December 1770 Earthquake: Manila, Philippines

Reference #414:

1770, December [no date], 21:00. A strong shock was felt at Manila. Several homes were destroyed. The earthquake began with a sharp southern wind, which caused a rough sea.

Reference #1072:

1770, December, 23:00, intensity VIII. Destructive earthquake. Mr. Sonnerat states that it wrecked many houses in Manila. This traveler was at the time on board a ship in the very Bay of Manila; hence it is very strange that he does not give the day of the month on which the disaster took place.

Reference #1187:

1770, December, 9-11 p.m. Manila: Violent, and destroyed many houses. Within an hour, felt three shocks which caused the author a sudden jump of the heart. Vessels in the bay felt the shocks and thought they had struck the bottom of a reef.

Reference #1058:

1770, December, intensity VII. Manila, destructive.

Reference #3029:

1770 December. 9:00-11:00 p.m. Manila. These earthquakes were reported by Sonnerat without giving the date: "There are many volcanoes in the island of Luzon and they may well be the cause of the frequent earthquakes to which the island is subjected; there is not a year without two, three, or four being felt. The Spaniards of Manila build their houses appropriately; the first floor is of wood and all the frame of the house is supported by wooden posts. For an emergency they also have a little hut of bamboo in their court or garden. The whole family sleeps there when the weather indicates an earthquake. It seems, as M. Legentil has forcefully said, that the earthquakes come more frequently at the end of the year, and most of them occur at night; I felt two in 1770, in the month of December; the first was violent and destroyed some houses; it was preceded at nine o'clock in the evening by a very strong south wind, which agitated the sea; the sky was covered with a reddish haze; and during two hours I felt three successive shocks, which gave me a palpitation of the

heart. The ships which were anchored in the roadstead felt the same motions and one would believe they had touched bottom." MSo, II, 111-112, in the two-volume set. AP, p. 165.

Legentil's comment referred to above is the following: "According to my observations, it would seem that this city is a little more subject to earthquakes in the last months of the year. Bouguer has noticed a similar condition in Peru. Furthermore, Bouguer suspects that the spring tides of September and October, together with the increasing heat contribute to it. Nevertheless, the last months of the year in Manila do not have an increase of heat, as in Peru; for in this city January and February are the coldest months of the year. It is necessary for physicists to find some other cause for this, other than increasing heat." GJL, II, 365-366. AP, p. 164. Legentil's reference

to Bouguer is Voyage au Pereu, relation abregee, p. lxxiv.

Rudolph includes this earthquake of December in his list of submarine earthquakes, using Sonnerat's report. BG, Bd. II, p. 590.