The 1981 Japan Earthquake Rule.

It’s one of the first things people memorize when they get interested in buying a house in japan.

1981. I need a house built after that date.

That’s the year japan standardized its earthquake code nationwide... every home built in 1981 or later had to meet the modern seismic standard.

Designed so the house doesn’t collapse on you in a major earthquake.

They tightened the code again in 2000, but a post-2000 build is out of reach for most of our clients. I know it was out of reach for us.

So the peace of mind that comes with 1981 is real.

I’m not here to take that away from anyone.

And I get where the fear comes from... because I come from the same place. Outside the west coast, the US isn’t really earthquake country.

I’m from just outside NYC and as far as anyone can tell, nobody here has ever died in an earthquake. Not once in recorded history.

The only earthquake I can remember happened a couple years ago... It was tiny. I didn’t feel a thing.

Rightfully so earthquakes feel foreign and scare people a lot of us.

And unfortunately, when Americans think of Japan, they think natural disasters, earthquakes, tsunamis, volcanos.

1981 becomes a security blanket you can wrap around a purchase you’re making from 6,000 miles away.

But as always there’s nuance... Japan is not equally dangerous across the board. not even close.

The 1981 rule is a building answer to a location question.

Earthquake risk isn’t one number. It’s two numbers multiplied together... how likely is the ground under your house to shake violently, and how likely is your house to fail if it does.

The 1981 rule only answers the second question. It says nothing about the first. and the first number varies across japan by a factor of HUNDREDS.

Focusing on the 1981 rule and disregarding every house built before it, everywhere, automatically, is sometimes foolish in my opinion.

There are parts of Japan... frankly MOST of Japan... Where I would absolutely want a post-81 house, the pacific coast, the Nankai trough belt, Tokyo.

If I were buying there, 1981 wouldn’t be a preference, it would be a requirement.

I just happened to buy my house in one of the safest, lowest-risk earthquake areas in the entire country and so do a lot of our clients.

The Japanese government publishes a national seismic hazard map... The whole country, in 250-meter squares. the headline stat:

The probability of experiencing shindo 6-lower shaking or stronger, the level where houses start failing and people start dying, within the next 30 years.

• Tokyo: roughly 47%
• The pacific side is loud everywhere: Mito 81%, Nemuro 80%, Kochi 75%
• Otaru: under 1%. lowest probability band in japan. outside any mapped active fault zone.

That’s not a small gap. Thats 100x difference.

Now the building side. the best real-world stress test we have is the 2016 kumamoto earthquake... the town of mashiki took shindo 7 TWICE in 28 hours, and the government autopsied every wooden house in the center of town:

• pre-1981 homes: 28.2% collapsed
• 1981–2000 homes: 8.7% collapsed
• post-2000 homes: 2.2% collapsed

So yes... a 1967 house like mine is roughly 13x more likely to collapse than a new build IF the worst shaking ever recorded shows up at the door.

But risk is the multiplication, not either number alone:

• brand-new build in Tokyo: 47% × 2.2% ≈ about 1 in 100 over 30 years
• my 1967 house in Otaru: under 1% × 28.2% ≈ somewhere between 1 in 350 and 1 in 3,000

Run the math and a creaky 1967 house in Otaru carries meaningfully lower earthquake risk than a brand-new build in Tokyo... conservatively, several times lower.

And remember my NYC upbringing? on the hazard scale, the lowest-risk pockets of japan, the japan sea side of Hokkaido among them, sit far closer to NYC than to Tokyo, in terms of real risk. Nowhere on earth is zero... NYC itself got a small reminder of that in 2024.

Otaru vs. New York City

• Odds of severe, house-breaking shaking (30 years): Otaru is under 1%, the lowest band on japan’s national hazard map. NYC’s odds of comparably damaging shaking, per USGS modeling, are in that same low territory. Same order of magnitude.
• Earthquake deaths in recorded history: NYC, zero, as far as anyone can tell. Otaru, you have to go back to 1792... before Otaru even existed as a town to find any: An offshore earthquake sent a tsunami into Oshoro cove and five Ainu fishermen out on the water drowned. 234 years, five deaths, all tsunami... zero from shaking.
• What you actually feel day to day: Here they differ. Otaru feels small harmless rumbles now and then... it’s still Japan. NYC goes decades feeling nothing.
• The worst-case scenario: The biggest quake in NYC’s recorded history is roughly M5.2 (1884). Otaru’s wider region has produced real monsters, a ~M7.5 off the Shakotan peninsula in 1940 and the M7.8 Okushiri quake in 1993, both Japan sea events. The yearly odds are similarly tiny, but Otaru’s tail is longer.
• The buildings: Even my 1967 house was built in a country that has taken earthquakes seriously for generations. Huge swaths of NYC are unreinforced brick that was never designed for ANY shaking at all.

So do you consider earthquake risk when buying a place in NYC?

No of course not…

So when can you or should you ignore the 1981 rule?

It always comes down to personal risk. But here is how I look at it.

If the house is in high-hazard Japan (which is frankly most of Japan), the pacific belt, the big metros, anywhere near a mapped fault, follow the rule buy a post 1981 house.

But if the house sits in one of japan’s quiet pockets like Otaru, the map matters more than the rule.

If your serious about buying a home in Otaru. Check out our Investment Guide. $39.99. Well worth it in my opinion.

CHECK THE RISK MAP. We built one into Nipponhomes.com

And if 1981 helps you sleep at night that’s totally okay to.

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This content is for informational and educational purposes only and reflects my personal opinions and experience. I am not a licensed financial advisor, tax advisor, or attorney. Readers should conduct their own due diligence and consult qualified professionals before making any investment decisions.