74 research outputs found
Seismicity Pattern Changes before the M = 4.8 Aeolian Archipelago (Italy) Earthquake of August 16, 2010
We investigated the seismicity patterns associated with an earthquake recorded in the Aeolian Archipelago on 16, August, 2010, by means of the region-time-length (RTL) algorithm. This earthquake triggered landslides at Lipari; a rock fall on the flanks of the Vulcano, Lipari, and Salina islands, and some damages to the village of Lipari. The RTL algorithm is widely used for investigating precursory seismicity changes before large and moderate earthquakes. We examined both the spatial and temporal characteristics of seismicity changes in the Aeolian Archipelago region before the earthquake. The results obtained reveal 6-7 months of seismic quiescence which started about 15 months before the earthquake. The spatial distribution shows an extensive area characterized by seismic quiescence that suggests a relationship between quiescence and the Aeolian Archipelago regional tectonics
On-line image analysis of explosive activity captured by surveillance cameras allows major eruptive events forecasting
The use of stationary remote cameras for visual monitoring of the eruptive activity was implemented in the monitoring system of Etna and Stromboli volcanoes since 1993 and 1994 respectively. Camera records of eruptive activity became the major information source for describing eruptive phenomena occurred at Etna and Stromboli in the last years. However, the main goal of the continuous visual monitoring of active basaltic volcanoes is to analyze eruptive activity images in search of precursors of the paroxysmal events that suddenly interrupt the persistent mild strombolian activity. Stromboli represent the perfect test site for this investigation because its typical activity consists of intermittent mild explosions lasting a few seconds, which take place at different vents and at variable intervals. However, the routine activity can be interrupted by more violent, paroxysmal explosions, that eject m-sized scoriaceous bombs and lava blocks to a distance of several hundreds of meters from the craters, endangering the numerous tourists that watch the spectacular activity from the volcano's summit located about two hundreds meters from the active vents. Using image analysis we identified any change of the explosive activity trend that preceded a particular eruptive event, like paroxysmal explosions, fire fountains and lava flows. The analysis include the counting of the explosions occurred at the different craters and the parameterization in classes of intensity for each explosion on the base of tephra dispersion and kinetics energy. From September 2001 an on-line image analyzer called VAMOS (Volcanic Activity MOnitoring System) operates detection and classification of explosive events in quasi real-time. The system has automatically recorded and analyzed the change in the energetic trend that preceded the 20 October 2001 paroxysmal explosion that killed a woman and the strong explosive activity that preceded the onset of 28 December 2002 lava flow and landslide forming eruption
On-line image analysis of the Stromboli volcanic activity recorded by the surveillance camera helps the forecasting of the major eruptive events
The typical activity of Stromboli consists of intermittent mild explosions lasting a
few seconds, which take place at different vents and at variable intervals, the most
common time interval being 10-20 minutes. However, the routine activity can be interrupted by more violent, paroxysmal explosions, that eject m-sized scoriaceous
bombs and lava blocks to a distance of several hundreds of meters from the craters,
endangering the numerous tourists that watch the spectacular activity from the
volcano's summit located about two hundreds meters from the active vents. On
average, 1-2 paroxysmal explosions occurred per year over the past century, but this statistic may be underestimated in absence of continuous monitoring. For this reason from summer 1996 a remote surveillance camera works on Stromboli recording continuously the volcanic activity. It is located on Pizzo Sopra la Fossa, 100 metres above the crater terrace where are the active vents.
