Great Pyramid’s – Scientists have pinned down why the Great Pyramid of Giza has endured nearly 5,000 years of earthquakes: its natural vibration frequency differs from the slower shaking of the surrounding soil, reducing harmful resonance. The pyramid’s massive, weight-distribu
The Great Pyramid has stood for almost 5,000 years, surviving quakes that should have left marks. Now, after painstaking measurements inside and around the monument, researchers say they finally understand the mechanics behind that longevity.
Egypt’s Great Pyramid of Giza has resisted earthquake damage for nearly 5. 000 years. and scientists know why. researchers write May 21 in Scientific Reports. The key is the way the pyramid moves during shaking. The monument tends to vibrate at a different frequency compared with the surrounding soil. which prevents excessive shaking during an earthquake.
That frequency mismatch is only part of the story. The pyramid’s sturdy shape and its internal design that distributes stress also helped keep the structure intact and stable.
“It’s no surprise that they are very seismically resistant,” says Sherif El-Tawil, a civil engineer at the University of Michigan in Ann Arbor, who was not involved in the research. “But the new study offers important insight into why the pyramids are so resistant to seismic damage,” he adds.
The implications reach well beyond Egypt’s desert plateau. The Great Pyramid—still the last ancient Seven Wonders of the World standing—was built in Giza around 2600 B.C. to serve as the tomb of the Pharaoh Khufu. It contains about 2.3 million stone blocks and took more than two decades to construct.
Egypt generally has low seismic activity, but it does occasionally experience strong earthquakes. The article cites a magnitude 6.8 earthquake in 1847 and a magnitude 5.8 earthquake in 1992. Despite these powerful tremors, the Great Pyramid has suffered only minimal damage.
To uncover the origins of that enduring stability. geophysicist Mohamed ElGabry and colleagues monitored subtle vibrations at 37 points within and around the pyramid. The team did not use direct shaking. Intentionally shaking the pyramid could be damaging. so instead they relied on tiny disturbances caused by far-off ocean waves. traffic. or other human activities to set the structure vibrating.
At about three-quarters of the measurement sites inside the pyramid. the structure naturally vibrated back and forth at frequencies between 2 and 2.6 times per second. The narrow distribution of frequencies indicates that stress is evenly distributed throughout the pyramid. The surrounding soil, meanwhile, vibrated more slowly—oscillating a little more than once every two seconds.
Because the natural frequencies of the building materials and the soil are different. the pyramid is less likely to experience resonance. Resonance is the process in which a structure absorbs energy from vibrations at matching frequencies; it can significantly increase the strength of the vibrations. though not necessarily their frequency. raising the risk of damage during an earthquake.
The pyramid’s internal spaces also played a role. Ancient Egyptian builders constructed pressure-relieving chambers above the king’s chamber, where the pharaoh was entombed. Those chambers were built to distribute the pyramid’s weight and protect the burial chamber in the event of a collapse. The researchers also found that the chambers decreased the strength of the vibrations closer to the top of the pyramid.
There’s a further twist to the motion. Most buildings behave like upside-down pendulums, ElGabry says. Their bases are anchored to the ground, while their tops have more room to sway and shake. In the Great Pyramid. this meant vibrations were amplified by a factor of four in the king’s chamber. which is situated well above the bedrock and near the center of the pyramid. But in the pressure-relieving chambers above the king’s chamber, the vibrations were amplified by only a factor of three. It’s not yet clear what factors of the chamber’s design contribute to this effect.
“All of this is really amazing to look at from today’s engineering point of view,” ElGabry says. “But it’s more amazing and more impressive when you look into the tools and available resources we had 4,600 years [ago].”
Still, the team’s findings do not prove intention. The results can’t confirm whether ancient Egyptians intentionally designed the pyramids with earthquakes in mind, the researchers write in the study.
What the study can do is offer a blueprint for modern construction that aims for centuries, not decades. Modern builders can use similar strategies to plan projects, choose materials and create enduring structures, ElGabry says. “When we design our buildings, we design for 100 years [or] for 500 years,” he says. To apply principles that make an edifice last far longer than that. “it’s important to understand how this building has survived.”.
Great Pyramid Giza earthquake resistance seismic engineering vibration frequency resonance pressure-relieving chambers Scientific Reports Khufu Mohamed ElGabry