We analyzed the P and S wave displacement spectra of 717 microearthquakes in the moment range 4 × 10 9 À 2 × 10 14 N m recorded at the dense networks operating in southern Apennines (Italy) and deployed along the 1980 M s 6.9 Irpinia earthquake fault zone. Source, attenuation, and site parameters are estimated by using a parametric modeling approach, which is combined with a multistep, nonlinear inversion strategy. We found that in the analyzed frequency band, an attenuation model with constant Q has to be preferred to frequency-dependent Q models. Consistent estimates of the median P and S quality factors e Q P ¼ 167 (90; 296) and e Q S ¼ 226 (114; 417) are obtained from two different techniques and relatively high values of Q S /Q P (median value 1.3, (0.8; 2.1)) are found in the same depth range where high V P /V S and a peak in seismicity distribution are observed. This is the evidence for a highly fractured, partially, or completely fluid-saturated medium embedding the Irpinia fault zone, down to crustal depths of 15-20 km. A nearly constant stress drop ( f Δσ ¼ 1:4 MPa, (0.4; 5.0)) and apparent stress (e τ a ¼ 0:1 MPa, (0.03, 0.4)) scaling of P and S corner frequencies and seismic energies is observed above a seismic moment value of about 10 11 N m. The measured radiation efficiency is low (g η SW ¼ 0:06; 0:03; 0:13 ð Þ ), e.g., the radiated energy is only a small fraction of the whole energy spent by friction and fracture development. A large positive dynamic overshoot (high dynamic shear strength) can be the dominant mechanism controlling the microearthquake fractures along the Irpinia fault zone.

The prevalence of nasal polyps in a group of paediatric patients with cystic fibrosis was prospectively studied in comparison with a control group with cystic fibrosis but without polyps. Clinical variables, including pulmonary function tests, skin testing and mucociliary transport, were carried out in both groups, as well as genotype analysis. Endoscopic intranasal evaluation identified polyps in 29 of 89 patients (33%). Statistical analysis revealed that patients with nasal polyposis had better pulmonary function, a higher rate of Pseudomonas aeruginosa colonization, more hospitalizations, and more prevalence of allergy to Aspergillus fumigatus than did the comparison group. We found no statistically different genotype distribution between the polyposis and the control group. However, it can be emphasized that the prevalence of the compound heterozygous genotype is higher in the nasal polyposis group than in controls. Our observations suggest that other genetic and environmental factors could play an important role in the development of nasal polyposis.

The analysis of similar earthquakes, such as events in a seismic sequence, is an effective tool with which to monitor and study source processes and to understand the mechanical and dynamic states of active fault systems. We are observing seismicity that is primarily concentrated in very limited regions along the 1980 Irpinia earthquake fault zone in Southern Italy, which is a complex system characterised by extensional stress regime. These zones of weakness produce repeated earthquakes and swarm-like microearthquake sequences, which are concentrated in a few specific zones of the fault system. In this study, we focused on a sequence that occurred along the main fault segment of the 1980 Irpinia earthquake to understand its characteristics and its relation to the loading-unloading mechanisms of the fault system.

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International audienceThe 6 April 2009 Mw 6.3 L'Aquila earthquake, central Italy, has been recorded by the Irpinia Seismic Network (ISNet) about 250 km southeast of the epicenter. Up to 19 three-component accelerometer stations could be used to infer the main source parameters with different seismological methods. We obtained an approximate location of the event from arrival times and array-based back-azimuth measurements and estimated the local magnitude (6.1) from an attenuation relation for southern Italy. Assuming an omega-square spectral model, we inverted S-wave displacement spectra for moment magnitude (6.3), corner frequency (0.33 Hz), stress drop (2.5 MPa), and apparent stress (1.6 MPa). Waveform modeling using a point source and an extended-source model provided consistent moment tensors with a centroid depth around 6 km and a prevalently normal fault plane solution with a dominant directivity toward the southeast. The relatively high corner frequency and an overestimated moment magnitude of 6.4 from moment tensor inversions are attributed to the rupture directivity effect. To image the rupture geometry, we implemented a beamforming technique that back-projects the recorded direct P-wave amplitudes into the earthquake source region. A northwest-southeast striking rupture of 17 km length is imaged, propagating with an average velocity up to 3 km/s. This value is significantly higher than our estimate of 2.2 km/s from S-wave spectra. Our case study demonstrates that the use of array techniques and a dense accelerometer network can provide quick and robust estimates of source parameters of moderate-sized earthquakes located outside the network