Publication Date:
2017-04-04
Description:
In the period 2-6 April 2007 a seismic survey was carried out at Solfatara Volcano,
(Campi Flegrei, Southern Italy) with the aim of inferring the shallow structure and
evaluating local site effects.
Five circular seismic arrays equipped with 1-Hz 3-component Mark LE3Dlite sensors,
were installed in the Solfatara crater. Each array consisted of 4 sensors, 3 of them
evenly spaced (120°) around the circumference and the fourth placed at its center.
The arrays were designed with radii of 5, 10, 25, 50 and 100 m. Some stations of the
arrays shaped two orthogonal profiles of about 250-m-length, roughly oriented in the
N-S and E-W directions. A further seismic station was installed outside the crater, on
the Eastern rim.
The particular geometry of the station deployment was adopted to apply the spatial
autocorrelation technique (Aki, 1957) and its modifications (MSPAC, Bettig et al.,
2001, CCA, Cho et al., 2004), to the data recorded by each array and to infer shearwave
velocity models for different areas of the crater. Further information about the
shallow structure will come from the application of Nakamura’s technique (1989) to
microtremor recorded at each sampled site. The two orthogonal profiles oriented N-S
and E-W will be useful to map possible variations of the resonance frequencies and
amplification values along the N-S and E-W directions.
The results of the preliminary spectral analysis of some samples of seismic noise
recorded during the 2-6 April 2007 survey at Solfatara Volcano, are already indicative
of differences among the spectral content of the microtremor recorded in different
areas of the crater. In particular the most evident differences are observed between the
recordings of the stations located in the central part of the crater and those deployed
in the Northern and Eastern areas. Moreover, the seismic noise recorded outside the
crater has spectral characteristics that are very different from those observed for the
array stations.
The observed differences in the spectral content of the seismic noise could be due both
to the presence of horizontal velocity contrasts and to variations of the thickness of the
shallower layers.
The high density of the deployment and the large number of the sampled sites will
allow to obtain a detailed shallow velocity structure, to investigate about the presence
(or not) of lateral heterogeneities and to map resonance frequencies and amplifications
values in different areas of the crater.
Description:
Published
Description:
Vienna
Description:
open
Keywords:
Solfatara
;
velocity model
;
site effects
;
04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Poster session
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