The core idea: shindo is how hard it shook here
Shindo (震度) is literally shaking degree: 震 is the shin of jishin, earthquake, and 度 the do of ondo, temperature. It is a number for one place. The Japan Meteorological Agency, Kishōchō, and local governments run about 4,400 intensity meters, shindokei, and each reports how strongly the ground moved where it stands. Since 1996 the readings have come from instruments, not from people's impressions.
So one earthquake never has just one shindo. Near the source the ground may reach 5 jaku while a city a hundred kilometres away records 2; magnitude, by contrast, is one figure for the whole quake. Hold on to this picture, a map of many local numbers. Phone alarms and evacuation signs have their own posts; for what to do in a quake, follow JMA and your city office. After a small tremor, friends use the casual lines below and colleagues the polite ones.
| Japanese | Romaji | Meaning |
|---|---|---|
| 今、揺れたね。 | Ima, yureta ne. | That was a tremor just now, wasn't it? |
| 震度いくつだった？ | Shindo ikutsu datta? | What shindo was it? |
| 東京は震度3だったみたい。 | Tōkyō wa shindo san datta mitai. | Looks like it was shindo 3 in Tokyo. |
| うちのほうは震度4でした。 | Uchi no hō wa shindo yon deshita. | It was shindo 4 where I live. |
| 震源はどこですか。 | Shingen wa doko desu ka. | Where was the quake centred? |
The ten levels and what you feel at each
JMA publishes an explanation table, the Kishōchō shindo kaikyū kanren kaisetsuhyō, describing what typically happens where each level is recorded: what people feel, what happens indoors and outdoors, and how buildings fare. The diagram condenses the first two columns. Read it as a ladder: up to 4, the story is who notices; from 5 jaku, whether you can stay on your feet.
JMA stresses that the table is a description, not a checklist: the level comes from the instrument, and not every effect appears every time.
| Level | Reading | What JMA says people typically feel |
|---|---|---|
| 震度0 | shindo zero | Not felt, though seismometers record it |
| 震度1 | shindo ichi | Some people sitting quietly indoors feel a slight shake |
| 震度2 | shindo ni | Most people sitting quietly indoors feel it; some sleepers wake |
| 震度3 | shindo san | Almost everyone indoors feels it; dishes may rattle |
| 震度4 | shindo yon | Nearly everyone is startled; hanging lights swing widely |
| 震度5弱 | shindo go-jaku | Most people are frightened and want to hold on to something |
| 震度5強 | shindo go-kyō | Most people find it hard to walk without holding on |
| 震度6弱 | shindo roku-jaku | Standing is difficult; doors may jam |
| 震度6強 | shindo roku-kyō | You cannot stand and can move only by crawling |
| 震度7 | shindo nana | Tossed about by the shaking; unfixed furniture may even fly |
Why 5 and 6 are split into jaku and kyō
The scale has eight numbers but ten steps. Levels 5 and 6 cover the range where damage starts and grows quickly, so a single 5 or 6 was too broad, and since 1996 each has been divided in two. Jaku (弱) is literally weak and kyō (強) strong, so 5 jaku is the weaker half of five.
The instrument calculates a decimal value, the keisoku shindo, literally measured intensity, and converts it into a level in half steps: 4.5 to under 5.0 is 5 jaku, up to 5.5 is 5 kyō, up to 6.0 is 6 jaku, up to 6.5 is 6 kyō, and 6.5 and above is 7. So 7 has no ceiling, which is why it was never split.
Here 弱 and 強 take their Chinese-derived readings, jaku and kyō; nobody says go-yowai. And 7 is read nana, which broadcasters prefer because shichi is easy to mishear as ichi.
| Japanese | Romaji | Meaning |
|---|---|---|
| 震度5弱を観測しました。 | Shindo go-jaku o kansoku shimashita. | Shindo 5 lower was observed. |
| 震度6強の揺れでした。 | Shindo roku-kyō no yure deshita. | The shaking was shindo 6 upper. |
| 震度7は一番強い揺れです。 | Shindo nana wa ichiban tsuyoi yure desu. | Shindo 7 is the strongest shaking. |
Beyond the basics: how a news bulletin reads the map
When a quake reaches shindo 3 somewhere, JMA's information arrives in stages. About a minute and a half later, the shindo sokuhō, literally intensity quick report, names the regions that recorded 3 or more. After about five minutes, the shingen shindo jōhō adds the source, depth and magnitude, and lists every place that registered 1 or more. For 5 jaku or above, an estimated intensity map, suikei shindo bunpuzu, follows.
Television turns this into one screen, drawn below. The headline is saidai shindo, literally largest shaking degree: the highest value anywhere. Then comes kakuchi no shindo, literally shaking degree of each place, read from the strongest level down. Magnitude and depth are one-off figures about the source. The numbers fall away with distance: the local-reading idea made visible.
