In the short time that has passed since the Bam earthquake, the awareness of the country's technical community about the characteristics of this earthquake has reached saturation, and we know that the Bam earthquake — in terms of vertical acceleration, long shaking duration, and a return period of two to three thousand years — was one of the exceptional earthquakes in Iran. Had its return period been less than 2,500 years, the old Bam Citadel would have been razed to the ground long before this.
In confronting the earthquake problem, the country's management and engineering systems deal at minimum with two fundamental issues. First, urgent assistance and relief for rescuing the injured and treating the wounded, burial of the victims, and swift sanitary measures to prevent the outbreak and spread of contagious diseases. Second, longer-term actions for returning life to the region and re-establishing the vital arteries of work, livelihood, and the people's subsistence — which itself requires reconstructing the city and the earthquake region.
In the first movement, the government — despite its extensive and long experience facing devastating earthquakes from Boein-Zahra and Qaen and Lar through Roudbar and Manjil — loses its head and feet at the outbreak of every earthquake and calls for help with great noise and uproar. Relief work is complex, orderly, and methodical work — exactly the opposite of agitation. The principal role of relief workers is to reduce tension and emotion. The role of the government and state mass media is likewise to counter agitation and create calm.
Iran's relief organizations, with more than 50 years of repeated and similar experience confronting the problem of earthquakes and floods, and access to the vast international experience that with a single sign can be freely placed at their disposal, have so far not succeeded in creating a regular regional network — one that could answer the immediate needs at the scale of 100,000 to 200,000 people — so that, in the face of disaster, they could act with the composure and coolness that should be the principal characteristic of these organizations' work. From the first day of the Bam earthquake we witnessed relief workers being called upon to receive blankets, water, cooking-stoves, blood, food, and the rest. This practice causes disorder in the assistance effort and leads to misuse and corruption. The day will come when a significant portion of public donations ends up in the markets of Zahedan and the Afghan border and other cities.
The second issue, reconstruction of the destroyed buildings or rebuilding of the entire damaged region, must in principle begin from a guiding urban-planning scheme. Building regulations must be drafted and enforced such that if a similar earthquake occurs, the buildings can endure; and if the intensity, acceleration, and duration of the earthquake are such that the buildings are again destroyed, human losses are reduced to the minimum. Then the experiences gained from this effort can be extended across the country.
To reach this goal, we must first know why the buildings in the earthquake that occurred were entirely demolished. What are the exceptional cases? How did the destruction take place, and why was the death toll so high? Then, in order to create resistance in buildings — especially residential buildings, which bear the greatest losses — what measures should be employed so that, considering the lifespan of the building and its economics, these reinforcement measures are not unjustifiable.
The knowledge and engineering of building construction at the present time allow us to build a building as resistant as we wish, so that it stands not only against the most severe earthquakes but also against any stress and explosion. Examples of such buildings are constructed in military and defense facilities and in shelters. In cities — especially small cities and rural areas — making the residential building resistant in such a way that it withstands every storm of events is possible, but not necessary.
A residential building (where most casualties occur) is built for a lifespan of about 50 years. They make public facilities more resistant, and their lifespan can be 100 to 200 years or more. Mosques, temples, universities, public libraries, and metro stations are buildings of this kind. More resistant and more enduring buildings — such as the Egyptian pyramids and ziggurats — are made of resistant materials and built for eternal life. The very Bam Citadel is an astonishing example of a long-lived building yet of non-resistant materials. The Soltaniyeh complex in Zanjan and its dome, which has global fame, is a notable example of a building with relatively resistant materials and good execution. Good execution doubles the resistance of a building even if the materials are not very strong, while bad execution even diminishes the value of good materials. In the continuation of this writing, the focus of our discussion is on low-rise residential buildings built in townships, smaller cities, and villages. These buildings grow in importance day by day, because — with the bouquet that the automobile industry has handed to large cities (a negative factor for life in densely populated cities) and the facilities that advanced communication and information systems have placed at our disposal — the future life of the educated classes will be in the suburbs and small cities, not in cities like Tehran. Mobile phones, the internet, and teleconferencing facilities will permit even service companies to take refuge in the lap of nature. Our supplementary assumption is also that in the reconstruction of Bam there will be no high-rise building, and short residential buildings will be constructed.
