A shallow‐dipping dike fed the 1995 flank eruption at Fernandina Volcano, Galápagos, observed by satellite radar interferometry

Satellite radar interferometry data reveal strong localized uplift in a semi- circular pattern on the southwest flank of Fernandina volcano, Galapagos, where an eruption took place in January to April, 1995. The observations show a maximum decrease in radar range of 0.75 m, and they are consistent with a model of a shallow-dipping dike intrusion feeding this fissure eruption. We solve for the best-fit single rectangular dislocation dike source using non-linear inver­ sion techniques where simulated annealing searching algo­ rithm is used to avoid local minima. The best-fit dike is 3.8 km long, 2.3 km high, 0.86 m thick and with a 34° dip. The total dike volume (7.5 x 10- 3 km 3 ) is ~40% of the vol­ ume of extrusive materials estimated to have been produced during the eruption. The data do not permit a sub-vertical dike, implying that the least principal stress direction is not horizontal as is usually assumed.

[1]  P. Rosen,et al.  On the derivation of coseismic displacement fields using differential radar interferometry: The Landers earthquake , 1994, Proceedings of IGARSS '94 - 1994 IEEE International Geoscience and Remote Sensing Symposium.

[2]  W. Chadwick,et al.  The pattern of circumferential and radial eruptive fissures on the volcanoes of Fernandina and Isabela islands, Galapagos , 1991 .

[3]  D. Massonnet,et al.  Readjustment of the Krafla Spreading Segment to crustal rifting measured by satellite radar interferometry , 1997 .

[4]  P. Rosen,et al.  Analysis of Active Lava Flows on Kilauea Volcano, Hawaii, Using SIR-C Radar Correlation Measurements , 1996 .

[5]  R. Tibshirani,et al.  An introduction to the bootstrap , 1993 .

[6]  Robert Tibshirani,et al.  Bootstrap standard errors: some examples , 1993 .

[7]  S. Rowland.  Slopes, lava flow volumes, and vent distributions on Volcán Fernandina, Galápagos Islands , 1996 .

[8]  T. Simkin,et al.  Caldera Collapse in the Galapagos Islands, 1968: The largest known collapse since 1912 followed a flank eruption and explosive volcanism within the caldera. , 1970, Science.

[9]  W. Chadwick,et al.  The September 1988 intracaldera avalanche and eruption at Fernandina volcano, Galapagos Islands , 1991 .

[10]  Riccardo Lanari,et al.  Dynamic deformation of Etna volcano observed by satellite radar interferometry , 1998, IGARSS '98. Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing. Symposium Proceedings. (Cat. No.98CH36174).

[11]  J. Dieterich,et al.  Mechanical modeling of circumferential and radial dike intrusion on Galapagos volcanoes , 1995 .

[12]  S. Rowland,et al.  The caldera of Volcan Fernandina: a remote sensing study of its structure and recent activity , 1992 .

[13]  P. Rosen,et al.  Atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps , 1997 .

[14]  K. Feigl,et al.  The displacement field of the Landers earthquake mapped by radar interferometry , 1993, Nature.

[15]  Giovanni Alberti,et al.  The TOPSAR interferometric radar topographic mapping instrument , 1992, IEEE Trans. Geosci. Remote. Sens..

[16]  Charles Werner,et al.  On the derivation of coseismic displacement fields using differential radar interferometry: The Landers earthquake , 1994 .

[17]  Martin J. Wooster,et al.  Time-series analysis of effusive volcanic activity using the ERS along track scanning radiometer: The 1995 eruption of Fernandina volcano, Galápagos Islands☆ , 1997 .

[18]  D. Massonnet,et al.  Deflation of Mount Etna monitored by spaceborne radar interferometry , 1995, Nature.

[19]  Ian Parsons,et al.  Surface deformation due to shear and tensile faults in a half-space , 1986 .

[20]  C. Werner,et al.  Satellite radar interferometry: Two-dimensional phase unwrapping , 1988 .