The preferred response is to immediately scream "incoming" at the top of your lungs, quickly dip you fingers into your water glass and then into the ashtray, shoulder roll behind the potted plants, smear your face with the ashes, pull your weapon, and while maintaining your very best bug-eyed and throbbing-vein expression shout that "Charlie is in the wire" and scan the room with your sidearm. Lacking a firearm hold a butter knife in an aggressive stance. A large soup spoon is a good option and adds a bit of comedy relief.

I'm always leery about the whole survival mindset riff. Those who have it don't focus on it. Those who worry about it don't have it. Most people who worry about it avoid the clear. calm awareness needed and instead adopt some macho BS like: 'have a plan to kill everyone you meet'. Or some form of generalized hyper-alertness and nervousness that usually guarantees they are half exhausted before any emergency rolls around. Those are not a survival mindsets. They are paranoia and psychopathology disguised as preparedness. It is also a very fine way of wearing yourself down, alienating people who might help you, and a long-term strategy for dying alone.

I think you did well enough but quite frankly I would sit back and enjoy my meal. If you were part of a planned emergency response and had reason to think something might be going on you might phone the dispatcher and make sure they have your cellphone number in case they need people.

A single explosion is not much to go on. A truck driving over a sealed two-liter plastic bottle makes a noise like a shotgun going off. A transformer going bad typically has a 60 cycle growl often followed shortly by a rather impressive explosion. Living in Florida we got sonic booms every time the shuttle landed. Typically a double boom like two deep thunderclaps. The military also provides the occasional sonic boom.

Seattle is below a mountain that will some day make a very large boom. But jumping up based on a single distant explosion and clearly inadequate information is a waste of effort. I suspect the urge to jump up and 'do something' indicates you are too nervous and need to unwind a bit. Big emergencies develop over time, those that don't have no effective response, and the world will let you know when you need to act.

There is no need to 'strain at gnats' or jump at every loud noise. Save your energy for things that matter.