Philippines

NDRRMC Update: Situational Report No. 44 re Taal Volcano Eruption, 26 January 2020, 6:00 PM

Source
Posted
Originally published
Origin
View original

Attachments

I. SITUATION OVERVIEW

Taal Volcano's status has lowered from Alert Level 4 (hazardous eruption imminent) to Alert Level 3 (decreased tendency towards hazardous eruption).

Taal Volcano's condition in the two weeks following the 12-13 January 2020 phreatomagmatic eruption (main eruptive phase) has generally declined into less frequent volcanic earthquake activity, decelerated ground deformation of the Taal Caldera and Taal Volcano Island (TVI) edifices and weak steam/gas emissions at the Main Crater. These observations are supported by the following monitoring parameters:

• Significant earthquakes recorded by the Philippine Seismic Network (PSN) across the Taal region declined from 959 to 27 events/day and peak magnitudes of M4.1 to M2.1 between 12 and 24 January. The Taal Volcano Network (TVN) likewise recorded a downtrend in volcanic earthquakes from 944 to 420 events/day between 17 and 24 January with a corresponding decline in the daily total seismic energy released. In particular, hybrid earthquakes that tracked post-eruptive recharge from Taal's deep magma reservoir to a shallow magma region beneath TVI ceased on 21 January, while the number and energy of low frequency events associated with activity in the shallow magma region diminished.

• Global Positioning System (GPS) data recorded ground deformation after the main eruptive phase that included sudden widening of Taal Caldera by -1 meter, uplift of its northwestern sector by -20 centimeters and subsidence of the southwestern part of TVI by -1 meter. These patterns were followed at much smaller rates between 15 and 22 January 2020 and were generally supported by field observations of lakewater recession by -30 centimeters around Taal Lake as of yesterday. Field observations also measured a -2.5 m lakewater recession along the southwestern lakeshore denoting uplift of portions of the Pansipit River Valley where fissuring has been reported. The overall pattern of ground deformation is for most part supported by InSAR (satellite) data and yields a net inflation of western Taal Volvano as a consequence of magma intrusion to the shallow magma region until 21 January.