S. Jonsson et al., A shallow-dipping dike fed the 1995 flank eruption at Fernandina Volcano, Galapagos, observed by satellite radar interferometry, GEOPHYS R L, 26(8), 1999, pp. 1077-1080
Satellite radar interferometry data reveal strong localized uplift in a sem
i-circular pattern on the southwest flank of Fernandina volcano, Galapagos
where an eruption took place in January to April, 1995. The observations sh
ow a maximum decrease in radar range of 0.75 m, and they are consistent wit
h a model of a shallow-dipping dike intrusion feeding this fissure eruption
. We solve for the best-fit single rectangular dislocation dike source usin
g non-linear inversion techniques where simulated annealing searching algor
ithm is used to avoid local minima. The best-fit dike is 3.8 km long, 2.3 k
m high, 0.86 m thick and with a 34 degrees dip. The total dike volume (7.5
x 10(-3) km(3)) is similar to 40% of the volume of extrusive materials esti
mated to have been produced during the eruption. The data do not permit a s
ub-vertical dike, implying that the least principal stress direction is not
horizontal as is usually assumed.