Scientific Responsibility for Earthquakes in Japan

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Introduction

Evolution through scientific development has taken the most credit for the modernization of mankind. It is rather interesting how a simple invention like the wheel over 5000 years ago played its part in todays the automobile. Critics are however worried that mankind is getting ahead of himself with his ingenuity which is causing more harm than good. The best example is global warming where excessive combustion of fossil fuels is regarded as the most likely factor for climatic changes.

Blaming these climatic changes squarely on the technological developments is overkill because excessive consumption of anything will be hazardous. Science has played a huge part especially in the prediction of certain natural occurrences that used to cause serious damages. Hurricanes can now be easily predicted and the path they will follow helps in the evacuation process. Prediction of the amount of rainfall falling in a particular area has moved from an art to a science. Farmers can now plan their harvest well before they plant the seeds and local authorities in cities use available rainfall data to prepare their flood barriers.

Earthquakes

Similar results have unfortunately not been achieved in the prediction of earthquakes. Earthquake prediction has proved to be an Achilles heel to geologists. The only species that seem to have got the hang of it are birds and animals whose instincts can give keen observers a few minutes warning just before an earthquake hits; but then again, maybe they are running away from an approaching prey. My essay will focus on earthquakes in Japan and more specifically the Kobe earthquake of 1995 which proved to be the most catastrophic yet. I do not think there is any link between human activity and seismic activity in the earths crust.

Massive structures like dams and football stadiums have been blamed for weakening the earths sub-structure they overlay but the biggest threat they pose if they are poorly constructed is to trigger landslides. Other activities like underground nuclear tests do produce tremors similar to those experienced in an earthquake but as to the long-term effects of such activities, only time will tell. Various organizations around the world are working day and night to come up with mechanisms that can predict earthquakes but even the best devices only give a few seconds warning which is already too late. The various early warning devices being employed will be keenly looked at in this essay. (Bolt: p 331)

What scientists should be faulted on is the inability to construct structures that can withstand an earthquake. Even though they cannot predict the occurrence of an earthquake, the magnitude after it hits can be roughly estimated and this data should be used when constructing skyscrapers and laying railway lines. This miscalculation was glaringly evident in Kobe where structural engineers thought the structures constructed before the earthquake of 1995 could withstand the strongest earthquakes; well, the 5000 fatalities beg to differ. The various early warning devices being employed will be keenly looked at in this essay.

After the Kobe earthquake, important lessons were learned and previously employed flaws in construction were abandoned for proven methods that could save lives should another disaster of similar magnitude occur. All these innovations will be looked at in this essay. (McNutt et al: p 12)

Reasons for High Frequency of Earthquakes in Japan

Extensive geological studies of the occurrence of earthquakes not only in Japan but also around the world have uncovered useful information on their devastating potential and the locations where they are most likely to occur; especially the large quakes. The only blind sport remains the inability to predict earthquake days or months in advance. Here are a few facts about earthquakes.

Worldwide, each year there are about 18 earthquakes of magnitude (M) 7.0 or larger (Agnew et al: p 959) Research has shown the worlds largest earthquakes display a similar pattern in terms of their location and strength. Most large earthquakes occur on long fault zones around the margin of the Pacific Ocean (Agnew et al: p 959) There is a reason for this. The Atlantic Ocean grows a few inches wider each year and the Pacific shrinks as the ocean floor is pushed beneath Pacific Rim continents (Agnew et al: p 959) Adding this, the plates that characterize the earths crust are in constant movement due to the constant streaming of magma.

These plates slide over each other and fault lines do occur due to the friction. These fault lines like the ones on the Pacific are not smooth and they are sub-divided by geological irregularities into smaller fault segments that rupture individually. Therefore earthquakes around the Pacific Rim are normal and expected. (Ikeya: p 25) If the fault lines and plate motions can be identified, the fault segments that are most likely to break and cause an earthquake can be definitively determined like for example the San Andreas Fault. (Agnew et al: p 959)

In poorly understood faults, the occurrence of an earthquake is as much a surprise to the scientists as it is to the general public. This is what happened in Kobe in 1995 where the fault lines were complex and prediction almost impossible. Besides Kobe, Japans landmass in general lies along the intersection of these major fault lines in the Pacific Rim and that is why the entire country is almost prone to earthquakes.

