Strong earthquake hits northern Japan, tsunami warning issued

Tsunami size, models, and risk

• Early links from tsunami agencies and USGS suggested up to ~1 m waves; later JMA maps showed observed waves around 0.7 m.
• Some posters argue 1 m is still dangerous, stressing debris, sewage, chemicals, and retreating flows.
• Others compare 1–2 m tsunamis with typical storm or hurricane waves, noting tsunami waves carry more energy because the entire water column moves.
• There’s criticism of Japan’s Meteorological Agency tsunami-height estimates: one commenter claims the model “defaults” to ~3 m and erodes trust by over-warning; others push back that estimates and measurements are different things.

How the quake felt and local impact

• People in northern Japan (Misawa, Rokkasho, Sapporo, Niseko) describe very strong but largely non-destructive shaking: items off shelves, sloshing fish tanks, some lobby evacuations, but little structural damage reported by individuals.
• One local notes it was the strongest recorded in that region, yet their house suffered only minor interior disruption; later confirms the tsunami warning was lifted with no major damage.
• Tokyo residents report clear, sustained shaking. Depth is discussed: a relatively deep hypocenter is seen by some as reducing destructive potential, though aftershocks include shallower events.

Psychology, safety, and preparedness

• Reactions to earthquakes range from excitement (trust in Japanese/Californian building codes) to intense panic, especially for those unused to ground motion.
• Balance-heavy sports (skating, skiing) are suggested as making people more comfortable with instability.
• Practical advice: stay inside modern buildings rather than running out; avoid falling debris and glass; secure bedroom items; keep shoes, water, and an emergency kit ready.
• Some visitors consider leaving Hokkaido due to official advisories about elevated risk of a larger quake; others argue you can’t meaningfully “time” megaquakes.

Earthquake science, “small quakes,” and megathrust fears

• Commenters debate whether frequent smaller quakes reduce the chance of a “big one.”
• One side: earthquakes release stored stress, so many small events should help; they cite videos and some research on stress and fault strength.
• The other side: solid-earth seismology often calls “small quakes prevent big ones” a myth; small events don’t reliably predict or forestall major ruptures, and most energy is released in the largest quakes.
• Official estimates (e.g., ~5% chance of a larger quake within a week after a big one) are referenced, emphasizing high uncertainty in prediction.
• Casual claims that this is “buildup for a 9+ megathrust earthquake” are widely dismissed as unsupported speculation.

Alerts, information systems, and language trivia

• Japanese emergency phone alerts are reported to work for at least some foreign eSIM users.
• Tsunami.gov’s UI is criticized as confusing and uninformative.
• There’s some seismological terminology/etymology talk (epicenter vs. hypocenter, Greek roots) and comparisons to past events (2011 Tōhoku, Christchurch, liquefaction videos).