[1] Univ Granada, Dept Signal Theory Telemat & Commun, Granada, Spain
[2] Univ Liverpool, Dept Earth Ocean & Ecol Sci, Liverpool, Merseyside, England
[3] Univ N Carolina, Dept Geol Sci, Chapel Hill, NC 27515 USA
[4] Univ Granada, Dept Theoret Phys & Cosmos, Granada, Spain
[5] Ist Nazl Geofis & Vulcanol, Sez Pisa, Pisa, Italy