Philippines

Philippines: NDCC Update - Sitrep No. 23 Mayon Volcano update

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DATE: 04 January 2010, 7:00 AM

Sources: DOST-PHIVOLCS, DSWD, OOH, DepEd, OCDRC-V, ALBAY PDCC, AFP, JTF MAYON, DPV11H V

l. SITUATION OVERVIEW

Alert Level

On 2 January, 7:00 PM, DOST-PHIVOLCS had lowered the alert level of Mayon Volcano from Alert Level 4 to Alert Level 3 to reflect the overall gradual decrease of activity. Alert level 3 means that there is less probability of a hazardous explosive eruption

However, the lowering of the alert should not be interpreted that the unrest of the volcano has ceased. If there is resurgence in the volcano's activity and the potential for explosive eruptions is perceived to be forthcoming, the alert level may be raised back to 4 but if there is noticeable downward trend in the monitored parameters, then the alert will be further lowered to Alert Level 2

Observations

As of 7:00 AM 4 January 2010, Mayon Volcano's seismic monitoring network detected 7 volcanic earthquakes and 33 rockfall events related to the detachment of lava fragments at the volcano's upper slopes during the past 24-hour observation period

Steaming activity was not observed due to thick clouds that covered the summit crater. Pale crater glow was observed last night, 3 January.

Sulfur Dioxide (S02) measurement was not conducted yesterday due to rain that occurred aver the volcano area. Emission rate in morning of 2 January 2010 was measured at an average value of 2,094 tonneslday.

The PAF aircraft was requested to be on standby for aerial survey around Mayon Volcano as soon as weather improves

From 28 December to present, a declining trend in Mayon Volcano's activity was noted as reflected in the following observations:

- No ash ejection was observed since 29 December 2009. Steam emission was most of the time weak and white in color indicating considerable decrease in energy and absence of ash

- Majority of the type of earthquakes that were recorded during the past days were associated with rockfalls and rolling down of fragments from the lava deposits along Bonga gully and the advancing lava front

- Measured SO2 levels have also showed a decreasing trend from a maximum of 8,993 tons per day to 2,621 tons per day. The still high concentration of SO2 gas emission only suggests that there is residual magma degassing at shallow depth

At Alert Level 3, sudden explosions may occur due to localized pockets of gas within the magmatic system, the effects of which are expected to be contained within 6-km radius Permanent Danger Zone (PDZ) around the volcano and within the 7-km radius EDZ in the southwest quadrant