Progressive deflation began after July 13. This apparently triggered rapid but shallower inflation (Phase 2) in the hydrothermal region of the volcano under the northern edge of Main Crater Lake from June 11 to July 13 just to the SE of the initial deeper source as indicated by northward tilting of the volcano’s northern flank. This resulted in an eastward tilting of the northern flank of the volcano. Phase 1 appears to correspond to inflation at a depth of about 5 km just to the NW of Main Crater Lake from April 20 to June 11, 2010. Although only a single tiltmeter was in operation, it recorded three phases of deformation that correspond generally with the pulses in seismic activity. Overall, we can identify three periods of seismic activity, from April 20 to August 4–8, from August 4–8 to November 18, and from November 18 to March 28, 2011. The numbers increased sharply after April 29 with repeated pulses of seismicity that ended finally in March 2011. On April 20, 2010, felt earthquakes first started to occur.
While the 2010 seismovolcanic crisis was preceded by unusual changes in electric field, ground tilting and uplift, the major signals from all data were concomitant with the evolution of the crisis. This paper reports various types of geophysical data (electric/magnetic field, ground temperature, seismicity and ground deformation) taken during this period of activity together with the current state of geophysical knowledge about the volcano in order to throw light on activity evolution. One such event occurred between April 2010 and March 2011. Since this time, volcanic crises involving episodes of seismicity, deformation, gas release, temperature change, etc., have occurred frequently.Įach of these did not, but possibly could have, evolved into an explosive eruption. For this and other earlier events, no warnings of impending eruptions were issued. The last devastating phreatomagmatic eruption from 1965 to 1977 resulted in the death of about 200 persons. Typical eruptions of Taal Volcano in the Philippines are frequent and violently explosive.
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