Seismic Swarm S20230127.1 in the Canary Islands Region

On 27 January 2023, a seismic swarm designated S20230127.1 was recorded in the Canary Islands, Spain. The sequence began at 00:35 UTC and concluded at 15:57 UTC, encompassing 28 earthquakes over a span of 15 hours and 21 minutes. Magnitudes ranged from 1.8 to 2.6, with focal depths varying between 1 km and 46 km. The events clustered primarily in the central and eastern sectors of the archipelago, consistent with patterns observed in this volcanically active province.

The Canary Islands form an intraplate volcanic archipelago situated on the African tectonic plate, approximately 100 km off the northwest coast of Africa. Their origin is attributed to a mantle hotspot that has generated successive shield volcanoes over the past 20 million years. The islands exhibit a clear east-to-west age progression, with Fuerteventura and Lanzarote representing the oldest formations and El Hierro the youngest. This hotspot-driven volcanism produces frequent seismic swarms as magma ascends through the crust, fracturing rock and inducing microseismicity.

Historical records document numerous swarms preceding or accompanying eruptions. Notable examples include the 2011–2012 submarine eruption off El Hierro, which followed months of elevated seismicity, and the 2021 Cumbre Vieja eruption on La Palma, preceded by a swarm that began in September of that year. These episodes typically feature low-magnitude events (below 3.0) distributed across a range of depths, reflecting both shallow crustal adjustments and deeper magmatic processes.

The January 2023 swarm displayed characteristics common to Canary Islands unrest. Early events occurred at moderate depths around 12 km, followed by a cluster of deeper shocks between 30 km and 46 km during midday hours. Shallower activity resumed later, with several events at depths of 1–9 km. This vertical distribution suggests interaction between ascending magma and pre-existing fault systems within the oceanic crust and volcanic edifice. No surface deformation or eruptive activity was associated with this particular sequence.

Seismic monitoring in the region is maintained by Spain’s Instituto Geográfico Nacional, which operates a dense network of stations across the islands. Data from such networks allow precise location of events and tracking of swarm evolution, aiding in the differentiation between tectonic and volcanic sources. The 2023 swarm remained well below thresholds that would trigger elevated alert levels.

In summary, swarm S20230127.1 exemplifies the background seismic activity inherent to the Canary Islands’ volcanic setting. Continued monitoring remains essential given the archipelago’s history of episodic unrest linked to its hotspot origin.

References

Instituto Geográfico Nacional (IGN). Seismic catalog and volcanic monitoring reports for the Canary Islands.
Global Volcanism Program, Smithsonian Institution. Canary Islands volcanic summaries.
Carracedo, J.C. et al. (various publications). Geological evolution of the Canary Islands hotspot.