This is a very specialized aspect of support by the U.S. Navy.
The military's branches can all bring specialized equipment and personnel to assist with disaster response. In the case of coastal communities impacted by hurricanes or in the case of a Cascadia Subductiion Fault, they have the ability to bring in supplies and equipment to coastal areas cut off by destroyed bridges and roads. See this article, Navy Hovercraft Storm Beaches In Oregon And Washington In Preparation For "The Big One"
I'd like to argue for a different purpose than bringing in supplies and equipment, that being evacuation of the disaster survivors. Much of coastal communities' buildings and infrastructure are focused on being as close to the water as possible. Great for vacations and sunsets here on the West Coast, bad for when a tsunami wave is headed your way.
The other major factor that is briefly mentioned in the article is the destruction of the land-based transportation system. These roads and bridges will suffer major, if not total, destruction. Re-establishing transportation routes will take months, perhaps years in some cases. Rather than trying to supply survivors with all their logistical needs by bringing them in over the beach — which I think is impossible — the evacuation of people (who are willing to go) should be the major priority. Those who refuse to go need to be told they are "on their own." Tough talk — yes — but totally realistic and likely no one is saying this to these communities today, or to the people flocking to "live by the sea."
The other major point I'll make is that for Disaster Exercise Cascadia Rising 2016, the military, including the Navy, said it would be eight (8) days before active duty military forces would "begin" to reach the area of destruction. Thus, Washington and Oregon stating that you need to be prepared to be on your own for 14 days, in the case of an earthquake, is totally realistic and might actually be too little for places like coastal communities.
And, NO there are not enough helicopters to air supply these communities either.
The link above was shared by Don Villeneuve.