The U.S. Geological Survey (USGS) reported that the Mammoth Lakes region has experienced more than 600 small earthquakes in 36 hours.
The ripples were created by the active volcanic areas in California. This is the largest earthquake swarm in 10 years, and the quake was recorded to have magnitudes ranging from 1.0 to 3.8. The first ones started at 5 a.m. on Thursday.
Residents near the area shared that they felt small rattles throughout the day, but they were not alarmed because occurrences such as this were normal.
"I just happened to be sitting at a table and it felt as if someone really heavy was walking by me. It was pretty minor," said Ed Roski, chief pilot of SkyTime Helicopter Tours and 50-year resident of the region, told NBC News.
Swarms of earthquakes are common phenomena in the Mammoth Lakes area as there are many crisscross faults, especially in the region called the Long Valley Caldera. USGS research seismologist, David Shelly, explained that this 20-mile wide crater was created from pumice and ash deposits spewed out by volcanic activity that happened 760,000 years before.
"This is one of the largest earthquake swarms we've seen in the past decade or so. We'll be tracking it closely," Shelly told the Los Angeles Times.
The center of the Long Valley Caldera was observed to elevate slowly in the past years. Shelly explained that small swarms of relatively weak earthquakes happen due to the tectonic activity in this area. There are magma deposits deep down, and earthquakes occur when a mixture of carbon dioxide and water pushes the magma up to the outer layers of the earth. Magma seeps into the crevices of the faults and this pressure causes the ground to move.
"It doesn't mean that the volcano is any more active," Shelly clarified. "It's an ongoing process in a volcanic system."
