At 5:12 a.m. on April 18, 1906, San Francisco shook violently. A 7.9 magnitude earthquake struck just 2 miles off the coast.

On the 100th anniversary of the quake that changed the city forever, the clock is ticking for the next Big One.

In California, where the next "Big One" is an always-looming threat, some lessons learned from the 1925 Santa Barbara quake resonate even 100 years later, experts say.

The San Andreas fault is capable of magnitude 7.8 earthquakes. Two have occurred twice in recent times: the 1906 San Francisco earthquake and one in 1857 in Southern California.

The last “big one”-level moments in California’s recorded earthquake history were the 1857 quake in the central third of the San Andreas Fault and the 1906 earthquake in the northern third.

We associate earthquakes with specific areas of the world, like California, which lies along the San Andreas fault.

The 800-mile-long San Andreas Fault is one of the more famous faults in the United States, known as the cause of the Great 1906 San Francisco earthquake.