Everyone else has alarm clocks. The city of Los Angeles has earthquakes.
An earthquake struck the city just after 6.25am local time, just in time to jolt everyone out of bed.
The epicentre of the quake - the point on the surface directly above the heart, or "hypocentre" - was in the Santa Monica Mountains, between the suburbs of Westood and Encino, and only 8 kilometres below the surface.
The net effect of that is that the quake, which lasted only a few seconds, seemed much stronger than it actually was.
The earthquake was initially measured at a 4.7 magnitude, but was "downgraded" a few minutes later by the United States Geological Survey (USGS) to only 4.4.
But that didn't stop people talking about it.
"That was a very scary earthquake," Modern Family star Sarah Hyland wrote on the social networking site Twitter.
"Just thrown out of bed by an earthquake," wrote author Jackie Collins. "One of the joys of living in Southern California."
"We will rebuild," joked actor/director Nick Nicotera.
And even the satirical Twitter account @TheTweetofGod got in on the act. "Good morning, California! That was Me," it said.
Based on the volume of online chatter, it is clear many Los Angelenos were shaken by the quake, though none perhaps as shaken as the morning news team on the local channel KTLA, who were broadcasting during it.
Morning news co-anchor Chris Schauble's face froze in shock when the quake struck. A moment later he pointed at the ceiling and said "we're having an earthquake".
Schauble and co-host Megan Henderson then took the "duck and cover" option and retreated under the newsdesk, leaving the camera operators (and the audience) to make what they could of the shaking studio set.
Because the quake occurred on the morning of St Patrick's Day in the US, it was quickly dubbed the "shamrock shake" on Twitter.
There were no reports of injuries or damage.
The Los Angeles Fire Department was in "earthquake emergency mode" with crews surveying the city by ground and air to assess any possible damage.
According to Dr Lucy Jones, a USGS seismologist, it was one of the largest quakes to hit Los Angeles since the Northridge earthquake in 1994.
That quake, which measured 6.7 in magnitude, killed 57 people and caused more than NZ$23.35 billion in damage.
This morning's quake was "not that large by California terms", she said.
"It's the size of earthquake we have across the state once every couple of months. But we haven't had one like this in LA for quite a while."
- Sydney Morning Herald