Megathrust Prediction, BMKG Calculates When the Tsunami Arrives in South Central Java

Megathrust Prediction, BMKG Calculates When the Tsunami Arrives in South Central Java

Illustration. Megathrust south of Java has the potential to trigger a tsunami of up to 34 meters. (WikiImages/Pixabay)

The Megathrust earthquake in southern Java has the potential to trigger a tsunami with a height of up to 18 meters in the southern coastal area of ​​Central Java. 

This was revealed in the event of an earthquake and tsunami field school (SLG) in Kebumen Regency, which is a southern coastal area of ​​Central Java, Saturday (30/9). 

Head of BMKG Dwikorita Karnawati, in a press release. explained that Kebumen Regency is one of the potential earthquake and tsunami zones in Indonesia because of its position directly opposite the megathrust zone south of Java. 

This Megathurst has, he said, a potential maximum magnitude of M 8.7. The source of this megathrust earthquake is in the subduction zone which is a collision between the Indo-Australian Plate and the Eurasian Plate on the seabed of the Indian Ocean south of Kebumen. 

Modeling the propagation of tsunami waves due to an earthquake using this scenario, said Dwikorita, is estimated to reach 14 - 18 meters in Kebumen Regency, "with an arrival time on the coast of around 38 - 46 minutes."

The impact of the shock caused by the earthquake is estimated to reach VII-VIII MMI, which means it is a strong to very strong shock and can cause moderate to heavy damage. 

As a result, his party continues to hold SLG as part of community disaster literacy in order to "realize zero victims in areas prone to earthquakes and tsunamis."

In the same place, Member of the Indonesian House of Representatives Commission V Lasmi Indaryani assessed that Kebumen and areas along the south of Java really need SLGs to minimize casualties if an earthquake and tsunami occur. 

"Earthquakes and tsunamis are God's will. Because they cannot be predicted, like it or not, whether we like it or not, we have to be prepared. This preparedness must be accompanied by education through this SLG," he concluded. 

Previously, a team of experts, including Dwikorita, in the journal 'On the Potential for Megathrust Earthquakes and Tsunamis Off the Southern Coast of West Java and Southeast Sumatra, Indonesia' published in Natural Hazard in October 2022, predicted a 34 meter tsunami following the 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 can reach 34 m along the western coast of southernmost Sumatra and along the southern coast of Java near the Ujung Kulon Peninsula," quoted from the journal in Springer Natural Hazard. 

The research also revealed that the average tsunami height along the coast of Sumatra and the coast of Java was 11.8 meters and 10.6 meters respectively, a result that combines the effects of back-thrust forces. 

Prediksi Megathrust, BMKG Hitung Kapan Tsunami Tiba di Selatan Jateng

Ilustrasi. Megathrust selatan Jawa berpotensi memicu tsunami hingga 34 meter. (WikiImages/Pixabay)

Gempa Megathrust di selatan Jawa berpotensi memicu tsunami dengan ketinggian hingga 18 meter di kawasan pesisir selatan Jawa Tengah.

Hal ini terungkap dalam gelaran sekolah lapang gempabumi dan tsunami (SLG) di Kabupaten Kebumen, yang merupakan daerah pesisir selatan Jawa Tengah, Sabtu (30/9).

Kepala BMKG Dwikorita Karnawati, dalam siaran persnya. menjelaskan Kabupaten Kebumen merupakan salah satu zona potensi gempa dan tsunami di Indonesia karena posisinya yang berhadapan langsung dengan zona megathrust selatan Jawa.

Megathurst ini, katanya, memiliki potensi magnitude maksimum M 8,7. Sumber gempa megathrust ini berada di zona subduksi yang merupakan tumbukan antara Lempeng Indo-Australia dan Lempeng Eurasi di dasar laut Samudra Hindia selatan Kebumen.

Pemodelan Penjalaran Gelombang Tsunami akibat gempa dengan skenario tersebut, kata Dwikorita, diperkirakan mencapai 14 - 18 meter di Kabupaten Kebumen, "dengan waktu tiba di pesisir pantai sekitar 38 - 46 menit."

Dampak guncangan akibat gempa tersebut diperkirakan mencapai VII-VIII MMI, yang berarti merupakan guncangan yang kuat hingga sangat kuat dan dapat mengakibatkan kerusakan sedang hingga berat.

Walhasil, pihaknya pun terus menggelar SLG sebagai bagian literasi kebencanaan masyarakat demi "mewujudkan zero victim di wilayah-wilayah yang rawan gempabumi dan tsunami."

Di tempat yang sama, Anggota DPR RI Komisi V Lasmi Indaryani menilai Kebumen dan daerah di sepanjang selatan Jawa sangat membutuhkan SLG untuk meminimalisasi jatuhnya korban jika gempa dan tsunami terjadi.

"Gempa dan tsunami adalah kehendak Tuhan. Karena tidak dapat diprediksi maka mau tidak mau, suka tidak suka harus siap. Kesiapan ini harus disertai dengan edukasi melalui SLG ini," tutupnya.

Sebelumnya, tim ahli, termasuk Dwikorita, dalam jurnal 'On The Potential for Megathrust Earthquakes and Tsunamis Off The Southern Coast of West Java and Southeast Sumatra, Indonesia' yang terbit di Natural Hazard pada Oktober 2022, memprediksi tsunami 34 meter buntut megathrust.

Para peneliti mengungkapkan penyebab potensi tsunami besar di selatan Jawa berkaitan dengan tingkat kegempaan yang tinggi di dalam dan sekitar Jawa Barat dan Sumatra sebagai akibat pertemuan lempeng Indo-Australia dan subduksi di bawah lempeng Sunda.

"Kami menunjukkan bahwa ketinggian maksimum tsunami bisa mencapai 34 m di sepanjang pantai barat Sumatra paling selatan dan di sepanjang pantai selatan Jawa dekat Semenanjung Ujung Kulon," dikutip dari jurnal di Springer Natural Hazard tersebut.

Penelitian juga mengungkap ketinggian tsunami rata-rata di sepanjang pantai Sumatera dan pantai Jawa masing-masing adalah 11,8 meter dan 10,6 meter, hasil yang menggabungkan efek gaya dorong balik.