January 27, 1911 Earthquake: Taal Volcano, Luzon, Philippines

1911, Jan. 27, 20h20m. The seismographs of Manila Observatory began to register frequent seismic disturbances which were of small amplitude in the beginning, but increased rapidly in frequency and intensity. The first earthquake, perceptible in Manila with intensity III (Rossi-Fore1 scale), occurred at 23h6m5s when the number

of imperceptible shocks of force I registered during the preceding 3 hours, had already exceeded 20. Before midnight 4 additional shocks of force II and III were felt, while 4 or 5 of intensity I were recorded by the instruments.... by the aid of telegrams from the meteorological station at Batangas... the Observatory was able to locate the epicenter in the region of Taal Volcano... no definite notice was received that Taal had entered into a period of eruption, until the afternoon of that day, when telegrams reported that ever since the early morning a huge column of black smoke was rising from it and that in the nearest towns sinister rumblings could be heard at intervals, which brought consternation to the inhabitants of Batangas Province, since some awful catastrophe was feared to be imminent. This increase in volcanic activity coincided with the first microseismic movements registered in Manila at 20h20m of the 27th.

This seismic commotion continued during the 28th, with the same frequency, but increasing intensity, so much so that of the 197 disturbances registered by the instruments during that day, 10 were felt in Manila with force IV, 21 with force III, 31 with force II, while the remaining 135 did not exceed force I.

But what intensity did they [earthquakes] develop in the immediate neighborhood of the epicenter? From what we ourselves distinctly felt at a distance of about 12 km from the volcano, as well as from the effects on the buildings of the nearest towns of some importance, especially of Taal and Lemery which are 19 km from the crater, we are convinced that at this distance from the volcano, the intensity of the earthquakes was approximately 3 degrees of the De Rossi-Forel scale above that... at Manila. Hence, the severest shocks felt at Manila with intensities III and IV, developed forces VI and VII in the zone surrounding Lake Bombon, and probably VIII or IX at the epicenter, Volcano Is ...in the said region [Taal] the earthquakes were continuous and the people terror-stricken... as for 6 days they felt the earth tremble under their feet about once every 10 minutes.

The report of the district engineer who examined the public buildings of Taal and Lemery is in perfect agreement with our statements regarding the effects of the earthquakes, viz, that they are of small importance. An arch of the old bridge east of Taal was cracked, but it can easily be repaired. The filled-up approaches to another bridge sank and were fissured. The walls of the municipal building of Taal show numerous small cracks, but most of them seem to be old ones, produced by former earthquakes and now made visible by the falling away of the plaster which covered them. In the same town a corner of the baptistry of the church was cracked, and the kitchen of the convent brought to the ground. The church of Caysasay lost a portion of its front and its towers, and the church of Lemery was left in a tottering condition. But all these structures had been greatly weakened by age, humidity, and the earthquakes of other times. In the town of Lemery, which is built close to the seashore, on the alluvial delta formed by the Pansipit River, many fissures opened which ruined several houses. Nevertheless we believe that all these effects must be ascribed to the repetition of so many hundreds of earthquakes rather than to their intensity, quite aside

from the fact that they are precisely those which correspond to shocks of intensities VII and VIII of the De Rossi-Forel scale.

(above from ref #2340)