Penjelasan Peneliti BRIN soal Ancaman Megathrust

Summary

The script discusses the significant mega-fault locations in Indonesia, particularly in West Sumatra to South Java, which are as large as the island of Java itself. It explains the concept of 'megatrust' and how these massive fault areas can cause significant earthquakes and tsunamis. The script also touches on the historical seismic activity in South Java, highlighting the potential for future large-scale events. It mentions the ongoing preparation for an updated seismic map for 2024 and the importance of understanding seismic gaps, which are areas expected to experience significant earthquakes in the future.

Takeaways

• 🌍 The primary mega-thrust locations in Indonesia are along the western coast of Sumatra to the southern part of Java, covering a vast area comparable to the size of the island of Java.
• 🔍 An update to the mega-thrust location map is being prepared for 2024, which will provide more detailed information on these areas.
• 🏞️ The mega-thrust areas are significant because they can cause large-scale movements, such as the hypothetical scenario of Java moving 20 meters, causing significant seismic activity.
• 🌊 Historically, there have been many tsunami events in Indonesia, with 18 compiled by the Indonesian Meteorology, Climatology, and Geophysical Agency (BMKG) from the 1600s to the 2000s.
• 📍 The South Java region is particularly highlighted due to its seismic activity and the potential for tsunamis, including the Mentawai Islands which have been a focus of concern.
• 🚨 The concept of 'seismic gap' is introduced, referring to areas that are expected to experience significant earthquakes due to the lack of recent seismic activity.
• 🌋 The movement of tectonic plates, particularly the Indo-Australian plate subducting under the Sunda plate, is a key factor in the occurrence of mega-thrust earthquakes in the region.
• 🌊 Tsunamis are generated when the movement of the earth's crust at the bottom of the ocean causes a displacement of water, creating waves that can be much larger than wind-generated waves.
• 🏔️ The Palung area, located in the southern part of Java, is highlighted as a significant location for past mega-thrust earthquakes and tsunamis.
• 📊 The script discusses various earthquake events, including the 2006 Pangandaran earthquake and tsunami, which was unique due to the high tsunami waves despite the earthquake's epicenter in a soft sediment area that reduced the shaking.

Q & A

What is the primary location of the mega-thrust zone in Indonesia?

The primary location of the mega-thrust zone in Indonesia is along the western coast of Sumatra to the southern part of Java.

How large is the area of the mega-thrust zone in Indonesia?

The area of the mega-thrust zone in Indonesia is quite large, comparable to the size of the island of Java.

What is the significance of the mega-thrust zone in terms of seismic activity?

The mega-thrust zone is significant because it is an area where the movement of tectonic plates can cause large earthquakes and tsunamis.

What is the term used to describe the expected but yet-to-occur large earthquakes in certain seismically active areas?

The term used to describe the expected but yet-to-occur large earthquakes in certain seismically active areas is 'Seismic gap'.

What is the role of the Indo-Australian Plate in the formation of the mega-thrust zone in Indonesia?

The Indo-Australian Plate plays a role in the formation of the mega-thrust zone in Indonesia by subducting or being pushed under the continental plates, causing the plates to move and potentially leading to earthquakes.

Why is the southern part of Java often mentioned in the context of mega-thrust earthquakes?

The southern part of Java is often mentioned in the context of mega-thrust earthquakes because it is located along the mega-thrust zone where significant seismic activity can occur.

What is the term 'megatrust' mentioned in the script, and what does it refer to?

The term 'megatrust' seems to be a mistranslation or mispronunciation of 'megathrust', which refers to the large-scale movement of tectonic plates that can cause significant earthquakes.

What is the expected update to the earthquake map of Indonesia in 2024?

In 2024, an update to the earthquake map of Indonesia is expected, which will likely include new data and insights regarding the locations and potential risks of mega-thrust earthquakes.

How does the movement of tectonic plates under the ocean floor lead to tsunamis?

The movement of tectonic plates under the ocean floor can cause a displacement of water, creating a column of water that moves upward. This movement, if significant, can generate tsunami waves that propagate across the ocean.

What is the 'Palung' mentioned in the context of the 2006 Pangandaran earthquake?

The 'Palung' refers to the subduction zone where the 2006 Pangandaran earthquake occurred. This earthquake was unique because, despite the epicenter being in a region with soft sediments that reduced the shaking, it generated a large tsunami.

