But I just did that. Second time in my 41+ years, felt an earthquake aftershock. Epicenter happens to be in Iran. I thought I was getting nauseous and close to fainting. Then it registered in my brain that I got this feeling almost 15 years ago. Except, back then, it was my bed rocking forward and backward, almost like a baby's cradle. This time, it was sideways motion. My head felt like a pendulum. All the occupants of my 17th floor flat gathered in the living room. The chandelier was rocking a bit. Flat owner joked that this is one of the benefits of a chandelier. Good earthquake detector to rule out the possibility of imagining things.
IIRC, Iran has had some gigantic earthquakes. Where I live a pretty monster quake could happen any time. I am right now exactly where I was during the Loma Prieta earthquake of 1989. I don't remember feeling sick or freaking out. It was pretty alarming. An overpass (the
Cypress Structure) collapsed about 4 miles from here and maybe 20 people died right there.
I do feel small EQs here occasionally. I don't need a chandelier to tell me if it's just my imagination. I've read some very interesting books on earthquakes. Most fascinating are the monstrous ones, like the Lisbon 1755 or the 1920 in China. Japan has had many monstrous quakes including pretty recently.
Earthquakes have much variety, not just the intensity. The depth of the epicenter is important as well as the geography of the region. Usually it takes a few seconds for the intensity to build for a large earthquake, perhaps something like 20 seconds. Then the really intense ones keep on going for up to a minute, sometimes more. Then there are the aftershocks, which can come at any time and aftershocks can keep coming for days, weeks, months. The aftershocks are usually smaller than the initial quake, but frequently not by much and sometimes the aftershocks are equal or greater than the initial earthquake. Given that it usually takes some seconds for the intensity to build you generally have a moment to situate yourself for safety, duck under a table or something or even run outside, possibly. It's one reason they have invested in earthquake warning systems. I have an app driven by one installed on my smartphones. People who live in areas of great seismicity often have some ideas on how to protect themselves. After a major quake, for one thing, they are antsy, run outside at the hint of a tremor or refuse to stay inside at all while aftershocks are a thing, if possible, if they inhabit structures that might collapse.
With giant earthquakes, in particular the ones with epicenter under the ocean, the concern isn't just everything shaken, disrupted and destroyed by the tremors, there's the ensuing tsunami, sometimes traveling thousands of miles across the ocean at high speed. Once reaching shallower water the speed decreases but the height of the wave increases. Maybe you've seen some of the video of tsunamis charging inland. I'm sure you can see some on Youtube. I saw some video of a tsunami hitting the coast of Japan within the last 20 years that looked like CGI.