How the 2004 Indian Ocean earthquake reworked tsunami science

December 26, 2024, marks the twentieth yr for the reason that 2004 Indian Ocean earthquake and tsunami. The tsunami generated by the quake of magnitude 9.1 was sourced off the Sumatran coast and was the third largest (by magnitude) on this planet since 1900. The supply was 30 km under the ocean flooring, within the Sunda trench, the place a part of the Indo-Australian plate subducts beneath the Burma microplate, which is part of the Eurasian plate.

The 2004 earthquake ripped via 1,300 km of the plate boundary, the fault tearing from Sumatra within the south to Coco Islands within the north. The quake was felt in Indonesia, Bangladesh, India, Malaysia, the Maldives, Myanmar, Singapore, Sri Lanka, and Thailand. It brought on extreme injury and killed a whole lot in Northern Sumatra and within the Andaman and Nicobar Islands. The tsunami was most impactful on distant shores, affecting 17 nations lining the Indian Ocean.

In all, with an astounding loss of life toll of round 227,000 plus 1.7 million extra displaced, the 2004 tsunami is the deadliest in recorded historical past.

Unprecedented magnitude

In lower than six years, on March 11, 2011, a magnitude 9.1 earthquake hit the east coast of Japan, the biggest ever recorded in that nation. It generated a tsunami that reached as excessive as 39 metres and travelled as much as 8 km inland. The dual disasters killed greater than 18,000 individuals, displaced greater than 500,000, and resulted within the Fukushima Daiichi nuclear energy plant accident.

Though devastating tsunamis have occurred prior to now — 1960 Chile and 1964 Alaska, for instance — the 2 twenty first century occasions taught us vital classes. Notably, the 2004 tsunami highlighted how weak the world was to pure hazards. It landed like a bolt from the sky, hitting probably the most surprising areas, and positioned a premium on the significance of tackling catastrophe danger via preparedness and resilience.

As Margareta Wahlström, head of the UN Workplace for Catastrophe Danger Discount (UNISDR), noticed in a panel dialogue: “Ten years after the Indian Ocean tsunami, the world has taken vital measures to make the world a safer place towards disasters.”

The 2004 tsunami shocked researchers and hazard managers alike with its transoceanic attain. With no recorded historical past of any occasion of such magnitude, the analysis neighborhood hadn’t anticipated it occurring alongside India’s japanese seaboard. The one earlier tsunamis had occurred in 1881, attributable to a big earthquake (magnitude ~8) off Automotive Nicobar island, and one other in 1883 as a result of explosion of Krakatoa. These occasions produced solely small sea surges as recorded by tide gauges at totally different factors on the east coast.

This view from the air exhibits coastal devastation on Katchal Island, a part of the Andaman and Nicobar Islands, in 2005. The island misplaced some 90% of it’s inhabitants within the December 26, 2004, tragedy.
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AFP/Getty Photos

Nonetheless, within the twenty years since 2004, researchers have made large leaps within the scientific understanding of tsunami technology and the technical facets of earthquake monitoring. The Indian Tsunami Early Warning Centre (ITEWC), established in 2007 by the Union Ministry of the Earth Sciences of the Authorities of India, is probably probably the most vital step on this course.

Working from the Indian Nationwide Centre for Ocean Info Companies (INCOIS) at Hyderabad, ITEWC operates seismological stations in addition to backside stress recorders and tidal stations throughout the Indian Ocean basin — all 24/7. These methods can transmit offshore and deep ocean tsunami observations that allow early warnings. Earthquake knowledge from the stations operated by the India Meteorological Division (IMD) and 350 international stations are additionally out there at INCOIS.

Ocean monitoring methods additionally go knowledge in real-time. In about 10 minutes, for instance, the system can determine a possible tsunami-producing earthquake and problem tsunami alerts or warnings — relying on the anticipated severity — for nations bordering the Indian Ocean. India is the fifth nation on this planet, after the U.S., Japan, Chile, and Australia, to have a sophisticated tsunami warning system of this type.

A brand new follow

The 2004 incident additionally spurred vital new developments in analysis. The work of tsunami geology, pioneered by Brian Atwater of the U.S. Geological Survey, prompted researchers in Asian nations together with India to seek for proof of tsunamis in historical past. Atwater’s work alongside the Washington coast of the western U.S. had revealed proof of an earthquake and tsunami in 1700, plus their predecessors. One fascinating a part of this work was the usage of land elevation modifications attributable to the earthquake, which left bushes pressured or simply killed them. Atwater had used the imprints of those results to find out when some piece of land had been deformed and thus when it was struggling the consequences of a tsunamigenic earthquake.

Inspections of subsided mangrove swamps revealed how the 2004 earthquake had rendered modifications in elevation of as much as 3.5 metres at some locations alongside the Andaman and Nicobar Islands. Scientists additionally puzzled if there may have been previous occasions that additionally brought on the mangroves to subside. Because it turned out the 2004 earthquake had reopened the coffins of the previous and uncovered their skeletons, within the type of lifeless roots protruding from tidal platforms throughout a low tide. Such roots uncovered close to Port Blair have been used to deduce that the final earthquake had occurred a few thousand years in the past.

