Unrest at Cayambe Volcano revealed by SAR imagery and seismic activity after the Pedernales subduction earthquake, Ecuador (2016)

International audienceFor the first time in decades, a sudden increase in seismicity has been observed and monitored at Cayambe volcano in Ecuador, in 2016. This seismic unrest, which occurred a few months after the April 2016, Mw 7.8 Pedernales subduction earthquake, has raised many questions, especially as there is no record of recent eruptions at Cayambe volcano. Here we analyze a time series of 104 images from Sentinel 1 (SAR) data spanning the period 2014–2018 using the NSBAS processing chain in order to quantify surface deformation around this potentially explosive and ice-covered volcano. We evidence a large-scale uplift reaching a maximum mean displacement rate of about 0.44 cm/yr in Line of Sight. This uplift is mainly due to a significant and sudden acceleration of the deformation pattern, focused on the SE flank starting in November 2016. We model this signal as related to magma emplacement at around 6 km depth below the summit, with a sudden volume influx of about 2.6 million m3. The inflation and surface deformation pattern is concomitant in time with two Mw 3 seismic events recorded at Cayambe volcano in November 2016 and is consistent with the location at the summit of the volcano-tectonic (VT) seismic swarm from September 2016 onwards. This VT swarm follows an earlier swarm in June 2016 located on the northern side of the volcano and closer to a western branch of the Chingual-Cosanga-Pallatanga-Puna (CCPP) fault system, that plays a major role in accommodating plate tectonic processes in South America. We thus propose that static stress changes from the Pedernales megathrust earthquake triggered magma ascent below the Cayambe volcano, through reactivation of the CCPP fault system. Finally, volcanic hazards around Cayambe ice-capped volcano, previously dormant for the last 300 years, should be reassessed in light of this recent unrest

A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee

Many clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of clinical thrombotic events. Aspirin and ticlopidine have been shown to be effective, but both have potentially serious adverse effects. Clopidogrel, a new thienopyridine derivative similar to ticlopidine, is an inhibitor of platelet aggregation induced by adenosine diphosphate. METHODS: CAPRIE was a randomised, blinded, international trial designed to assess the relative efficacy of clopidogrel (75 mg once daily) and aspirin (325 mg once daily) in reducing the risk of a composite outcome cluster of ischaemic stroke, myocardial infarction, or vascular death; their relative safety was also assessed. The population studied comprised subgroups of patients with atherosclerotic vascular disease manifested as either recent ischaemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease. Patients were followed for 1 to 3 years. FINDINGS: 19,185 patients, with more than 6300 in each of the clinical subgroups, were recruited over 3 years, with a mean follow-up of 1.91 years. There were 1960 first events included in the outcome cluster on which an intention-to-treat analysis showed that patients treated with clopidogrel had an annual 5.32% risk of ischaemic stroke, myocardial infarction, or vascular death compared with 5.83% with aspirin. These rates reflect a statistically significant (p = 0.043) relative-risk reduction of 8.7% in favour of clopidogrel (95% Cl 0.3-16.5). Corresponding on-treatment analysis yielded a relative-risk reduction of 9.4%. There were no major differences in terms of safety. Reported adverse experiences in the clopidogrel and aspirin groups judged to be severe included rash (0.26% vs 0.10%), diarrhoea (0.23% vs 0.11%), upper gastrointestinal discomfort (0.97% vs 1.22%), intracranial haemorrhage (0.33% vs 0.47%), and gastrointestinal haemorrhage (0.52% vs 0.72%), respectively. There were ten (0.10%) patients in the clopidogrel group with significant reductions in neutrophils (< 1.2 x 10(9)/L) and 16 (0.17%) in the aspirin group. INTERPRETATION: Long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischaemic stroke, myocardial infarction, or vascular death. The overall safety profile of clopidogrel is at least as good as that of medium-dose aspirin