58 research outputs found
Array Analyses of Low-Frequency (0.1-0.5 Hz) Ambient Noise in Central Italy
In the framework of the seismological studies related to the activity of the Alto Tiberina Fault (ATF), a seismic array composed by 9 stations was deployed in the vicinity of Gubbio, central Italy
Source geometry from exceptionally high resolution long period event observations at Mt Etna during the 2008 eruption
During the second half of June, 2008, 50 broadband seismic stations were
deployed on Mt Etna volcano in close proximity to the summit, allowing us to
observe seismic activity with exceptionally high resolution. 129 long period
events (LP) with dominant frequencies ranging between 0.3 and 1.2 Hz, were
extracted from this dataset. These events form two families of similar
waveforms with different temporal distributions. Event locations are performed
by cross-correlating signals for all pairs of stations in a two-step scheme. In
the first step, the absolute location of the centre of the clusters was found.
In the second step, all events are located using this position. The hypocentres
are found at shallow depths (20 to 700 m deep) below the summit craters. The
very high location resolution allows us to detect the temporal migration of the
events along a dike-like structure and 2 pipe shaped bodies, yielding an
unprecedented view of some elements of the shallow plumbing system at Mount
Etna. These events do not seem to be a direct indicator of the ongoing lava
flow or magma upwelling
First deep underground observation of rotational signals from an earthquake at teleseismic distance using a large ring laser gyroscope
Recent advances in large ring laser gyroscopes (RLG) technologies opened the
possibility to observe rotations of the ground with sensitivities up to
over the frequency band of seismological interest
(0.01-1Hz), thus opening the way to a new geophysical discipline, i.e.
rotational seismology. A measure of rotations in seismology is of fundamental
interest for (a) the determination of all the six degrees of freedom that
characterize a rigid body motion, and (b) the quantitative estimate of the
rotational motions contaminating ground translation measurements obtained from
standard seismometers. Within this framework, this paper presents and describes
GINGERino, a new large observatory-class RLG located in Gran Sasso underground
laboratory (LNGS), one national laboratories of the INFN (Istituto Nazionale di
Fisica Nucleare). We also report unprecedented observations and analyses of the
roto-translational signals from a tele-seismic event observed in such a deep
underground environment
Detecting slow deformation signals preceding dynamic failure: a new strategy for the mitigation of natural hazards (SAFER)
Detecting Slow Deformation Signals Preceding Dynamic Failure: A New Strategy For The Mitigation Of Natural Hazards (SAFER)
Rock slope monitoring is a major aim in territorial risk assessment and mitigation. The high velocity that usually
characterizes the failure phase of rock instabilities makes the traditional instruments based on slope deformation
measurements not applicable for early warning systems. On the other hand the use of acoustic emission records
has been often a good tool in underground mining for slope monitoring. Here we aim to identify the characteristic
signs of impending failure, by deploying a “site specific” microseismic monitoring system on an unstable patch of
the Madonna del Sasso landslide on the ItalianWestern Alps designed to monitor subtle changes of the mechanical
properties of the medium and installed as close as possible to the source region.
The initial characterization based on geomechanical and geophysical tests allowed to understand the instability
mechanism and to design the monitoring systems to be placed. Stability analysis showed that the stability
of the slope is due to rock bridges. Their failure progress can results in a global slope failure. Consequently the
rock bridges potentially generating dynamic ruptures need to be monitored. A first array consisting of instruments
provided by University of Turin, has been deployed on October 2013, consisting of 4 triaxial 4.5 Hz seismometers
connected to a 12 channel data logger arranged in a ‘large aperture’ configuration which encompasses the entire unstable
rock mass. Preliminary data indicate the occurrence of microseismic swarms with different spectral contents.
Two additional geophones and 4 triaxial piezoelectric accelerometers able to operate at frequencies up to
23 KHz will be installed during summer 2014. This will allow us to develop a network capable of recording events
with Mw < 0.5 and frequencies between 700 Hz and 20 kHz.
