A California golf course is rocked by a swarm of 45 earthquakes in a t

Crow Canyon Country Club in Danville, Calif., east of San Francisco, might need a new local rule, that if your ball moves at address, you may replace it without penalty.

See, the earth beneath the ball at Crow Canyon seems to be somewhat unstable. It is, at least, the epicenter of attention in the wake of a swarm of earthquakes, 45 of them in the last two days alone (see the United States Geological Survey map below).

“Maybe we need to rethink about aerifying the fairways,” head professional Mark Naylor said jokingly, suggesting that at least the quakes haven’t shaken the sense of humor out of them.

The largest of the quakes, striking at 6:10 on Thursday morning, registered 3.4 on the Richter Scale. The second largest of them hit at 3:58 a.m. on Wednesday and registered 3.1

“All it’s doing so far is waking folks up,” Naylor said.

A 3.4 quake falls in the range of II to III on the Abbreviated Modified Mercalli Intensity Scale, according to the USGS, which means at minimum it is “felt only by a few persons at rest, especially on upper floors of buildings” and at maximum is “felt quite noticeably by persons indoors, especially on upper floors of buildings.”

Is there a fault line running beneath the golf course? “There’s something there,” he said. “But I was not aware that we had anything running through there.”

However, the Calaveras Fault, a branch of the renowned San Andreas Fault, runs from just north of Danville down into the Salinas Valley.

Meanwhile, no one is alarmed, yet, “knock on wood,” Naylor said.

Crow Canyon, incidentally, is located about 50 miles south of Napa, where the PGA Tour’s frys.com Open is being played.