Scientists unravel one of the Great Pyramid's main secrets — how it managed to withstand earthquakes

The Great Pyramid of Pharaoh Khufu, built approximately 4600 years ago, remains one of the most magnificent engineering structures in human history. Over millennia of its existence, it has survived many powerful earthquakes, including tremors with magnitudes up to 6.8. Earthquakes of such intensity are capable of causing catastrophic damage to buildings within a radius of up to 250 kilometers from the epicenter. However, the pyramid suffered no critical damage — neither external nor internal.

Now, a group of scientists from Egypt's National Research Institute of Astronomy and Geophysics has proposed a well-founded explanation for this unusual stability. The results of their work were published in Scientific Reports.

As part of the study, scientists recorded vibrations of the structure at 37 different points: inside the chambers, directly on the building blocks, and in the ground around the pyramid.

It was found that most of the vibrations recorded within the structure have a frequency of 2.0–2.6 hertz. This indicates that mechanical stress is distributed uniformly throughout the entire structure. At the same time, vibrations in the surrounding soil had a frequency of about 0.6 hertz.

It is this significant difference that allows the pyramid to successfully withstand earthquakes. The point is that when a building and the ground vibrate at the same frequency, resonance occurs, leading to the destruction of walls. But the Great Pyramid turned out to be much more "rigid" than the surrounding earth, so seismic energy simply cannot be effectively transmitted into its structure.

The team also found that the amplitude of vibrations increases as one ascends and reaches its peak in the King's Chamber. However, in the five cavities located directly above this chamber, the level of vibrations significantly decreased.

This suggested that they were not created by chance, but served as a kind of protective mechanism to reduce the load on the main burial chamber. Scientists believe that the geometry of these five compartments helps to dissipate or redirect stress during strong tremors.

The construction site itself also played an important role. Ancient Egyptians erected the pyramid on a solid limestone foundation, which resists seismic waves much better than soft soil. In addition, the very shape of the structure is ideal from a physics perspective: a wide base and a low center of gravity make the pyramid extremely stable and protected from overturning.

While it is impossible to assert with full certainty that ancient builders understood geophysics in the modern sense, their engineering solutions were remarkably close to the principles used today in earthquake-resistant construction.

"The observed frequency gap between the soil (0.6 Hz) and the pyramid structure (2.3 Hz) indicates a natural reduction in resonance risk, which contributed to the monument's exceptional seismic resilience over millennia," the study authors conclude.

They admit, however, that any assumptions about ancient architects consciously conducting "anti-seismic optimization" remain at the level of hypotheses for now.

In parallel, new theories are emerging about how this massive structure was built. A separate study, presented this year, proposes a version involving a hidden spiral ramp.

Computer modeling specialist Vicente Luis Russell Roig believes that workers did not build gigantic external embankments, but used a "perimeter ramp."

This was an inclined path that spiraled along the outer walls, like a winding road. As the pyramid grew, this path was simply walled up with successive layers of stones and external cladding. As a result, the ramp was hidden within the walls, and the pyramid itself served as a supporting structure for further lifting of blocks.

Modeling shows that such a system allowed for extremely fast work: a new block could be installed every 4-6 minutes. At such a stable pace, the main framework of the pyramid could be completed in just 14-21 years. If one considers the time for material extraction and transportation, the total construction period would be about 20-27 years, which fully corresponds to the official estimates of historians and archaeologists.

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