Dataset of seismic ambient vibrations from the quaternary Norcia basin (central Italy)

Abstract

Central Italy was affected by a long seismic sequence in 2016 and 2017, characterized by five main-shocks with Mw>5.0. The Mw 6.5 mainshock occurred on 30 October 2016 close to the town of Norcia, located in the intra-Apennine Norcia basin. Different degrees of damages were observed during this seismic crisis, caused by a variable seismic shaking. This was also due to important 1D and 2D variation of Quaternary fluvio-lacustrine sediments infilling the basin. Following such considerations, a new geophysical dataset of seismic vibration measurements was acquired in the study area during the period April 2017-November 2019. We collected mainly single-seismic station noise data, to infer the distribution of resonance frequency (f₀) of the basin. A total of 60 sites were measured to cover the entire extension in the basin. We deployed seismometers along three transects of a total length of 21 km, mostly along the main structural directions of the basin (i.e. NNW-SSE and NE-SW). Two 2D arrays of seismic stations with a elicoidal-shaped geometry, and a set of MASW active data were also acquired in the northern sector of the basin, in order to better constrain the seismic velocity of the sedimentary infilling. These new records have been integrated with available geological information in order to reconstruct the deep structure of the basin, as discussed in the research paper by [2]. The entire dataset used in [2] is here provided, together with 7 additional records recovered for the basin (i.e. N54-N60) and ancillary open-source geospatial data. The dataset can be used for different purposes: specific research on the Norcia basin, comparative studies on similar areas around the world, development of new data modeling and testing of new analysis software, and as a training dataset for machine learning applications.

Keywords: Active seismic; GIS data; Norcia basin; Seismic ambient vibrations; Seismic array and ambient noise analysis; Site effects.

Fig. 1

Location map of the study site (Norcia basin). The blue dots display the location of the single-station noise measurements across three main cross-sections (black lines) overlying a high-resolution Digital Elevation Model as basemap . The red and blue circles provide the position of the arrays in the North sector, whilst the yellow dashed is the velocity model boundary used in .

Fig. 2

An example of a single-station station measurement (N09 site) at the Norcia basin; (a) contemporary acquisitions carried-out with two different seismic equipment; (b) comparison of the recorded time-series: the Sara Geobox (_S) XYZ traces are displayed close to the corresponding three Reftek (_R) records.

Fig. 3

Signals recorded by the vertical components of stations of NW oriented linear array in the southern part of Norcia basin. (a) About 2 h of raw signal acquired by the different stations. In the red box there are seismic events recorded during the acquisition time window. In order to better emphasize the similarities and differences between the signals recorded at the different stations in (b) and (c) the seismic signals are filtered using a band-pass filter from 1 Hz to 10 Hz and a low pass filter at 1 Hz, respectively.

Fig. 4

2D array of seismic stations collected at the Fontevena site; (a) picture displaying the position of four stations during the deployment of FS array; (b) geometry of the two arrays FS and FB; (c) portion of the recorded time-series for all the eleven seismic stations of FS array (Z component).

Fig. 5

Linear array acquisition at the Marcite site; (a) picture displaying the energization located at the south side of M2; (b) geometry of both M2 and M4; (c) seismogram of the 12 traces recorded (M2_24 file).