Publication Date:
2017-04-04
Description:
We have analyzed a multiparametric data set of seismological, geodetic and
geochemical data recorded at Campi Flegrei caldera since 1982. We focus here on the
period 1989–2010 that followed the last bradyseismic crisis of 1982–1984. Since then,
there have been at least five repeated minor episodes of ground uplift accompanied
by seismicity. We have reanalyzed old paper and digital seismic data sets dating back to
1982. The paper recordings show evidence of long‐period events in January 1982 and
March 1989, and we have digitized some of these significant waveforms. Furthermore, the
revision of digital seismograms dating back to 1994 shows a significant swarm of
long‐period events in August 1994. Volcano‐tectonic and long‐period events hypocenters
have been relocated in a three‐dimensional velocity model. Statistical analysis of
volcano‐tectonic seismicity shows many similarities and few differences between
1982–1984 and the following period 1989–2010. Long‐period waveforms have been
analyzed using spectral analysis, which shows a grouping into three macrofamilies.
Similarities in the seismic signature of episodes of minor uplift suggest that they originate
from the injection of fluids into the deep part of a geothermal reservoir (about 2.5 km
depth) and in its transfer toward a shallower part (about 0.75 km depth). Most of the
observed geophysical signals are related to this second phase. The evidence consists of
spatial and temporal connections between the ground deformation, long‐period and
volcano‐tectonic seismicity and changes in the geochemical parameters of fumaroles. In
this study we focused our analysis on two uplift episodes observed in 2000 and 2006. The
joint inversion of Differential Synthetic Aperture Radar (DInSAR) and tiltmeter data
show that during these periods the ground deformation was generated by at least two
distinct sources located at different depths, with the shallower activated in the later stages
of the uplift episodes. Our interpretation of the recent dynamics of Campi Flegrei is
that the deep part of the geothermal reservoir inflates in response to mass and heat input
from a magmatic source. When the pressure exceeds a threshold, fluids starts to migrate
into the shallower part. During this transfer, long‐period sources are activated in response
to the fluid motion. The gradual diffusion of fluids in the surrounding rocks lowers the
resistance of a pervasive fracture system generating shallow microseismicity. Finally, fluids
reach the surface, which gives a distinct geochemical signature to the overlying fumaroles.
Description:
Published
Description:
B04313
Description:
1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
Description:
JCR Journal
Description:
reserved
Keywords:
fluid‐transfer episodes
;
Campi Flegrei caldera
;
04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy
;
04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
;
04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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