Unofficial Guide to Inca Masonry
Different groups of people throughout Peru's long history have dealt with this geologic threat in different ways. The colonial Spanish handled earthquakes by falling down a lot. To be fair, the Spanish, not having lived on the Ring of Fire, probably were not accustomed to thinking of earthquakes as a regular part of the weather you have to protect your buildings from. This could be seen as an accident of geography: the Spanish lived in western Europe, so they did not have earthquake skills. They did live in Eurasia, so they did have guns and horses. The Spanish built some really lovely churches in Arequipa out of the beautiful, but brittle sillar. They knocked down Inca buildings in Cuzco and built some stunning, impressive Gothic churches and one cathedral (I can't forgive them for that). The churches in Arequipa are still falling down occasionally. The churches in Cuzco collapsed in a fairly recent earthquake, revealing the Inca foundations and building remnants beneath, because the Incas, like many other cultures, built anti-seismic buildings. Thus, the Incas' very skill at stonework ensured that future generation would come to appreciate a civilization the Conquistadors tried to make us forget.(section of Santa Catelina closed due to earthquake damage).
Pre-Inca Anti-Seismic Construction
When you've been building in an area for five thousand years, you get to know it. The Peruvian civilizations knew about the tremors that affected their land, and some of them did something about it. The Lima culture, so called because it was in the area of present-day Lima, built many huacas, or complexes containing walls, rooms, and pyramids/mounds out of mud bricks. The most important of these is Pachacamac, a long-standing oracle and pilgramage site. A less famous one is Huaca Pucllana (built 700 A.D.) in Lima's affluent Miraflores district. As you can see in this photograph, the bricks are laid out in a pattern called "book style" for obvious reasons. This arrangement apparently lends the construction a little flexibility, allowing it to shake without cracking, so the waves propagating through it will do no harm.
Inca stonework
When you look at the constructions of the Incas, it is important to bear the earthquakes in mind, because thats what the Incas did. This first became apparent when a strong earthquake hit Cuzco, their former capital. The Spanish buildings fell down. What was left of the Inca buildings did not. The subject is inseparable from a discussion of their stonework, so here goes: there are two categories of masonry buildings in Inca architecture. Houses for low-ranking types, factory-type buildings where things got processed and manufactured, and other "blue collar" kinds of edifices were built with stone walls held together by mortar. There are tons of these buildings at Machu Picchu, in the area sometimes referred to as the "urban sector," on the right. Other things they built that way seem to include the stone buttressing walls of the andenes, some staircases, and the fountains at Machu Picchu. The advantage of this kind of building is that it enables the builder to make strong, waterproof walls quickly out of small, unshaped stones. The houses at Machu Picchu that were built according to this method seem to have held up pretty well for at least 500 years, but don't show much in the way of anti-seismic innovation.
The other category of stonework the Inkas used was dry-masonry. The ways in which they would build with it actually varied a great deal, with different edifices using different earthquake-resistent construction techniques. One aspect of all the dry-masonry constructions is one of very tight joints; each stone is so perfectly fitted to its neighbors that you can't slip anything between them. This technique is most obvious in constructions such as the Sun Temple of Machu Picchu (left), whose walls were designed as a smooth continuation of the surface of the rock on which it was perched. The dry-masonry design has two advantages with regard to earthquakes: the lack of mortar means that the building is slightly less rigid, but the tight seal between the rocks may hold them together, like suction. Although all of the dry-masonry involves such tight fits, the stoneworkers appear to have poured molten metal into the joints in some constructions.
Another characteristic of Inka stonework is the shapes of the stones. They are often irregular. The famous "sacred rock" of Saqsaywaman (left) is a classic example. Even when the basic geometry of the stones is rectangular, they might be cut with multiple angles, and varying sizes, like the rock on the right, in Machu Picchu, which is cut with over twenty angles. The advantage of that design is to prevent cracks from forming during an earthquake. Of course, such a profusion of interlocking shapes, fitted perfectly together, requires really good engineering and rock-cutting skills. Nobody knows exactly how they got the rocks to fit so exactly. The mystery is compounded by the fact that some of the rocks used to build Saqsaywaman weighed over 29 tons. It is possible to come up with ways to do what they did using the tools they had, but to build so much, so quickly, they certainly must have done it very well.
