Mayon Volcano Bulletin

09 August 2006

8:00 AM

Seismic activity and gas output at Mayon (13.2576°N, 123.6856°E) over the past 24-hours declined anomalously. The number of volcanic quakes decreased from the previous 109 to only 21 events since six (6) o’clock yesterday morning. The Sulfur Dioxide (SO₂) emission rate also decreased from a high of 12,745 tonnes per day (t/d) measured on 07 August to 7,829 t/d yesterday. These changes or large swings in activity, along with the recent explosions, are indicators of the variability of the conditions of the magma system inside the volcano, and also reflect the high prevailing unrest.

Although clouds obscured the summit the whole observation period, seismic instruments continued to record ground vibrations induced by the flow and impact of lava fragments onto the volcano’s slopes. About 294 brief episodes of tremor were therefore generated as hot lava blocks tumbled from the accumulating lava deposits upslope in the general directions facing Mabinit and Bonga.

PHIVOLCS reminds the public that Alert Level 4 is still in effect, to indicate the very high probability of a hazardous explosive eruption. Due to adverse effects of a highly explosive eruption, the EXTENDED DANGER ZONE (EDZ), defined as an area within eight (8) kilometers from the summit crater located in the general southeast sector, should be observed. At other areas around the volcano, this EDZ is seven (7) kilometers from the summit crater. The public is therefore enjoined to observe all existing precautionary measures relevant to this alert level. Areas outside of the EDZ are advised to be on the alert for updates regarding their status for possible evacuation in case volcanic activity intensifies.