ALBERT

Description: The 2021 Tajogaite eruption in La Palma, Canary Islands, was accompanied by strong volcanic tremor. In September 2021, during the first two weeks of eruption, we deployed two small-aperture seismic arrays. We chose two locations around Montaña Caldero and Llano del Jable, located about 4 km SE and 2 km NE of the eruption site. The arrays were composed of 1 three-component and 9 vertical-component short-period seismometers, sampled at 100 sps by a 12-channel data acquisition system. In each array, the receivers were spread with an aperture of about 400 m. Although they operated intermittently due to failures in the power supply related to ash fall, they provided long time series of multichannel seismic data that allow for the characterization of the syn-eruptive tremor. The analysis of the recorded wavefields reveals a persistent tremor source linked to the activity of the eruptive vents. The main component of the wavefield in the 1-3 Hz frequency band propagates with apparent slowness around 1 s/km, impinging on the arrays from directions of ~300 and 260ºN, respectively. These directions are slightly deviated from the active vents azimuths, a fact that we attribute to propagation effects produced by the topography and heterogeneous velocity structure. Subtle variations in the apparent slowness and propagation azimuths are investigated using the relative slowness estimate method, that allows for a precise determination of the apparent slowness vectors.