Structural health monitoring and earthquake early warning: preliminary studies for application in eastern Sicily

In this work, the reduction of seismic hazard in eastern Sicily is addressed by both studying the fundamental resonant frequency of strategic buildings through low cost geophysical investigation techniques, and exploring a practical approach to earthquake early warning EEW) system. The fundamental period and the corresponding amplification of some selected strategic buildings has been estimated using ambient vibration and earthquake data. We analyzed the basic dynamic parameters of buildings chosen as target, by using continuous vibration measurements at different floors. The dynamic behavior of structures was evaluated considering both small strains induced by ambient vibrations and larger excitation levels due to the earthquakes occurrence. A practical approach to earthquake early warning in the investigated area was dealt with by using empirical relationships between parameters measured on the initial portion of seismic recordings and related to the earthquake magnitude and peak ground motion. In particular, we performed the first preliminary tests by using empirical relationships calibrated for the considered area and taking into account the geometry of the existing permanent seismic network deployed in the eastern Sicily. The estimated relationships have been used to provide onsite warning around a given seismic station and evaluate the potential damaging effects. The joint of EEW system and geophysical investigation shown in this work may be deemed a useful guide for the future implementation of the in real time seismic monitoring in the region.This work has been supported by the following project: “Attività di sviluppo sperimentale finalizzata alla riduzione del rischio sismico nella Sicilia Orientale” inside the PO-FESR 2007-2013 Sicilia; MED-SUV funded from the European Union Seventh Framework Programme (FP7) under Grant agreement n°308665. This work is sponsored by European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement n° 798480. We are thankful to Salvatore Rapisarda and Danilo Contrafatto to support us in the field work

Seismic amplification effects and soil, to, structure interaction study nearby a fault zone: the Tremestieri fault and Madre Teresa di Calcutta School (Catania)

Results of passive seismic surveys, in terms of both amplification and polarization effects in a section of the Tremestieri Etneo Fault (Sicily Eastern center - Catania) are discussed. For the purpose, velocimetric and accelerometric records of seismic ambient noise were analyzed. The polarization analysis of particle motion was performed and azimuthally dependent resonant frequencies were estimated. Ambient noise data were also used to assess the dynamic properties of a reinforced concrete building, located on the fault zone. The fundamental modes have been estimated through ambient noise recordings acquired by three-directional accelerometers, installed at the highest accessible floor and outside the building. The study revealed a clear oriented seismic amplification in the fault zone. This effect was observed in intensely jointed rock masses, located inside the fault area, as the result of specific geometries and significant directional impedance contrasts characterizing the area under study. The analyses show that the direction of the largest resonance motions has transversal relationship with the dominant fracture orientation. The directional amplification is inferred to be produced by stiffness anisotropy of the fault damage zone, with larger seismic motions high angle to the fractures. The results obtained are in complete agreement with those obtained by a previous study which analyzed the fault section located to the north-west.Finally, comparing the dynamic properties of the school building and the vibrational characteristics of the soil in the direction of maximum amplification, no clear resonant effect in the soil-structure interaction has been observed.This paper has been funded by the following research projects: “Attività di sviluppo sperimentale finalizzata alla riduzione del rischio sismico nella Sicilia Orientale” inside the PO-FESR 2007-2013 Sicilia; MED-SUV funded from the European Union Seventh Framework Programme (FP7) under Grant agreement n°308665. This work is sponsored by European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement n° 798480

THE SHALLOW MAGMA CHAMBER OF STROMBOLI

AbstractIn this work, we integrate artificial and natural seismic sources data to obtain high‐resolution images of the shallow inner structure of Stromboli Volcano. Overall, we used a total of 21,953 P readings from an active seismic experiment and an additional 2731 P and 992 S readings deriving from 269 local events. The well‐defined Vp, Vs, and Vp/Vs tomograms have highlighted the following: (i) the region where magma cumulates at shallow depths (2–4 km below sea level (bsl)), forming an elongated NE‐SW high‐velocity body (Vp ≥ 6.0 km/s and Vs ≥ 3.5 km/s), with a very fast velocity core (6.5 ≤ Vp < 7.0 km/s) of ~2 km3; (ii) the presence of some near‐vertical pipe‐like structures, characterized by relatively high P velocities values, mainly linked to past activity (e.g., Strombolicchio); and (iii) a near‐vertical pipe‐like volume with high Vp/Vs (1.78 ÷ 1.85), located beneath to the craters (down to ~1.0 km bsl), overlying a deeper region (1.0 to 3.0 km bsl) with low Vp/Vs (1.64 ÷ 1.69), interpreted as the actual and preferential pathway of magma toward the surface. Our results demonstrate the importance of combining passive and active seismic data to improve, in a tomographic inversion, the resolution of the volcanic structures and to discover where magma may be stored

Individual Patient Data Subgroup Meta-Analysis of Surgery for Spontaneous Supratentorial Intracerebral Hemorrhage

Peer reviewe

The Borehole Experiment: Investigation of Cortical Structures Through 3D Array Techniques

