First recorded eruption of Nabro volcano, Eritrea, 2011

We present a synthesis of diverse observations of the first recorded eruption of Nabro volcano, Eritrea, which began on 12 June 2011. While no monitoring of the volcano was in effect at the time, it has been possible to reconstruct the nature and evolution of the eruption through analysis of re- gional seismological and infrasound data and satellite remote sensing data, supplemented by petrological analysis of erupted products and brief field surveys. The event is notable for the comparative rarity of recorded historical eruptions in the region and of caldera systems in general, for the prodi- gious quantity of SO2 emitted into the atmosphere and the significant human impacts that ensued notwithstanding the low population density of the Afar region. It is also relevant in understanding the broader magmatic and tectonic signifi- cance of the volcanic massif of which Nabro forms a part and which strikes obliquely to the principal rifting directions in the Red Sea and northern Afar. The whole-rock compositions of Editorial responsibility: G. Giordano the erupted lavas and tephra range from trachybasaltic to trachybasaltic andesite, and crystal-hosted melt inclusions contain up to 3,000 ppm of sulphur by weight. The eruption was preceded by significant seismicity, detected by regional networks of sensors and accompanied by sustained tremor. Substantial infrasound was recorded at distances of hundreds to thousands of kilometres from the vent, beginning at the onset of the eruption and continuing for weeks. Analysis of ground deformation suggests the eruption was fed by a shal- low, NW–SE-trending dike, which is consistent with field and satellite observations of vent distributions. Despite lack of prior planning and preparedness for volcanic events in the country, rapid coordination of the emergency response miti- gated the human costs of the eruption

Pre-seismic radio anomaly observed on the occasion of the MW=6.5 earthquake occurred in Crete on October 12, 2013

On October 12, 2013 an earthquake with Mw=6.5 occurred in the southern Hellenic Arc, about 20km off the west coast of Crete. The mainshock, whose focal depth is of the order of 40km, was followed by aftershocks felt in the nearby cities and villages, even though the aftershock sequence was rather poor. The epicenter is located at about 60 km from the CRE receiver of the European VLF/LF Radio Network. Some day before the earthquake a clear disturbance appeared in one of the ten radio signals sampled by the CRE receiver . The disturbance, considered as an anomaly, appears in the 216 kHz radio signal radiated by the transmitter MCO that is the main broadcasting facility for long and medium wave broadcasting of Radio Monte Carlo near Roumoules, France. The site is an exclave of Monaco and extraterritorial area. The signal radiated by MCO transmitter can be well received, mainly at night time, in whole Europe. The radio path MCO-CRE crosses exactly the epicenter area of the previous earthquake. Here we present a detailed study of the anomaly by means of statistical and spectral tools and analyze also the behavior of other sampled radio signals in the European network, and take into account other possible causes of disturbances. We conclude that the possibility that the disturbance in the MCO radio signal is a precursor of the earthquake is rather convincing

The seismicity of Ghana

Although West Africa is generally an area of very low seismicity, an exception is a concentration of activity in Southern Ghana, especially near to the capital, Accra, which was heavily damaged by earthquakes in 1862 and 1939. Modern instrumental seismicity is poorly understood due to the limitations of seismic monitoring in the country. In this study, all available data are brought together to provide an earthquake catalogue for Ghana, and a new interpretation of the data for the 1862 earthquake is made. It is tentatively suggested that much of the recorded seismicity around Accra is in fact a very protracted aftershock sequence of the 1862 event