Having lived in earthquake country, California), most of my life.

Standing in a doorway IS NOT considered a good idea, for couple of reasons

An open doorway is a weak spot in a wall.
And an open door may swing shut on a hand doing major damage.

From FEMA:
If indoors

# DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON until the shaking stops. If there isn’t a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building.
# Stay in bed if you are there when the earthquake strikes. Hold on and protect your head with a pillow, unless you are under a heavy light fixture that could fall. In that case, move to the nearest safe place.
# Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, loadbearing doorway.
# Stay inside until the shaking stops and it is safe to go outside. Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave.
# Be aware that the electricity may go out or the sprinkler systems or fire alarms may turn on.
# DO NOT use the elevators.

From California Dept of Conservation:
During an Earthquake
#If you're indoors, stay there. Get under -- and hold onto --a desk or table, or stand against an interior wall. Stay clear of exterior walls, glass, heavy furniture, fireplaces and appliances. The kitchen is a particularly dangerous spot. If you’re in an office building, stay away from windows and outside walls and do not use the elevator.
#If you're outside, get into the open. Stay clear of buildings, power lines or anything else that could fall on you.
#If you're driving, move the car out of traffic and stop. Avoid parking under or on bridges or overpasses. Try to get clear of trees, light posts, signs and power lines. When you resume driving, watch out for road hazards.
#If you're in a mountainous area, beware of the potential for landslides. Likewise, if you're near the ocean, be aware that tsunamis are associated with large earthquakes. Get to high ground.
#If you’re in a crowded public place, avoid panicking and do not rush for the exit. Stay low and cover your head and neck with your hands and arms.

Elsewhere, I have been told that if you can get to an interior hallway, do so, and close the door behind you. This will protect you from flying glass if a window breaks, and closing the door will strengthen the wall,by eliminating the weak area of the open door.

In the 1989 quake during the start of the World series, I was on the lower floor of a 2 story apartment, lying on my bed. The building flexed so much the window, frame and all, popped out onto the ground. The sliding glass door in the other bedroom went to pieces and popped out of its track.

In that case, I broke the rule, yelling for Elaine to run out back through the open doorway, and I went out the window. We both got far enough from the building it would not fall on us. Our building stayed up, but an 'identical' unit near us did collapse.

Luckily, the only people inside were not killed. One was knocked down in the kitchen, but the stove prevented the second floor from crushing her. The other two were more seriously injured, though they were on the upper floor, and only the roof came down on them.