Towards a Fully Open Seismometer Network: Expanding Free and Open-Source Seismic Monitoring Tools through Modular Hardware-Software Integration

Seismic networks play a crucial role in monitoring earthquakes, understanding Earth's structure, mitigating seismic hazards and enabling rapid response over potentially destructive events. However, the high cost of professional-grade instrumentation has traditionally limited network density, especially in sensitive low-income regions, and the opacity surrounding proprietary solutions has hindered innovation in this field. Furthermore, maintenance of each different-design seismometer in the network is often a restrictive task, requiring costly in-situ visits for software updates or calibration.To address these challenges, we present the Open Seismometer Network, a robust and low-cost solution that builds upon traditional open-source seismic monitoring tools. Our approach leverages the latest advances in wireless microcontrollers and open-source management solutions, combining them with the novel Open Seismometer design, to effectively deploy new instruments that are significantly more sensitive and flexible than commercial alternatives. The modular approach aims to provide the missing parts that integrate hardware and software to facilitate network deployment and long-term instrument maintenance.The proposed seismic network stack is built upon fully Free and Open-Source (FOSS) solutions: ESPHome is the efficient firmware that runs low-level acquisition in the Open Seismometer design; WireGuard provides a VPN to securely connect each node; and industry-standard RingServer and SeisComP effectively orchestrate data distribution and processing. A further layer leverages Home Assistant to enable effective remote updates and management, adding the capability to visualize and store contextual sensor modalities to better monitor deployment sites. This creates a streamlined seismic network solution that allows for fully remote management, reconfiguration and updating of the nodes.A key innovation is our Open Seismometer design, which incorporates advanced period extension techniques to achieve a level of sensitivity comparable to broadband instruments. These techniques enhance the response of standard short-period geophones, effectively extending their capabilities into the lower frequency domain and enabling the detection of local, regional, and teleseismic events.The Open Seismometer Network brings together traditional seismic software solutions, open-source home sensing infrastructures, and a high-sensitivity low-cost seismometer design to enable highly effective deployments. We believe it has the potential to significantly enhance the density of seismic monitoring in underserved regions, including many low-income countries, and provide valuable data for seismic hazard assessment, early warning systems, and fundamental research due to its open nature. Additionally, the network can complement existing seismic infrastructure, filling spatial gaps and providing supplementary data to achieve a higher level of global seismic monitoring detail.By making all aspects of seismic networks accessible and modifiable under Free and Open-Source licenses, we aim to foster a global community of collaboration. Researchers and developers are invited to improve the hardware design, refine the software, and develop new applications for the data. This collaborative model accelerates innovation and ensures that new seismic networks remain adaptable to the evolving needs of the seismological community.