Usually, for any emergency, no new cases are started, and those that are underway are continued if possible. If evacuation is necessary, like for a fire, the wound is packed and the patient transported.

Fortunately, never been in such a situation. I have been in the OR during power outages, and the time between the power going off and the generator kicking in seems like FOREVER (I have no monitors at that time). We have emergency equipment available that requires no electricity, so patients can be kept safe.

If the building was shaking, I imagine most surgeons would stop and wait for things to stabilize, and then get back to work. Other OR personnel would check out the severity of the situation and let the surgical team know what was going on and what needed to be done.