Excavations at Mahabalipuram, a port of the Pallava dynasty, unearthed proof of a tsunami of the identical classic. It was the primary proof of a pre-2004 tsunami reported by an Indian group. Researchers additionally sifted via sedimentary deposits alongside the islands and coastal areas of the mainland to seek out proof of different historic tsunamis, whereas studying to tell apart between tsunami and storm deposits.

This effort is an efficient instance of how the 2004 tsunami prompted the science of tsunami geology to grow to be a brand new follow, resulting in many new analysis papers and doctoral theses. The demand for extra data about tsunamis additionally facilitated quantum leaps in the usage of GPS methods and earthquake instrumentation. With funding from the Ministry of Earth Sciences, analysis institutes established a number of new stations alongside the Andaman and Nicobar Islands, strengthening seismic observations and geodetic research.

In one other vital step, the tsunami modelling utilizing mathematical instruments helped researchers decide inundation limits. Particularly, the catastrophe offered a stark reminder that nuclear energy vegetation established alongside Indian coasts might be weak to a hitherto underestimated danger. Whereas the Kalpakkam nuclear energy plant withstood the enormous waves, it additionally shut down robotically after the rising water ranges tripped the detectors. There was no launch of radioactive materials and the reactor was restarted six days later.

The no. 3 nuclear reactor of the Fukushima Daiichi nuclear energy plant is seen burning after a blast following an earthquake and tsunami on this handout satellite tv for pc picture taken March 14, 2011.
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DIGITALGLOBE

However the 2011 Tohoku earthquake reminded the world, and India, how rapidly a nuclear catastrophe can occur within the absence of a failsafe. It was clear the radiation from the Fukushima facility had entered the human meals chain. Researchers even discovered radioactive caesium within the breast milk of some ladies examined close to Fukushima prefecture three months after the catastrophe. What if the waves in 2004 had been excessive sufficient to wreck the reactors at Kalpakkam?

This query continues to resonate as the federal government has been pursuing giant developmental tasks in Nice Automotive Nicobar, together with the development of a world transshipment terminal. Some consultants have additionally argued that the final nice earthquake that affected the area earlier than 2004 was a millennium in the past, so there is no such thing as a imminent hazard. However this query hinges on how a lot we nonetheless don’t know. What if an unbroken patch of the subduction zone between Myanmar and India offers method? A still-unexamined portion of the crust between Nice Nicobar and Automotive Nicobar out of the blue breaking into a strong earthquake and a tsunami can’t be dominated out.

Consultants and policymakers should additionally give attention to different downside spots, just like the Makran Coast within the northern Arabian Sea and the Myanmar coast adjoining the Northern Indian Ocean. Each of them have the potential to supply giant tsunamis. The Makran Coast, chopping via Iran and Pakistan, may direct a tsunami’s vitality in the direction of India’s west coast, which additionally hosts nuclear reactors and town of Mumbai.

A significant milestone

Science tells us that stress builds between tectonic plates till it reaches a essential pressure, at which level the amassed potential vitality is launched as an earthquake. Subduction zones just like the Andaman-Sumatra area have gotten vital as they supply clues to earthquake technology. The invention of sluggish slips — tectonic faults that transfer many orders of magnitude slower and usually only a bit deeper — has additionally added a brand new dimension to this image.

Of late, researchers have been finding out seismic slips at plate boundaries to grasp the processes that happen earlier than and after main earthquakes. They’ve elucidated the incidence of premonitory and post-seismic slip transients utilizing laboratory experiments and numerical simulations. A few of these research have implications for earthquake prediction: they point out a inventive course of that originally includes secure, sluggish rupture development inside a confined zone on a fault simply earlier than unstable, high-speed rupture.

One paper revealed in 2015 (coauthored by one of many authors of this text) indicated a perceptible downward floor motion in South Andaman between 2003 and 2004, earlier than the earthquake — a silent occasion with a second magnitude of 6.3. This occasion may have been the precursor to the megathrust earthquake. Analyses of geodetic knowledge on a wider set of worldwide earthquakes revealed in Science additionally confirmed short-term precursory fault slips earlier than giant earthquakes.

After it occurred, the 2004 Andaman-Sumatra earthquake grew to become a significant milestone in fashionable seismological analysis, offering science with a treasure trove of information to assist glean new insights about earthquake technology and associated hazards.

Kusala Rajendran is a former professor on the Centre for Earth Sciences, Indian Institute of Science, Bengaluru. CP Rajendran is an adjunct professor on the Nationwide Institute of Superior Sciences, Bengaluru. They’re authors of the e-book ‘The Rumbling Earth – The Story of Indian Earthquakes’.