The 2016 Tenerife (Canary Islands) Long-Period Seismic Swarm

Abstract

On 2 October 2016, a significant seismic swarm of long-period events was recorded on Tenerife (Canary Islands, Spain). The swarm lasted more than 5 hr and consisted of at least 766 detected events. We found a positive correlation between the amplitude of each event and the preceding interevent time together with a stability of the spectral properties and waveform similarity during most of the swarm duration. Toward the end of the swarm, individual events merged into a continuous tremor. These observations can be explained by postulating an unsteady transonic choked flow within a crack-like conduit as a source mechanism for this swarm. The flow resulted from a sudden discharge of magmatic fluids from a pressurized reservoir into the hydrothermal system of Tenerife. The injected fluids reached the surface starting about 1 month after the swarm, as evidenced by the macroscopic increase in the diffuse CO2 emissions from the crater of Teide volcano. The lack of ground deformation and the absence of relevant seismicity at depths greater than 10 km exclude the ascent of a basaltic magma batch as a causative source mechanism. Instead, we hypothesize the sudden release of fluids accumulated at the top of a magma chamber as a possible mechanism. Another possibility is the injection of a small batch of mafic magma into a cooling magma chamber, triggering a convective mixing. Both cases imply the presence of a magma chamber at depths greater than 8.6 km. These results have important implications for the development of the volcano monitoring system of Tenerife.