Owing to the internal actions and reactions of the earth — which are entirely known in seismology — forces arising from the displacement of enormous rock slabs are released and reach the surface of the earth. If we decompose these complex forces into simple vectors and depict them, three principal movements are seen in them: a vertical and perpendicular movement that chiefly attacks the roofs of buildings; horizontal and lateral movement whose reverberation resembles waves arising from a stone falling into water; and these two movements affect the walls and twist the structure of the building together. The more durable the building materials, the more the building is expected to have greater resistance. But in practice this is not so. For example, in non-metallic and semi-metallic buildings, if horizontal and vertical tie-beams (shenazh) are not built, no matter how durable and resistant the materials may be, the building will not endure against the earthquake and will collapse.
Good materials and bad execution — non-durable materials and good execution
Before the establishment of the Ministry of Housing and Urban Development and in the absence of building codes, especially Code 2800 (which oversees the seismic strengthening of buildings), use of traditional materials in a building's roof but with a better method caused fewer casualties than roofs in which iron beams and brick jack-arches were employed. Today's common residential buildings in small cities and villages have little resistance against earthquakes, and their casualties are several times greater — though both brick and iron beam are among the resistant materials. Why? The answer must be sought in the manner of execution.
Formerly, traditional buildings used mainly wooden beams, and the spacing between beams was less than the spans of today's iron beams. Across the beams "parvāz" (wooden lath) was nailed throughout, which produced an integrated roof skeleton. Where it was not possible to obtain smooth and uniform laths, mats were placed between the lath and the wooden beam. The load that was placed on it helped this. At the time of an earthquake, if its intensity caused the building to be crushed, the roof did not collapse all at once; rather, the beams fell to one side and created a triangular cross-section in the room, which served as a shelter for the inhabitants until they could exit the room.
Today, the iron beam has taken the place of the wooden beam, and between iron beams a brick jack-arch is mostly placed. Use of joist-block is also customary, but the difficulty of cement distribution throughout Iran, together with the availability of iron beam and brick, leads people more to use the latter. This tendency must be halted in favor of cement roofs. Master craftsmen who lay jack-arches in effect eliminate the arch and build a flat vault. Nor do they take care in choosing the type of brick. The iron beams are also not properly bound together at the top. The strap or round rod that anchors the iron beams together from above has only a single spot weld at its joint. At the building's first movement — and as a result of a slight displacement arising from vertical acceleration and lateral forces — the distance between iron beams opens up, and suddenly a vast volume of brick crashes down throughout the room, against which it is natural that no living being will come out alive. In this matter, both iron beam is more resistant than wooden beam and brick is more resistant than adobe — yet wrong execution produces the opposite result. In big cities, the application of Code 2800 must be carried out together with stricter supervision. Unfortunately the issue of technical supervision in Iran has not yet been resolved and is bound up with corruption.
Beyond that, in laying brick walls, bricklaying is not executed in a technical manner. To avoid prolonging the construction period, employers contract the work out to master masons on a wage basis, or wage-and-materials. In the first case, the mason takes a thick mortar so the work finishes sooner; in the second, he takes a thin mortar so less cement is consumed. The vertical distance between bricks is so small that mortar between bricks (the vertical joint) does not penetrate, and a lock-and-fastening of the bricks does not come into being. The result is that even in moderate earthquakes the walls are quickly damaged and collapse. Collapse of the wall facilitates collapse of the roof.
Reflections on the reconstruction of Bam
The relief works in Bam had not yet ended when government officials, in the course of visiting the region, declared that the reconstruction of the city of Bam had been placed on the serious order of business, and they promised to build a city far better than the city that has been ruined. This is a timely and blessed decision. But in reconstructing the city of Bam, several fundamental points must be considered:
Should the city of Bam be built where its ruins now lie and on its previous wreckage, or should its location be changed? Reconstruction on the previous ruins has these advantages: the city, its past, and its memories form identity. The grounds and qualities and ownerships are known and local affinities exist. Part of the public services — such as parks, schools, banks, and mosques — are sound or close to sound. Water-supply networks and their sources and electricity, even if damaged, can be repaired without difficulty. Stockpiled building materials at the work site can be used; perhaps the steel skeletons may still serve. Against these possibilities, attention must be paid to the fact that reconstruction is not confined to the city of Bam itself. A considerable number of villages around Bam have been destroyed and require reconstruction.
