The Alaska Volcano Observatory (AVO) reported that a significant increase in low-frequency earthquakes (both shallow and deep-level earthquakes) started to develop in the region of Katmai volcanic cluster since May this year.
The shallow earthquake swarm is currently located 4 km north of Trident volcano at 5 km depth. Deep events are distributed beneath the area of Trident and Novarupta volcanoes at depths between 30 and 35 km. These types of earthquakes often suggest an elevated flux of magma under the surface accompanied by long-lasting of continuous tremor.
The seismic activity at Trident volcanic complex has continued at fluctuated levels since August 2022. In November 2022, the activity escalated and consisted of shallow earthquakes less than 5 mi (8 km) below sea level. Most quakes were less than magnitude 1, but dozens of magnitude 2 and 3 earthquakes have occurred. The earthquake rate averaged between 10 to 20 daily earthquakes, occasionally reaching rates several times higher. The largest event took place on 20 November with a magnitude M 4.6. Since early January, earthquakes have become more intense at an average rate of ten per day. In late February 2023, depths of quakes were mostly deep in the beginning, about 25 km, but became rapidly shallower at a depth approx. 5 km beneath the volcano over the following four days.
Following the elevated activity, the AVO volcano observatory raised the alert status to „yellow“ in February and still remains valid so far.
Moreover, deformation-based recordings detected a ground vertical uplift on the south flank on 3 June by 5 cm since 6 October 2022. Snow cover prohibits winter observations, which limits the ability to provide precise timing.
Prognosis
Migration of a new batch of magma beneath the surface increases the likelihood of potential eruption. However, the unrest under the volcanic group may last for weeks, months or even years and end up without imminent eruption.
Once magma becomes shallower and gets closer to the surface, this will likely lead to an inflation pattern change, increase of the seismic activity, ground surface temperatures and/or gas emissions. Unlike many active volcanoes, which consist of a large cone formed from repeated eruptions from a single vent, Trident eruptions tend to issue from new vents and form individual cones or domes. A new vent was formed during the most recent Trident eruption from 1953 to 1974. Therefore, if an eruption occurs, it is uncertain exactly where the vent would be, though monitoring data will likely help pinpoint the site as magma rises closer to the Earth’s surface.
Potential hazards
If an eruption were to occur, the main hazards would pose a spewed ashfall that could present a danger to aviation, marine travel and local communities and infrastructure.
The warning bulletin states that pyroclastic flows or lahars (mud-flows) or ballistic impacts of volcanic bombs could affect areas closer to the eruption site, near the edifice in particular.