HAYWARD (KPIX 5) – We now know what caused a big water main break in Hayward.

The USGS says the water main break was caused by what’s called a creep – a constant or periodic movement – on the Hayward Fault.

The pipe suddenly snapped, causing a flood along Highland Boulevard.

The water main break on Highland Boulevard was so powerful it forced the street to rise and buckle. It looked as if the Earth was about to burst from the extreme pressure.

The rupture sent water, rocks and mud down the street and opened up a sinkhole that almost swallowed a car.

Hayward resident Reyna Sanchez said, “It’s kind of scary because this time it was really close to the house and I guess to any of the neighbors it’s scary and some of our neighbors, the water went inside their houses.”

The water flooded the space behind her home on Sunday.

USGS says the fault is slipping about 1/5 of an inch per year. So any pipeline that crosses it is vulnerable.

Hayward resident Maureen Scully said, “Kind of nerve wracking, like we’re waiting for an earthquake or something, and then something that we were totally not expecting happens.”

Scully shared a video of water rushing past her home.

The city says the water pipe that failed was installed in 1976.

Most of the pipes in the area are decades-old and made of concrete.

“If other pipes were put in at the same time, they’re going to start going’ just like this one…”Scully said.