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Parts of Arizona were shaken by a moderate earthquake just before the lunch hour Wednesday.

According to the United State Geological Survery, the 5.9 magnitude quake struck at 11:48 a.m. in northwest Mexico, 13 miles away from Guadalupe Victoria.

A group of 15 people at the Imperial Sand Dunes outside Yuma said the quake felt like a big semi-truck passing by.

On Twitter, user duznn wrote, "That earthquake must have been a big one - we just felt it in Phoenix!"

User wmd404 wrote, "Here in downtown Phoenix we just felt the aftershock of another earthquake in Baja ... building swaying back and forth again."

According to the USGS, the first quake was followed by a 4.9 magnitude aftershock at 11:53 a.m.

There was also a 3.4 aftershock at 12:04 p.m. and 4.0 aftershock at 12:07 p.m.

There are reports the quake was felt in San Diego too.