Seismic Swarm VS20211002.1 in the Canary Islands Region

The Canary Islands form a volcanic archipelago off the northwest coast of Africa, part of Spain. Their geology stems from a mantle hotspot beneath the African plate, producing a chain of shield volcanoes. The islands include Tenerife, La Palma, El Hierro, and Gran Canaria, with active volcanic systems such as Teide and Cumbre Vieja. Seismic activity frequently accompanies magma movement, resulting in swarms of low-to-moderate magnitude earthquakes at shallow to intermediate depths.

Swarm VS20211002.1 began at 09:13 on 1 October 2021 and concluded at 23:09 on 27 December 2021, spanning 2101 hours and 56 minutes. During this period, 6967 earthquakes were recorded in the Canary Islands region. Analysis of the first 100 events shows magnitudes ranging from 2.2 to 3.6, with the majority falling between 2.4 and 3.2. Depths clustered between 3 km and 35 km, indicating predominantly shallow crustal sources consistent with volcanic processes.

The initial sequence on 1 October featured events at 09:13 (magnitude 2.5, 10 km), 10:56 (3.2, 14 km), and 14:13 (3.6, 10 km). Subsequent days through 4 October maintained similar patterns, with peak magnitudes of 3.6 and depths rarely exceeding 35 km. This distribution suggests progressive stress release along volcanic fissures or magma pathways.

Historical records since 2000 indicate only three such swarms in the region. One occurred in 2020, while two took place in 2021, underscoring the episodic nature of seismic unrest tied to the archipelago’s volcanism. These events align with the islands’ long-term eruptive history, which includes documented activity at Cumbre Vieja and other centers over centuries.

The Canary Islands continue to experience monitoring through national and international networks, providing data essential for understanding hotspot-driven volcanism. Swarm VS20211002.1 contributes to this record by illustrating the scale and characteristics of recent unrest in the region.