The Philippine Sea plate is trying to force its way under the Eurasian sea plate. Scientists have realized this and the majority of their efforts have been focused on minimizing the damage after the earthquake has occurred. Some experts argue a lot more research should be devoted to detecting an earthquake just before it occurs instead of preparing for the aftermath. As explained earlier, this is only possible along faults like the San Andreas, and instead of vilifying these scientists, we should be supporting them since they have been able to identify which areas are the most prone to earthquakes.

Besides research into earthquake prediction has been ongoing for several years even before the Kobe earthquake. Several innovations have been suggested and some of them have been identified as effective by the scientific community. (Schiff: p 206)

Earthquake Prediction

The VAN Method

VAN is a method of earthquake prediction proposed by Professors Varotsos, Alexopoulos and Nomicos in the 1980s.(William: p 123) This method tries to detect seismic electrical signals that are emitted just before an earthquake occurs.

It involves the sinking of conductive metallic rods deep into the ground which is then able to pick up the electric noise and amplify it on their telemetric network. Researchers claimed this method was able to detect an earthquake of magnitude 5.0 and greater within a 100km radius of the epi-center from a 2 hour to 11 days to time window (William p 123) before the earthquake strikes. Due to its success, this method appealed to many scientists especially in Japan but it later attracted some criticism as to its effectiveness forcing scientists in Japan to look for other alternative ways of predicting earthquakes.

Changing water Levels in Deep Wells

Both China and Japan have extensively adapted this method to predict earthquakes just before they happen. Some 93 wells in Japan have been sunk to monitor earthquakes. (Ansal: p 203) It involves sinking of wells to depths of over 1000m then monitoring the variations in their water levels. Peculiar variations in a deep wells water levels had been noted moments before an earthquake struck.

First of all, there was a gradual reduction of water levels months or years before an earthquake happened. This decline was accelerated at an exponential rate in the final months or weeks preceding the earthquake. Lastly, there was a rebound or rapid increase in water levels in the days or hours before the mainshock. (Ansal: p 203) A lot of care has to be taken when collecting such data since the variations in water levels could be due to changes in the water table and these errors need to be factored in the final measurements.

Chemical Changes in Ground Water

After the Kobe earthquake, scientists at the University of Tokyo noted that the chemical composition of groundwater in terms of the changes in concentration of the dissolved minerals could be affected by seismic events. They collected mineral water samples from the nearby springs for analysis. The results showed that the chemical composition of the water changed significantly in the period around the Kobe earthquake. (Ansal: p 205) A steady rise in the levels of chloride and sulfate concentration was observed from July 1994 to January 1995. (Ansal: p 205) The research was however termed inconclusive in terms of predicting the occurrence of earthquakes since mineral concentration levels fluctuate with seasons.

Levels of Radon in Ground Water Wells

Radon is an element that is found deep in the earths crust and is very soluble in water which explains its occurrence in springs and wells. However, it is highly unlikely that it will seep through the rocks to the surface due to its relatively short half-life of 98 hours. When monitoring the levels of radon in groundwater before the Kobe earthquake, researchers at the University of Tokyo noted that the concentration levels increased rapidly from 20 Bq/l in 1993 to as high as 250Bq/l on 7th January in 1995. The conclusion they drew was levels of radon do increase in the months and weeks preceding a major earthquake but as to the reasons for the increment they could not definitively determine. (Schiff: p 207)

Minimizing the Damage Caused by Earthquakes

While prediction has proved to be a hard nut to crack, scientists have made tremendous progress in minimizing the damage they cause. In the aftermath of the Kobe earthquake, scientists learned that close to 90% of the fatalities was due to crushing or asphyxia caused by collapsing fragile buildings.(Sunfellow 1995) While some buildings were strong enough to remain upright, a lot of injuries occurred from falling interior fixtures and equipment.

Furthermore, providing sufficient emergency service to the survivors was almost impossible due to the carnage and inaccessibility caused by the debris. Efforts, therefore, had to be directed towards designing buildings that could be prevented from swaying in the event of an earthquake.

