On August 8, the Japanese Meteorological Agency issued its first-ever “megaquake alert” following a magnitude 7.1 earthquake that hit the Miyazaki prefecture in southern Japan. This quake caused injuries to at least 16 individuals and triggered minor tsunamis up to 50 centimeters tall along the country’s coastline half an hour later.
The epicenter of the Miyazaki quake was located offshore, about 25 kilometers underground, near the Nankai Trough. Experts are concerned that this earthquake may have changed the stress distribution along the fault zone beneath the trough, potentially leading to a more significant megaquake of magnitude 8 or greater in the future. The Japanese government estimates that such a quake could result in the loss of hundreds of thousands of lives.
The Japanese Meteorological Agency stated that the risk of a large-scale earthquake is higher than usual, with the chance of a magnitude 8 or 9 earthquake in the Nankai Trough within the next 30 years being 70 to 80 percent. Seismologist Naoshi Hirata mentioned that the likelihood of a larger quake occurring in the area in the next week is around one in several hundred times.
It is not uncommon for an earthquake to be followed by a larger one shortly afterward. On average, there is a 5 percent chance of a quake being succeeded by a bigger one nearby within a week. Last year, researchers reported that the probability of another megaquake occurring nearby within a week of the Nankai megathrust quake could be significantly higher.
Japan introduced the world’s first publicly available, nationwide earthquake early warning system in 2007 to prepare for tremors. This system aims to issue warnings before the arrival of more damaging waves. In 2011, during the magnitude 9.1 Tohoku earthquake, the system provided residents of Tokyo with one minute of warning before strong shaking began.
In the United States, the Cascadia megathrust fault off the coast of North America is another area where megaquakes are possible. The US operates an early warning system called ShakeAlert for earthquake preparedness. Residents in earthquake-prone areas are advised to have emergency supplies ready and to be familiar with safety protocols during an earthquake.
It is essential to stay informed and prepared for earthquakes, as they can strike without warning. By having a plan in place and knowing what to do during and after a quake, individuals can increase their chances of staying safe in the event of a seismic event.
