The earthquakes began on Sunday night, July 27, 1902, around 11:00 PM, when a strong shock awakened the residents of Los Alamos. Within 20 minutes four more earthquakes were felt, followed by others at 12:55, 2:40, 3:10, 5:20, 7:40, 8:20, and 11:00 AM on the 28th. This series of earthquakes broke glassware and dishes in Los Alamos, cracked the walls of older adobe buildings, knocked down telephone lines, and destroyed an oil tank at the Careaga Oil fields a few miles from town.

One of the more interesting effects of these earthquakes was the transformation of Los Alamos Creek (also called San Antonio Creek) from a dry creek bed to a flowing river two feet deep and 18 feet wide. Some of the earthquakes were said to be preceded by rumbling sounds, likened to the sound of a thousand cannon.

This series of earthquakes unnerved the residents of Los Alamos, with the worst still to come. The quakes continued with a large one at 5:30 PM, Monday the 28th, which destroyed one of the old adobe buildings. More earthquakes were felt until the morning of the 31st, at 1:20 AM, when the biggest earthquake struck. People rushed into the street in their night clothes, many of them spending the rest of the night camped out in their yards. Numerous chimneys were destroyed, merchandise in stores and saloons were thrown to the floor, some residents were thrown from their beds, trees were uprooted, and landslides occurred in the surrounding hills.

Based on a rumor that the president of the University of California had recommended to residents that they leave the area, approximately 60 of the town's 500 citizens evacuated, only to return sheepishly a few days later. Earthquakes continued to be felt as late as December 13 of that year.