An insight into ALTRUIST: how to use GNSS Variometry for Natural Hazards Detecting and Monitoring
Authors: Ravanelli Michela , Astafyeva Elvira , Sakic Pierre , Baucry Raphael , Crespi Mattia 
Published: March 2024

This work aims to present and to disseminate the ALTRUIST (totAL variomeTry foR tsUnamI hazard eStimaTion) project.ALTRUIST is one of the eight projects selected worldwide for the Joint Call by the AXA Research Fund and the Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) on Coastal Livelihood within the framework of the United Nations Ocean Decade [1].ALTRUIST&#8217;s main goal is to improve the reliability and accuracy of real-time tsunami warning systems leveraging the recent findings of Global Navigation Satellite System (GNSS) remote sensing. GNSS remote sensing employs the GNSS signal to infer information about atmosphere, oceans and ground.In detail, ALTRUIST leverages the Total Variometric Approach (TVA) methodology [2]. GNSS Variometry is based on single time differences of suitable linear combinations of GNSS carrier-phase, allowing a GNSS receiver to provide valuable real-time information in a standalone operative mode. TVA jointly employs VADASE (Variometric Approach for Displacement Analysis Stand-alone Engine) and VARION (Variometric Approach for Real-Time Ionosphere Observation) algorithms.TVA allows for the simultaneous and real-time estimation of ground shaking, co-seismic displacements and ionospheric Total Electron Content (TEC) disturbances, using the same real-time GNSS data stream. The joint use of the information from the ground and ionosphere can be really beneficial.&#160; Coseismic displacements can be used to retrieve important parameters about the seismic source and the seafloor displacement. The ionospheric observation, can, in turn, give information about the seismic source and, to some extents, about the ground motion.These data are, hence, crucial in natural hazards management and can support traditional instruments to improve the quick estimation of the tsunami hazard.ALTRUIST is currently being tested within the GNSS network of the Observatoire Volcanologique et Sismologique de Guadeloupe of Institut de Physique du Globe de Paris (IPGP), in the Caribbeans.In detail, ALTRUIST is built to be a scalable and modular architecture that provides the first joint ground and ionosphere real-time solutions. In detail, it provides the real-time visualization on a dashboard and allows access to information and historical solutions through API.These attributes embody a key point of the ALTRUIST project: sharing historical solutions foster discussion within the scientific community, whereas the interactive dashboard empowers local communities to access additional information on natural hazards.Finally, ALTRUIST framework is versatile and can be easily applied to the monitoring of any kind of natural hazards events such as volcanic eruptions and explosions impacting ground and ionosphere geosphere.This is the first feasibility demonstration of the ALTRUIST real-time capabilities.References[1] https://axa-research.org/funded-projects/climate-environment/mitigating-tsunamis-threats-and-destructive-impacts-through-enhanced-navigation-satellite-system[2] Ravanelli, Michela, et al. "GNSS total variometric approach: first demonstration of a tool for real-time tsunami genesis estimation." Scientific Reports 11.1 (2021): 3114