Using image analysis we seeks to identify any change of the explosive activity trend
that could precede a particular eruptive event, like paroxysmal explosions, fire
fountains, lava flows. From the day of the camera installation up to present 12 paroxysmal events and lava flows occurred. The analysis include the counting of the
explosions occurred at the different craters and the parameterization in classes of intensity for each explosion on the base of tephra dispersion and kinetics energy. The plot of dissipated energy by each crater versus time shows a cyclic behavior with max and min of explosive activity ranging from a few days to a month. Often the craters show opposite trends so when the activity decreases in a crater, increases in the other. Before every paroxysmal explosions recorded, the crater that produced the event decreased and then stopped its activity from a few days to weeks before. The other crater tried to compensate increasing its activity and when it declined the paroxysmal explosion occurred suddenly at the former site. From September 2001 an on-line image analyzer called VAMOS (Volcanic Activity MOnitoring System) operates detection and classification of explosive events in quasi real-time. The system has automatically recorded and analyzed the change in the energetic trend that preceded the 20 October 2001 paroxysmal explosion that killed a woman and the strong explosive activity that preceded the onset of 28 December 2002 lava flow eruption
Automatic Classification of eruptive events by the VAMOS system
An automatic system named VAMOS (Volcanic Activity
MOnitoring System) for monitoring volcanic activity at Mt. Etna and
Stromboli volcanoes, is at the present under test at the data collection
center at IIV (Istituto Internazionale di Vulcanologia, CNR, Catania). This
system allows automatic recognition of volcanic activity by on-line
processing of images collected by the surveillance cameras positioned close
to the summit crater of two above mentioned volcanoes which are
worldwide known to be characterized by a persistent eruptive activity.
Based on this automatic system, a new software tool to extract quantitative
information from collected images is now under developing. Several tasks
have been planned to solve by using this tool such as the automatic
classification of recorded events and the computation of relaxed energy
based on stereo-vision and thermal images. One of the first result of the
undertaken research activity has been the automatic classification of the
type of volcanic events and the localization of the eruptive event
Massive black hole binaries in LISA: multimessenger prospects and electromagnetic counterparts
In the next decade, the Laser Interferometer Space Antenna (LISA) will detect
the coalescence of massive black hole binaries (MBHBs) in the range , up to . Their gravitational wave (GW) signal
is expected to be accompanied by an electromagnetic counterpart (EMcp),
generated by the gas accreting on the binary or on the remnant BH. In this
work, we present the number and characteristics (such as redshift and mass
distribution, apparent magnitudes or fluxes) of EMcps detectable jointly by
LISA and some representative EM telescopes. We combine state-of-the-art
astrophysical models for the galaxies formation and evolution to build the
MBHBs catalogues, with Bayesian tools to estimate the binary sky position
uncertainty from the GW signal. Exploiting additional information from the
astrophysical models, such as the amount of accreted gas and the BH spins, we
evaluate the expected EM emission in the soft X-ray, optical and radio bands.
Overall, we predict between 7 and 21 EMcps in 4 yrs of joint observations by
LISA and the considered EM facilities, depending on the astrophysical model. We
also explore the impact of the hydrogen and dust obscuration of the optical and
X-ray emissions, as well as of the collimation of the radio emission: these
effects reduce the number to EMcps to 2 or 3, depending on the astrophysical
model, again in 4 yrs of observations. Most of the EMcps are characterised by
faint EM emission, challenging the observational capabilities of future
telescopes. Finally, we also find that systems with multi-modal sky position
posterior distributions represent only a minority of cases and do not affect
significantly the number of EMcps.Comment: 28 pages, 18 figures. Submitted to PR
Multimessenger study of merging massive black holes in the Obelisk simulation: gravitational waves, electromagnetic counterparts, and their link to galaxy and black hole populations
Massive black hole (BH) mergers are predicted to be powerful sources of
low-frequency gravitational waves (GWs). Coupling the detection of GWs with
electromagnetic (EM) detection can provide key information about merging BHs
and their environments. We study the high-resolution cosmological
radiation-hydrodynamics simulation Obelisk, run to redshift , to assess
the GW and EM detectability of high-redshift BH mergers, modelling spectral
energy distribution and obscuration. For EM detectability we further consider
sub-grid dynamical delays in postprocessing. We find that most of the merger
events can be detected by LISA, except for high-mass mergers with very unequal
mass ratios. Intrinsic binary parameters are accurately measured, but the sky
localisation is poor generally. Only of these high-redshift sources
have sky localisation better than . Merging BHs are hard to
detect in the restframe UV since they are fainter than the host galaxies, which
at high are star-forming. A significant fraction, , of BH mergers
instead outshines the galaxy in X-rays, and about are sufficiently
bright to be detected with sensitive X-ray instruments. If mergers induce an
Eddington-limited brightening, up to of sources can become observable.
