Today is the 3rd Sunday after Easter. In traditional Guam, especially Hagåtña, that meant the finakpo' (conclusion) of the Nobenan Promesa - a novena prayed since 1835 against earthquakes.
Guam was rocked by a strong earthquake in 1825, and again in 1834, prompting the people to make a solemn pledge to pray to La Purisima (the Immaculate Conception of Mary) for protection. This was a vow made by the whole city, not just the church or some of the faithful. The Bishop of Cebu, responsible for the Marianas in those days, approved this promise in 1835. Even the civil government formally approved this vow in 1836. The nobena was to begin on the Saturday before the 2nd Sunday after Easter, and end on the 3rd Sunday after Easter. The novena to the Immaculate Conception was used.
This promesa, or vow, was strongly observed but since the 1970s it has been kept by just a handful of old-timers.