Fact: people without vestibular function will not get motion sickness/ people with lesions in the vestibular cerebellum (nodulud/uvula) will be immune to motion sickness.

motion sickness susceptibility relies on 1)sensitivity of vestibular system; 2) The sensitiveity of autonomic system.

Motion sickness can be elicited in a lab by cross-coupled rotation (coriolis force is too small in this case). The reason that cross-axis acceleration can induce motion sickness is that the reponse vector of vestibular system is off the preferred orientation vector of vestibular system. There is nothing to do with infrasound.

To understand motion sickness, one has to know about vestibular and oculomotor system. Optokinetic nystagmus stimulation can also induce motion sickness for as long as the stimulus vector is not aligned with the orientation vector of vestibular system.

So far the role of vestibular system in generating motion sickness is clear although the precice mechanism is still being formulated. However, the role of autonomic system that receivies the conflicting vestibular signal to generate the symptoms of motion sickness is largely unknown.

One interesting variant of motion sickness is Mal De Debarquement - after a cruise, you are still feeling on the ship, a sensation walking on clouds. Thiis can last as long as 7 years in some women who are the major victims.