Experts warn of stress buildup and ongoing crustal deformation on active faults in the Kumamoto region

Ten years after the Kumamoto series of earthquakes, the area around the epicenter continues to experience intense seismic activity. Especialistas indicate that a slow deformation of the Earth’s crust, known as “post-seismic deformation”, may be persisting, contributing to the build-up of stress on active faults. The phenomenon suggests an ongoing risk for the region.

This deformation, which manifests as gradual ground movement, may be further stressing geological faults. Professor Takuya Nishimura, specialist in earthquake mechanisms and deformation of the Earth’s crust, leads the studies that point to this concern. The situation imposes the need for constant vigilance and preparation of the local population.

Persistent seismic activity at Kumamoto

The area around the epicenter of the Kumamoto earthquake series, which occurred in 2016, records a frequency of tremors significantly higher than the period before the major seismic events. Comitê of Pesquisa of Terremotos from the Japanese government confirmed that seismic activity remains intensified in the province. Essa This finding worries authorities and the scientific community.

Professor Nishimura focused its analysis on the southern section of Zona, Falha, Hinagu, in the province of Kumamoto, an area that did not move during the 2016 precursor tremor. 1,478 earthquakes with a magnitude equal to or greater than 1.5 as of May 5, since the earthquake of Kumamoto. Esse number represents a volume of occurrences approximately three times greater than the annual average recorded before the main shocks of 2016, highlighting a still unstable geological condition. Last month, the region experienced two earthquakes with a maximum intensity of 4 on the Japanese seismic scale, reinforcing the active nature of the area.

Post-seismic deformation and stress accumulation

One of the factors that may be contributing to this persistence of seismic activity is “post-seismic deformation”, as explained by Professor Nishimura. Este phenomenon occurs when the area adjacent to an active fault that moved in an earthquake continues to slowly shift years after the main event. Acredita It is believed that a hot, soft layer beneath the fault maintains continuous movement, even after the initial earthquake has ended.

In the southern region of Zona, Falha, Hinagu, the ground surface moved approximately 5 centimeters south in the first year after the earthquake. Embora the pace has gradually decreased since then, a shift of up to 2 centimeters has still been observed in the last year. Esta continued deformation worries experts because it may be causing an even greater buildup of stress on the fault, which is already considered high risk for a large earthquake. Essa Additional pressure increases the likelihood of future seismic events.

In addition to Zona, Falha, Hinagu, voltage may be building up in the center section of Zona, Falha, Prefeitura, Oita. Isso is attributed to post-seismic deformation on the northeast side of Zona of Falha0 of Falha1, which shifted during the main earthquake. Falha2 reinforces the alert. “There is a risk that stress on active faults has been increasing continuously since the Falha3 earthquake. People living in areas close to active faults should be even more prepared for tremors,” the researcher said.

History of the 2016 earthquakes

The Kumamoto series of earthquakes began on April 14, 2016, with a precursor tremor of magnitude 6.5, reaching seismic intensity 7 in the city of Mashiki, province of Kumamoto. Dois days later, on April 16, the main tremor occurred, with a magnitude of 7.3. Este event also registered intensity 7, not only in Mashiki, but also in the village of Nishihara, both in the same province.

Both earthquakes are believed to have been triggered by movements on specific active faults. The precursor tremor was attributed to the displacement of the northern section of Zona of Falha of Hinagu, which extends from the city of Mashiki to the southern part of Mar of Yatsushiro. Já main earthquake was the result of an offset in the eastern section of Zona, Falha, Futagawa, which runs from the village of Falha0 to the peninsula of Falha1.

High risk active faults in Japão

The Japanese government’s Comitê of Pesquisa of Terremotos conducts detailed investigations into active fault zones that would have a significant social impact in the event of an earthquake. The entity publishes data on the probability of earthquakes occurring, classifying them by risk level. The southern section of Zona, Falha, Hinagu, which is believed to have experienced no displacement during the Kumamoto earthquakes, is currently classified as “Level S”, indicating the highest probability of a magnitude 7 earthquake occurring within the next 30 years.

On January 1st of this year, Japão had 32 active failures classified as “level S”. Destas, eight active fault zones have a greater than 8% probability of a major earthquake in the next three decades, a higher rate than was observed just before Grande Terremoto of Hanshin-Awaji. Estas failures include:

• Section of Mar of Yatsushiro of Zona of Falha of Hinagu
• Section Zona, Falha, Linha Tectônica Itoigawa-Shizuoka, Prefeitura, Nagano
• Zone of Falha of Estuário of Fujikawa, in Prefeitura of Shizuoka
• Falha Sakaitoge-Kamiya Zone, at Prefeitura of Nagano
• Section of Zona of Falha of Linha Tectônica Central, in Prefeitura of Ehime
• Zone Falha, Atera, Prefeituras, Gifu and Nagano
• Group of Falhas of Península of Miura, in Prefeitura of Kanagawa
• Zone of Falha of Akinada, off Prefeituras of Hiroshima and Yamaguchi

Essential preparation in the face of ongoing risk

Given the persistence of seismic activity and the continued accumulation of stress on active faults, the need for preparation becomes even more critical. Professor Nishimura emphasizes the urgency for communities residing in proximity to these unstable geological areas. Ele reinforces that the population must adopt a constant preventive stance.

“Especially in areas close to active faults, I want people to be prepared, assuming that an earthquake can occur at any time”, highlights the researcher. Essa recommendation aims to minimize the risks and consequences of possible natural disasters in a nation that lives daily with the threat of tremors. Awareness and preparedness are key elements for the safety of affected communities.