Earthquake swarm at Soufriere Hills volcano, Montserrat
A swarm of earthquakes shook the Soufriere Hills volcano in Montserrat on Thursday, December 19, 2024. The MVO reported 93 Volcano-Tectonic (VT) earthquakes during this period with the 2 largest measuring up to M3.3.
Soufrière Hills volcano - Montserrat. Image credit: MVO
An earthquakes swarm began at Soufriere Hills volcano at 10:20 LT (14:20 UTC) on December 19 and continued for approximately 90 minutes, prompting temporary restrictions in hazard zones.
The earthquakes occurred at depths of 2 to 3 km (1.2 to 1.9 miles) beneath the volcano’s dome. No ash venting or changes in fumarole activity were observed although the swarm had a higher count of events.
Seismic activity during the swarm peaked with 2 earthquakes measuring M3.3, a level capable of causing noticeable ground tremors in nearby areas. Around 3 000 people live within a 5 km (3 miles ) radius, 9 400 within 10 km (6.2 miles), and 448 900 within 100 km (62 miles).
“This swarm was probably the most intense seen since the pause began on February 11, 2010,” said Montserrat Volcano Observatory (MVO).
To ensure public safety, MVO implemented temporary restrictions in Zone V, a designated hazard area near the volcano. Seismic activity had returned to normal levels by 12:40 LT (16:40 UTC) and access to the restricted zone was restored following MVO’s confirmation of safety.
The sequence of VT earthquakes surpassed a similar event on March 23, 2012, which involved 54 VT earthquakes and ash venting. That event lasted nearly 3 hours, with the strongest earthquake reaching M3.6.
Despite the differences in intensity and associated phenomena, both events exhibited similar depths and seismic characteristics.
The Soufriere Hills Volcano is a complex andesitic stratovolcano with a summit elevation of 915 m (3 002 feet). The summit area includes lava domes formed along an east-southeast trending zone. The volcano has a history of major eruptions and periods of heightened seismic activity.
Main eruptions include long-term events from July 18, 1995, to February 5, 2013, which caused extensive pyroclastic flows, ashfalls, and lava-dome growth. The eruptions led to the evacuation of the southern half of the island and the destruction of the capital city, Plymouth.
The geological structure also includes English’s Crater, a 1 km (0.62-mile) wide formation created by an edifice collapse approximately 2 000 years ago. The event produced submarine debris avalanches and its deposits can still be observed on the flanks of the volcano.
References:
1 MVO Activity Report – MVO – December 19, 2024
2 Soufrière Hills – GVP – Accessed on December 21, 2024
Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.
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