# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DaMTmYfxc3Y
- **Gondola URL:** https://gondola.cc/posts/67391863-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/ed7546d871.jpg
- **Posted:** 2026-06-30T01:58:21.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Terrifying?

Technical facts:

The ocean floor is not a passive boundary. It is where Earth’s largest earthquakes are born, along the grinding interfaces of subduction zones where one tectonic plate is forced beneath another.

A megathrust earthquake begins with elastic strain. As an oceanic plate descends into the mantle, friction locks it against the overriding plate. The two surfaces do not slide smoothly; they stick. For centuries the overriding plate is dragged downward and compressed, storing elastic energy like a loaded spring. When accumulated stress exceeds the frictional strength of the locked interface, the fault ruptures and the seabed lurches upward by metres in seconds. The rupture front itself can race along the fault at two to three kilometres per second, unzipping hundreds of kilometres of interface faster than the ground can settle.

This vertical displacement is the critical detail. A strike-slip fault, which moves horizontally, displaces relatively little water. A thrust fault on a subduction megathrust lifts the entire water column above it. That sudden uplift is what seeds a tsunami: the ocean surface mirrors the deformed seafloor, then collapses outward as long-wavelength waves travelling at the speed of a jet aircraft in deep water, losing almost no energy until they shoal against a coastline.

The 2011 Tohoku earthquake ruptured a fault patch roughly 500 km long, releasing a seismic moment equivalent to magnitude 9.1. Seafloor displacement near the trench exceeded 50 metres horizontally and around 10 metres vertically, measured directly by GPS-acoustic seabed stations. Crucially, the slip reached all the way to the trench, where soft sediments amplified the uplift and produced wave heights far beyond what models had predicted.

The seabed records every rupture. We are only learning to read it.

#stemantics #geophysics #earthquakes #tsunami #platetectonics

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## Tags

tsunami, earthquakes, geophysics, platetectonics, stemantics

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