Why do some areas in Indonesia experience more frequent seismic activity than others?

Some areas in Indonesia experience more frequent seismic activity due to their location along the boundaries of tectonic plates, where the movement and interaction of these plates are more pronounced.

Outlines

00:00

🌏 Megathrust Earthquake Zones in Indonesia

The paragraph discusses the primary locations of megathrust earthquakes in Indonesia, which are situated along the western coast of Sumatra to the south of Java. It highlights that the area is quite large, comparable to the size of the island of Java. The speaker mentions that the megathrust zones are significant due to their potential for large-scale seismic activity. They also reference a map from 2017 and mention that an updated map is being prepared for 2024. The paragraph includes a discussion of the potential movement of the Java island, which could cause significant tremors in the surrounding areas. It also touches upon historical tsunami events in Indonesia, emphasizing that while many have occurred along Sumatra, Java, and Eastern Indonesia, there are also seismic gaps where large earthquakes are expected but have not yet occurred. The paragraph concludes with a mention of the recent heightened activity in South Java and the Mentawai Islands, which is of particular concern due to historical tsunami patterns.

05:02

🌊 Tsunami Generation and Plate Tectonics

This paragraph delves into the mechanics of how tsunamis are generated during megathrust earthquakes. It explains that when oceanic plates move and collide with continental plates, the movement can cause a significant displacement of water, leading to tsunamis. The speaker uses the example of the 2006 Pangandaran earthquake and tsunami to illustrate how the unique geological conditions of the area can influence the intensity of both the earthquake and the resulting tsunami. The paragraph also discusses the ongoing research and monitoring of seismic activity in Java, highlighting the importance of understanding the tectonic processes that underlie these natural disasters. It concludes with a mention of the various types of earthquake sources in Indonesia, not just megathrust earthquakes, but also other sources of seismic activity both on land and at sea.

Keywords

💡Mega Thrust

Mega Thrust refers to a type of fault where one tectonic plate is forced under another, a process known as subduction. This is a significant concept in the video as it explains the geological forces behind the occurrence of large earthquakes and tsunamis in Indonesia. The video mentions that the main Mega Thrust areas in Indonesia are located along the western part of Sumatra to the southern part of Java, and these areas are vast, comparable to the size of the island of Java itself.

💡Subduction Zone

A subduction zone is a geographical region where one tectonic plate moves under another, leading to the formation of a Mega Thrust. The video discusses the subduction of the Indo-Australian plate beneath the Eurasian plate, particularly under the southern part of Java, as an example of a subduction zone. This process is crucial for understanding the seismic activity in the region.

💡Seismic Gap

A seismic gap is an area along a plate boundary that has not experienced a significant earthquake for a long period, despite the presence of tectonic stresses. The video highlights that there are areas in Indonesia, such as Enggano to the south of the Mentawai region, that are considered seismic gaps, where large earthquakes are expected to occur. These areas are of particular interest for seismic monitoring and preparedness.

💡Tsunami

A tsunami is a series of large ocean waves caused by a sudden displacement of water, often resulting from undersea earthquakes. The video script discusses historical tsunamis in Indonesia, such as the one caused by the 2004 Indian Ocean earthquake off the coast of Banda Aceh, and how the movement of tectonic plates can generate these massive waves.

💡Earthquake

An earthquake is the shaking of the Earth's surface caused by the sudden release of energy in the Earth's crust. The video explains how earthquakes occur in the Mega Thrust areas, particularly in Indonesia, and how they can lead to tsunamis. The script also mentions various historical earthquakes, such as the 2006 Pangandaran earthquake, which was accompanied by a tsunami.

💡Plate Tectonics

Plate tectonics is the theory that the Earth's lithosphere is made up of several large plates that move over the Earth's mantle. The video discusses how the movement of these plates, particularly the subduction of the Indo-Australian plate, contributes to the formation of Mega Thrust zones and the occurrence of earthquakes and tsunamis in Indonesia.

💡Convection

Convection refers to the movement of fluids (like the Earth's mantle) due to differences in temperature and density. The video script uses the analogy of a boiling egg to explain how convection in the Earth's mantle causes the tectonic plates to move, which in turn can lead to earthquakes and tsunamis.

💡Sediment

Sediment is material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice. The video mentions that the area around Palung in Java is composed of soft sediment, which can reduce the intensity of ground shaking during an earthquake, as was the case with the 2006 Pangandaran earthquake.

💡Pangandaran Earthquake

The Pangandaran Earthquake of 2006 is a specific event mentioned in the video script. It was a Mega Thrust earthquake that occurred in Java and was accompanied by a tsunami. The video uses this example to illustrate the destructive power of such events and the importance of understanding the geological processes involved.

💡Seismotectonic

Seismotectonics is the study of the relationship between seismic activity and the tectonic processes that cause earthquakes. The video discusses the seismotectonic setting of Indonesia, highlighting the complex interactions between the tectonic plates and the resulting seismic and tsunami risks.

Highlights

The main mega thrust location in Indonesia is situated along the western coast of Sumatra to the southern coast of Java.

The size of the mega thrust field is comparable to the size of the island of Java.

In 2024, an update to the earthquake map of 2017 is being prepared, which may include slight updates to the location of mega thrusts.

The mega thrust in Indonesia is a very large field that can cause significant ground movement, such as the example of Java moving 20 meters.

The historical distribution of tsunamis in Indonesia from the 1600s to the 2000s shows a pattern of seismic activity.

The South Java region is particularly highlighted due to its history of tsunami-causing earthquakes.

The concept of a 'seismic gap' is introduced, referring to areas with a potential for large earthquakes that have not yet occurred.

The South Java mega thrust is of particular interest due to its potential for significant seismic activity.

The movement of tectonic plates and their interaction with the Earth's mantle and core contribute to the occurrence of earthquakes.

The process of subduction, where one tectonic plate moves under another, is a key mechanism behind the formation of mega thrusts.

The 2006 Pangandaran earthquake and tsunami is highlighted as a unique case of a mega thrust event.

The tsunami from the 2006 Pangandaran earthquake reached a significant height of 8 meters despite the earthquake's relatively reduced impact on land.

Smaller earthquakes, such as the Tasik earthquake in 2008, can still be felt in distant areas like Bandung and Jakarta.

Indonesia has a variety of earthquake sources, including not only mega thrusts but also other types of seismic activity.

The upcoming 2024 earthquake map will include more detailed fault lines and segments compared to the 2017 map.

The interaction between the Indo-Australian and Eurasian plates is a significant factor in the seismic activity in the Java region.

The geological processes beneath the Java region, including the subduction of plates, contribute to the formation of land and the potential for earthquakes.

Transcripts

tetapi secara umum ee lokasi megatras

yang EE utama di Indonesia itu memang

terletaknya di ee apa namanya di sisi

Barat Sumatera sampai ke selatan Jawa

dan ini bidangnya cukup besar karena ee

ini kalau kita lihat yang kotak ini

adalah bidang megatrasnya bidang

megatrasnya ini kan seukuran pulau Jawa

ya tapi di sini saat kita bicara

megatrust maka eh megatrust itu mrefer

ke eh trust ini adalah bidang sesar naik

Mega besar ya jadi bidang sesar naik

yang sangat besar dan bidang megatras

ini kalau di Indonesia ini berdasarkan

peta gempa tahun 2017 ee kebetulan

sebetulnya sekarang di tahun 2024 itu

kita sedang menyiapkan pemutahirannya

Jadi mungkin nanti di akhir tahun 2024

akan ada update sedikit eh terkait

dengan lokasi megatrust tetapi secara

umum eh lokasi megatrus yang e utama di

Indonesia itu memang terletaknya di eh

apa namanya di sisi Barat Sumatera

sampai ke selatan Jawa dan ini bidangnya

cukup besar karena Eh ini kalau kita

lihat yang kotak ini adalah bidang

megatrasnya bidang megatras ini kan e

seukuran pulau Jawa ya jadi bayangkan

kalau misalkan pulau Jawa bergerak

katakan 20 m secara serentak kan lumayan

tuh goncangannya ya artinya 20 m ini

bisa bergerak dari ee apa bidangbidang

lempeng yang ada di Selatan Jawa ee dan

itu bisa bergerak ee bisa bergerak

kecil-kecil seperti yang terjadi kemarin

beberapa kali bisa juga ee bergeraknya

langsung sekaligus seperti gempa Aceh

gempa Aceh itu Dia ee bergeraknya 1600

km dari ee eh Banda Aceh sampai ke

Andaman itu 16600 KM dia bergerak ee dan

apa namanya eh lebar bidangnya itu 200

KM kalau di Selatan Jawa itu panjangnya

dari Selat Sunda sampai Bali itu sekitar

1.000 km nah bidang megatras lainnya itu

ada di utara Sulawesi di apa ee Sisi

sini jadi di utara Sulawesi juga ada

tapi bidangnya ee sedikit lebih kecil

daripada yang ada di Sumatera sama Jawa

pun ee ada bidang yang masih bidang

megatras yang masih tumbuh itu ada di ee

Utara Papua nah ini bidang megatras yang

di utara Papua ini masih sangat muda ee

sehingga juga mungkin ee treatmennya

berbeda Nah mungkin kemarin beritanya

mencuat cukup heboh di Selatan Jawa ya

Nah kenapa memang Selatan Jawa kemudian

menjadi sangat heboh tapi mungkin juga

ada Mentawai yang EE heboh karena secara

sejarah ini eh sebaran ee gempa yang

menyebabkan tsunami sebaran tsunami di

Indonesia eh dari tahun 1600-an sampai

2000 18 yang dikompilasi oleh eh BMKG

jadi ee Indonesia ini sebenarnya

Kejadian gempa megatrust dan e tsunami

itu bukan pertama kali kita lihat ada

cukup banyak kejadian yang terjadi dan

kalau kita melihat sebagian besar itu

terjadi di ee sepanjang Sumatera

beberapa di eh Jawa dan eh cukup banyak

di Indonesia Timur nah eh tapi juga kita

bisa melihat nih ada ee lokasi-lokasi

Yang kok Kayaknya masih agak Kosong gitu

Nah itu sebenarnya bukan tidak ada

potensi tsunami di situ tetapi di

situlah yang kita katakan ee Seismic gap

atau ee lokasi yang kita tunggu gempa

bukan kita tunggu ya tapi ini lokasi

yang sebetulnya eh gempa besar ini bisa

terjadi Eh kapan saja nah Seismic gap

itu e kami menemukannya di daerah eh

Enggano ke selatan daerah Mentawai

Enggano ke selatan Selat Sunda sampai

Selatan Jawa sampai ke Bali Lombok

makanya mungkin ini mendapat ee apa

highlight dan peringatan yang cukup kuat

ya dari

ee apa ya dari beberapa pihak nah ee si

megatras Selatan Jawa ini ee tentunya

Dia ee apa terjadinya itu

ee saya enggak masang slide ini ya Ee

terjadinya itu kalau misalkan kita

melihat animasi yang tadi kita berikan

jadi di sini ada pulau Jawa nah di

bawahnya pulau Jawa itu ada ee

lempeng lempeng samudra ee dari

indoaustralia yang Menghujam ke bawahnya

Selatan Jawa nah e dia dari Menghujam di

bawah Selatan Jawa itu Sedangkan di

atasnya kan kita punya lempeng

kontinental ya jadi lempeng kontinental

ini dia bertemu dengan lempeng oseanik

Nah si bidang pertemuannya ini Eh itu

yang kemudian dinamakan bidang megatras

Nah kalau kita melihat eh bidang eh bumi

itu kan dia berrotasi dan berevolusi ya

Jadi kalau ada yang nanya bisa enggak

enggak ada gempa gitu ya ya bisa bisa

kalau buminya berhenti kalau buminya

berhenti kan kita enggak nafas kalau

bumi berputar berotasi dan berevolusi

bumi ini kan kalau kita belah di

dalamnya itu ada kerak bumi ada mantal

bumi e ada inti bumi gitu nah pada saat

dia memiliki mantal bumi itu mantal bumi

kan sifatnya cair ya jadi dia akan ee

seperti telur yang kita rebus itu dia

akan

apa namanya memang akan terjadi proses

eh konveksi jadi karena ada proses

konveksi itu maka kerak bumi ini dia

bergerak nah kerak-kerak bumi ini saat

kerak samudra Menghujam ketemu ee dengan

kerak benua maka ee dia sebagian bidang

yang nempelnya

ini akan ee apa ya akan ikut bergerak

bersama-sama jadi kalau kita lihat ini

karena dia bergerak tapi dia juga nempel

sama bidang di atasnya artinya bidang di

atasnya itu dia akan ikut ke bawa

bergerak ke bagian bawahnya jadi dia

akan ikut ke bawah bergerak tapi

sebetulnya kan lempeng lempeng samudr

nya kerak lempeng benuanya tetap ada di

atas jadi dia enggak akan ikut

terus-terusan toh pada pada satu titik

di mana dia sudah mencapai puncak

energinya maka dia akan mengembalikan

posisinya ke posisi semula nah pada saat

dia mengembalikan posisinya ke posisi

semula itulah yang kemudian kita namakan

ee kejadiannya terjadi gempa Nah karena

dia terjadinya gempanya di apa bidangnya

ada di bawah laut ya kalau kita lihat

lagi di sini jadi karena dia ada di

dasar laut Tapi saat dia bergerak maka

dia bergerak geraknya bergerak naik nah

saat dia bergerak naik ada air di

atasnya artinya dia akan menggerakkan

satu kolom air Nah kalau satu kolom air

itu kan beda sama gelombang angin ya

gelombang angin kan dia hanya terjadi di

peruka di permukaan aja tapi kalau ini

dia karena ada gerakan yang sangat besar

terjadi dari dasar dasar ee laut

menggerakkan air di atasnya maka dia

akan mengirimkan e juga gelombang

tsunami artinya saat dia secara secara

alamiahnya itu kan sebetulnya dia

melepaskan ee apa energinya itu ya

proses bergerak tadi itu ya n itu yang

akan kemudian terasa di kita itu sebagai

sebuah goncangan eh Eh ini Eh kalau kita

melihat kasus pulau Jawa mungkin karena

saya risetnya banyak di Jawa jadi

case-nya juga akan lebih banyak Jawa pun

yang sekarang lagi heboh kan di Jawa ya

Eh jadi kalau kita melihat pulau Jawa di

bawahnya ini kan di selatannya ada eh

apa ada gempa megatrasnya itu nih yang

yang warna hitam ada segitiga segitiga

ini adalah Palung ya lokasi palungnya di

situ Di mana lokasi hunjamannya itu

mulai terjadi Nah kalau kita melihat di

sini yang titik-titik merah ini adalah

eh data-data gempa jadi kejadian

sismisitas yang terjadi di Satan Jawa

itu ya tersebarnya seperti ini ee kita

lihat di sini ada sesmisitas yang cukup

banyak ini waktu gempa Pangandaran tahun

2006 yang juga disertai tsunami ini juga

salah satu tipe megatrust tapi

terjadinya ee Dia ee dia tipikalnya unik

karena ee gempanya gempanya itu terjadi

di di bagian Palung tapi dia ee

mereduksi goncangannya karena di di

daerah Palung itu justru dia terdiri

dari sedimen lunak jadi karena sedimen

lunak dia mereduksi goncangannya

goncangannya Enggak seberapa keras

terasa di Pangandaran tapi tsunaminya

sangat tinggi ya sangat tingginya 8 m

kan tinggi ya jauh lebih tinggi dari

saya walaupun kadang orang mikirnya Oh

tsunami besar itu seperti Aceh 30 M ya

Jangankan tsunami Aceh ya Tsunami 2 M

aja kan sudahah lebih tinggi dari kita

kan udah ke bawa ombak kita G kita pasti

dimakan itu sama A udah dimakan betul

nah kita juga pernah ngalamin gempa

serupa ee dengan tsunami di Pacitan

tahun ee 94 kemudian kita punya

gempa-gempa yang lebih kecil-kecil

misalkan gempa yang tadi malam terjadi

gempa Tasik tahun ee tahun 2008 gempa di

Lebak itu beberapa kali terjadi di sini

tapi terasa kan ya sampai ke Bandung

sampai ke Jakarta Nah ini ee karena dia

ee apa dorongan dari ee subduksi Selatan

Jawa ini juga dia karena dia menekan

Pulau Jawa di Jawanya juga akhirnya

terbentuk ee beberapa Cesar darat ya

jadi Ee Kita enggak hanya ada Cesar

megatrust aja nih tapi di Indonesia itu

kita punya Cesar punya sumber gempa dari

megatras tapi kita juga punya eh sumber

gempa darat eh juga sumber gempa tipe

lainnya di laut yang di Jawa ini kalau

di peta gempa 2021 eh 2017 itu ada 31

segmen ee yang warna biru ee nanti eh

kita akhir 2024 akan launching peta

gempa 2024 itu ee akan ada lebih banyak

ee patahan yang sekarang sedang kita

detailkan