Japan Was Shaken Again: What Happened After the 5.9-Magnitude Earthquake?

Japan was jolted awake in the early hours of Sunday, August 23, when a magnitude 5.9 earthquake struck eastern Japan, sending strong shaking through Tokyo and surrounding parts of the Kanto region.

The earthquake was powerful enough to injure dozens of people, disrupt some train services and damage local infrastructure.

But there was one major piece of good news:

There was no tsunami threat.

At least 37 people were injured across five prefectures, with most injuries described as minor. One person suffered a serious injury. Authorities also reported no abnormalities at nearby nuclear facilities.

For a country as accustomed to earthquakes as Japan, the event was a reminder that even moderate earthquakes can have significant consequences when they strike densely populated areas.

And this time, the shaking came while many people were asleep.

The Earthquake Struck at About 2 a.m.

The earthquake occurred at approximately 2:00 a.m. local time on Sunday, August 23.

Its epicentre was in southern Ibaraki Prefecture, northeast of Tokyo, at a depth of roughly 68–70 kilometres.

The Japan Meteorological Agency initially measured the earthquake at magnitude 5.9, while the U.S. Geological Survey recorded it at magnitude 5.8.

Although the epicentre was outside Tokyo, the earthquake was strongly felt across the capital and neighbouring prefectures.

That was partly because the earthquake occurred relatively close to the huge Tokyo metropolitan area.

Millions of people live across Tokyo and the surrounding prefectures, meaning even an earthquake that does not cause widespread structural destruction can still affect a large number of people.

Tokyo Was Among the Areas Hit

Parts of Tokyo recorded lower 5 on Japan's seven-level seismic intensity scale.

That is different from the earthquake's magnitude.

Magnitude measures the overall energy released by an earthquake, while seismic intensity describes how strongly the ground shakes at a particular location.

The lower-5 level of shaking can cause objects to fall from shelves and make it difficult for people to remain standing or move normally.

Other parts of Tokyo experienced intensity 4 shaking, while similar levels were recorded across parts of Ibaraki, Saitama, Chiba, Tochigi, Gunma and Kanagawa prefectures.

For residents suddenly awakened in darkness, the experience was frightening.

Mobile phones issued earthquake alerts shortly before or as the shaking arrived.

Buildings moved.

Furniture shifted.

Objects fell.

And people had to react within seconds.

At Least 37 People Were Injured

The latest reports put the number of injured at 37 people across five prefectures.

The breakdown included:

• 15 in Tokyo
• 9 in Saitama
• 8 in Kanagawa
• 4 in Chiba
• 1 in Ibaraki

Most injuries were not caused by buildings collapsing.

Instead, many people were hurt while trying to get out of bed or move around after being startled by the earthquake.

Some fell.

Others collided with furniture or doors.

One elderly woman in Yokohama suffered a serious hip injury after falling from her bed.

The pattern is a reminder that earthquake injuries do not always come from spectacular structural destruction.

Sometimes the danger is simply the sudden movement of people and objects.

Why Did the Earthquake Feel So Strong?

A magnitude of 5.9 might not sound enormous compared with some of the much larger earthquakes Japan has experienced.

But magnitude alone does not tell the whole story.

The earthquake's location, depth, distance from populated areas and local ground conditions all influence how strongly people experience shaking.

In this case, the earthquake occurred close enough to Tokyo and surrounding communities to produce significant shaking.

Japan also uses its own shindo intensity system, which is designed to describe the actual shaking experienced at different locations.

That helps explain why people in one part of the country might experience very strong movement while people farther away experience considerably less.

High-Rise Buildings Were Also Affected

Another feature of the earthquake was the presence of long-period ground motion.

This type of movement can be particularly noticeable in tall buildings.

Instead of the sharp shaking people might associate with an earthquake, long-period motion can cause buildings to sway slowly for an extended period.

Furniture and objects on upper floors can move significantly.

Authorities reported level-2 long-period ground motion in parts of Tokyo, Saitama and Chiba.

For people living or working high above the ground, that kind of movement can be particularly unsettling.

