Brain Inc.'s "YureZuba" Successfully Predicts Sanriku-oki M7.4 Earthquake on April 20, Contributing to Over 850 Days of Zero Earthquake Casualties
Brain Inc.'s "YureZuba" app successfully predicted the M7.4 Sanriku-oki earthquake on April 20, 2026, contributing to zero casualties. This achievement extends the period of zero earthquake casualties in Japan to over 850 days since the Noto Peninsula earthquake on January 1, 2024.
📋 Article Processing Timeline
- 📰 Published: May 1, 2026 at 17:00
- 🔍 Collected: May 1, 2026 at 08:31
- 🤖 AI Analyzed: May 1, 2026 at 11:02 (2h 31m after Collected)
Brain Inc. (Shizuoka City), which operates an earthquake forecasting service, successfully predicted and forecasted the M7-class major earthquake that occurred off the coast of Sanriku on April 20, 2026 (Mw7.4, Mj7.7, maximum seismic intensity 5+), using its app "YureZuba." This contributed to achieving zero casualties from the major earthquake, extending the period of zero earthquake casualties in Japan to over 850 days since the Noto Peninsula earthquake on January 1, 2024.
**[Background and Content of Sanriku-oki Earthquake Prediction and Forecast]**
At observation points in northern Hokkaido and northern Tohoku, a significant geomagnetic and geoelectric anomaly (Figure 1) appeared on March 23, 2026 (UTC (UTC+9 hours = Japan time)), and the "b-value" based on the Gutenberg-Richter law in the region decreased to around 0.2. As a result, a major earthquake of M7 class was predicted to occur in the northern Tohoku region (offshore), centered off Sanriku or Iwate Prefecture, and an emergency major earthquake forecast was distributed nationwide on March 24 at 11:22 AM, with a forecast period of two weeks.
Subsequently, a major earthquake of Mw7.3 occurred in Vanuatu in the South Pacific on March 30, which slightly relaxed the stress on the Japan Trench from the North Pacific Plate, making it likely that the earthquake's occurrence would be delayed. Based on past empirical rules, a major earthquake of similar magnitude occurs domestically two to three weeks after a major earthquake in Vanuatu, so the initial forecast deadline was extended by another two weeks to April 22 as the final forecast deadline (Figure 2 shows the final forecast distributed on April 19 at 12:22 PM).
Figure 1: Observed waveform of geomagnetic anomaly (Northern Hokkaido observation point, March 23, 2026 (UTC))
Figure 2: "YureZuba" regular earthquake forecast (Distributed on April 19, 2026, 12:22 PM)
**[Results of the Predicted Earthquake]**
As a result of this forecast, a moment magnitude Mw7.4 earthquake (Japan Meteorological Agency magnitude Mj7.7, maximum seismic intensity 5+) occurred off the coast of Sanriku around 4:53 PM on April 20, and a maximum tsunami height of 80cm was observed at Kuji Port in Iwate Prefecture. According to the USGS (United States Geological Survey), the epicenter was in the boundary area between off Sanriku and off Iwate Prefecture. The timing, location, and magnitude of the earthquake were all within the forecast range, although the forecast deadline was extended by two weeks from the original deadline.
**[Achievements and Future Outlook]**
From the above, earthquake forecasting by the "YureZuba" app significantly strengthened pre-disaster preparedness and initial response capabilities, helping to prevent any casualties even from an M7-class, maximum seismic intensity 5+ major earthquake like the recent Sanriku-oki earthquake. This has accumulated useful case studies as an earthquake disaster prevention scheme.
Furthermore, by achieving zero casualties (total of direct and disaster-related deaths) in this Sanriku-oki earthquake, the period of zero earthquake casualties in Japan has exceeded 850 days as of April 30, 2026, since the Noto Peninsula earthquake on January 1, 2024.
For future inland direct-hit major earthquakes, including the anticipated M7-class direct hit on Tokyo, it is expected that areas around the strong seismic source region will be caught off guard because emergency earthquake warnings will not be timely.
To prevent such situations, we will continue to deploy earthquake disaster prevention schemes utilizing "YureZuba" and "Emergency Major Earthquake Forecast" for major, giant, and damaging earthquakes occurring nationwide. By doing so, we intend to continue protecting the lives, safety, and security of the public, and to maintain the period of zero casualties from disasters for as long as possible, making the Hokkaido earthquake and Noto Peninsula earthquake the last ones.
(For your reference and additional explanatory materials below)
**[Method and History of Earthquake Prediction and Forecast]**
Brain Inc. developed the highly accurate "Three-type Precursor Earthquake Prediction Method," which comprehensively analyzes and determines three types of earthquake precursors—geomagnetic and geoelectric anomalies, low-frequency sound, and foreshock activity—by combining seismology with electromagnetism, acoustics, vibration engineering, and fracture mechanics. Since 2016, it has put into practical use an earthquake forecasting network that distributes prediction results to end-users nationwide via email and apps.
Among the three types of precursor phenomena, low-frequency sound occurs about one to two months before an earthquake, so it is applied to medium- to long-term earthquake prediction. Geomagnetic and geoelectric anomalies occur about one to two weeks before, so they are applied to short-term earthquake prediction. Foreshock activity occurs a few hours to a few days before an earthquake, so it is used for immediate earthquake prediction and to determine whether an earthquake that has occurred will converge or lead to a larger main shock.
