La Palma volcano update: Volcano remains calm, but small quakes continue
Fri, 17 Dec 2021, 16:4516:45 PM | BY: T
View of La Palma's new volcanic edifice from the Llano del Jable Astronomical Viewpoint at 11.00 am Canarian time (image: INVOLCAN / Twitter)
Depth vs time of quakes under La Palma showing an apparent increase of quake numbers, especially at depth
3D-View of quakes under the island since 14 Dec (image: info.igme.es)
Quakes and combined seismic energy past 30 days - maybe a very weak increase in the past 48 hours, but overall decreasing trend
Current seismic signal at La Palma's TBT station - absence of tremor makes tiny quakes visible and detectable (image: IGN)
For 3 days, no eruptive activity has taken place, and the likelihood that the eruption is actually over is clearly increasing. The cone only shows mild degassing and no lava flows are active any more.
Current tremor amplitude - near zero (image: IGN)
Official confirmation when the eruption is declared over will likely need to wait a little longer. Some doubt remains as to the significance of the continuing earthquake activity: although of low energy and overall on a decreasing trend, it remains significant, and could indicate that magma at depth is still able to pressurize and fracture rocks at depth and create intrusions that might eventually allow it to rise further. However, this is far from certain - it could also be adjustments of the system triggered by the massive shifts of masses that has occurred during the eruption. In the latter case, the quakes should slowly die out.
During the past 24 hours, there were 3 quakes of magnitudes 3.3-3.5 at 35-36 km depth, in addition to many more smaller quakes (22 quakes of magnitudes 2.0-2.9 and 48 quakes below magnitude 2.0). If looking at the various maps published of recent quakes, it might seem that there is a a strong increase of quakes. This apparent increase, however, is mostly in the number of quakes, especially for those in the deeper region around 30-40 km. This is mostly an artifact caused by the absence of volcanic tremor, which acted as noise during the eruption and was simply hiding smaller quakes in its signal. Now, the very sensitive seismic devices are again able to pick up very small quakes below magnitudes 2, as well as quakes deeper down (whose signals at the surface are much weaker). In other words, most of the apparent increase of quakes is only an increase in detection sensitivity. Still, a weak increase in the total energy of the seismic activity remains visible for the past 48 hours or so. With most likelihood, it is part of a normal fluctuation, but nobody can be sure.
Wed, 15 Dec 2021, 18:15
No new activity has been reported at the eruption site since it ceased yesterday. Chances increase that the eruption is over, although this is far from certain (read below for more background). ... Read all
Wed, 15 Dec 2021, 16:14
La Palma volcano (Spain) - Smithsonian / USGS Weekly Volcanic Activity Report for 15 December-21 December 2021 (Continuing Activity)
Observations at La Palma on 15 December showed no lava flowing from vents at the W base of the main cone, from tubes, or at the lava delta in the Las Hoyas area. During 15-20 December tremor levels were at background levels and seismicity was very low at all depths. Sporadic gas emissions rose from the vents and from cooling lava flows. ... Read all