The >earthquake in Nepal has jolted the world. According to initial estimations by the United Nations, eight million people in 39 districts have been affected. Of them, over two million people live in 11 severely affected districts. Ninety per cent of the houses there have been “flattened”. Heritage buildings are now rubble, thousands are homeless, many have lost livestock, and have little food. On behalf of all Japanese citizens, I extend my heartfelt condolences and prayers to those who have lost their lives, their families and those affected. I hope international help is able to ensure rapid rehabilitation and reconstruction.
I recollect how Nepal and India were quick to support >Japan when it faced a similar situation in 2011 , during the To¯hoku tsunami where more than 20,000 people died.
Japan falls in a seismically active region and earthquakes are a part of life. Japanese seismologists and engineers are always working on solutions to mitigate the loss and damage caused by earthquakes. Most difficulties stem from the fact that the occurrence of major earthquakes spans intervals that are generally longer than the average lifespan of citizens. And memory is short. There is a saying here: “When danger passes, even god is forgotten.” For example, memories of the 2011 tsunami have long passed. Therefore, the question is: how long will you remember a disaster? And how do you pass on the lessons learnt? In this article, I would like to address this issue and look at what needs to be done, from the point of view of someone who lives in a seismic zone.
Earthquake forecasting An earthquake is a sudden violent shaking of the ground, typically causing great destruction, as a result of volcanic action or movements deep within the earth’s crust. The Nepal quake resulted from a collision between the Indian crustal block and the Eurasian continent. Geophysicists know that the entire Indian subcontinent is being driven slowly but surely beneath Nepal at a speed of five centimetres a year. This generates a five-metre contraction over a century and results in silent stress build-up in the inner crustal rock. An earthquake occurs when stress accumulation reaches critical point. Over millions of years, the squeezing has crushed the Himalayas, raising mountains and triggering earthquakes on a regular basis. This will continue. This dynamic process will also induce stress accumulation in India. The Gujarat earthquake of 2001 was a result of this process. This shows that a quake is sure to occur in future.
Like Japan, Nepal is also located in one of the most seismic active zones. “An earthquake repeats itself”, which is a Japanese proverb, is apt here as well. Earthquake forecasting is a kind of historical science. If you can find documentation of a quake in ancient literature or legend, that place is bound to be earthquake prone. I pose this question next: do you know the earthquake history of your region? But let me not be an alarmist. The India Meteorological Department keeps track of all this. However, I suppose most people don’t know. It is perfectly natural that people do not worry about such things; it’s the same in Japan as well. As scientists, we try to create awareness about earthquake risk in the form of public lectures, mass media campaigns, science shows and governmental meetings. Therefore, “risk recognition” is the first step towards disaster mitigation.
In Nepal, researchers did track active earthquake history and issued warnings about a possible and destructive quake. For example, my colleague visited Nepal frequently to research strong ground shaking to help in disaster mitigation studies. Earthquake science still does not have a tool for imminent earthquake prediction. Therefore, being prepared for one is a crucial, and, often, the only step for disaster mitigation.
Disaster and public policy In an earthquake, most of the damage is caused by collapsing buildings. In Nepal, most victims died this way. This is a major problem confronting architects. Recent architectural developments, however, allow for the construction of quake-resistant buildings, but such construction is more expensive than an ordinary building. Therefore, cost-effective solutions are also a challenge.
The Japanese believe and agree that anti-disaster investments are lifesavers. If the Indian government makes a public investment in this area, it should first come to some sort of social agreement in disaster mitigation. The role of the mass media is also important because it plays a key role in creating awareness about disaster preparedness. This must be emphasised. We must remember that it is people and commercial companies that are involved in construction and not the government. So, disaster mitigation cannot achieve optimal results unless there is understanding and cooperation. The media should also highlight the benefits of public and commercial investments.
Japanese anti-quake construction technology places a premium on high performance. Hence, what is suitable for Japanese conditions may not work elsewhere, in terms of applicability and cost. I suppose the export of such technology may not solve problems elsewhere. Therefore, the Government of India must develop an anti-disaster technology that suits Indian construction and conditions.
