Let's talk about earthquake shaking. Ppl who feel earthquakes sometimes talk about "rollers" versus "shakers." The shaking you feel in any earthquake depends to some extent on geology: if you live in a valley, you tend to feel waves sloshing, or rolling.
But shaking also depends on earthquake magnitude and distance. Earthquakes release energy with a range of frequencies, like music has a range of tones. The bigger the quake, the stronger the booming low tones. That's thing one.
Thing two is that the high tones damp out faster as they move through the crust. If a small quake happens nearby you feel the high tones ("shaking") strongly because they haven't damped out yet.
If you feel a big quake some distance away, the high tones damp out before they get to you, leaving only the booming low tones.
Statistically, you're more likely to feel either a small quake close to you or a big quake that's farther away. But if you are close to a big quake, the whole symphony crashes down on you at once. Low tones, high tones, everything in between.
For tsunami hazard, those booming low tones are the signal you need to especially watch out for if you're along a coast, cause they tell you that a good-sized earthquake just happened some distance from you.
Even if the rolling doesn't feel that strong, a big earthquake offshore can generate a tsunami that can travel some distance. Dangerous tsunamis can arrive from distant earthquakes you don't even feel.
But, again, if you're at a coast and you do feel strong shaking, especially those booming low tones, don't panic, but also don't wait, get your butt to higher ground. A tsunami may not arrive, but the worst thing that will happen is that you will get some exercise.
