The Earth is randomly struck by uncharted but potentially destructive asteroids with perhaps three to 10 times the frequency previously estimated, according to a visual Earth Day presentation unveiled by the nonprofit B612 Foundation that features records of 26 high-altitude detonations triggered by impacts over the last dozen years.

Scattered around the globe and mostly over remote ocean locations, the blasts from those impacts ranged in energy from one to 600 kilotons of TNT. The nuclear weapon dropped on Hiroshima at the end of World War II unleashed 15 kilotons.

The April 22 presentation, compiled from infrasound signatures recorded by the Comprehensive Test Ban Treaty Organization established to monitor the globe for nuclear explosions, suggest the Earth is struck by a multi-megaton asteroid powerful enough to destroy a major city about once a century, said Ed Lu , the former NASA astronaut, co-founder and CEO of the Silicon Valley-headquartered foundation.

“We think it will force people to re-think their assumptions about how often asteroids hit the Earth,” Lu said of the video depiction produced from an international analysis of the threat based on the Feb. 15, 2013, high-altitude detonation of a 19-20 meter (62-65 ft.) asteroid over Chelyabinsk in the Ural region of Russia.

“There is a popular misconception that asteroids are extraordinarily rare— millions of years between large asteroid impacts, and that is incorrect. We think actually seeing these things on a globe of the Earth will help people understand that,” said Lu. “It’s not super-duper rare. That is the important part.”

The analysis , led by Canadian planetary scientist Peter Brown, was published Nov. 6 in the journals Science and Nature.

The blast force from Chelyabinsk exceeded 500 kilotons, enough to shatter windows, damage structures and cause injuries serious enough to warrant medical treatment for an estimated 1,500 residents of the villages below.

The largest asteroid impact in recent times occurred in 1908, when an asteroid two to three times larger than the Chelyabinsk meteor exploded over the vast unsettled Tunguska region of Siberia with a force estimated at between five and 15 megatons. Powerful enough to level an area of 800 sq . mi., Tunguska was greatly outclassed by the 100-megaton blast from the impact of an eight to 16 kilometer-wide (5-10 mi.-wide) asteroid that wiped out the dinosaurs and much of the life on Earth 65 million years ago.

Reassessments triggered by Chelyabinsk suggest asteroids 40 meters across—the lower limits of the Tunguska impactor —qualify as “city killers” and they can occur with a frequency of once a century.

“While most large asteroids with the potential to destroy an entire country or continent have been detected, less than 10,000 of the more than a million dangerous asteroids with the potential to destroy an entire major metropolitan area have been found by all existing space or terrestrially - operated observatories,” said Lu, who was joined by Tom Jones, also a planetary scientist and retired shuttle - era NASA astronaut, and William Anders, a former NASA Apollo astronaut, for the presentation at the Seattle Museum of Flight. “Because we don’t know where or when the next major impact will occur, the only thing preventing a catastrophe from a ‘city-killer’ - sized asteroid has been blind luck.”

The 12-year-old foundation expects to mount the privately funded Sentinel Space Telescope Mission for launch in 2018. After settling into a Venus-like orbit around the Sun, Sentinel’s sensors would map, track and chart the future trajectories of small, Earth orbit-crossing asteroids.

Sentinel should detect and track more than 200,000 of the objects during the first year of its mission, according to the foundation.

The spacecraft is headed for a system architecture level review later this year, following the evaluation of prototype infrared detectors that will form the cornerstone of the observatory.

B612 has entered into a Space Act Agreement with NASA for use of the agency’s Deep Space Network for communications with Sentinel.

The foundation also has endorsed NASA’s Asteroid Grand Challenge, an effort along with the agency’s Asteroid Redirect Mission (ARM) to enlist the help of organizations, individual experts and “citizen scientists ” from around the world to better define the impact threat posed by asteroids. ARM, which Congress has so far not embraced, would send an unpiloted craft to rendezvous with a yet-to-be selected asteroid and either return the entire object or a small piece of it to a stable lunar orbit to demonstrate the ability to alter the course of a large asteroid on a collision course with Earth.

U.S. astronauts would rendezvous with the lunar orbiting asteroid sometime in the 2020s as part of an early test flight of the new Orion capsule and Space Launch System heavy-lift rocket.