A 5.6-magnitude earthquake struck a rural part of northern California on Wednesday. Hours later, a 7.2-magnitude earthquake hit the northern coast of Japan and two powerful earthquakes rocked Venezuela in a devastating mass casualty event.

The tremors happened in the span of eight hours, prompting online speculation over whether they were related.

Experts say they were not.

The episodes do share a similarity in that they all occurred along well-known plate boundaries with high seismic hazard, according to William Barnhart, assistant coordinator for the US Geological Survey’s earthquake hazards program. But their timing on Wednesday was simply a coincidence.

“Earthquakes happen every day all over the world. Most of them happen far from people,” Barnhart said. “Yesterday was just a very peculiar day where you had a couple of fairly significant earthquakes happen in areas where people felt them.”

It is possible for a large earthquake to trigger tremors in other parts of the world, Barnhart said.

But it’s unusual that such a cascade effect would happen thousands and thousands of miles apart, according to Martin Hudson, an adjunct professor of civil and environmental engineering at UCLA.

“If you look at the last 100 years of earthquakes, we’ve never seen earthquakes this far apart be related,” he said.

In comparison, the initial 7.1-magnitude temblor in Venezuela likely triggered the ensuing 7.5-magnitude quake because of their proximity.

“A fault might be ready to go, and then if there’s a nearby earthquake, it causes it to tip over the edge,” Hudson said.

In any given year, there are dozens of earthquakes greater than magnitude 7 across the world, Hudson said.

“It was a terrible happenstance that it was in a populated area in Venezuela,” he added of the ongoing calamity, where at least 188 people have been confirmed dead.