Poas volcano (Costa Rica) - Smithsonian / USGS Weekly Volcanic Activity Report for 7 September-13 September 2022 (Continuing Activity)

On 9 September OVSICORI-UNA reported that activity at Poás had increased since mid-August, characterized by notably increased seismicity. Seismic signals consisted of tremors with variable amplitudes and durations, prolonged harmonic tremors, and some long-period earthquakes with magnitudes greater than those recorded during 2022; there was no increase in low-frequency earthquakes. The energy of the seismicity had also dramatically increased in the previous few days.
Sulfur dioxide emissions around the crater were mainly stable at 100 tons per day, though on a few occasions the concentrations were higher; about 300 tons per day was recorded during 17-18 August and higher than 500 tons per day was recorded on 2 September. The volume of water in Boca A lake had significantly increased during August 2021-September 2022, stabilizing at 1.4 million cubic meters between July and September with minor variations measured from week to week. Convection cells in the lake were more active and a new one formed in the N part of the lake (over the Boca C vent) since mid-August.
OVSICORI-UNA stated that these data indicated disturbances to the shallow (less than 2 km) hydrothermal system and did not reflect an influx of magma. Fumarolic degassing and lake convection continued during 9-13 September.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)
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From: Global Volcanism Program, 2022. Report on Poas. In: Mayberry, G (ed.), Weekly Volcanic Activity Report 7 September-13 September 2022. Smithsonian Institution and US Geological Survey.