The European Integrated Data Archive (EIDA) is the infrastructure that provides access to the seismic-waveform archives collected by European agencies. This distributed system is managed by Observatories and Research Facilities for European Seismology. EIDA provides seamless access to seismic data from 12 data archives across Europe by means of standard services, exposing data on behalf of hundreds of network operators and research organizations. More than 12,000 stations from permanent and temporary networks equipped with seismometers, accelerometers, pressure sensors, and other sensors are accessible through the EIDA federated services. A growing user base currently counting around 3000 unique users per year has been requesting data and using EIDA services. The EIDA system is designed to scale up to support additional new services, data types, and nodes. Data holdings, services, and user numbers have grown substantially since the establishment of EIDA in 2013. EIDA is currently active in developing suitable data management approaches for new emerging technologies (e.g., distributed acoustic sensing) and challenges related to big datasets. This article reviews the evolution of EIDA, the current data holdings, and service portfolio, and gives an outlook on the current developments and the future envisaged challenges.

The Romanian Seismic Network consisting of 8 short-period stations (S13), 60 Altus — K2 and Q330 seismic stations, is primarily designed to survey the Vrancea seismic region (strong and moderate Vrancea earthquakes). Since July 2002, a new seismic monitoring system, Bucovina Seismic Array (BURAR) has been operating. BURAR consists of 12 seismic stations distributed on a 5 km × 5 km area. 9 stations are equipped with short-period (SP) vertical sensors (GS-21 res) and one station is equipped with broad-band (BB) three component sensor (KS 54000). Broad-band sensors GMG40T (1000V/cm/s) were installed at 5 of the short-period stations, at the beginning of 2008. Recently, NIEP has developed its real-time digital seismic network. This network consists of 21 broad band stations and one seismic array. In the next year NIEP will install additional broad band stations in the central part of Romanian territory and other 40 strong motions stations in Bucharest.At the National Data Centre (NDC) runs BRTT’s Antelope™ 4.9 data acquisition and processing software on two HP workstations for real-time and post processing. The Antelope Real-Time System is also providing automatic event detection, arrival picking, event location and magnitude calculation.The Romanian Seismic Network is already linked with IRIS and ORFEUS organizations and other European countries via Internet and is contributing in near real time with waveform data from 5 broadband stations.The seismotectonic characteristics of the Vrancea region offer the opportunity to create and develop a rapid seismic warning system. This system allows warning in an approximately 25 seconds time window for Bucharest.

The Vrancea seismic region represents a unique case of well-defined and intense intermediate-depth earthquake activity as a consequence of specific geodynamic processes at the continental contact between East-European, Moesian and Intra-Alpine plates. Apart the subcrustal earthquakes generated in the Vrancea slab, the analysis of seismicity puts into evidence two other clusters of subcrustal earthquakes ( > 50 km) toward the back-arc side of the SE Carpathians bend, one to the west (Sinaia), the other to the north-west (Braşov Depression) relative to the Vrancea seismic source. The hypocenters lay down between 50 to 105 km in Sinaia and between 50 and 136 km in Brasov Depression. The rate of seismic energy release is much lower ( ≤ 3.7 in Sinaia and ≤ 3.1 in Braşov Depression) than for Vrancea activity. The seismicity pattern in the SE Carpathians back-arc region upper mantle correlates well with the high-velocity structures depicted by seismic tomography investigations suggesting possible remnant deep lithospheric roots apart from the narrow well-defined slab generating Vrancea major earthquakes. The results outline significant lateral heterogeneities in the mantle and provide new data for incorporating seismological, geotectonic and volcanological data in a unified modeling of the complex processes taking place in the study region.

This study presents a seismic tomography analysis of the Târgu Jiu region in southwestern Romania, an area that experienced an unusual earthquake sequence in 2023. Using P- and S-wave arrival times local earthquakes, we applied the LOTOS algorithm to produce high-resolution 3D crustal seismic velocities models. High Vp and Vs values in the northern and northeastern areas suggest the presence of dense, rigid geological formations, likely associated with consolidated magmatic or metamorphic units. In contrast, the central region exhibits low Vs values, coinciding with an active seismic zone and intersecting major fault structures. This suggests the presence of highly fractured and weakly consolidated rocks, potentially saturated with fluids. The Vp/Vs ratio in the central region reached values of ≥1.8–1.9, indicating fluid-filled fractures that may influence fault dynamics and earthquake occurrence. In the southern region, velocity anomalies suggest weakly consolidated sedimentary units with a high degree of fracturing. These findings contribute to a better understanding of the geodynamic behavior of the Târgu Jiu area and its seismic hazard potential.