Underwater records of submarine volcanic activity: El Hierro (Canary Islands 2011–2012) eruption

Monitoring submarine volcanic eruptions is quite an ambitious task, and it is difficult to accomplish. We present the monitoring of a submarine volcanic eruption that took place near the southernmost emerged land of El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. Right after the beginning of the eruption, in mid-October 2011, a geophone array was deployed offshore for the purpose of monitoring the submarine eruptive activity signals. It acquired continuous data from October 2011 to May 2012, sometime after the end of the eruption. The array consisted of 8 high frequency, 3-component geophones assembled into a cable string, with 6 m of separation. The geophone string was installed in La Restinga Harbor at a distance of less than 2 km away from the volcanic edifice. The dataset acquired with the array is a unique continuous acoustic record of the activity associated with the eruption. We analyzed the continuous signal of the eruptive activity, with special interest in high frequency events. Our results show that the geophone array was recording acoustic waves from a back-azimuth source compatible with the position of the submarine vent, travelling at a speed of 1510 m/s, compatible with the speed of sound in the water. Acoustic data shows a good correlation with the seismic data recorded on land and with the observed sea surface activity (ash, lava emission and degassing) indicating that this methodology can be successfully used in cases of remote submarine eruptions.
M.J. Jurado's research was funded by the Spanish Ministry project CGL2010-21568.