Imperial Valley 
June 22, 1915 | M6.1
June 22, 1915 | M6.3
On June 22, 1915, two separate earthquakes occurred about an hour apart near El Centro. The first, a magnitude 6.1 (ML) earthquake, occurred around 7 p.m. and weakened many structures in the region. The second, a magnitude 6.3 (ML) earthquake occurred around 9 p.m. and caused many of the structures weakened in the first quake to collapse.
The first shock had caused many people to exit buildings and move into the streets, and because many of them had not yet returned to the buildings when the second quake occurred, severe injuries were limited.
However, in Mexicali, Mexico, less than 20 miles south of El Centro, dance halls and gambling halls had been busy before the first quake and continued to operate afterward, so many people returned to them. As a result, six deaths and many injuries occurred in Mexicali when weakened structures collapsed with patrons inside them or when materials inside the structures fell.
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