Phones fell silent across a wide alert area
NTT Docomo failed to deliver an earthquake warning issued at about 12:40 p.m. on October 16, 2026, to eligible customers across seven Japanese regions. The company identified an internal system fault and warned that emergency messages could continue to go undelivered until repairs were completed.
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The affected areas were Hokkaido, Tohoku, Hokuriku, Kanto, Koshin, Tokai and the Izu Islands. Docomo said all users eligible to receive its emergency Area Mail in those areas were affected, putting the failure across much of eastern Japan rather than in a single city or prefecture.
The Japan Meteorological Agency later withdrew the warning because it was a false alarm. Its initial estimate described a magnitude 9.9 earthquake in the Kuril Islands. The actual earthquake was magnitude 6.9 near the Kamchatka Peninsula, with shaking of intensity 1 recorded in Hakodate, Hokkaido.
Docomo explained that its system had incorrectly judged data received from the agency to be abnormal. The company said its delivery failure was unrelated to the agency's subsequent withdrawal of the warning. Two separate problems therefore occurred: an inaccurate earthquake warning was issued, and Docomo's system failed to pass that warning to customers.
The immediate concern for subscribers extended beyond the false alarm. Docomo expected repairs to take several days, leaving a period during which further earthquake alerts might also fail to arrive. Its public notice confirmed that the cause had been identified and that work to fix the fault was under way.
What happened at lunchtime
The warning prompted sharply different experiences among people in the same place. Many phones sounded when the warning was issued and again when it was withdrawn. Some Docomo customers, however, heard neither the initial warning they expected nor the sounds coming from their own devices while nearby phones rang.
A male Docomo customer described eating lunch with two colleagues when both companions received alerts but his phone remained silent. Posts on X described similar experiences, including an ahamo customer whose device did not sound and a user who said a Rakuten phone received the alert while a Docomo phone did not.
The sequence on October 16 was:
- At about 12:40 p.m., the Japan Meteorological Agency issued an earthquake early warning covering a broad area from Hokkaido toward central Japan.
- Docomo's system failed to distribute the corresponding Area Mail to eligible customers in seven regions.
- The agency subsequently withdrew the warning as a false alarm.
- Later that day, Docomo acknowledged the delivery failure, identified a system fault and warned that further alerts might not arrive before repairs were finished.
Customers were describing a failure of a specific emergency warning service. The company's announcement concerned Area Mail delivery, rather than a general outage affecting ordinary calls or internet access.
What Docomo confirmed
Docomo's October 16 official apology notice identified the cause as a malfunction in its own system. It said the earthquake early warning distributed by the meteorological agency following the earthquake near Kamchatka had not been delivered to customers who should have received it.
The notice listed all seven target regions and warned that Area Mail might remain unavailable until the fault was resolved. Docomo also said it had identified the cause and was moving urgently to correct it.
Docomo apologised to customers in the notice:
We sincerely apologise for the inconvenience and concern caused to our customers.
The company subsequently explained that its system had mistakenly classified incoming agency data as abnormal. That places the delivery problem at the stage where Docomo processes information received from the meteorological agency before sending an alert to phones.
Docomo said the incident was not caused by unauthorised access or a cyberattack. It expected the malfunction to be resolved within several days, although no exact restoration date or number of affected subscribers was announced.
Why the earthquake warning was withdrawn
The meteorological agency's initial warning described a magnitude 9.9 earthquake in the Kuril Islands and covered an extensive area of Japan. The earthquake that actually occurred was magnitude 6.9 near the Kamchatka Peninsula, farther northeast.
Hakodate recorded a seismic intensity of 1, the lowest numbered level on Japan's shaking scale. That was far below the strong shaking conditions used to trigger the emergency distribution described in Docomo's notice.
Magnitude and seismic intensity describe different things. Magnitude measures the size of an earthquake at its source. Seismic intensity describes how strongly the ground shakes at a particular location. One earthquake has a magnitude, while different towns can experience different levels of shaking.
The agency was investigating why it issued the erroneous warning and said a cyberattack was not responsible. Its investigation concerned the earthquake information itself. Docomo's repair work concerned the separate failure to deliver the warning through its network.
The distinction matters for customers: the agency's withdrawal corrected the public warning, while Docomo still needed to repair its delivery system so later emergency messages could reach the phones meant to receive them.
How Area Mail decides where to send alerts
Docomo's Area Mail service uses the meteorological agency's earthquake early warnings to send emergency messages simultaneously to mobile phones in selected areas. Japan is divided into about 200 areas for this distribution process, allowing warnings to be directed toward places where strong shaking is forecast.
The company's notice describes two stages in deciding when and where to send a message. First, the forecast must indicate a maximum seismic intensity of at least 5 lower, or long period ground motion of class 3 or higher. Once that condition is met, alerts go to areas expecting intensity 4 or higher, or long period ground motion of class 3 or higher.
Japan's intensity scale divides levels 5 and 6 into lower and upper categories. Intensity 5 lower is therefore a shaking category, not an earthquake magnitude. Long period ground motion means slow swaying that can strongly affect tall buildings, and it is measured on a separate scale.
The service is designed to act on predicted shaking. Emergency warnings have to reach people quickly, before the full extent of an earthquake is known. On October 16, the initial forecast made the seven regions eligible for distribution, but Docomo's processing fault stopped the messages from reaching its customers.
Other networks had different results
KDDI and SoftBank said they had confirmed no similar incident. Rakuten Mobile was investigating at the time of the announcements. A customer's account of a Rakuten phone sounding offered one local example of successful delivery, while the company's wider checks were still in progress.
Japan's four major mobile operators distribute earthquake early warnings through their own network equipment to devices in areas designated by the meteorological agency. People sitting together can therefore receive different results when one operator's distribution system fails.
Reception also depends on whether a phone can receive a signal from a base station. A device in a place with weak coverage may miss an emergency message. For this incident, however, Docomo identified a fault within its own system affecting the eligible users across the seven target regions.
The lunchtime accounts made the practical effect easy to recognise: some people received an immediate signal to react, while a Docomo customer beside them received no corresponding warning. The company acknowledged the same broad delivery problem in its announcement.
Repairs leave a temporary warning gap
Docomo's warning that messages could continue to fail was the most pressing information for customers after the false alarm ended. A later earthquake could generate another alert while the company was still repairing its system.
The company expected restoration within several days. Until it confirmed a fix, customers faced uncertainty about whether an earthquake Area Mail message would reach their phone. People in the affected regions could also follow earthquake information through television, radio and official public announcements rather than depend on a single device.
Docomo listed its Information Center for customer enquiries, open daily from 9 a.m. to 8 p.m. Customers calling from a Docomo mobile phone could dial 151 free of charge. The number for calls from other phones was 0120-800-000.
The two organisations had separate tasks to complete: the meteorological agency was investigating its incorrect warning, while Docomo was correcting the system fault that blocked delivery. For subscribers, the next concrete milestone was confirmation that the emergency distribution service had been restored.
Key Points
- Docomo failed to deliver the earthquake alert issued at about 12:40 p.m. on October 16, 2026.
- Eligible customers in Hokkaido, Tohoku, Hokuriku, Kanto, Koshin, Tokai and the Izu Islands were affected.
- The company said its system incorrectly judged incoming meteorological agency data to be abnormal.
- The agency withdrew its warning after an initial magnitude 9.9 estimate. The actual earthquake was magnitude 6.9 near Kamchatka.
- Docomo expected repairs within several days and warned that further Area Mail messages might fail before restoration.
- KDDI and SoftBank confirmed no similar incident; Rakuten Mobile was investigating.