After an earthquake, most buildings sway because they are not able to efficiently transmit and damp the shock waves generated by the mechanical force of the earthquake. The new buildings, therefore, had to incorporate mechanisms that can successfully damp shockwaves generated by earthquakes greater than 7.0 like the one in Kobe. Lead Rubber Bearings were incorporated in buildings as a type of base isolation. This base isolation device plus others suppressed vibrations generated by seismic activity. Tuned Mass Dampers is also a new technology that has already been implemented in some buildings like Taipei 101. Huge concrete blocks are mounted on structures and are supposed to oppose resonant frequency oscillations caused by earthquakes hence prevent swaying. (Ansal: p 209)

Conclusion

A similar earthquake to Kobe struck Northridge California exactly one year earlier. The Kobe city officials were smug and said that if a similar earthquake struck their city, they were much better prepared. The Northridge earthquake claimed 61 people and caused $20 billion worth of damage. The Kobe earthquake on the other hand struck one year later and claimed 5000 lives, injured 26,000 people, destroyed 50,000 buildings, and caused over $60 billion worth of damage. The Kobe officials were left scratching their heads even though they had spent a lot more time and resources reinforcing their buildings. Several key points came out after extensively comparing the two situations. (Fujita Research, 1997)

The buildings that were constructed to withstand earthquakes of search magnitude did so perfectly while the old ones that had not incorporated such mechanisms came down like a house of cards. While a majority of the deaths were caused by falling objects, the deaths and injuries in Kobe were mostly caused by untreated injuries and fires. Broken gas lines exploded and started fires that raged for days.

The difference in the policies drafted in the two cities proved to be the decisive factor as to the magnitude of damaged caused. While Kobe focused on retaining the structural integrity of its buildings in the event of an earthquake, Northridge focused on the emergency preparation of its workers after the earthquake. The lower casualty rate in Northridge was attributed to the speedy response of its emergency services.

The injured were quickly ferried to hospitals and the fires that started were immediately put out. The Kobe situation on the other hand brought back painful memories of the 2nd world war where stoic citizens walked through the rubble of buildings damaged by allied bombs. Like back then, the response from emergency services was painfully slow and a majority of people died as a result of the indirect impact of the quake. (Ludwin, 2004)

The painful lessons learned in Kobe were expertly implemented in the Niigata Chuetsu Earthquake that struck on 23rd October 2004. (Ludwin, 2004) An earthquake countermeasure headquarter was immediately established at the scene and one of its main goals was to restore transport and communication via the roads and railways. This earthquake did not cause a lot of damage and this is attributed to the design brilliance of its buildings.

Concluding, the prediction of earthquakes will probably never be a direct science and if it ever becomes one, it will still present a logistical nightmare in huge metropolitan cities where large tracks of land for providing a safe spot for the millions of citizens are unavailable. The best solutions are still in improving the design of buildings and access to emergency services in the event of an earthquake. (Ludwin, 2004)

References

Agnew D C, Jones L M (1991) Prediction Probabilities from Foreshocks, Journal of Geophysical Research, Vol. 96, pp 959-971.

Ansal Atilla (2004) Recent advances in earthquake geotechnical engineering and Earthquake Engineering, Springer, pp 200-210.

Bolt B A, (1992) Earthquakes, Freeman W H and Company, 331 p.

Fujita Research: Industry Report, (1997) Earth Prediction. Web.

Ikeya M (2004) Earthquakes and animals, World Scientific, pp 21-25.

Ludwin Ruth, The Pacific Northwest Seismograph Network (2004) Earthquake Prediction. Web.

M. McNutt and T.H. Heaton (1981) An Evaluation of the seismic-window theory for Earthquake prediction, California Geology, pp. 12-16.

Schiff Anshel J (1998) Hyogo-ken-Nanbu (Kobe) earthquake of 1995, ASCE Publications, pp 206-209.

Sunfellow David, Reuters, Associated Press, Time (1995), Newsweek Japan Takes a Beating: What Is Happening & What We Can Learn from It. Web.

William Hung Kan Lee (2002) International handbook of earthquake and engineering Seismology, Academic Press, pp 123-127.

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