Rock physical and mechanical characterization along with rock deformation laboratory experiments during
which the evolution of related physical parameters under simulated conditions of stress and fluid content will
be also studied and theoretical modelling will allow to come up with a full hazard assessment and test new
methodologies for a much wider scale of applications within EU
First deep underground observation of rotational signals from an earthquake at teleseismic distance using a large ring laser gyroscope
Recent advances in large ring laser gyroscopes (RLG) technologies opened the possibility to observe rotations of the ground with sensitivities up to 10 11 rad/sec over the frequency band of seismological interest (0.01-1Hz), thus opening the way to a new geophysical discipline, i.e. rotational seismology. A measure of rotations in seismology is of fundamental interest for (a) the determination of all the six degrees of freedom that characterize a rigid body’s motion, and (b) the quantitative estimate of the rotational motions contaminating ground translation measurements obtained from standard seismometers. Within this framework, this paper presents and describes GINGERino, a new large observatory-class RLG located in Gran Sasso underground laboratory (LNGS), one national laboratories of the INFN (Istituto Nazionale di Fisica Nucleare). We also report unprecedented observations and analyses of the roto-translational signals from a tele-seismic event observed in such a deep underground environment
The deep structure of the Larderello-Travale geothermal field (Italy) from integrated, passive seismic investigations
AbstractWe report the preliminary results from a project (GAPSS-Geothermal Area Passive Seismic Sources), aimed at testing the resolving capabilities of passive exploration methods on a well-known geothermal area, namely the Larderello-Travale Geothermal Field (LTGF). Located in the western part of Tuscany (Italy), LTGF is the most ancient geothermal power field of the world. GAPSS consisted of up to 20 seismic stations deployed over an area of about 50 x 50 Km. During the first 12 months of measurements, we located more than 2000 earthquakes, with a peak rate of up to 40 shocks/day. Preliminary results from analysis of these signals include: (i) analysis of Shear-Wave-Splitting from local earthquake data, from which we determined the areal distribution of the most anisotropic regions; (ii) local-earthquake travel-time tomography for both P- and S-wave velocities; (iii) telesismic receiver function aimed at determining the high-resolution (<0.5km) S-velocity structure over the 0-20km depth range, and seismic anisotropy using the decomposition of the angular harmonics of the RF data-set; (iv) S-wave velocity profiling through inversion of the dispersive characteristics of Rayleigh waves from earthquakes recorded at regional distances. After presenting results from these different analyses, we eventually discuss their potential application to the characterisation and exploration of the investigated area
Performances of the UNDERground SEISmic array for the analysis of seismicity in Central Italy
This paper presents the first results from the operation of a dense seismic array deployed in the underground Physics Laboratories at Gran Sasso (Central Italy). The array consists of 13 short-period, three-component seis- mometers with an aperture of about 550 m and average sensor spacing of 90 m. The reduced sensor spacing, joined to the spatially-white character of the background noise allows for quick and reliable detection of coher- ent wavefront arrivals even under very poor SNR conditions. We apply high-resolution frequency-slowness and polarization analyses to a set of 27 earthquakes recorded between November, 2002, and September, 2003, at epi- central distances spanning the 20-140 km interval. We locate these events using inversion of P- and S-wave back- azimuths and S-P delay times, and compare the results with data from the Centralized National Seismic Network catalog. For the case of S-wave, the discrepancies among the two set of locations never exceed 10 km; the largest errors are instead observed for the case of P-waves. This observation may be due to the fact that the small array aperture does not allow for robust assessment of waves propagating at high apparent velocities. This informa- tion is discussed with special reference to the directions of future studies aimed at elucidating the location of seismogenetic structures in Central Italy from extended analysis of the micro-seismicity
Horizontal rotation signals detected by "G-Pisa" ring laser for the Mw=9.0, March 2011, Japan earthquake
We report the observation of the ground rotation induced by the Mw=9.0, 11th
of March 2011, Japan earthquake. The rotation measurements have been conducted
with a ring laser gyroscope operating in a vertical plane, thus detecting
rotations around the horizontal axis. Comparison of ground rotations with
vertical accelerations from a co-located force-balance accelerometer shows
excellent ring laser coupling at periods longer than 100s. Under the plane wave
assumption, we derive a theoretical relationship between horizontal rotation
and vertical acceleration for Rayleigh waves. Due to the oblique mounting of
the gyroscope with respect to the wave direction-of-arrival, apparent
velocities derived from the acceleration / rotation rate ratio are expected to
be always larger than, or equal to the true wave propagation velocity. This
hypothesis is confirmed through comparison with fundamental-mode, Rayleigh wave
phase velocities predicted for a standard Earth model.Comment: Accepted for publication in Journal of Seismolog
Deep underground rotation measurements: GINGERino ring laser gyroscope in Gran Sasso
GINGERino is a large frame laser gyroscope investigating the ground motion in
the most inner part of the underground international laboratory of the Gran
Sasso, in central Italy. It consists of a square ring laser with a m
side. Several days of continuous measurements have been collected, with the
apparatus running unattended. The power spectral density in the seismic
bandwidth is at the level of . A maximum
resolution of is obtained with an integration time of few
hundred seconds. The ring laser routinely detects seismic rotations induced by
both regional earthquakes and teleseisms. A broadband seismic station is
installed on the same structure of the gyroscope. First analysis of the
correlation between the rotational and the translational signal are presented.Published0345027TM. Sviluppo e Trasferimento TecnologicoJCR Journa
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