| Japanese | Romaji | Meaning |
|---|---|---|
| 先ほど、強い地震がありました。 | Sakihodo, tsuyoi jishin ga arimashita. | A strong earthquake occurred a short while ago. |
| 震度5弱を観測したのは、県東部です。 | Shindo go-jaku o kansoku shita no wa, ken tōbu desu. | The area that recorded shindo 5 lower is the east of the prefecture. |
| 各地の震度をお伝えします。 | Kakuchi no shindo o otsutae shimasu. | Here are the intensities by area. |
| 震源の深さは10キロ、地震の規模を示すマグニチュードは5.8と推定されています。 | Shingen no fukasa wa jukkiro, jishin no kibo o shimesu magunichūdo wa go ten hachi to suitei sarete imasu. | The source was 10 kilometres deep, and the magnitude, which shows the size of the quake, is estimated at 5.8. |
| この地震による津波の心配はありません。 | Kono jishin ni yoru tsunami no shinpai wa arimasen. | There is no threat of a tsunami from this earthquake. |
Confusable pairs: shindo, magnitude and the words around them
JMA explains the first pair with a light bulb. Magnitude is how bright the bulb is; shindo is how bright it is where you are standing. A magnitude 7 far out at sea can therefore give only shindo 3 on land, while a magnitude 5 directly under a town can give 5 jaku.
| Japanese | Romaji | Meaning |
|---|---|---|
| マグニチュードは大きいけど、震度は小さかったね。 | Magunichūdo wa ōkii kedo, shindo wa chiisakatta ne. | The magnitude was big, but the shindo was small, wasn't it? |
| Term | Reading | What it tells you |
|---|---|---|
| 震度 | shindo | Shaking at one place; many values per quake |
| マグニチュード | magunichūdo | Size of the quake itself; one value, with a decimal |
| 震源 | shingen | Where the rupture began underground, literally shaking source |
| 震央 | shin'ō | The spot on the surface above the shingen, literally shaking centre |
| 最大震度 | saidai shindo | The single highest shindo anywhere |
| 各地の震度 | kakuchi no shindo | The list of shindo by area |
| 震度相当 | shindo sōtō | A level estimated without an instrument, literally shindo equivalent |
News speech says shingen or shingenchi even when the map shows the shin'ō, so that difference rarely matters. Shindo sōtō marks a level JMA estimated from surveys, deliberately kept apart from meter readings.
What a shindo number does not tell you
JMA itself lists the limits. The meters sit on the ground or the ground floor of low buildings, so upper floors of taller buildings generally shake more than the published value. Soft ground amplifies shaking, so neighbouring towns at the same distance can differ, and even one town can record different values in different spots.
Tall buildings add a second measure. Large quakes send out slow, rolling waves, chōshūki jishindō, literally long-period earthquake ground motion, which can sway a high-rise far more than the shindo suggests; JMA reports it on a separate four-class scale. Damage also varies with construction, and JMA's table notes that buildings from about 1981 or earlier tend to be less resistant. Colleagues compare notes the next morning.
| Japanese | Romaji | Meaning |
|---|---|---|
| うちは15階なので、かなり揺れました。 | Uchi wa jūgo-kai na node, kanari yuremashita. | I live on the 15th floor, so it shook quite a lot. |
| 長い間、ゆっくり揺れていました。 | Nagai aida, yukkuri yurete imashita. | It swayed slowly for a long time. |
| 同じ市でも、場所によって震度が違います。 | Onaji shi demo, basho ni yotte shindo ga chigaimasu. | Even in the same city, the shindo differs from place to place. |
| 発表より強く感じました。 | Happyō yori tsuyoku kanjimashita. | It felt stronger than the announced level. |
| ここは地盤が弱いそうです。 | Koko wa jiban ga yowai sō desu. | Apparently the ground here is soft. |
Talking about a quake the morning after
The day after a noticeable quake, it is the first topic at work. Friends use plain forms, yureta ne; colleagues add desu and masu; station staff switch to humble keigo such as orimasu. Kekkō, quite a bit, turns a small tremor into a story.
JMA's table also lists what typically stops. From around shindo 4, railway and expressway operators pause or slow services for safety checks, each by its own rules. From around 5 jaku, lifts with earthquake sensors stop automatically, and gas meters with a safety device, maikon mētā, shut off the gas.
| Japanese | Romaji | Meaning |
|---|---|---|
| 昨日の地震、結構揺れましたね。 | Kinō no jishin, kekkō yuremashita ne. | Yesterday's quake shook quite a bit, didn't it? |
| 棚から本が落ちてきました。 | Tana kara hon ga ochite kimashita. | Books fell off my shelf. |
| 地震の影響で、運転を見合わせております。 | Jishin no eikyō de, unten o miawasete orimasu. | Services are suspended because of the earthquake. |
| ただいま安全確認を行っております。 | Tadaima anzen kakunin o okonatte orimasu. | We are currently carrying out safety checks. |
| 地震でエレベーターが止まっています。 | Jishin de erebētā ga tomatte imasu. | The lift has stopped because of the earthquake. |
| ガスが止まったみたいです。 | Gasu ga tomatta mitai desu. | It looks like the gas has cut off. |
Common mistakes with shindo
Reading 5弱 as go-yowai. The cause is that yowai is the first reading learners meet for 弱. Level names use the Chinese-derived readings: go-jaku, roku-kyō.
Treating shindo as magnitude. Someone hears magnitude 7 and pictures shindo 7 everywhere. The cause is that English-language news often gives only the magnitude. The fix is the decimal rule: 6.4 is magnitude; a whole number or a level with jaku or kyō is shindo.
Expecting a scale of ten or twelve. Newcomers used to the twelve-step Modified Mercalli scale read shindo 5 as mid-range. On JMA's scale, 5 jaku is already the level at which dishes and books can fall, so learn the ladder on its own terms.
Assuming the saidai shindo is your shindo. The headline number belongs to the worst-hit point. Check kakuchi no shindo for your area, and remember that your floor and ground may change what you felt.