[HN Gopher] The Orphan Tsunami of 1700 [pdf]
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       The Orphan Tsunami of 1700 [pdf]
        
       Author : oliverkwebb
       Score  : 31 points
       Date   : 2025-10-08 22:02 UTC (3 days ago)
        
 (HTM) web link (pubs.usgs.gov)
 (TXT) w3m dump (pubs.usgs.gov)
        
       | ogogmad wrote:
       | Just learnt something from the article: It's interesting that the
       | warping of the seafloor is what causes tsunamis, and not the
       | shaking itself. It explains why a shoreline might sometimes
       | recede away before a tsunami's crest strikes: The recession is
       | caused by the seawater dropping with the seafloor, while the
       | forward surge is caused by the ensuing bounce.
        
         | MontagFTB wrote:
         | The largest tsunami on record came from a landslide in a bay:
         | https://en.wikipedia.org/wiki/1958_Lituya_Bay_earthquake_and...
        
           | buildbot wrote:
           | Yeah that'll happen when a good chunk of a mountain basically
           | drops into your body of water, lol:
           | 
           | "The large mass of rock, acting as a monolith (thus
           | resembling high-angle asteroid impact), struck with great
           | force the sediments at bottom of Gilbert Inlet at the head of
           | the bay. The impact created a large crater and displaced and
           | folded recent and Tertiary deposits and sedimentary layers to
           | an unknown depth."
           | 
           | With updated modeling showing that impact triggering the
           | glacier to lift and subsequently release even more material,
           | it's shocking anyone in the bay survived at all.
           | 
           | Edit - found a video with said papers modeling implemented,
           | pretty neat: https://www.youtube.com/watch?v=B1axr5YGRwQ
        
         | pixl97 wrote:
         | Dropping or rising. At the borders of the sea and land plates
         | the sea plates are slipping slowly below the continental crust.
         | Pieces of the land crust get caught and dragged down. Over long
         | periods of time you'll see forested land get dragged down below
         | sea level and flooded to die.
         | 
         | The a rupture will occur, and in the biggest earthquakes you
         | can get a fault that can rise 20 meters almost instantly
         | causing trillions of tons of ocean to suddenly have to go
         | somewhere. After the quake and tsunami you'll see the flooded
         | forests can be many meters above land were new forest will grow
         | and slowly start sinking again.
        
       | jmward01 wrote:
       | Cascadia has become a little bit of an obsession for me. I had my
       | house retrofitted to help it withstand the inevitable next really
       | big one that is coming because of what I have learned about it (I
       | am also well above the tsunami flood zone). Subduction zones are
       | crazy powerful but it looks like we are finally starting to learn
       | important things about them. The challenge though is getting
       | people to accept that they are real and will happen and entire
       | cities need to move because of them (I'm looking at you Ocean
       | Shores).
       | 
       | Side note, any actual geologists in the room? The recent
       | Philippians 7.6 looks like it may be following a growing pattern
       | of megathrust forshocks to my -deeply- untrained eye. Does
       | someone with actual knowledge and training have a take on that?
        
         | VoidWarranty wrote:
         | Got any recs for contractors in the area to do the work?
         | 
         | What should I get done? (ranch 2 story built in 90s). Cost to
         | expect? Been having bad luck lately with bids and sketch
         | contractors. Takes a lot of effort to sift through.
        
           | jmward01 wrote:
           | This was close to DYI with me and the local handyman figuring
           | out a good way to tie my house to its foundation. Not a full
           | retrofit but pretty good for my 100yo house with nothing
           | remotely close to modern design. Here are some resources I
           | found useful though.
           | 
           | https://dnr.wa.gov/sites/default/files/2025-03/ger_homeowner.
           | ..
           | 
           | https://www.wabo.org/earthquake-home-retrofit
        
             | VoidWarranty wrote:
             | Thanks! I'll check this out!
        
         | ogogmad wrote:
         | Sea wall?
        
           | jmward01 wrote:
           | I'm not an expert by any means, but I think the issue with
           | seawalls is they are built to stop waves, not something that
           | acts more like the ocean getting deeper. The water a tsunami
           | brings in is pretty different than a simple wave on the
           | ocean.
        
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       (page generated 2025-10-11 23:01 UTC)