On the other hand, the Bam earthquake — with a very long return period of more than two thousand years — will probably have prolonged aftershocks that may take several years. If we look at the question of reconstructing the old city from this perspective, insistence on rebuilding the existing fabric is a kind of obstinacy against nature. If a new aerial photograph is taken of the earthquake-stricken region of Bam, the fissures and cracks that have appeared on the ground due to the earthquake will be clearly visible. Atmospheric precipitation and floods that have been flowing over Bam's land since the spring of 1383 (2004) will penetrate to the depth of the earth through the fissures and cracks that have been created in the ground. These waters, on encountering limestone layers, will produce explosions whose released energy will cause tremor at the surface. Even the edges of rocks that are currently locked together and under pressure may, upon the arrival of water and steam, soften and collapse. The subterranean water sources, which in the past were tapped by digging deep wells, have most probably all been broken and their water has receded or is in the course of receding. It will take several years for it to assume another form through the formation of new sediments.
Given these points, perhaps the better option is to choose a new location for the city, and to use the old city for five to six years only for light and safe tourist services with low-rise buildings combined with park-making, and then to take action on its reconstruction. If we are to base our choice on selecting a new location for the city, the choice of the new location must be considered within the complex of the city and the villages surrounding it.
The best path is to avoid improvised decisions and to entrust this matter to a group of experts in regional development, geology, seismology, natural resources, agricultural economy, environment, land-use planning and urban planning, and architecture — and, before acting, to take an aerial photograph of the region and place it at this group's disposal.
We now stand before a historic opportunity to undertake the reconstruction of the city and region of Bam and of the world's most magnificent adobe structure. The old Bam Citadel is like a luminous gem at the crown of world archaeology, and thousands of eager researchers are ready to participate in its study and restoration. The world's urban-planning engineers and specialists in architecture and seismology also look toward us to see how we confront this painful event.
The reconstruction of Bam is an opportunity for our 40-year experience in urban planning and architecture to be put to the test and to prove its creativity. Let the next step, then, be to put the design of the urban and rural complex of Bam to a competition. Let bureaucracy stir itself, and let the best designs be selected.
The work of constructing a new city for the earthquake-stricken should not be accompanied — like the relief experience — by noise and costly publicity and inter-organizational rivalry. The economics of construction work dictates that the highest yield be obtained from the least energy. To reach this goal, popular and governmental and international donations and bank credits must be concentrated within a single system as a Bam Reconstruction Fund and placed under the supervision of the head of the executive branch. If the gathered funds are scattered across various organizations and bodies, a significant part of them will not reach reconstruction; rather, in practice they will be absorbed by those same organizations. Oversight mechanisms must necessarily be activated, and the Governor of Kerman and the people's representatives must be present in them, and decision-making on reconstruction programs — within the framework of supplied credits — must be carried out by a strong council established for that purpose, which will be answerable to this council.
For once, the government must decide not to build houses for the people but rather to bring infrastructural facilities into being. The concrete houses built for the survivors of the Boein-Zahra earthquake are even today used as cattle stalls and storehouses, and the people have built their own preferred houses next to them — even though those houses had been designed extraordinarily well in terms of strength and beauty. House-building by the prefabricated method is accomplished rapidly, but it imposes a particular architectural style uniformly on the people, which the people do not accept.
The work that the Ministry of Housing and Urban Development can well undertake is creating facilities for strengthening building materials, not only in Bam but in all parts of Iran. People build mud and adobe houses in villages precisely because they lack the financial capacity to buy brick. That capacity has been taken from them by city-dwellers. Instead of building houses directly, the Ministry of Housing and Urban Development could set up a vast network of brick kilns across the country and ask rural people to bring their adobe for firing in these kilns: bring an adobe, take a brick. The rural people themselves can, using standardized molds that the government places at their disposal, make adobe — since the procurement of its materials costs the people nothing. Then they would be guided in how to make their houses resistant, and more important still: by resolving the problems of cement distribution, arrangements should be made so that cement is placed within reach of the rural people.
And as a final point: the technical and engineering community of Iran must put under discussion simple and inexpensive methods to prevent the collapse of brick jack-arch roofs in the bedrooms of residential units that lack tie-beams (shenazh) and that currently exist throughout the country — and place the results of that discussion at the community's disposal.
