Research project SR/00/113 (Research action SR)
Context and objectives
The region of Goma lies under the direct threat of volcanic hazards with the Nyiragongo and Niamulagira volcanoes that are amongst the most active in Africa. The recent eruption that occurred in January 2002 produced a spectacular lava flows that destroyed part of the city. Although the amount of casualties was limited, hundred thousands of refugees were pushed out of the area which added some more pressure in a highly politically sensitive area at the border with neighbouring Rwanda. The mitigation of the direct volcanic risks is depending on the availability of an efficient volcanic activity monitoring system.
The GORISK project is oriented towards the improvement and implementation of techniques dedicated to the study and monitoring of the Nyiragongo. An important GORISK segment concerns the ground deformations monitoring that are amongst the most important parameters to monitor; it is addressed by both space borne and ground based observations. Volcanic plume fallouts are also a big concern as it causes damage to vegetation and cultivations. GORISK takes benefit from the ongoing EU project NOVAC and US-NSF project VISOR that are focused on ground based and space borne respectively monitoring of the plume. These observations are combined to additional geochemical ground measurements of water quality. In situ measurements can provide useful and sometime crucial clues. Carbon dioxide (CO2), methane (CH4), and radon (Rn), together with other gases, can migrate from deep reservoirs and exhale through micro seepages to the surrounding areas therefore producing significant enrichments in the atmosphere. CO2 for example can locally concentrate and become a major concern for the population. GORISK also involves the study of the possible impact on health of the volcanic activity. A Belgian NGO, the CEMUBAC is providing an epidemiological study based on data acquired in health centres for the last ~10 years, and on plume dispersion maps created from the VISOR and NOVAC projects.
Methodology
• Ground-based deformation monitoring systems involve a network of 5 telemetred tiltmeters deployed on the southern flank of the volcano, in areas selected based on preliminary space borne InSAR measurements (through the SAMAAV – ESA Cat-1 3224 project). Continuous InSAR measurements are performed using ENVISAT ASAR data acquired on a regular basis.
• The project also benefits from a GPS network currently under construction installed by the Luxembourg MNHN GORISK partner.
• Geochemical measurements are made for meteoric and spring waters. These systematic measurements are intending to study the eventual fluctuations of the geochemical parameters and the modelling of the aqueous and hydrothermal systems in relation to the volcano.
• Gas measurements are made in the air, in water (springs), and in the subsurface. The simultaneous recording of various gases (e.g. CO2 , and CH4 ) together with continuous measurements of radon will be performed in the air at the surface and (deleted) in the soil. Radon is a very valuable tracer in connection with its carrier gases, it is easy to measure continuously produces very sensible responses. The analyses of micro seepage of these gases from natural gas reservoirs will be performed by exhalation measurements.
• Health data are studied by using a probabilistic approach for the plume dispersion. Health data are gathered in centres located in plume prone and free areas.
• GORISK data are integrated into a common GIS platform as a tool to be exploited by the local users (GVO, CEMUBAC, and UN-RMU)
• The sustainability of the methods is ensured by training of the GVO staff members.
Results expected
GORISK will strengthen the capacity of GVO to observe ground deformations. Previous works, especially the one developed under SAMAAV, has evidenced the efficiency of InSAR in detecting regional scale deformations related to the Nyiragongo eruption in 2002, Nyamulagira in 2002 and 2004. More recently, in November 2006, a large scale deformation occurred with the eruption of Nyamulagira. GORISK is expected to demonstrate that routine InSAR monitoring is providing valuable data for the study of these two active volcanoes. The telemetred ground based measurements will provide in near real time deformation information which will be combined to the other data (seismic network, geochemistry, visual observations… ). That systematic measurement will help in the understanding of the mechanisms which in turn will contribute to the mitigation of the associated risks.
New field of investigation are developed for the monitoring of subsurface gas emanation; that will provide new information datasets. In particular the monitoring of the radon may provide valuable information to be interpreted with the other data.
The monitoring of the environmental impact is also of a major importance as the area is under high demographic pressure and needs a real management. Much is expected from the epidemiological investigation which should be facilitated by the large available database provided by the health centres and the monitoring of the plume direction and SO2 content.
