Structural results for La Palma island using 3‐D gravity inversion

[1] A recent gravity survey composed of 317 bench marks all over the island of La Palma (Canary Islands) is used, in combination with satellite data for regional aspects, to obtain results about structural properties of the island connected with the tectonic environment and local volcanism. To that end, a nonlinear three-dimensional gravity inversion approach is considered. The inversion scheme provides, in a nonsubjective form, the geometry of the anomalous bodies constructed in a random growth process. Results from the inversion can be interpreted in the framework of the geologic evolution of this ocean island volcano as a complex composite volcano with a large central body with high-density corresponding to the older intrusive part of the basalt complex. New unexpected features are enlightened, such as large thermal anomalies in the upper mantle southward of La Palma, as well as fracture en echelon zones associable to a slow active process of dislocation related to the recent volcanism in the southern half of the island. The results obtained for La Palma as a test site testify to the usefulness of the developed gravity inversion methodology for structural studies on islands in general.

[1]  T. L. Bas,et al.  Recurrent large‐scale landsliding on the west flank of La Palma, Canary Islands , 1999 .

[2]  Helmut Moritz,et al.  Geodetic Reference System 1980 , 1980 .

[3]  A magnetic anomaly study offshore the Canary Archipelago , 2003 .

[4]  J. Collier,et al.  Lithospheric response to volcanic loading by the Canary Islands: constraints from seismic reflection data in their flexural moat , 2001 .

[5]  J. Gottsmann,et al.  Shallow structure beneath the Central Volcanic Complex of Tenerife from new gravity data : Implications for its evolution and recent reactivation , 2008 .

[6]  J. Carracedo,et al.  Growth, structure, instability and collapse of Canarian volcanoes and comparisons with Hawaiian volcanoes , 1999 .

[7]  J. Collier,et al.  A detailed geophysical study in the Canary Basin (eastern Atlantic): implications for the internal structure of 130 Ma oceanic crust , 1998 .

[8]  M. Chiappini,et al.  Magnetic imaging of the feeding system of oceanic volcanic islands: El Hierro (Canary Islands) , 2008 .

[9]  João B. C. Silva,et al.  Gravity inversion of basement relief using approximate equality constraints on depths , 1997 .

[10]  G. Walker.  “Coherent intrusion complexes” in large basaltic volcanoes — a new structural model , 1992 .

[11]  D. Page,et al.  Ground deformation monitoring of a potential landslide at La Palma, Canary Islands , 1999 .

[12]  D. J. Macfarlane,et al.  Crustal structure of the western Canary Islands from seismic refraction and gravity data , 1970 .

[13]  A. Tarantola.  Inverse problem theory : methods for data fitting and model parameter estimation , 1987 .

[14]  M. Torné,et al.  Gravity and multichannel seismic reflection constraints on the lithospheric structure of the Canary Swell , 1995 .

[15]  J. Arnoso,et al.  The crustal structure of El Hierro (Canary Islands) from 3-D gravity inversion , 2006 .

[16]  S. Day,et al.  Giant Quaternary landslides in the evolution of La Palma and El Hierro, Canary Islands , 1999 .

[17]  J. Lénat,et al.  Complete gravity study of Piton de la Fournaise volcano, Reunion Island , 1989 .

[18]  M. Al-Chalabi,et al.  SOME STUDIES RELATING TO NONUNIQUENESS IN GRAVITY AND MAGNETIC INVERSE PROBLEMS , 1971 .

[19]  Ricardo Vieira,et al.  A 3-D gravity inversion tool based on exploration of model possibilities , 2002 .

[20]  Carlos Segovia Fernández,et al.  Stress fields associated with the growth of a large shield volcano (La Palma, Canary Islands) , 2002 .

[21]  H. Rymer,et al.  Gravity fields and the interpretation of volcanic structures: Geological discrimination and temporal evolution , 1986 .

[22]  F. Anguita,et al.  The Canary Islands origin: a unifying model , 2000 .

[23]  J. Carracedo,et al.  Geology and volcanology of La Palma and El Hierro, Western Canaries , 2001 .

[24]  R. Vieira,et al.  Gravity inversion by means of growing bodies , 2000 .

[25]  T. Hansteen,et al.  Changing depths of magma fractionation and stagnation during the evolution of an oceanic island volcano: La Palma (Canary Islands) , 2006 .

[26]  Simon Day,et al.  Recent structural evolution of the Cumbre Vieja volcano, La Palma, Canary Islands: Volcanic rift zone reconfiguration as a precursor to volcano flank instability? , 1999 .

[27]  S. Day,et al.  Cumbre Vieja Volcano—Potential collapse and tsunami at La Palma, Canary Islands , 2001 .

[28]  J. Arnoso,et al.  Modelling of crustal anomalies of Lanzarote (Canary Islands) in light of gravity data , 2001 .

[29]  H. Moritz.  Geodetic reference system 1980 , 1980 .

[30]  P. Ryan.  Neutral buoyancy and the mechanical evolution of magmatic systems. , 1987 .

[31]  J. Lénat,et al.  Structure of Réunion Island (Indian Ocean) inferred from the interpretation of gravity anomalies , 1999 .

[32]  Walter H. F. Smith,et al.  Marine gravity anomaly from Geosat and ERS 1 satellite altimetry , 1997 .

[33]  A. Watts.  Crustal structure, gravity anomalies and flexure of the lithosphere in the vicinity of the Canary Islands , 1994 .

[34]  J. Canales,et al.  The Canary Islands swell: a coherence analysis of bathymetry and gravity , 1998 .

[35]  Gerald W. Hohmann,et al.  Nonlinear magnetic inversion using a random search method , 1983 .

[36]  J. Canas,et al.  Coda-Q distribution in the Canary Islands , 1995 .

[37]  G. Walker.  Volcanic rift zones and their intrusion swarms , 1999 .

[38]  L. B. Pedersen,et al.  CONSTRAINED INVERSION OF POTENTIAL FIELD DATA , 1979 .

[39]  R. Vieira,et al.  Gravimetric determination of an intrusive complex under the Island of Faial (Azores): some methodological improvements , 2007 .

[40]  K. Tiampo,et al.  DInSAR, GPS and gravity observation results in La Palma, Canary islands , 2008, 2008 Second Workshop on Use of Remote Sensing Techniques for Monitoring Volcanoes and Seismogenic Areas.

[41]  J. White,et al.  Phreatomagmatic eruptive and depositional processes during the 1949 eruption on La Palma (Canary Islands) , 1999 .

[42]  Simon Day,et al.  Hotspot volcanism close to a passive continental margin: the Canary Islands , 1998, Geological Magazine.