Figure 3: Principle of geomagnetic and geoelectric anomalies
**[Principle of Earthquake Precursor Phenomena (Geomagnetic and Geoelectric Anomalies)]**
Geomagnetic and geoelectric anomalies (Figure 3) have been confirmed and verified through rock fracture experiments and various seismic observations to occur due to the "piezoelectric effect" just before rocks forming troughs and faults fracture.
Since this phenomenon is a precursor process (the fracture process itself) of rock fracture, it has an almost 100% correlation with earthquake occurrence and is essential as a precursor phenomenon.
**[Background and Content of Sanriku-oki Earthquake Prediction and Forecast]**
At observation points in northern Hokkaido and northern Tohoku, a significant geomagnetic and geoelectric anomaly (Figure 1) appeared on March 23, 2026 (UTC (UTC+9 hours = Japan time)), and the "b-value" based on the Gutenberg-Richter law in the region decreased to around 0.2. As a result, a major earthquake of M7 class was predicted to occur in the northern Tohoku region (offshore), centered off Sanriku or Iwate Prefecture, and an emergency major earthquake forecast was distributed nationwide on March 24 at 11:22 AM, with a forecast period of two weeks.
Subsequently, a major earthquake of Mw7.3 occurred in Vanuatu in the South Pacific on March 30, which slightly relaxed the stress on the Japan Trench from the North Pacific Plate, making it likely that the earthquake's occurrence would be delayed. Based on past empirical rules, a major earthquake of similar magnitude occurs domestically two to three weeks after a major earthquake in Vanuatu, so the initial forecast deadline was extended by another two weeks to April 22 as the final forecast deadline (Figure 2 shows the final forecast distributed on April 19 at 12:22 PM).
Figure 1: Observed waveform of geomagnetic anomaly (Northern Hokkaido observation point, March 23, 2026 (UTC))
Figure 2: "YureZuba" regular earthquake forecast (Distributed on April 19, 2026, 12:22 PM)
**[Results of the Predicted Earthquake]**
As a result of this forecast, a moment magnitude Mw7.4 earthquake (Japan Meteorological Agency magnitude Mj7.7, maximum seismic intensity 5+) occurred off the coast of Sanriku around 4:53 PM on April 20, and a maximum tsunami height of 80cm was observed at Kuji Port in Iwate Prefecture. According to the USGS (United States Geological Survey), the epicenter was in the boundary area between off Sanriku and off Iwate Prefecture. The timing, location, and magnitude of the earthquake were all within the forecast range, although the forecast deadline was extended by two weeks from the original deadline.
**[Achievements and Future Outlook]**
From the above, earthquake forecasting by the "YureZuba" app significantly strengthened pre-disaster preparedness and initial response capabilities, helping to prevent any casualties even from an M7-class, maximum seismic intensity 5+ major earthquake like the recent Sanriku-oki earthquake. This has accumulated useful case studies as an earthquake disaster prevention scheme.
Furthermore, by achieving zero casualties (total of direct and disaster-related deaths) in this Sanriku-oki earthquake, the period of zero earthquake casualties in Japan has exceeded 850 days as of April 30, 2026, since the Noto Peninsula earthquake on January 1, 2024.
For future inland direct-hit major earthquakes, including the anticipated M7-class direct hit on Tokyo, it is expected that areas around the strong seismic source region will be caught off guard because emergency earthquake warnings will not be timely.
To prevent such situations, we will continue to deploy earthquake disaster prevention schemes utilizing "YureZuba" and "Emergency Major Earthquake Forecast" for major, giant, and damaging earthquakes occurring nationwide. By doing so, we intend to continue protecting the lives, safety, and security of the public, and to maintain the period of zero casualties from disasters for as long as possible, making the Hokkaido earthquake and Noto Peninsula earthquake the last ones.
(For your reference and additional explanatory materials below)
**[Method and History of Earthquake Prediction and Forecast]**
Brain Inc. developed the highly accurate "Three-type Precursor Earthquake Prediction Method," which comprehensively analyzes and determines three types of earthquake precursors—geomagnetic and geoelectric anomalies, low-frequency sound, and foreshock activity—by combining seismology with electromagnetism, acoustics, vibration engineering, and fracture mechanics. Since 2016, it has put into practical use an earthquake forecasting network that distributes prediction results to end-users nationwide via email and apps.
Among the three types of precursor phenomena, low-frequency sound occurs about one to two months before an earthquake, so it is applied to medium- to long-term earthquake prediction. Geomagnetic and geoelectric anomalies occur about one to two weeks before, so they are applied to short-term earthquake prediction. Foreshock activity occurs a few hours to a few days before an earthquake, so it is used for immediate earthquake prediction and to determine whether an earthquake that has occurred will converge or lead to a larger main shock.
Figure 3: Principle of geomagnetic and geoelectric anomalies
**[Principle of Earthquake Precursor Phenomena (Geomagnetic and Geoelectric Anomalies)]**
Geomagnetic and geoelectric anomalies (Figure 3) have been confirmed and verified through rock fracture experiments and various seismic observations to occur due to the "piezoelectric effect" just before rocks forming troughs and faults fracture.
Since this phenomenon is a precursor process (the fracture process itself) of rock fracture, it has an almost 100% correlation with earthquake occurrence and is essential as a precursor phenomenon.