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.

Changes in Diffuse Degassing From the Summit Crater of Teide Volcano (Tenerife, Canary Islands) Prior to the 2016 Tenerife Long‐Period Seismic Swarm

“…The seismological characteristics of the swarm indicated it was caused by a substantial injection of magmatic fluids into the hydrothermal system (D'Auria et al, 2019). Considering that during 2016 and 2017 no significant ground deformation was recorded on Tenerife, it is unlikely that the fluids originated from a shallow magmatic intrusion (D'Auria et al, 2019). Instead, D'Auria et al (2019) suggested the source was a small magma reservoir located beneath the seismic source, which released considerable amounts of magmatic fluid as a consequence of some instability or disturbance of the system.…”

“…On October 2, 2016, a remarkable seismic swarm of long‐period events, starting at 13:16 UTC until 18:34 UTC of the same day (D'Auria et al., 2019) was recorded beneath Tenerife Island. This significant seismic event consisted of at least 766 discrete events; overlapping of events during the initial and final phases, formed a continuous volcanic tremor.…”

“…The source of the swarm was located beneath the southern rim of Las Canadas caldera at an approximate depth of 8.6 km b.s.l. The seismological characteristics of the swarm indicated it was caused by a substantial injection of magmatic fluids into the hydrothermal system (D'Auria et al., 2019). Considering that during 2016 and 2017 no significant ground deformation was recorded on Tenerife, it is unlikely that the fluids originated from a shallow magmatic intrusion (D'Auria et al., 2019).…”

“…Background microseismicity normally occurs beneath Tenerife (D'Auria et al., 2019). A minor seismo‐volcanic unrest, interpreted as a result of a small magmatic intrusion with subsequent release of magmatic gases, took place between 2004 and 2005.…”

“…D'Auria et al. (2019) hypothesized two possible mechanisms: the release of fluids which had accumulated at the top of a magma reservoir or the injection of a small batch of fresh magma into a cooling magma reservoir, triggering convective mixing.…”