Thursday, 13 September 2012


Weighing the economic and social cost of earthquakes 

An article by Emanuela Guidoboni for INDERC

Italy is an ancient country, but is politically young. It achieved unification only 150 years ago, first as a kingdom, then as a republic. In 2011, the one-and-a-half centenary year, a book was published that explored the disastrous chapter of earthquakes that have stuck the country in the course of its history as a unified nation. The aim of the book is to do some serious groundwork towards better prevention of seismic risk. Italy is the only high-seismicity industrialised country that has not made a concerted attempt to tackle the earthquake scenario. That there should be widespread awareness of the issue may be a first step. The authors of the book were Emanuela Guidoboni, a historical seismologist – coming from a historian background – and Gianluca Valensise, an earthquake geologist. Historical seismology in Italy is an advanced research area on which the Istituto Nazionale di Geofisica e Vulcanologia has been engaged for decades. The data it yields are crucial in calculating the parameters of past quakes and assessing the hazard status of an area or site.

Geologically, Italy has had the same seismic profile as now for millennia, an expression of its complex geodynamic history and the life of Earth itself. In fact, the seismic hazard of a territory is by definition ‘stationary’: it varies little in thousands or tens of thousands of years. 

What does change over the epochs – and greatly so – is the seismic risk, since the pattern of habitation in such areas changes (the demographic density, the amount and quality of buildings). What impact have Italy’s major earthquakes had since the time of unification? 

An enormous impact in human life, loss of property, abandonment, emigration, and long and costly reconstructions, often not brought to completion or simply shirked. There have been about 150,000 deaths (an average of 1,000 per year, though they bunch together into a few seismic catastrophes), although Italy’s level of seismicity is lower than that of other Mediterranean countries like Greece, Turkey or Syria. On average Italy gets two or three magnitude 7 or larger earthquakes every century. Yet in the history of the past 150 years there was 34 seismic disasters, meaning earthquakes of high destructive impact, such as all those in the magnitude range 5.8 - 6.9. The twentieth century brought two earthquakes exceeding 7 M (1908, Messina Straits, M 7.1 and 1915, Marsica-Abruzzo, M 7.0), but on average there has been a disastrous earthquake every 4-5 years. In all, there has been significant damage and destruction in 1,560 settlements, including 10 main towns. 


Besides these 34 disasters there have been 86 lesser quakes, though their effects were not much lighter than what the authors term ‘disaster’. Bracketed with these there are major flooding and landslip events. And let us not forget two World Wars. All in all, a chapter of history bristling with tragedy (but the Italians are ‘resilient’ people!). The worst earthquakes in Italy are bound up with the dynamics of the Apennines, that still youthful mountain chain running full length from Liguria to Sicily. Epicentres tend to lie along the Apennines ridge and hence strike mountain and hill centres much more. 

So much for the main seismic area, but there are secondary areas that are not a bit less dangerous: indeed, the seismic risk is much greater since these zones tend to be more built-up and productive. They include the Alpine foothill belt in Veneto and Friuli, western Liguria, a large swath of the Po valley, the Gargano and Capitanata (both in Puglia), eastern Sicily and parts of northen and western Sicily.

Clearly the relationship between the energy released by an earthquake and its surface effects depends largely on the housing pattern and the quality or vulnerability of buildings involved each time. As the authors tried to point out, the vulnerability of Italian building is due to various factors, the main being the widespread poverty in rural areas and small townships, especially in the central and southern parts of the country. But vulnerability factors include also the decadence of traditional building techniques and the huge number of architecturally valuable ancient monuments which have never been properly protected from such risk. Another important factor is contemporary building negligence (witness the industrial buildings affected by this latest earthquake, Emilia 2012), and the low quality of public buildings, ancient and modern, which really ought to be closely monitored and rendered safe. Another point is the site of construction, often inappropriate since already impaired by landslips that get tragically re-activated in an earthquake, or on soft or unstable ground that causes amplification of the ground motion.


The book presents many photographs: it forms a valuable data store, ruthlessly chronicling the heaps of rubble, loose stones or strewn cubes of tufa and houses dissolving into dust. We see floors that have fallen through, resting on unduly thin beams, already misshapen, hardly anchored at all to side walls that can barely support the weight of their roofs. To the experienced eye our pictures also reveal the dismay of survivors surveying the rubble-heaps that were their homes, streets and squares all out of kilter, signs of social life at times obliterated for ever. The rubble mounds spell a waste of previous toil and new labours to be endured ahead in the solitude of depopulation.

We can but wonder why in these past fifty years in Italy – those of the cultural and welfare boom – there has been no broad concerted reaction to the earthquake effects. This should be a vital part of national culture, such as other developed countries have witnessed wherever the earthquake risk was high. One can hardly lay the blame on lack of economic resources and materials, as was the sad case in the last decades of the nineteenth century and the crisis following World War I, which stretched from 1915 to around 1930. One is forced to conjecture that other factors are at work. One is struck by the persisting short-sightedness of territorial planning – just where decades of stable forethought might be expected to tackle environmental hazards. There has been and still is no shared awareness of housing safety.

Alarmingly, there has been limited let-up in the seismic disaster pattern even during the past ten years, as emerges that even low-magnitude recent quakes have caused serious damage. This chapter of seismic disaster highlights the repeated weakness of institutions in applying norms to protect the building heritage, whether monuments or private homes - though rules and laws have proliferated on paper in the course of the years. The chief weakness to come to light is the failure to check up on construction quality. This has become tragically evident where relatively smalle quakes have nonetheless brought destructive consequences. 

All seismic risk countries know that applying the anti-seismic laws is a basic step in making buildings safer. It is also well-known that such rules can only be concretely enforced when the people involved are informed of the risk they are running and are prepared to adhere scrupulously to modern techniques of risk-reduction. The latest earthquake, Emilia 2012, struck the population and local administrations like a bolt from the blue. It shows how woefully seismic maps fail to convey the risk to the population and decision-makers alike. We still have a long, long way to go.

No comments:

Post a Comment