Project equipment

One of the main goals of the CROSSNET project is the installation of 95 new seismological stations throughout Croatia for improved monitoring of the seismicity of our homeland (and neighbouring countries, because earthquakes know no borders). The stations will be equipped with the highest quality measuring instruments, i.e seismometers, accelerometers, accelerographs, and data digitizers. Their task will be to continuously record and store data on the ground shaking and transfer it to the central system in the Operational Center of the Seismological Survey of the Republic of Croatia. The geological diversity of our homeland, which makes it so beautiful and special, from alluvial deposits to karst, makes the job of setting up seismological stations more challenging. Different types of foundations require different approaches for setting up seismological stations. Therefore, it is not possible to choose the same deployment methods and deploy the same types of devices in all locations. One type of device is needed for installation in boreholes to maximally reduce surface noise in the terrains of northern Croatia, Slavonia, and Baranja, another type of device will be installed on the built objects of seismological stations in the mountainous and coastal areas of our country, and a special type of device that can be placed at the bottom of our Adriatic Sea. In the rest of the text, you can read more details about the selected devices and instruments that will be installed as part of the CROSSNET project. The instruments that have gone through the public procurement procedure are shown here, while for open public procurement procedures, the announcement will follow only after the successful completion of the same. 


The Etna2 consists of a chassis with three orthogonal mounted EpiSensor force balance accelerometers. The signals from the accelerometers are directed to the printed circuit board and digitized by individual analogue-to-digital converters (ADC). They are then filtered and passed to the system’s main processor, which consists of a highly integrated, low-power processor running Linux and Kinemetrics Rockhound software. The user’s interaction with the system is through the software for setting up, controlling, and operating the system and through the front panel connector for physically connecting the power supply of communication devices and GNSS (GPS) signals. 

The accelerograph is independent, so in case of failure of one device, the other device at the station works (it will always be paired with the seismometer at the station). It is used to record strong nearby earthquakes when a seismometer designed to record weak ground motion (to record even the weakest ground tremors near the station, as well as distant earthquakes around the world) stops being able to record ground motion. As part of the project, 100 pieces of this device were purchased. 



The STS-2.5 is a high-performance seismometer designed for the best seismological stations. STS-2.5 is the successor of the legendary STS-2 model, with 10 times increased insensitivity to barometric pressure. Like all modern sensors, it gives an output signal proportional to the speed of ground movement, but in a wide range and with a very low level of instrumental noise. It consists of 3 identical obliquely oriented mechanical sensor components. This three-axis design ensures that the horizontal and vertical components are aligned as well as possible. The instrument will be placed in the facility at the seismological station. 

This is the Rolls-Royce of seismometers. It is extremely sensitive and capable of recording even the weakest cherry soils. To be of maximum use, it requires special installation conditions (specially selected “quiet” locations to minimize the level of ambient noise). As part of the project, 20 pieces of this device were purchased. 



The Omnisensor is a global reference force balance accelerometer (Model Episensor) and seismometer (Model MBB-2), together in one package ready for direct deployment as a conventional sensor or downhole. It covers more than 205 dB of dynamic range in a single waterproof housing, with a single marine connector and cable for installation in poles and boreholes. Omnisensor records earthquakes from the weakest to the strongest magnitudes and intensities. The sensors in this device are coordinated with each other and do not need to be additionally centred and mass locked. Installation of this device is also possible at a depth of 600 m in a dry well. A Y-ended cable connects to the Quanterra Q8 Qantix digitizer. This compact device will be installed in seismological stations throughout the Republic of Croatia. As part of the project, 50 pieces of this high-quality device were purchased. 


Miniature broadband seismometer MBB-2 

The MBB-2 is a three-axis broadband seismometer that provides a bandwidth sensitive to the speed of ground motion from 120 seconds to approximately 150 Hz. The sensor is housed in a stainless steel housing to enable reliable operation in shallow boreholes. Easy deployment is enabled in environments typically considered “non-ideal” for broadband sensors. The sensor is designed to be powered directly by the Quanterra Q8 digitizer. 

This sensor can be installed in boreholes as well as in underground and above-ground installations. The device is waterproof, so it doesn’t even get in the way of water ingress into the station itself (if they don’t knock it over, of course!). As part of the project, this device was purchased in a total number of 45 pieces, of which 20 pieces will be in a special version for field research, and 25 pieces will be installed in seismological stations on the territory of the Republic of Croatia. 



Q8 is a digitizer of data obtained from accelerometers and seismometers and represents the world’s most advanced system for collecting data from seismological sensors. This device contains a “FrontEnd” module that manages all real-time tasks, including digitization, timestamping, sensor control, and health monitoring of connected instruments, their power supply, and the like. The memory buffer provides flexibility in transferring time-stamped digitized data to a “BackEnd” module that captures data and manages external interfaces. 

The “FrontEnd” runs the OS in real time and is designed to run at the lowest possible power consumption of around 250 mW. The device enables recording with continuous power and real-time telemetry with low latency, power cycling, and ultra-low power in autonomous deployments, and on-demand with power cycling. The very low latency makes it suitable for early warning systems as well. 

This device connects to all seismometers and accelerometers. It represents the very top of the offer in the world of seismological equipment and enables the expansion of measurement parameters by connecting other sensors (environmental conditions, e.g. temperature, relative humidity, air pressure, …). As part of the project, a total of 140 pieces of this digitizer were acquired, of which 20 are in a special version for field research with the MBB-2 seismometer. 


The network of newly installed seismological stations will enable better and more detailed monitoring of seismic activity, a reduction in the level of instrumental noise in most locations compared to the existing one, and a reduction in the minimum magnitude that can be recorded on the entire territory of the Republic of Croatia. A new and modern network accompanied by a modern system of data collection and processing will enable fast communication with the Ministry of Internal Affairs – Directorate of Civil Protection of the Republic of Croatia and citizens, as well as the creation of a more extensive catalogue of earthquakes in the Republic of Croatia as well as earthquake hazard maps of Croatia. The data collected by measurements of the improved seismological network of the Republic of Croatia will help in the mapping of active faults and will create conditions for the further advancement of the seismological profession in the Republic of Croatia. 

New knowledge of all of the above will enable the further development of anti-earthquake construction in the Republic of Croatia, the creation of high-quality spatial plans, and the development of seismology and related professions. 

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