World Organization of Volcanic Observatories
Observatoire Volcanologique du Karthala
Centre National de Documentation et de la Recherche Scientifique des Comores
République Fédérale Islamique des Comores
|Telefax :||(269) 744189, 731550|
Patrick Bachèlery - Volcanology, Petrology, Deformations,
Jean Louis Cheminée - Volcanology
Jean Claude Delmond - Technical Manager, Electronics
Houmadi Naoildine - Seismology
Hamidou Nassor - Geology
Bernard Robineau - Structural Geology, Deformations
Karthala Volcanological Observatory was installed in 1988 by mutual consent between the " Centre National de Recherche Scientifique des Comores ", the " Institut de Physique du Globe de Paris" and the " Department Sciences de la Terre " of the Reunion University. Financing was provided by the french Ministry for Cooperation.
A close collaboration exists with Piton de la Fournaise Volcanological Observatory specially for technical support in the good working of the seismic and deformation network, and for geodetic measurements.
STRUCTURAL AND GEOLOGICAL STUDIES
Researchers involved in the functioning of the observatory are greatly interested in geological and structural studies. The first aim was to characterise the volcanological patterns of this poorly known volcano. Mapping of the entire Grande Comore island was completed and a new volcanological map of Grande Comore is now available (send requests to the CNDRS). Petrological and structural studies, evaluation of historic activity features, dynamic of the eruptions are the main researches topics.
Monitoring of Karthala volcano is presently based on seismic and ground deformations surveys.
The seismic network consists now in 7 seismic stations. There are 1 vertical-component and one is 3-components Mark Product 1 Hz seismometers. Each station is composed of a seismometer and a protection frame that supports antenna, solar power supply, and that contains a 12 V accumulator and various electronic devices for radio transmissions (modulator, transceiver).
Telemetered radio analogical signals of seismic stations are received at the Observatory where they are digitalized, then processed and stored on a PC-compatible computer. Periodically, data are transferred on magneto-optic disks. Data processing is realised according to the IASPEI procedure with two PC-compatible computers.
A real time analogical control is supplied for 3 stations at the observatory using a Lennartz drum recorder with thermic paper.
Deformations monitoring is performed with :
- a permanent inclinometric station composed by 4 Blum-type silica inclinometers installed in an old lava tube within the eastern part of the caldera. Measurements are repeated each minute and transmitted to the observatory by radio link every hour.
- a geodetic network composed of 32 benchmarks (23 distributed over the caldera rim and inside the caldera, and 9 along the seacoast). At the summit of the volcano, angle measurements are performed using a WILD T3000 electronic theodolite and a KERN DKM2 theodolite, and EDM measurements with a WILD D2002 distancemeter. Measurements are also realised using the GPS technique. Measurements between the summit zone and the coast are made by GPS.
- a network composed of 10 spirit-level tilt ("dry-tilt") stations distributed all over the caldera floor, and on both sides of the northern rift-zone. This network is measured twice yearly and after each seismic or eruptive crisis using a precise optical level WILD NA2 equipped with a micrometer.
- a 3 kms long levelling profile in the Caldera northern part.
On the caldera floor, two 3-components strainmeters are fixed across open fractures.
Information updated October 2001