The study of the preparation phase of large earthquakes is essential to understand the physical processes involved, and potentially useful also to develop a future reliable short-term warning system. Here we analyse electron density and magnetic field data measured by Swarm three-satellite constellation for 4.7 years, to look for possible in-situ ionospheric precursors of large earthquakes to study the interactions between the lithosphere and the above atmosphere and ionosphere, in what is called the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC). We define these anomalies statistically in the whole space-time interval of interest and use a Worldwide Statistical Correlation (WSC) analysis through a superposed epoch approach to study the possible relation with the earthquakes. We find some clear concentrations of electron density and magnetic anomalies from more than two months to some days before the earthquake occurrences. Such anomaly clustering is, in general, statistically significant with respect to homogeneous random simulations, supporting a LAIC during the preparation phase of earthquakes. By investigating different earthquake magnitude ranges, not only do we confirm the well-known Rikitake empirical law between ionospheric anomaly precursor time and earthquake magnitude, but we also give more reliability to the seismic source origin for many of the identified anomalies.

[1] The Kasatochi 2008 eruption was detected by several infrared satellite sensors including Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Very High Resolution Radiometer (AVHRR), and Atmospheric Infrared Sounder (AIRS). In this work a comparison between the volcanic cloud SO 2 and ash retrievals derived from these instruments has been undertaken. The SO 2 retrieval is carried out by using both the 7.3 and 8.7 mm absorption features while ash retrieval exploits the 10-12 mm atmospheric window. A radiative transfer scheme is also used to correct the volcanic ash effect on the 8.7 mm SO 2 signature. As test cases, three near-contemporary images for each sensor, collected during the first days of the eruption, have been analyzed. The results show that the volcanic SO 2 and ash are simultaneously present and generally collocated. The MODIS and AVHRR total ash mass loadings are in good agreement and estimated to be about 0.5 Tg, while the AIRS retrievals are slightly lower and equal to about 0.3 Tg. The AIRS and MODIS 7.3 mm SO 2 mass loadings are also in good agreement and vary between 0.3 and 1.2 Tg, while the MODIS ash corrected 8.7 mm SO 2 masses vary between 0.4 and 2.7 Tg. The mass increase with time confirms the continuous SO 2 injection in the atmosphere after the main explosive episodes. Moreover the difference between the 7.3 and 8.7 mm retrievals suggests a vertical stratification of the volcanic cloud. The results also confirm the importance of the ash correction; the corrected 8.7 mm SO 2 total masses are less than 30-40% of the uncorrected values.

On 6 April 2009, a Mw = 6.3 earthquake occurred in the central Apennines (Italy) damaging the city of L'Aquila and the surrounding country. We relocate the October 2008 to 6 April 2009 foreshocks and about 2000 aftershocks occurred between 6 and 30 April 2009 by applying a double‐difference technique and determine the stress field from focal mechanisms. The events concentrate in the upper 15 km of the crust. Three main NW‐SE to NNW‐SSE striking, 30°–45° and 80°–90° dipping faults were activated during the seismic sequence. Among these, a normal fault and a thrust were reactivated with dip‐slip movements in response to NE‐SW extension. The structural maturity of the seismogenic fault system is lower than that displayed by other systems in southern Apennines because of the lower strain rate of the central sector of the chain with respect to the southern one. VP/VS increases progressively from October 2008 to the 6 April 2009 main shock occurrence along a NW‐SE strike because of an increment in pore fluid pressure along the fault planes. Pore pressure diffusion controls the space‐time evolution of aftershocks. A hydraulic diffusivity of 80 m2 s−1 and a seismogenic permeability of about 10−12 m2 suggest the involvement of gas‐rich (CO2) fluids within a highly fractured medium. Suprahydrostatic, high fluid pressure (about 200 MPa at 10 km of depth) within overpressurized traps, bounded by preexisting structural and/or lithological discontinuities at the lower upper crust boundary, are required to activate the April 2009 sequence. Traps are the storage zone of CO2‐rich fluids uprising from the underlying, about 20 km deep, metasomatized mantle wedge. These traps easily occur in extensional regimes like in the axial sector of Apennines but are difficult to form in strike‐slip regimes, where subvertical faults may cross the entire crust. In the Apennines, fluids may activate faults responsible for earthquakes up to Mw = 5–6. Deep fluids more than tectonic stress may control the seismotectogenesis of accretionary wedges.

We find that the double-difference relocated seismicity, which occurred over the last 30 years at Campi Flegrei, was triggered by the uprising of fluids preferentially concentrated along onshore and offshore NW striking preexisting caldera faults. Focal volumes of the 2005-2014 seismicity do not overlap that of the 1982-1984 period, when a major uplift of 1.8 m occurred in the central sector of the caldera. This indicates a transition from an elastic to a plastic behavior due to fluid saturation and heating of the rocks in the hydrothermal reservoir. The 2012-2014 deeper earthquakes are located in a low V P ∕V S zone at the western boundary of the hydrothermal reservoir, where a volume increase from a magmatic body at 3.5 km depth has been recognized. The progressive rheological change from elastic to plastic in the upper 4 km of the crust implies that a slow upward migration of magma may not necessarily be preceded by earthquakes or swarms.

BackgroundSurgical site infection (SSI) is a common post-operative complication causing significant morbidity and mortality. Many SSI occur after discharge from hospital. Post-discharge SSI surveillance in low and middle income countries needs to be improved.MethodologyWe conducted an observational cohort study in Dodoma, Tanzania to examine the sensitivity and specificity of telephone calls to detect SSI after discharge from hospital in comparison to a gold standard of clinician review. Women undergoing caesarean section were enrolled and followed up for 30 days. Women providing a telephone number were interviewed using a structured questionnaire at approximately days 5, 12 and 28 post-surgery. Women were then invited for out-patient review by a clinician blinded to the findings of telephone interview.ResultsA total of 374 women were enrolled and an overall SSI rate of 12% (n = 45) was observed. Three hundred and sixteen (84%) women provided a telephone number, of which 202 had at least one telephone interview followed by a clinical review within 48 h, generating a total of 484 paired observations. From the clinical reviews, 25 SSI were diagnosed, of which telephone interview had correctly identified 18 infections; telephone calls did not incorrectly identify SSI in any patients. The overall sensitivity and specificity of telephone interviews as compared to clinician evaluation was 72 and 100%, respectively.ConclusionThe use of telephone interview as a diagnostic tool for post-discharge surveillance of SSI had moderate sensitivity and high specificity in Tanzania. Telephone-based detection may be a useful method for SSI surveillance in low-income settings with high penetration of mobile telephones.