Magnetic observations made on la soufriere volcano (guadeloupe) during the 1976–1977 crisis

Magnetic observations on La Soufriere volcano (Guadeloupe; F.W.I.) over a quiet period; Background estimation.

“…2). In both cases, the value of the multiplicative factor is not significantly B MATOUBA As said before, the main characteristic time constants of the variations of the volcano-magnetic field as observed during the 1976-1977 crisis are on the order of a few days (Pozzi et al, 1979). This phenomenon can then be monitored using daily values; in order to avoid the errors due to SR variations, we use the values recorded each night around 2:00 local time.…”

“…1 We have considered the volcano-magnetic field observed at the repeat stations during the 1976-1977 seismo-volcanic crisis (in fact the difference between the actual volcano-magnetic field at the varying point and the one at Matouba). Pozzi et al (1979) have shown that this differential field was small (in any case smaller than 5 nT) in the summit area (Bains Jaunes, Savane, Carbet), but could reach 10 nT in some more remote stations after taking into account the reduction error (Palmiste, l'Habituee, Grand Maison, Dole, for instance). A model has been computed on the basis of a pure piezomagnetic anomaly (Pozzi et al, 1983).…”

“…Significant variain some stations; the main time constant of the variations was on the order of a few days, their amplitude decreased to the noise level at the end of the crisis (Pozzi et al, 1979).…”

“…Results were obtained during the 1976-1977 seismo-volcanic crisis of La Soufriere Volcano of Guadeloupe (F.W.I.) using a network of repreat stations settled on the volcanic dome (LE MOUEL, 1976;POZZI et al, 1979).…”

“…Then we can write (LE MOUEL, 1976;POZZi et al, 1979): where u is the unit vector of Br + Ba and k a scalar constant with respect to time. We call the third term of the right-hand side of (2) the projection error.…”