When the powerful April 18, 1906, earthquake struck northern California, staff of the U.S. Geological Survey stationed in Sacramento and Berkeley swung into action, bringing help to the residents of devastated San Francisco, documenting the effects of the quake, and investigating the causes of that major geologic event. It was the most devastating earthquake in California.s history. At 5:12 a.m. on April 18, 1906, the ground under the San Francisco Bay Area shook violently for more than 40 seconds. The magnitude 7.8 earthquake created a rupture along nearly 300 miles of the San Andreas Fault and was felt from southern Oregon to Los Angeles. Because the earthquake.s epicenter was just offshore from San Francisco, the impact on that city was catastrophic. Fragments of broken houses and buildings tumbled into the streets. The pipeline carrying water into the city was severed; fires triggered by broken gas mains raged out of control for 3 days. An area of almost 5 square miles in the heart of the city was destroyed by shaking and fire, and earthquake damage was widespread elsewhere. At least 3,000 people were killed, and 225,000 were left homeless. Drinking water, food, and supplies quickly became scarce.