Seismic-resistant features of Machu Picchu

PhotographerThomas McGuireTom’s Web site
Summary AuthorThomas 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
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