RENO — When the Sutter Mill’s meteorite streaked across the Nevada sky in April, it made a loud boom and shook homes throughout the region. Ken Smith, associate director for the Nevada Seismological Laboratory at the University of Nevada, Reno heard it and felt it that Sunday morning. His scientific curiosity drew him right to the lab’s earthquake monitoring network to see what registered on the more than 150 reporting stations. He found an astonishing series of registrations.
“I knew it wasn’t an earthquake, it sounded and felt like an explosion,” he said this week, reflecting on his participation as co-author in an article just published in the prestigious journal Science. “All along the western part of the state, the network had lit up. Recording stations in Mammoth Lakes, Calif., and Pyramid Lake and Walker Lake here in Nevada, picked it up, but I used our recording stations around the Tahoe Basin, Sierra Valley and some other California recording stations to track its trajectory.
The low angle and relatively slow speed of the pieces of the 100,000-year-old, 40-ton asteroid as it broke up 30 miles above the ground made it easy for the network to record its path from about 60 miles east of Reno to its impact in El Dorado County, Calif., about 85 miles to the southwest of Reno. It took the sonic waves from the meteorite about four minutes to reach the ground traveling at about 10 feet per second. A seismic wave from an earthquake travels about four miles per second.
“They mostly used radar in California to confirm the estimates of elevation for the fragments; we had the best estimates of the altitude of the explosion, which was the greatest altitude of a meteorite explosion ever recorded,” Smith said. “The energy of the fireball was about four kilotons of TNT as the piece of asteroid blew from about two to four meters in size to small fragments. Most of it vaporized.”
The Nevada Seismological Laboratory is a research and public service division within the University of Nevada, Reno’s College of Science.