Risk evaluation and management Disaster mitigation measures also require risk evaluation for rural and urban areas. In high-risk regions, there must be public investment. Policymakers in India must look at those parts of the country that have high quake potential. Records show that the western, coastal and northern regions are at high risk. Another important factor is “occurrence frequency and probability”. Shorter intervals between quakes indicate a high probability. At the same time, longer intervals also produce high probability. An evaluation of these factors will give one the basic information required. I would also like to add that earthquake research can’t operate on a commercial basis, so government funding is a must for scientific investigation.
The Japanese government operates the Headquarters for Earthquake Research Promotion based on Special Measure Law on Earthquake Disaster Prevention. Its director is a minister and its committees consist of government officers, governors, professors and researchers. The most important role of this special inter-ministry organisation is to publish probabilistic seismic hazard maps resulting from probability evaluation of earthquake occurrences. It also conducts unified national earthquake research — as geological surveys, earthquake monitoring and computer modelling. The results from all these projects produce the probability of earthquake occurrences. For instance, its research has shown that a strong shaking probability for the Tokyo Metropolitan area for next 30 years exceeds 80 per cent.
Earthquake risk is defined in the following way — multiplication of earthquake magnitude, probability and social fragility. Scientific data can only estimate magnitude and probability. This shows that if a place is “very fragile”, even a small earthquake can result in disaster. “High fragility” is the state of being unprepared by having non-quake-resistant construction. Mankind has no control over the magnitude and probability of a quake but architectural engineering can help reduce the fragility. Japanese quake-resistant house and building compliance is now about 80 per cent.
Response and supporting technology In a quake, the survival time of someone who is buried is 72 hours. Therefore, rapid initial rescue is crucial. Who does the rescue then? The fire department? The police? The military? In a quake, one must be able to think of how to survive and escape. This is the experience in Japan. What if help is inadequate?
A real-time earthquake observation system should support the quick start of a rescue. In Japan, any seismic activity of more than ‘5+’ intensity automatically activates governmental response. There is surveillance by self-defence forces, a disaster countermeasure preparation office starts working, and a medical assistance team is on standby. For any smooth operation, there has to be a drill. So, disaster prevention agencies and governments frequently conduct all kinds of training and simulate situations. But even the best trained rescue operation requires lead time to access sites.
In Japan, a real-time Earthquake Early Warning (EEW) is in operation. If a quake is in the sea, the speed of an earthquake wave is about 8 km per second, which is slower than an electric signal. If the epicentre is away from one’s location, an electric signal reaches faster than the shake that gives the lead time before the quake arrives. An EEW alert is automatically triggered whenever any seismometer detects a seismic signal. There are alerts to the public through the media and the Internet. Trains, elevators and industrial machines are stopped automatically.
These examples show how earthquake monitoring data might help decrease the impact of a disaster. However, for the full impact of such a system, there needs to be a high ratio of anti-quake construction. How does one minimise the chances of being buried alive? The point is that government investment in anti-quake construction takes precedence over a modern alert system.
The annual disaster prevention drill in Japanese schools also plays an important role. Students are taught to hide below their desks in a quake. In their syllabus, they learn about natural disasters, disaster history, and hazard mapping.
Importance of legislation
Legislation also plays a most important role in disaster mitigation. The Japanese government has amended the Building Standard Law at regular intervals to reflect the advances in science and technology, and the lessons learnt from the last earthquake that occurred. The present version requires that new constructions should not be damaged in a medium earthquake and must not collapse in a large earthquake. These stringent measures have successfully reduced human toll in recent quakes. There is also a programme of tax incentives for anti-quake construction, that has enabled a higher ratio of anti-quake constructions in Japan. Therefore, economic incentives are also required to achieve actual law implementation.
With a proper legal system in place, new constructions will be better adapted for high seismic activity. We should try to develop a legal system, especially a Building Standard Law for earthquake disaster mitigation. Another countermeasure against quake disaster is a city planning policy and advance reconstruction policies. I believe these insights based on actual disaster experiences in Japan will go a long way to help save precious lives.
(Hiroaki Takahashi is Associate Professor of Seismology, Institute of Seismology and Volcanology, Hokkaido University, Japan.)
Published - April 30, 2015 02:18 am IST
