Machu Picchu: Ancient Incan sanctuary intentionally built on faults


The ancient Incan sanctuary of Machu Picchu is considered one of humanity's greatest architectural achievements. Built in a remote Andean setting atop a narrow ridge high above a precipitous river canyon, the site is renowned for its perfect integration with the spectacular landscape. But the sanctuary's location has long puzzled scientists: Why did the Incas build their masterpiece in such an inaccessible place?

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Faults' hot streaks and slumps could change earthquake hazard assessments

For more than a century, a guiding principle in seismology has been that earthquakes recur at semi-regular intervals according to a 'seismic cycle.' In this model, strain that gradually accumulates along a locked fault is completely released in a large earthquake. Recently, however, seismologists have realized that earthquakes often occur in clusters separated by gaps, and one research group now argues that the probability of a tremor's recurrence depends upon whether a cluster is ongoing — or over.

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Geochemists measure new composition of Earth's mantle

Geochemists have investigated the volcanic rocks that build up the Portuguese island group of the Azores in order to gather new information about the compositional evolution of the Earth's interior. The results suggest that a larger amount of the Earth's mantle has melted and formed the Earth's crust than previously thought.

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Carp aquaculture in Neolithic China dating back 8,000 years

Researchers analyzed fish bones excavated from the Early Neolithic Jiahu site in Henan Province, China. By comparing the body-length distributions and species-composition ratios of the bones with findings from East Asian sites with present aquaculture, the researchers provide evidence of managed carp aquaculture at Jiahu dating back to 6200-5700 BC.

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