Over the last few years it is growing the need to monitor the volcanic activity with modern technology in order to mitigate volcanic hazard through the detection of any possible precursor phenomena. The use of high performance seismic stations, such as borehole instruments, may increase the signal to noise ratio (SNR), improving the capability to detect very small signals. Over the past 40 years much attention has been given to the use of seismic arrays to measure the slowness vector of coherent signals. The main advantage of seismic arrays consists in their ability to detect weak or emergent signals, and to allow for an effective noise reduction through multichannel waveform stacking. A reliable prediction of the ray-path back-propagated from the recording site to the source is strongly limited by the poor knowledge of the local shallow velocity structure. Usually in volcanic environments the propagation of seismic signals through the shallow layers is strongly affected by lateral heterogeneity, attenuation, scattering, and interaction with the free surface. Driven by these motivations, on May 2014, in collaboration with the colleagues of Osservatorio Vesuviano (INGV), we deployed a 3D seismic array in the area where the borehole seismic station called Pozzo Pitarrone is installed at a depth of about 130 meters. This will improve our knowledge about: • the structure of the top layer and its relationship with geology; • analysis of the signal to noise ratio (SNR) of volcanic signals as a function of frequency; • study of seismic ray-path deformation caused by the interaction of the seismic waves with the free surface; • evaluation of the attenuation of the seismic signals correlated with the volcanic activity. The results of these analyses will improve the general knowledge of wave propagation in the shallow layers and will give a new contribution to the seismic monitoring of Etna volcano.PublishedNicolosi (Catania), Italy1T. Struttura della Terr

Stable incidence but declining case-fatality rates of subarachnoid hemorrhage in a population

Objective: To characterize temporal trends in subarachnoid hemorrhage (SAH) incidence and outcomes over 5 time periods in a large population-based stroke study in the United States. Methods: All SAHs among residents of the Greater Cincinnati/Northern Kentucky region at least 20 years of age were identified and verified via study physician review in 5 distinct year-long study periods between 1988 and 2010. We abstracted demographics, care patterns, and outcomes, and we compared incidence and case-fatality rates across the study periods. Results: The incidence of SAH in the 5 study periods (age-, race-, and sex-adjusted to the 2000 US population) was 8.8 (95% confidence interval 6.8–10.7), 9.2 (7.2–11.2), 10.0 (8.0–12.0), 9.0 (7.1–10.9), and 7.7 (6.0–9.4) per 100,000, respectively; the trend in incidence rates from 1988 to 2010 was not statistically significant (p = 0.22). Advanced neurovascular imaging, endovascular coiling, and neurologic intensive care unit availability increased significantly over time. All-cause 5-day (32%–18%, p = 0.01; for trend), 30-day (46%–25%, p = 0.001), and 90-day (49%–29%, p = 0.001) case-fatality rates declined from 1988 to 2010. When we included only proven or highly likely aneurysmal SAH, the declines in case-fatality were no longer statistically significant. Conclusions: Although the incidence of SAH remained stable in this population-based region, 5-day, 30-day, and 90-day case-fatality rates declined significantly. Advances in surgical and medical management, along with systems-based changes such as the emergence of neurocritical care units, are potential explanations for the reduced case-fatality

Thrombolytic removal of intraventricular haemorrhage in treatment of severe stroke: results of the randomised, multicentre, multiregion, placebo-controlled CLEAR III trial

Background: Intraventricular haemorrhage is a subtype of intracerebral haemorrhage, with 50% mortality and serious disability for survivors. We aimed to test whether attempting to remove intraventricular haemorrhage with alteplase versus saline irrigation improved functional outcome. Methods: In this randomised, double-blinded, placebo-controlled, multiregional trial (CLEAR III), participants with a routinely placed extraventricular drain, in the intensive care unit with stable, non-traumatic intracerebral haemorrhage volume less than 30 mL, intraventricular haemorrhage obstructing the 3rd or 4th ventricles, and no underlying pathology were adaptively randomly assigned (1:1), via a web-based system to receive up to 12 doses, 8 h apart of 1 mg of alteplase or 0·9% saline via the extraventricular drain. The treating physician, clinical research staff, and participants were masked to treatment assignment. CT scans were obtained every 24 h throughout dosing. The primary efficacy outcome was good functional outcome, defined as a modified Rankin Scale score (mRS) of 3 or less at 180 days per central adjudication by blinded evaluators. This study is registered with ClinicalTrials.gov, NCT00784134. Findings: Between Sept 18, 2009, and Jan 13, 2015, 500 patients were randomised: 249 to the alteplase group and 251 to the saline group. 180-day follow-up data were available for analysis from 246 of 249 participants in the alteplase group and 245 of 251 participants in the placebo group. The primary efficacy outcome was similar in each group (good outcome in alteplase group 48% vs saline 45%; risk ratio [RR] 1·06 [95% CI 0·88–1·28; p=0·554]). A difference of 3·5% (RR 1·08 [95% CI 0·90–1·29], p=0·420) was found after adjustment for intraventricular haemorrhage size and thalamic intracerebral haemorrhage. At 180 days, the treatment group had lower case fatality (46 [18%] vs saline 73 [29%], hazard ratio 0·60 [95% CI 0·41–0·86], p=0·006), but a greater proportion with mRS 5 (42 [17%] vs 21 [9%]; RR 1·99 [95% CI 1·22–3·26], p=0·007). Ventriculitis (17 [7%] alteplase vs 31 [12%] saline; RR 0·55 [95% CI 0·31–0·97], p=0·048) and serious adverse events (114 [46%] alteplase vs 151 [60%] saline; RR 0·76 [95% CI 0·64–0·90], p=0·002) were less frequent with alteplase treatment. Symptomatic bleeding (six [2%] in the alteplase group vs five [2%] in the saline group; RR 1·21 [95% CI 0·37–3·91], p=0·771) was similar. Interpretation: In patients with intraventricular haemorrhage and a routine extraventricular drain, irrigation with alteplase did not substantially improve functional outcomes at the mRS 3 cutoff compared with irrigation with saline. Protocol-based use of alteplase with extraventricular drain seems safe. Future investigation is needed to determine whether a greater frequency of complete intraventricular haemorrhage removal via alteplase produces gains in functional status

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO