Reflecting on 20 years of the Aceh tsunami: From ‘megathrust’ threat to disaster mitigation
- Written by Zulfakriza Z., Associate Professor in Global Geophysics Research Group at FTTM, Institut Teknologi Bandung
Indonesia also has several megathrust zones – areas along tectonic plate boundaries prone to generating large earthquakes like the 2004 Aceh event. There are 13 identified megathrust zones[13] near the waters off western Sumatra, southern Java, Bali, Nusa Tenggara, northern Sulawesi, Halmahera, and Papua. These zones are prone to generate quakes of magnitudes ranging from 7.8 to 9.2 Mw, capable of delivering major destruction and tsunamis.
Over the last 30 years, some of Indonesia’s megathrust zones have been releasing seismic energy. These zones were the source of major earthquakes such as 1996 Biak[14], 1994 Banyuwangi[15], 2004 Aceh, 2005 Nias[16], 2006 Pangandaran[17], and 2007 Bengkulu[18].
However, data from the past 123 years[19] show that some parts of the megathrust zones rarely experience large earthquakes. This could be because tectonic movements in these locations are stuck, causing stress to build up over time. These “seismic gaps” indicate high-risk zones for future big earthquakes.
A seismic gap[20], for example, exists between the megathrust zones off the western and eastern coasts of Java. For instance, in western Java’s subduction zone, the slip deficit — or plate movement locked in place — has reached 40-60 mm per year. If this energy is eventually released, it might result in a significant earthquake and possibly a tsunami.
Advances in disaster research
Indonesia’s high disaster risk has attracted scholars from all around the world, particularly following the 2004 Aceh Tsunami. From 2005 to 2024, Google Scholar[21] recorded approximately 1,000 scientific works on Indonesian earthquakes and tsunamis.
These studies have improved our understanding of earthquake causes and trends. For example, research on the 2018 Palu and Sunda Strait tsunamis revealed that neither was directly caused by earthquakes. The Palu tsunami resulted from an undersea landslide[22] triggered by a 7.5 Mw earthquake[23] on September 28, 2018. Meanwhile, the Sunda Strait tsunami was caused by the fall of Mount Anak Krakatau’s volcanic side[24].
Indonesian academics have also investigated big earthquake origins and aftershocks. Teams from the National Research and Innovation Agency (BRIN), the Meteorology, Climatology, and Geophysics Agency (BMKG), and the Bandung Institute of Technology (ITB) have looked at aftershock patterns to learn more about where earthquakes come from and how they work. Among those closely studied are 2018 Lombok[25] and 2022 Cianjur[26]. This has led to new ideas for reducing risk and damage.
The Indonesian Tsunami Early Warning System (InaTEWS), managed by BMKG, continues to encourage seismic research collaborations. By 2024, the system would have 521 seismic stations[27] spread across Indonesia. This extensive network allows for faster broadcast of earthquake data to the public, notably timely tsunami warnings after major earthquakes.
Mitigation requires collaboration
While scientists continue to investigate tectonic motions, accurately predicting earthquakes and tsunamis remains impossible. Therefore, mitigation and risk reduction are crucial.
Disaster mitigation efforts include public education and the use of earthquake-resistant infrastructure. These require the support of a wide range of stakeholders.
In 2007, three years after the Aceh Tsunami, Indonesia passed a Disaster Management Law[28], detailing risk reduction activities, including mitigation. This law promotes collaboration among five major elements: government, communities, academics, corporations, and the media — a framework known as the “pentahelix.”
The government acts as a regulator, the media disseminates information, corporations provide financial and technological support, communities serve as field implementers, and academics act as innovators.
Collaboration is essential for successful catastrophe mitigation. However, problems such as sectoral ego frequently impede efforts. For example, a refusal to share data across authorities can jeopardise earthquake research and mitigation efforts.
Finally, disaster risk mitigation is a shared responsibility. Building a more robust and sustainable mitigation system requires improved institutional coordination and communication.
References
- ^ 20 years of efforts to rebuild Aceh (theconversation.com)
- ^ 30 kilometers (earthquake.usgs.gov)
- ^ Research in 2021 (link.springer.com)
- ^ Green’s Function (www.researchgate.net)
- ^ 2,050 aftershocks (earthquake.usgs.gov)
- ^ 167,000 (doi.org)
- ^ a tectonically active zone where four major plates (www.researchgate.net)
- ^ a tectonic plate (pubs.usgs.gov)
- ^ 35 meters high (www.academia.edu)
- ^ the Pacific Ring of Fire (education.nationalgeographic.org)
- ^ 127 active volcanoes (magma.esdm.go.id)
- ^ 14,820 earthquakes (earthquake.usgs.gov)
- ^ 13 identified megathrust zones (simantu.pu.go.id)
- ^ 1996 Biak (www.weatherbug.com)
- ^ 1994 Banyuwangi (www.kompas.id)
- ^ 2005 Nias (earthquake.usgs.gov)
- ^ 2006 Pangandaran (escweb.wr.usgs.gov)
- ^ 2007 Bengkulu (earthquake.usgs.gov)
- ^ the past 123 years (earthquake.usgs.gov)
- ^ seismic gap (doi.org)
- ^ Google Scholar (scholar.google.co.id)
- ^ an undersea landslide (agupubs.onlinelibrary.wiley.com)
- ^ 7.5 Mw earthquake (link.springer.com)
- ^ the fall of Mount Anak Krakatau’s volcanic side (nhess.copernicus.org)
- ^ 2018 Lombok (theconversation.com)
- ^ 2022 Cianjur (doi.org)
- ^ 521 seismic stations (inatews.bmkg.go.id)
- ^ a Disaster Management Law (bnpb.go.id)
Authors: Zulfakriza Z., Associate Professor in Global Geophysics Research Group at FTTM, Institut Teknologi Bandung