The transient flux change originating from such a brightening is often large,
allowing of mergers to be detected as EM counterparts. A fraction
of mergers is also detectable at radio frequencies. Observable merging
BHs tend to have higher accretion rates and masses and are overmassive at fixed
galaxy mass with respect to the full population. Most EM-observable mergers can
also be GW-detected with LISA, but their sky localisation is generally poorer.
This has to be considered when using EM counterparts to obtain information
about the properties of merging BHs and their environment.Comment: 17 pages, 11 figures, submitted to A&
Monitoring System of Eastern Sicily (Italy) devised by a specialist team (UFSO) at the INGV- Catania Section, Italy.
Eastern Sicily in Italy is well-known as a high seismic and volcanic risk area. From a monitoring point of view, a team/unit of people has been created (UFSO) with the task of managing all the activities connected to the faultless operation of the Working Room that is the strategic centre during periods of routine operations or in the case of emergency.
Among the primary activities of monitoring and surveillance, the management of the video camera network located on the main Sicilian active volcanoes represents a major goal. This task is achieved by means of permanent, visible and infrared cameras together with similar mobile systems, in order to observe each phenomenon related to the volcanic activity.
The expert staff can therefore make decisions, in real time, from useful information in order to understand the phenomena in action.
With the aim of maximizing the results and performance of all the networks, the UFSO is attentive to the planning and realization of hardware and software systems that are always available in the mobile van unit. In this context, the staff actively participates in national and European research projects dealing with the development and use of new systems with high technological content.
Another aspect of the work, moreover, is represented by the development of supervisory control software, namely software providing automatic control of the working systems. Such algorithms allow to immediately and remotely signal to the duty-personnel states of alert of several modules, indicating, when possible, the probable failure causes
Chasing Super-Massive Black Hole merging events with and LISA
The European Space Agency is studying two large-class missions bound to
operate in the s, and aiming at investigating the most energetic
phenomena in the Universe. is poised to study the physical conditions
of baryons in large-scale structures, as well as to yield a census of accreting
super-massive black holes down to the epoch of reionization; the Laser
Interferometer Space Antenna (LISA) will extend the hunt for Gravitational Wave
(GW) events to the mHz regime. While the science cases of the two missions are
independently outstanding, we discuss in this paper the science
that their concurrent operation could yield. We focus on the multi-messenger
study of Super-Massive (M) Black Hole Mergers
(SMBHMs), accessible to up to . The simultaneous measurement
of their electro-magnetic (EM) and GW signals may enable unique experiments in
the domains of astrophysics, fundamental physics, and cosmography. Key to
achieve these results will be the LISA capability of locating a SMBHM event
with an error box comparable to, or better than the field-of-view of the
Wide Field Imager (deg). LISA will achieve such an
accuracy several hours prior to merging for the highest signal-to-noise events.
While theoretical predictions of the EM emission are still uncertain, this
opens in principle the possibility of truly concurrent EM and GW studies of the
merger phase. LISA localization improves significantly at merging, and is
likely to reach the arcminute-level for a sizeable fraction of events at
and masses , well within the
detection capability of . We also briefly discuss the prospective of
studies for other classes of GW-emitting black hole binaries, for
which theoretical predictions are admittedly extremely uncertain. [abridged]Comment: 18 pages, 8 figures. Submitted to MNRA
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