the geometry of the faults and provide critical information for global, regional and local tectonic studies, as well as for many types of seismological investigations. In the last few years were recorded some significant earthquakes in Vrancea subcrustal domain and in other seismic regions at crustal depths. The National Seismic Network was continuously updated in the last years and now the recordings of these events contributes to a complete data base and very important to seismology and seismic hazard assessment studies. The substantial increase of the seismic recordings and the azimuthal gap leads to a more precise knowledge about focal mechanism, the structure and source parameters. The seismicity of Romania is distributed in several epicentral zones: Vrancea, Fagaras- Campulung, Banat, Crisana, Maramures and Dobrogea. The main goal of this paper is to study seismicity evolution and the focal mechanism analysis of recent earthquakes occurred in Romania (in last five years) and their correlation with the average stress field. We have determined fault plane solutions and analyzed the seismic activity recorded on the Romania territory in connection with seismogenic zones. At the same time, our results are integrated and interpreted in connection with the stress field characteristics, deduced from the available fault plane solutions on different depth intervals. [ABSTRACT FROM AUTHOR]

In this paper we present the results obtained during the study of swarm of earthquake close to the Galati city. In the last period the National Seismic Network was continuously upgraded, which allows presently to easily detect earthquakes with very low magnitudes in every seismic region of Romania. The seismogenic region of the swarm is situated between two main crustal faults, oriented SE-NW: Sf. Gheorghe fault (located in North Dobrogea, in the Scythian Platform) to the North, and Peceneaga Camena fault (which separates North Dobrogea block from the Moesian Platform) to the South. The epicentral zone belongs to a complex tectonic area, in which a secondary fault system -- lying NE-SW, perpendicular to the dominant system -- is present too. The seismic swarm started on September 23, 2013, close to Galati city, in Izvoarele region (Romania), and lasted until November 12, 2013. 406 earthquakes were recorded during several phases of seismic activity. The strongest events -- a magnitude 3.9 earthquake, occurred on September 29, and two ML 3.8 shocks, occurred on October 3 and October 4, respectively, were accompanied by specific seismicity bursts. The spatial distribution of the epicenters, which are aligned in NE-SW direction, indicates that the seismic swarm was generated by the second fault system. The focal mechanisms show normal slip, with one of the nodal planes oriented roughly in NE-SW direction. The results are discussed and interpreted in relation with the regional seismotectonics, our study aiming to emphasize new elements and implications for seismic hazard evaluation in the Galati area. [ABSTRACT FROM AUTHOR]

Earthquakes from Fagaras seismic zone are originating in the Southern Carpathians area and their foci are located at East and West of the Olt Valley. The most important events of the studied are is the seimic sequence from October 1916 of 6.4 (Mw) observed maximum magnitude. The earthquakes alignments are situated at the contact between the main tectonic units: Getic and Supragetic nappes and Danubian domain and at the contact between these three main cretaceous units with Moesian Platform. Also there are earthquakes alignments along Topolog Valley, Luncavatu Valley, Cerna Valleys. The seismogenic zone Olt Valley is characterized by a dominant compressional stress regime. Mostly, fault plane solutions belong to reverse component faulting (pure reverse fault and reverse fault with a strike-slip component) with tension axis almost vertical and pressure axis quasi-horizontal characterizes most of the major events, only two solutions showing strike-slip faulting. [ABSTRACT FROM AUTHOR]

An earthquake early warning system (EEWS) is a system that provides rapid notifications before the destructive waves arrives in the target area that has to be warned. EEW systems are used in several countries already: Japan, United States- California, Taiwan, Italy, Turkey and China. Some of them are operational. Some of them are already operational (Japan, Romania, Turkey, Taiwan and California) and some are in testing phase. Most of the EEWS are "regional" (based on a dense network of sensors installed in the earthquake source region) and send the earthquake alert notification to target area located far away from the source. Romanian territory is affected by strong intermediate depth Vrancea events (3 shocks/century with magnitude greater than 7). The recent upgrade of the Romanian Seismic Network (RONET) with strong motion sensors allows recording of strong earthquakes even at small epicentral distance (10-20 km). The Vrancea early warning system sends notifications for events with magnitude larger than 4.5 to 16 early warning receivers at the emergency response units located in Bulgaria and Romania: 7 in Romania at Constanta, Calara?i, Giurgiu, Teleorman, Dolj, Olt and Mehedinti and 9 receivers in Bulgaria, at: Montana, Vidin, Veliko Tarnovo, Ruse, Belene, Dobrich, Kozlodui, Kozlodui 2 and Silistra. Also the earthquake notification is sent to several governmental agencies in Romania. In this paper we present the earthquake early warning system designed for Vrancea area and we analyze its performance. [ABSTRACT FROM AUTHOR]

An earthquake early warning system allows to detect an ongoing earthquake in real time and it is able to issue fast notification alerts depending on the potential to cause damage in a target site before the destructive seismic waves arrives. All these earthquake early warning systems (EEWS) are using rapid telemetric analysis of real-time data from seismic sensors deployed in the epicentral area. The National Institute for Earth Physics (NIEP) operates a real-time seismic network designed to monitor the seismic activity on the Romania territory, dominated by the Vrancea intermediate-depth (60-200 km) earthquakes. The NIEP real-time network currently consists of 102 stations and two seismic arrays equipped with different high quality digitizers (Kinemetrics K2, Quanterra Q330, Quanterra Q330HR, PS6-26, Basalt), broadband and short period seismometers (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T,STS2, SH- 1, S13, Mark l4c, Ranger, gs21, Mark l22) and acceleration sensors (EpisensorKinemetrics). The seismicity of Romania is significantly affected by earthquakes produced by the Vrancea seismic source with intermediate depth events (3 shocks/century with magnitude Mw greater than 7.0). In this paper we present the performance of the seismic network in rapidly locate intermediate depth events occurring in the Vrancea area. Since rapid location of earthquakes is the first step in issuing early warning notifications, by reducing the time of the first valid location will lead to an increase the lead-time interval. Rapid location of events will allow a future upgrade of EEWS to cover the entire Romanian territory. [ABSTRACT FROM AUTHOR]