Java Island is surrounded by several megathrust zones that store massive energy capable of triggering powerful earthquakes and tsunamis. In this article, we will delve into the details of these megathrusts and their potential threats.
A megathrust is a region where tectonic plates meet, which can lead to powerful earthquakes and tsunamis. These zones are expected to “break” repeatedly with intervals of hundreds of years.
Daryono, Head of the Earthquake and Tsunami Center at the Indonesian Meteorological, Climatological, and Geophysical Agency (BMKG), warned about the threat from two megathrusts in Indonesia that have not “broken” for a long time.
Two Megathrusts with High Potential
The BMKG has identified two megathrusts with high potential to trigger powerful earthquakes and tsunamis: the Sunda Strait Megathrust (M8.7) and the Mentawai-Suberut Megathrust (M8.9). Both of these zones have not experienced a major earthquake in hundreds of years.
The Sunda Strait Megathrust, with a length of 280 km and a width of 200 km, has a slip rate of 4 cm per year. It last “broke” in 1699 and 1780 with a magnitude of 8.5.
The Mentawai-Suberut Megathrust, with a length of 200 km and a width of 200 km, also has a slip rate of 4 cm per year. It last experienced an earthquake in 1797 with a magnitude of 8.7 and in 1833 with a magnitude of 8.9.
Thirteen Megathrusts Surrounding Indonesia
According to the BMKG’s seismic hazard map, there are at least 13 megathrusts surrounding Indonesia. Some of these zones have already “broken” into smaller segments, such as the Mentawai segment which has split into two segments: Mentawai-Siberut and Mentawai-Pagai.
The Jawa segment has also split into three segments: Sunda Strait-Banten, Jawa Barat, and Jawa Tengah-Jawa Timur.
Predicting Megathrust Earthquakes
Although experts can predict the potential magnitude of an earthquake in a megathrust zone, they are still unable to predict when it will occur.
“Despite being able to calculate the maximum magnitude of an earthquake in a megathrust zone, current technology is not yet capable of predicting with certainty when the earthquake will occur,” said BMKG in a statement.
Tsunami Threat
Several studies have shown that these megathrusts, including those near Java, have the potential to trigger tsunamis reaching heights of tens of meters.
Java Island, with its large population, must be vigilant. According to data from the Directorate General of Population and Civil Registration at the Ministry of Home Affairs, as of semester I 2024, the total population of Indonesia is 282,477,584 people, with 55.93% living on Java Island.
List of Megathrusts Threatening Java
Here is a list of megathrusts threatening Java based on the BMKG’s seismic hazard map:
- Sunda Strait-Banten Megathrust: Potential magnitude 8.8, slip rate 4 cm/year, dimensions 280 km x 200 km, history M 8.5 in 1699 and 1780
- Jawa Barat Megathrust: Potential magnitude 8.8, slip rate 4 cm/year, dimensions 320 km x 200 km, history M 8.1 in 1903; M 7.8 in 2006
- Jawa Tengah-Jawa Timur Megathrust: Potential magnitude 8.9, slip rate 4 cm/year, dimensions 440 km x 200 km, history M 7.2 in 1916; M 7.8 in 1994
- Bali Megathrust: Potential magnitude 9.0, slip rate 4 cm/year, dimensions 500 km x 200 km, no recorded history of earthquakes
In conclusion, the megathrusts surrounding Java Island pose a significant threat to the island’s population and infrastructure. It is essential for authorities and residents to be aware of these threats and take necessary precautions to mitigate the impact of potential earthquakes and tsunamis.