Ancient Egyptian Engineering Choices Helped the Great Pyramid of Giza Survive Earthquakes, New Research Finds

Christian Thorsberg | Daily Correspondent Add as preferred source Built roughly 4,600 years ago, the Great Pyramid of Giza has survived several significant earthquakes. Douwe C. van der Zee via Wikimedia Commons under CC BY-SA 4.0 For some 4,600 years, the sheer size of the Great Pyramid of Giza helped it survive conflicts and threats. But how the architectural marvel endured severe natural disasters with limited damage was unknown. Now, a team of researchers think they have uncovered one secret to the pyramid’s longevity. It was designed, possibly by accident yet with undeniable effectiveness, to withstand the forces of strong earthquakes. In a study published this week in the journal Scientific Reports, researchers from Egypt and Japan explain how they placed sensors at 37 locations in and around the pyramid to test the structure’s fundamental frequency—a measurement of how a building naturally tends to vibrate in response to routine external forces, such as human activity or weather. “In heritage conservation, this information can provide important insights into structural stability, hidden vulnerabilities and long-term preservation strategies while fully respecting the integrity of the monument,” Asem Salama, a geoscientist at the National Research Institute of Astronomy and Geophysics (NRIAG) in Cairo, tells Live Science’s Stephanie Pappas in an email. Differently shaped buildings have different fundamental frequencies. When the vibrations of a large outside force—such as an earthquake—occur at the same frequency as a structure’s natural vibrations, the movement is amplified. But if an outside force vibrates at a frequency different from the structure’s natural vibration, this mismatch serves as a sort of buffer to protect the building from damage or collapse. “So the measured difference matters,” write Colin Caprani, an engineer at Monash University, and Scott Menegon, an engineer at the Swinburne University of Technology, in the Conversation. “If the ground and the structure vibrate at different rates, the ground is less likely to feed energy efficiently into the structure.” The authors of the Scientific Reports study measured the Great Pyramid’s fundamental frequency to be between 2.0 and 2.6 hertz, while the soil around it was 0.6 hertz. This wide difference helps explain why the historic structure was able to endure extreme tremors. In 1847, a 6.8 magnitude earthquake originating south of Cairo killed people and destroyed homes, though did negligible damage to the pyramid. In 1992, a 5.9 magnitude earthquake that hit the greater Cairo area hard did only light damage to the pyramid by knocking loose a stone, reports Olivia Maule for Science. Several specifications of the pyramid’s design help it withstand earthquakes: its wide base, built atop limestone bedrock; a low center of gravity; a tapering form; and the building’s symmetrical design, including interior chambers and passageways that help relieve pressure. “These elements together create a well-balanced, coherent structure,” Mohamed ElGabry, a seismologist at NRIAG and the study’s lead author, tells Reuters’ Will Dunham. According to the researchers, it is unlikely that these features were included with earthquakes specifically in mind. Rather, it is more likely that the pyramid proved stable in the face of seismic tremors as a happenstance result of its strong fundamental design. “Any suggestion of intentional seismic optimization by ancient Egyptian architects remains purely speculative and cannot be substantiated by geophysical measurements alone,” the researchers write in their study. Engineers Caprani and Menegon concur, arguing that “the safest conclusion is that the builders made excellent empirical engineering choices,” yet the survival of the pyramid “is not proof of ancient seismic design.” The Great Pyramid of Giza was built over more than two decades for the pharaoh Khufu. During its construction, thousands of workers stacked 2.3 million limestone and granite blocks to bring the 481-foot-tall pyramid to height. “We see this as the culmination of centuries of Egyptian builders learning from both successes and failures,” Salama tells National Geographic’s Taylor Mitchell Brown. “It felt like uncovering a masterpiece of empirical engineering that had been hiding in plain sight for thousands of years.” Christian Thorsberg is an environmental writer and photographer from Chicago. His work, which often centers on freshwater issues, climate change and subsistence, has appeared in Circle of Blue, Sierra magazine, Discover magazine and Alaska Sporting Journal. Email Powered by Salesforce Marketing Cloud (Privacy Notice / Terms & Conditions)

Ancient Egyptian Engineering Choices Helped the Great Pyramid of Giza Survive Earthquakes, New Research Finds

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