In the dawn hours of April 18, 1906, a sudden shock rattled San Francisco. Half a minute later, one of the largest quakes in California history pummeled the sleeping city awake.

Modern geologists estimate that the 1906 San Francisco earthquake measured somewhere between magnitude 7.7 and 8.3. The shock waves and subsequent fires from the quake destroyed 28,000 buildings, killed at least 700 people and rendered more than half of the city's 400,000 residents homeless. [Lost Footage: Shocking Still Images from the Great San Francisco Quake's Aftermath]

Now, after being lost for more than 100 years, footage of the quake's devastating aftermath has turned up. Providing hope for treasure hunters everywhere, photography collector David Silver found the rare roll of nitrate film stuffed in the trunk of a car at a California flea market.

According to Silver, it was a miracle the 9-minute reel was still intact; nitrate film is delicate and extremely flammable, and the man selling the reel was "standing there looking through a length of it with a lit cigarette hanging from his lips," Silver told SFGate.com.

With the help of a Facebook group called San Francisco Remembered, Silver sold the footage to photography historian Jason Wright, who had a hunch about the rare film's provenance.

"It sounded like it was an important film," Wright told Live Science. "It had the possibility of being a long-lost film from the Miles brothers."

The Miles brothers were film pioneers in San Francisco; they're best known today for a 12-minute film called "A Trip Down Market Street." Shot from the point of view of a moving cable car in 1906, the short film beautifully captures the hustle and bustle of downtown San Francisco life. In 2010, film historian David Kiehn determined that "A Trip Down Market Street" was taken just four days before the great earthquake struck.

"[The Miles brothers] shot more footage than anyone else after the earthquake, almost 7,000 feet of it," Kiehn told SFGate. "Practically none of it survived."

The newly recovered canister is a startling exception. Wright brought the new film to Kiehn, who helped determine that it was indeed a lost Miles brothers film — this one taken a few weeks after the 1906 quake.

In the post-disaster footage, the filmmaker brothers follow a similar path down Market Street as in their previous work. But what was once a road walled with grand buildings and bustling with commerce is now a ruin strewn with rubble and refugees, Wright said. Smoke and ash clog the air. Half-crumbled buildings are dynamited as bystanders look numbly on. Dispossessed families haul their remaining belongings to the city port, ready to leave and perhaps never return.

"When you see the trip down Market Street two days before the earthquake, the street was absolutely full of people, children smiling, running up and down the road," Wright said. "Little did they know that just four days later a lot of lives would be lost, a lot of those smiles would be missing and a lot of buildings would be gone.”

Wright and Kiehn are currently working to restore and digitize the footage, which they plan to exhibit in San Francisco on April 14. The restored footage will be released online later this summer, Wright said.

Originally published on Live Science.