While the unusually strong earthquake swarm under El Hierro Island continues, harmonic volcanic tremor has reappeared short time ago at about 16h10 UTC. The tremor, a low-frequency ground vibration, is thought to be caused by moving magma. It had been strong yesterday and correlated well with a southward propagation of earthquake locations, suggesting that magma at about 20 km depth flew from underneath the El Golfo area towards the EL Julan (south) coast, in a similar way as before the Oct 2011 eruption, but became blocked there, and did not reach the southern rift zone near La Restinga. After the...
