Publication Date:
2020-03-09
Description:
A critical issue in the performance of a seismic
network is the characterization of site response
where stations are located. This information is
essential to improve some aspects related to
seismic surveillance and the publication of
products in near-real time following an
earthquake. A proper evaluation of the site effect
is also necessary to improve the quality of
recordings databases, facilitating their use for
research purposes. The Italian National Seismic
Network of the INGV (Rete Sismica Nazionale,
RSN) consists of about 400 seismic stations
equipped with a velocimeter and, for one-third of
the sites, an accelerometer. They are connected in
real time to the INGV data center in order to locate
earthquakes for civil defense purposes and their
records are distributed through the EIDA node
(eida.rm.ingv.it/). Recently INGV has addressed
the site characterization of RSN with an internal
project (funded within the INGV research line T3
“Seismic hazard and contributions to the
definition of risk”), as well as within the INGV-DPC
Agreements (INGV-DPC Agreement 2016-17-18,
Annex B2 Objective 1 - Task B “Characterization of
accelerometric sites”, funded by the Civil
Protection Department), with the purpose of
characterizing the seismic response of all the
stations acquired in real time by its data center.
The basic goal is building a geographic relational
database, integrated with the other INGV
infrastructures, designed to archive homogeneous
parameters through the seismic network useful
for a complete site characterization, including
housing, geological, seismological and
geotechnical features as well as site and
topographic class according to the European and
Italian building codes. The system resides on a
dedicated server and the data are organized in an
internal storage based on PostgreSQL DBMS
(acronym CRISP). It will be directly related to
SeisNet, the INGV database used for the network
management, but it is still possible to insert new
sites not belonging to the RSN. The backend of the
system includes several procedures that allow the
information updating through web services
created ad-hoc, such as those of the Institute for
Environmental Protection and Research (ISPRA)
for geological and lithological attributes and for
visualization of geological maps and related
legends. On the other hand, specific programming
interface services – API- expose the shared
information to allow the transfer to other
strong-motion data providers (e.g. ITACA,
http://itaca.mi.ingv.it, and ESM,
http://esm.mi.ingv.it) in semi-automatic way. The
collection of geological, morphological and
seismological data followed a nationwide
approach, aimed at obtaining homogeneous data
for the RSN sites. We started from the revision of
all available geological and geophysical data and
the analysis of noise waveforms, storing the
analysis results as images and searchable data.
Thanks to the collaboration with the Geological
Survey of Italy (ISPRA-SGI), a review of the
geological map of Italy (at a scale of 1:100,000 and
1:50,000) and their relative explanatory notes,
including also many other available published data
(borehole logs, local geographical portal, etc.),
allowed to develop a stratigraphic conceptual
model under each site. As for the attribution to
each site of a topographic class according to the
Italian building code, a morphometric analysis
using an automatic procedure has been carried
out on two DEM datasets with resolution at 30 m
and 10 m. Regarding the seismological
parameters, noise velocimetric records at all the
stations were homogeneously analyzed by using
mostly continuous data, as follow: 1) estimation of
data quality with annual and seasonal noise
analysis; 2) selection of noise traces (day/night
and seasonal), horizontal-to-vertical spectral ratio
computation and determination of directionality
of the amplification peaks; 3) in case of
directionality, we proceeded with the polarization
analysis of the signal to identify the preferred
direction of the movement, slope and
straightness. A preliminary statistical analysis
highlights that only 26% of the RSN accelerometric
stations do not have amplification peaks, while
29% show a polarization of the signal in a
preferential direction. Finally, we are collecting all
the available information about the station
housing, to account for possible soil-structure
interaction. The database includes also 15 sites
that have been fully characterized by performing
a geological survey followed by the 1:5,000
geological and lithotechnical maps, a geological
cross section and report, the S-wave velocity
profile inferred through seismic noise arrays and,
for one site, downhole measurements. With the
contribution of the Site-Characterization Team: S.
Amoroso, R. Azzaro, R. Bianconi, M. Cattaneo, R.
Cogliano, D. Di Naccio, C. Felicetta, A. Fodarella, S.
Lovati, A. Mandiello, C. Marcocci, C. Mascandola,
M. Massa, A. Mercuri, G. Milana, S. Pucillo, G.
Riccio, G. Tusa, M. Vassallo, et al. (INGV); M.
Amanti, G. Conte, C. Cipolloni, G. M. Monti, C.
D’Ambrogi, M. D’Orefice, P. Di Manna, D.
Fiorenza, R. M. Gafà, B. Roberto, M. Roma, L. Vita
(ISPRA)
Description:
Published
Description:
La Valletta-Malta
Description:
5T. Sismologia, geofisica e geologia per l'ingegneria sismica
Keywords:
site characterization, engineering seismology, crisp project
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Conference paper
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