Seismologist here The technical rule would relate to the local intensity of the shaking.
That is defined by the Modified Mercalli Index (
https://en.wikipedia.org/wiki/Modified_Mercalli_intensity_scale)
Below III, buy the corn, but you probably did not feel it.
III-IV, Buy the corn. At most you would have looked around d and noticed it
V Buy or return the corn
VI leave the corn.
VII dive under something sturdy during the earthquake... and leave the corn
VIII see seven, and you can't buy the corn because no power
IX. Worry more about new underwear than the corn
X-XII. Buying corn is probably OBE as you are probably dead.
For 2011 in the DC area, we are between buy the corn and return the corn. Close to Mineral, leave the corn.