The story of the 32-year earthquake that ended in disaster

A slow motion earthquake that lasted 32 years, slowest ever, ultimately led to the catastrophic Sumatran earthquake in 1861. Researchers from the Nanyang Technological University, Singapore (NTU Singapore) believe their study highlights unconscious factors or possible errors in global earthquake risk assessments today.

Slow moving earthquakes or slow sliding events refer to a type of prolonged stress release phenomenon in which the Earth’s tectonic plates slide against each other without causing great shaking or destruction of the ground. They usually involve movements of a few inches per year to a few inches per day.

The NTU team made the surprise discovery by studying historic sea levels using ancient corals called microatolls on Simeulue Island., located off Sumatra. Growing both laterally and upward, disc-shaped coral microatolls are natural recorders of sea level changes and land rise, thanks to their visible growth patterns. NTY it is a statement.

Using data from microatolons and combining them with simulations of the movement of Earth’s tectonic plates, the NTU team discovered that from 1829 until the Sumatran earthquake in 1861, the southeast of Simeulue Island was sinking faster than expected into the sea.

This slow sliding event was a gradual process that eased tension in the area shallow where two tectonic plates met, the NTU team said. However, this stress was transferred to a neighboring segment deeper, culminating in the magnitude 8.5 earthquake and tsunami in 1861, which caused enormous damage and loss.

The discovery marks the longest slow-slide event on record and will change global perspectives on the time frame and mechanics of the phenomenon, the NTU team said. Scientists previously believed that slow slide events only took place for hours or monthsBut NTU’s research shows that they could, in fact, last for decades without triggering the disastrous earthquakes and tsunamis seen in historical records.

The results, published in the scientific journal Geosciences of nature in May, they led the authors to suggest that current earthquake risk assessments may overlook ongoing slow-slip events in observations and therefore not adequately account for the potential for slow slip events. trigger future earthquakes and tsunamis.

Located far from the land under miles of water, the shallow end of the subduction zone is generally quieter and does not produce as many earthquakes. Its remoteness also makes it difficult to terrestrial scientific instruments detect activities and that scientists understand what is going on.

Therefore, many scientists have tended to interpret the “calm” of the shallow end of the subduction zone in the sense that the tectonic plates below slide smoothly and harmlessly. While this may be correct in some cases, the NTU study found that this slip is not as constant as assumed and can occur during slow slip events.

Taking advantage of their research methodology, the NTU team also highlighted a possible prolonged slow-slide event on the island of Enggano, Indonesia, located about 100 kilometers southwest of Sumatra.

Europe Press

Conocé The Trust Project