No Tsunami Warning Was Issued

One of the biggest fears following an earthquake in Japan is the possibility of a tsunami.

That concern was quickly addressed after Sunday's earthquake.

Authorities said there was no tsunami threat.

The earthquake occurred deep enough and in a location that did not create conditions for a dangerous tsunami along Japan's coast.

That significantly reduced the potential scale of the disaster.

Without a tsunami, the main concerns became injuries, infrastructure damage, transportation disruptions and the possibility of aftershocks.

A Water Pipe Burst in Tokyo

The earthquake did cause at least one notable infrastructure problem in Tokyo.

An underground water pipe ruptured in the Koto Ward area, causing water to flood part of a street.

Emergency responders were called to the scene and repairs were carried out.

The incident illustrates how underground infrastructure can be vulnerable even when buildings remain standing.

Water systems, gas lines, electrical networks and transport infrastructure all have to be checked after a significant earthquake.

Train Services Were Disrupted

The earthquake also affected transportation.

Some train services in the Tokyo region were delayed while operators inspected tracks and infrastructure.

Services connecting Tokyo with Narita Airport were among those affected.

However, Japan's high-speed Shinkansen bullet trains continued to operate normally, according to reports.

That distinction is important.

Japan's railway system is designed with sophisticated earthquake detection and safety mechanisms.

When significant shaking is detected, services can be slowed or stopped while operators inspect infrastructure.

The objective is not simply to restore services quickly.

It is to make sure trains can operate safely.

What About Japan's Nuclear Plants?

Another major concern following earthquakes in Japan is nuclear safety.

The country has a history of devastating earthquake-related nuclear accidents, so even a moderate earthquake can trigger close monitoring of nuclear facilities.

Following Sunday's earthquake, authorities reported no abnormalities at nearby nuclear facilities.

Japan Atomic Power Company said checks were conducted at the Tokai nuclear facilities in Ibaraki Prefecture, while the Tokai No. 2 plant was also monitored.

That was another important positive development.

There were no reports of a nuclear emergency resulting from the earthquake.

Japan's Government Reacted Quickly

Japan's government immediately activated its crisis-response mechanisms.

Prime Minister Sanae Takaichi said authorities were working to establish the extent of the damage and provide accurate information to the public.

A liaison office was established at the Prime Minister's Office Crisis Management Center.

The government also urged residents in areas that experienced strong shaking to remain alert for the possibility of another earthquake of similar strength.

That warning was important because earthquakes can be followed by aftershocks.

Why Are Aftershocks a Concern?

Aftershocks are smaller earthquakes that can occur following a larger earthquake.

They may happen minutes, hours or days after the initial event.

Most are weaker.

But some can still be strong enough to cause additional damage, particularly to structures or infrastructure that may already have been weakened.

That is why Japanese authorities urged residents to remain vigilant for several days following the August 23 earthquake.

People in affected areas were advised to keep emergency supplies accessible and avoid unnecessary risks around damaged structures.

Japan's Earthquake Preparedness Was Put to the Test

One reason the earthquake did not become a much larger disaster is Japan's extensive earthquake-preparedness system.

Japan has invested heavily in:

• Earthquake early-warning technology
• Building regulations
• Emergency response systems
• Public education
• Disaster drills
• Railway safety systems
• Emergency communications
• Seismic monitoring

Residents are accustomed to receiving earthquake alerts on their phones.

Buildings are designed with seismic safety in mind.

And emergency agencies are trained to respond rapidly.

The system does not eliminate earthquake risk.

But it can dramatically reduce the consequences.

Why Japan Is So Prepared

Japan sits along the Pacific Ring of Fire, an area with intense tectonic activity.

Earthquakes are therefore part of life in the country.

The challenge is not preventing earthquakes.

That is impossible.

The challenge is reducing deaths and damage when they happen.

This philosophy has influenced Japanese construction, transportation and emergency planning for decades.

The August 23 earthquake provided another real-world test of that preparedness.

Most Injuries Were Avoidable

One of the most interesting aspects of the earthquake is that many injuries occurred because people were caught off guard.

Someone wakes suddenly.

They jump out of bed.

The floor is moving.

