Seismic-resistant features of Machu Picchu
Photographer: Thomas McGuire; Tom’s Web site
Summary Author: Thomas McGuire
Some of the most sacred Inca buildings in Peru were constructed with precisely fitting stones held together by gravity alone. Even a credit card can’t be inserted into these mortar-free cracks. Peru is highly seismic and majorearthquakes are part of its history. For example, a 1746 event completely destroyed the capital city of Lima. It was one of the strongest seismic events in modern times. But Inca construction has a remarkable number of design features that protect buildings against collapsing in an earthquake. These include:
- Terraces buttress steep mountain slopes
- Precisely fitting and mortar-free stone walls move (“dance”) during an earthquake, resettling as they were before the event
- Doors and windows are trapezoidal and tilt inward from bottom to top
- Corners are sometimes rounded
- “L”-shaped blocks were used to tie outside corners of the structure
- As you see here, the most precisely constructed walls incline slightly into the rooms