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BMKG Warns South Java Megathrust Will Last Until Doomsday

The Meteorology, Climatology and Geophysics Agency (BMKG) warned that the megathrust zone which could trigger a devastating tsunami in the south of Java Island would continue to exist at any time, even until the end of the world.

“Megathrust will continue, until the end of the world this potential will not end,” said Head of the Earthquake and Tsunami Center, Daryono at the BMKG Office, Jakarta, Friday (3/11).

Megathrust is an area where Earth’s tectonic plates meet at the location of a subduction zone. Earth’s tectonic plates can reach thousands of kilometers and form the basis of continents and oceans.

These plates collide, slide, and move away from each other.

The plates sometimes collide with each other or one plate is pushed beneath another plate in a subduction zone. In other words, a subduction zone is a zone where these plates meet.

When a number of tectonic plates meet, powerful earthquakes, volcanic eruptions and landslides can occur

Indonesia is surrounded by 13 megathrusts spread from Aceh to Papua, and two of them are in the south of Java, namely in the west and east.

These two megathrusts have the potential for a very large earthquake of up to a magnitude of 9.1. Megathrust earthquakes are a phenomenon that recurs over a certain period of time.

“For the complete tsunami potential, we have lots of tide gauges that the Geospatial Agency (BG) collaborates with to monitor, so our tide gauge is in South Java,” he said.

Tide Gauge is an instrument used to measure changes in sea level to detect wave variations.

He explained that almost all megathrust points are equipped with tide gauges, resulting in modeling when an earthquake occurs based on magnitude.

In this way, BMKG can provide a warning if the sea level falls, so that when the water level drops by a certain level the warning siren will come on.

Previously, a number of experts stated that the potential for tsunami waves in the southern part of western Java could reach 34 meters.

This is summarized in a scientific article entitled On The Potential for Megathrust Earthquakes and Tsunamis Off The Southern Coast of West Java and Southeast Sumatra, Indonesia, which was published in Natural Hazard in October 2022.

INFOGRAPHIC: Indonesia Surrounded by 13 Megathrust
Researchers revealed that the cause of the potential for a large tsunami in southern Java is related to the high level of seismicity in and around West Java and Sumatra as a result of the meeting of the Indo-Australian plate and subduction under the Sunda plate.

“We show that the maximum tsunami height could reach 34 m along the western coast of southernmost Sumatra and along the southern coast of Java near the Ujung Kulon Peninsula,” the journal was quoted as saying.

The western segment of the megathrust (in southern Sumatra) has a trench-parallel length of 325km, a width of 120km, and homogeneous slip (slip) of 24 m. The eastern segment is 442 km long, 109 km wide, with a homogeneous slip of 20 m.

Meanwhile, the backthrust is 312 km long and 55 km wide, with a homogeneous slip of 16m.

The researchers carried out tsunami modeling in the area with two scenarios, one without backthrust, the other including backthrust.

Source: CNN