Research project SR/00/305 (Research action SR)
CONTEXT AND OBJECTIVES
The East African rift valley is a major tectonic feature that shapes Central Africa and defines linear-shaped lowlands between highland ranges due to the action of geologic faults associated to earthquakes and volcanism. The region of interest, covering the Virunga Volcanic Province (VVP) in eastern DRC, western Rwanda and Burundi, and southwest Uganda, is affected by the early stage of continental rifting, a phenomenon still not fully understood and subject to scientific debate. A rare combination of several types of geohazards threatens that region, which is one of the most densely populated of Africa. These geohazards can globally be classified as seismic, volcanic and landslide hazards. Active volcanoes (Nyiragongo and Nyamulagira) are the source of spectacular events that occasionally provoke catastrophic disasters as in 1977 and 2002 when the Nyiragongo eruptions caused major destructions in the city of Goma. The region is also characterized by a strong seismicity as testified by historic strong (mag >7) earthquakes. In 2008 a magnitude 6.2 earthquake hit the Kivu area, causing important damages and casualties in DRC and Rwanda. Landslides include a wide range of ground movements, such as rockfalls, deep failure of slopes and shallow debris flows. Landslides are possibly the most important geohazard in terms of recurring impact on the populations, causing fatalities every year and resulting in structural and functional damage to infrastructure and private properties, as well as serious disruptions of the organization of societies.
RESIST aims at stepping towards the characterization of the mechanisms leading to volcanic eruptions and the detection of their precursory signals as well as landslides triggering, and improving the comprehension of underlying processes.
Main objective for volcanoes
To gain scientific insights into the mechanisms that lead to an eruption and what types of measurable phenomena and signals can be robustly considered as precursory information for eruptive activity. Improved knowledge of underlying processes will also contribute to the better comprehension of continental rifting, which is found to be at an early stage in the Virunga Volcanic Province.
Main objective for landslides
To capture the temporal pattern of the landslide occurrences and to understand the importance of the climatic control on the mechanisms driving these processes. Specific attention is given to the identification of the rainfall thresholds for different landslide types and the threshold regional variability according to the processes and the environmental conditions.
METHODOLOGY
RESIST is based on 5 different research tasks; some are transversal i.e. shared by the volcanoes and landslides themes, others are not:
Ground deformations (transversal)
- Ground deformation measurements and monitoring are achieved through both ground based and spaceborne systems.
- Ground based methods: geodetic GPS network.
- Spaceborne methods: advanced SAR interferometry (DInSAR, SBInSAR, SBAS, MSBAS) and VHSR optical data analysis.
- These techniques will be complemented by field observations.
Seismic and infrasound characterization
- RESIST is deploying an important seismic network through the region that will be complemented by infrasound measurement stations.
SO2 Gas flux
- Measurements of SO2 emissions by volcanoes in the Kivu rift zone.
- Creation of a unique long-term consolidated dataset of SO2 flux for the volcanoes in Congo. This is achieved by a combination of satellite instruments (from ongoing and future missions with improved signal-to-noise and spatial resolution).
- UV camera deployed on the ground.
Landslide processes and spatiotemporal characterization
- Inventory of the landslides and the prediction of their spatial occurrence (susceptibility).
- Study of the environmental factors explaining their occurrence.
- Identification of rainfall thresholds for the different landslide types.
- Usage of TRMM (Tropical Rainfall Measuring Mission) data, and once available, the GPM (Global Precipitation Measurement) mission data.
Process modelling (transversal)
- Assessment of the physical processes and mechanisms underlying pre-eruptive activity of the volcanoes in the VVP and landslide mechanisms.
- The proper characterization of the mechanisms related to dyke intrusions and/or volcanic eruptions in the VVP will contribute to improve our understanding of the not well known continental rifting process at its early stage. The proper identification and characterization of the pre-eruptive processes can eventually contribute to the aim of eruption forecasting.
- Assessment of the landslide mechanisms in order to anticipate their future occurrence according to rainfall distribution. The different processes will be analysed according to their spatiotemporal occurrence.
EXPECTED SCIENTIFIC RESULTS
RESIST will contribute to the understanding of the source mechanisms driving volcanic eruptions and landslides in the region by 1) filling the gap of knowledge on ground-based level through the installation of the densest seismic and infrasound network ever deployed in the region and first UV camera for SO2 monitoring and 2) combining this information with innovative EO approaches, using both archived data and new spaceborne acquisition possibilities in radar, optic, gas and precipitation monitoring. RESIST will exploit ground-based instrument networks, field surveys and modern EO techniques (Split Band and MSBAS InSAR time-series, SO2 flux, TRMM) to study and characterize the changes in the monitored parameters that could/should be considered as significant in terms of volcanic and landslide processes.
EXPECTED PRODUCTS AND SERVICES
Expected RESIST deliverables are:
For volcanic and pre-eruptive activity characterization and modelling:
- Classification of seismic and volcano-acoustic signals in a range of event categories based on signal decomposition results
- Spatiotemporal variations of seismic and volcano-acoustic activity
- Integration with other work packages and data sources involved in the project. Analysis of variations of seismicity and volcano-acoustic patterns and relation to other potential precursory signals (gas flux, ground deformation patterns obtained from GPS and DInSAR and InSAR time series)
- Combined source modeling of ground deformation, seismicity and gas flux data.
For landslide characterization:
- Understanding of the LS mechanisms for the studied region: for deep-seated failures, shallow movements and ground displacements within pre-existing landslides.
- Rainfall threshold regional variability according to the processes and the environmental conditions; influence of the regional settings such as climatic and topographic gradients
- Precursors for LS initiation
- Identification of potential earthquake-triggered LS
- Contribution to knowledge development on LS processes in Africa and in the humid tropics in general.
- New models and data for LS prediction applicable to other landslide prone areas.
- Hazard “nowcast” maps at the regional scale for the different LS types and regional models for LS hazard assessment.
- The project will create a methodology through which similar assessments can be made elsewhere.
