Weekly Report 31 March – 7 April 2017

Activity at the Soufrière Hills Volcano remains low.

The seismic network recorded two volcano-tectonic earthquakes this week.

Measurements of the SO2 flux were taken on 6 and 21 of January this year, with average values of 73 and 78 tonnes per day respectively. These are lower than the values of 151 and 213 tonnes per day measured on 7 November 2016, and lower than the long-term average of about 340 tonnes per day recorded by the permanent gas monitoring network prior to late 2015. It is not a simple task to compare these results. The recent values were taken in less than ideal conditions during short helicopter traverses beneath the gas plume – less than 20 minutes for 8 scans. Values from the permanent network are averages over a much longer period, typically 8 hours. Both methodologies require complex processing of the data, including corrections for the wind speed, which can introduce large errors in the result. It will not be possible to conclude with any certainty that there has been a change in the SO2 flux from the volcano until the new permanent gas network is installed in the next few months. Until that time, MVO will continue to take measurements from the helicopter whenever the opportunity arises.

Pyroclastic flows can occur at any time without warning on any side of the volcano, including Gages from where they can travel rapidly into Plymouth. Tracks across the Belham Valley can be destroyed or heavily modified by flash flooding or lahars, and caution should be exercised crossing the valley during and after rainfall.

The Hazard Level is 1. There is no public access to Zone V, including Plymouth. Maritime Zones E and W are daytime transit only between sunrise and sunset (boats may sail through the zone but must not stop). Anyone who ignores these restrictions is liable to be prosecuted.

This report along with additional information on the Soufrière Hills Volcano and the Hazard Level System can be found at the MVO website: www.mvo.ms. You can also follow @mvoms on both Facebook and Twitter.

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