Furniture is shifting.

The lights may be off.

In the confusion, a person falls or hits something.

This is why disaster experts often recommend keeping the area around beds free from dangerous objects and knowing what to do before an earthquake happens.

People should not automatically rush toward doors or stairways during intense shaking.

The safest immediate response is generally to protect yourself from falling objects and remain in a safe position until the strongest shaking stops.

What Can Other Countries Learn?

Japan's experience has lessons for countries around the world.

Earthquakes can happen without warning.

And countries that do not experience frequent earthquakes can still be affected by a major event.

Preparedness should therefore include simple measures such as:

• Securing heavy furniture
• Knowing emergency exits
• Keeping basic emergency supplies
• Having a family communication plan
• Learning how to turn off utilities if necessary
• Knowing how to respond during shaking

These measures can save lives.

The Earthquake Was Moderate — But the Location Mattered

It is important not to exaggerate what happened.

The August 23 earthquake was not comparable in scale with Japan's most catastrophic historical earthquakes.

There was no tsunami.

There was no widespread building collapse.

There was no major nuclear incident.

But it still injured at least 37 people and disrupted daily life across one of the world's most densely populated metropolitan regions.

That is why the story matters.

A moderate earthquake in a densely populated area can have a much larger human impact than the same earthquake occurring in a remote location.

Another Earthquake Later That Day

Japan's seismic activity did not end with the early-morning Tokyo-area earthquake.

Reports indicated that another earthquake of around magnitude 6.0 struck off Hokkaido later on August 23.

The second event was geographically separate from the Tokyo-area earthquake, but its occurrence on the same day added to the sense of an unusually active day for earthquakes across Japan.

This does not mean the two earthquakes were necessarily connected.

Japan is located in a highly active seismic region, and multiple earthquakes can occur within the country over short periods.

No Reason for Panic

The most important message for people following the story is that there is no reason to assume that a much larger earthquake is about to happen simply because a magnitude 5.9 earthquake occurred.

Earthquake scientists cannot reliably predict exactly when and where the next major earthquake will strike.

What authorities can do is monitor seismic activity and advise residents to remain prepared.

That is precisely what Japanese officials were doing.

The Bigger Picture

Japan's August 23 earthquake was a reminder of the unpredictable power beneath the ground.

It arrived while people were sleeping.

Phones sounded emergency alerts.

Buildings shook.

Trains were delayed.

A water pipe burst.

Dozens of people were injured.

But the country's extensive preparation helped prevent a moderate earthquake from becoming a much larger disaster.

And perhaps that is the most important part of the story.

Disaster preparedness does not mean disasters stop happening.

It means societies become better at surviving them.

What Happens Next?

Authorities will continue monitoring the affected regions for aftershocks and inspecting infrastructure.

Residents will remain alert, particularly in areas where shaking was strongest.

Transport operators will continue checking railway infrastructure.

Emergency services will assess reported damage.

And scientists will continue studying the earthquake to better understand what happened beneath southern Ibaraki.

For most people, life will gradually return to normal.

But the memory of those few frightening minutes will remain.

The Bottom Line

Japan was shaken by a magnitude 5.9 earthquake around 2 a.m. on August 23, with the epicentre in southern Ibaraki Prefecture at a depth of roughly 68–70 kilometres.

The earthquake was strongly felt in Tokyo and surrounding parts of the Kanto region. At least 37 people were injured across Tokyo, Saitama, Kanagawa, Chiba and Ibaraki, with most injuries considered minor.

Some train services were disrupted, a water pipe burst in Tokyo and authorities inspected infrastructure across the affected areas.

But there was no tsunami threat, and no abnormalities were reported at nearby nuclear facilities.

Japanese authorities have warned residents to remain vigilant because aftershocks of similar strength are possible.

For now, however, the most significant story is one of resilience.

Japan was shaken. Tokyo was startled. Dozens were injured. But the country's earthquake-preparedness system once again showed why preparation matters.

And for millions of people who woke up to the sound of earthquake alerts and moving buildings, Sunday morning delivered a powerful reminder:

When the ground moves, being prepared can make all the difference.