Publication Date:
2017-04-04
Description:
The complex volcanic system of Tenerife Island is known to have a highly heterogeneous
character, as recently confirmed by velocity tomography.We present new information derived
from intrinsic quality factor inverse maps (Qi
−1), scattering quality factor inverse maps (Qs
−1)
and total quality factor inverse maps (Qt
−1) obtained for the same region. The data set used
in this work is the result of the analysis of an active seismic experiment carried out, using
offshore shots (air guns) recorded at over 85 onshore seismic stations. The estimates of the
attenuation parameters are based on the assumption that the seismogram energy envelopes
are determined by seismic energy diffusion processes occurring inside the island. Diffusion
model parameters, proportional to Qi
−1 and to Qs
−1, are estimated from the inversion of the
energy envelopes for any source–receiver couple. They are then weighted with a new graphical
approach based on a Gaussian space probability function, which allowed us to create ‘2-D
probabilistic maps’ representing the space distribution of the attenuation parameters. The 2-D
images obtained reveal the existence of a zone in the centre of the island characterized by
the lowest attenuation effects. This effect is interpreted as highly rigid and cooled rocks. This
low-attenuation region is bordered by zones of high attenuation, associated with the recent
historical volcanic activity. We calculate the transport mean free path obtaining a value of
around 4 km for the frequency range 6–12 Hz. This result is two orders of magnitude smaller
than values calculated for the crust of the Earth. An absorption length between 10 and 14 km
is associated with the average intrinsic attenuation parameter. These values, while small in
the context of tectonic regions, are greater than those obtained in volcanic regions such as
Vesuvius or Merapi. Such differences may be explained by the magnitude of the region of
study, over three times larger than the aforementioned study areas. This also implies deeper
sampling of the crust, which is evidenced by a change in the values of seismic attenuation.
One important observation is that scattering attenuation dominates over the intrinsic effects,
Qi being at least twice the value of Qs.
Description:
This work has been partially supported by the Spanish project
Ephestos, CGL2011-29499-C02-01, by the EU project EC-FP7
MEDiterranean SUpersite Volcanoes (MED-SUV), by the Basque
Government researcher training program BFI09.277 and by the Regional
project ‘Grupo de Investigaci´on en Geof´ısica y Sismolog´ıa
de la Junta de Andaluc´ıa, RNM104’. EdP has been partly supported
by DPC-INGV projects UNREST SPEED and V2 (Precursori).
Description:
Published
Description:
1942-1956
Description:
3.1. Fisica dei terremoti
Description:
3.3. Geodinamica e struttura dell'interno della Terra
Description:
JCR Journal
Description:
restricted
Keywords:
Seismic attenuation
;
; Seismic tomography;
;
Volcano seismology
;
Wave propagation.
;
04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
;
04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
;
04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
