Global Seismic Hazard (see abstract for AAAS 2008 invited talk below)
The past half century of doubling and redoubling of global population has resulted in many more people being exposed to catastrophic earthquakes than ever before in Earth's history. Supercities with populations in the range 2-16 million people have now replaced the former villages after which they were named (e.g. Los Angeles and Karachi see city growth pdf from Hough and Bilham book ). More than half the world's super cities are located near seismic zones, and more than half of these are in the developing nations. The total population at risk exceeds 500 million and it is growing daily. It is only a matter of time before a large earthquake occurs close to one of these cities, with a possible death toll of more than a million people See Bilham (2004).
In the following articles my co-authors and I highlight some of the problems that attend this uprecendented growth in seismic vulnerability.
ARTICLES
Bilham, R., Earthquakes and urban growth, Nature, 336, 625-626, 1988.
Bilham, R., (2004) Urban earthquake fatalities: A safer world or worse to come? Seism. Res. Lett., December 2004. (pdf)
Bilham, R. S. Lodi, S. Hough, S. Bukhary, Abid Murtaza Khan, and S.F.A. Rafeeqi, (2007) Seismic Hazard in Karachi, Pakistan: Uncertain Past, Uncertain Future, Seism. Res. Lett.78(6), 601-631.
Bilham R. and S. E. Hough, 2006, Future earthquakes on the Indian Continent: Inevitable hazard, preventable risk. South Asia Journal , 12,1-9, April-June 2006 pdf
Bilham, R. (2006). Dangerous Tectonics, Fragile Buildings, and Tough Decisions, Science 31 March 2006: (311)5769, 1873 - 1875 DOI: 10.1126/science.1125176
BOOK
Hough S. E. and R. Bilham, 2005, After the Earth Quakes. Oxford University Press. pp. 366 (November 24, 2005) ISBN: 0195179137 see Review in Geotimes
POWERPOINT "Global death and construction" elementary intro to seismic hazards: 17 Mb
INVITED TALK Earthquakes are a preventable disease AAAS meeting abstract Boston February 2008
The repeated occurrence of disastrous earthquakes throughout history, leaves the seismologist and historian alike, shaking their heads in disbelief that earthquakes are still permitted to kill people - almost half a million dead in the past 8 years. It has been known for at least 3000 years, that most people are killed or maimed during earthquakes by the houses they live or work in. John Milne observing earthquake destruction at the end of the 19th century listed guidelines about how to construct buildings to survive repeated shaking. He also offered advice to cities prone to tsunami damage - "if the site is unfavorable, a city may have to be removed". His point, and one now well known to the earthquake engineer, is that if earthquakes are a disease, the cure, like penicillin, has been known for a century.
Indeed the cure has been adopted wholeheartedly by the developed nations. Construction in earthquake prone regions can only occur following the issuance of a permit that assures the building includes various levels of earthquake resistance. The permit comes with teeth in the form of a building inspector whose job is to assure adherence to its guidelines. The same earthquake-resistant guidelines can be found in all the developing nations (often adopted from California or European codes), but their implementation is accompanied by an elusive elasticity - caused partly by indifference, partly by corruption, and partly from ignorance.
The remedy for this elasticity in code adherence is obvious. Governments must get serious about protecting their people from sloppy construction. After a disaster it is easy to point the finger at contractors, or government officials, who were responsible for the collapse of a dozen schools, or a hundred dwellings. It is much more difficult to point the finger before the disaster at ineptness in planning, and avoidance of responsibility. The reason for this is well known. The time between earthquakes at a given point, even on a plate boundary where destructive earthquakes are common, is often several lifetimes. Thus the present generation knows nothing about earthquakes from direct experience.
All too often the response to an earthquake is to rebuild the damaged city and to continue business as usual. The inevitable result of this response is to leave every nearby city vulnerable to the next earthquake. The most remarkable example of this can be found in Iran where the past few centuries of earthquakes, if plotted on a map look like an outbreak of measles. Each earthquake after about 1950 has been accompanied by a band-aid of earthquake resistant construction, yet few of these rebuilt cities have been tested by a succeeding earthquake. The next earthquake has always destroyed a different city. The dismal result is that the percentage of the population killed by earthquakes in Iran has remained constant throughout the past century, despite the incorporation of earthquake resistance.
The Iran earthquake syndrome is a disease that is also endemic in Pakistan, in India and in Indonesia - all countries within the Alpine/Himalayan collision zone. There is no priority plan in place to fix future earthquake disasters before they happen. If anything, the national reaction is to treat each earthquake as the location of the next most likely disaster area, rather than the least likely. This occurs in spite of the protestations of an educated seismological community in each country. A tsunami the size of the 2004 disaster will not recur for possibly a thousand years again in Aceh, but billions have been spent on mitigating the effects of another similar event. The Pakistan earthquake of 2005 has resulted in reconstruction of western Kashmir, but nothing has been done to reinforce eastern Kashmir and nearby towns to the south where the next great Himalayan earthquake may strike.
Safe dwellings are surely as much a human right as freedom, or health, Is the mandatory construction of buildings that will not become tombs for their occupants such a heavy price to pay in our developing world? We would not think of purchasing a car that was guaranteed to kill its driver by design on impact. Why should we accept killer buildings? The population is about to double yet again, and as a result we are constructing more houses on Earth that any time in the history of civilization. Lets work together to insist that the 10% additional cost is worth it to make these buildings safe.