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Controversial Bosnian “pyramid”
Activating aftershocks

Controversial Bosnian “pyramid”

A tall, pyramid-shaped hill near the small town of Visoko in Bosnia is causing quite an international stir. An amateur archaeologist from Houston, Texas, says that the hill is the world’s oldest human-made pyramid — at more than 12,000 years old, he says, it was built 7,000 years before the pyramids at Giza in Egypt, and it is more than one-third larger. Geologists and professional archaeologists, however, dispute his claims and say the hill is just that — a hill.

An amateur archaeologist says that this hill, seen in the background, is the world’s oldest human-made pyramid, while most scientists say it is a natural formation. Photograph is courtesy of Meho Macic

The story begins about 30 kilometers from Sarajevo in a region that has perhaps been populated for more than 300,000 years, says Curtis Runnels, an archaeologist at Boston University in Massachusetts. “Artifacts and archaeological sites are littered” throughout the Balkans, he says, including this valley, where archaeologists have found a medieval fortress atop the hill, which is built atop Roman ruins, which lie above Illyrian ruins and even older Neolithic remains.

Nowhere in those ruins, however, is anything resembling a pyramid, Runnels says, especially not one built 12,000 years ago, when the area was sparsely populated with hunter-gatherers who lived in small family-based clans. “These are people who would not have been able to bring enough people together to build Stonehenge, much less a pyramid far larger than those in Egypt,” he says. “This claim is just completely nonsensical.”

The “claim” was made by Semir Osmanagich, a self-proclaimed pyramid buff who has written a book about Central American pyramids. Osmanagich says that the main hill, which he has named the Pyramid of the Sun, has perfect pyramidal geometry, reportedly visible in satellite images, and that the three main “pyramids” in the valley form “a perfect triangle.” The pyramids are connected by a series of underground tunnels, he says, which he and a team are excavating. “As far as I’m concerned, there is no controversy,” he says: The structure is human-made.

News reports have quoted a geologist from Egypt stating that the pyramid is indeed human-made, seemingly one of few folks who support Osmanagich’s claims. Other geologists, including a team from the University of Tuzla in Bosnia, have examined the site and say it is a natural geological formation.

“It looks like a hill composed of tilted bedrock,” says Paul Heinrich, a geologist at the Louisiana Geological Survey at Louisiana State University. Natural fracturing of the predominantly sandstone rocks caused the jointing that Osmanagich is interpreting as separate building blocks of the pyramid, Heinrich says, and Osmanagich is mistaking ripple marks as carvings and unusual concentric and parallel banding for paintings.

Other misinterpretations, Heinrich says, include interpreting spherically shaped stones as human-made stone balls, and groundwater carbonates encrusting bedrock blocks as either “mortar” or “glue.” And the so-called tunnels that Osmanagich says he has found could be any number of things, Heinrich says, including old mine shafts (mining has been occurring in the region for more than 1,000 years) or natural caves.

“The best analogy I can give,” Heinrich says, “is that of the Chimera,” a mythological creature composed of a mosaic of parts. “Unrelated components,” in this case both human-made and natural, he says, “are being put together erroneously.”

Despite efforts by world-renowned archaeologists and geologists to kill this “nonstory,” Runnels says, it is sticking around, likely because many Bosnians are embracing the “pyramid” out of local pride. Furthermore, he says, money is pouring into the region, with Osmanagich employing local people, and politicians, tourists and the media flocking there.

Currently, Osmanagich and a team are excavating the hill. Meanwhile, in June, UNESCO announced its intentions to check out the site.

Megan Sever


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Activating aftershocks

As residents of seismically active zones from Southeast Asia to California know, even after the rumbling from a large earthquake subsides, danger lurks. One large quake can spawn dozens of smaller temblors that can also cause significant damage, but scientists still puzzle over what causes these aftershocks. A new study suggests that the rapid pulses of ground-shaking during a main earthquake, rather than the steady stress from the rocks shifted along the fault, may trigger these follow-up events.

Aftershocks are both the most abundant and the most predictable kind of earthquake, “but we don’t really understand the physics” behind them, says Emily Brodsky, a geologist at the University of California in Santa Cruz. Current predictions of where aftershocks will occur are based on a compiled earthquake “catalog” for a given region, which lists the locations and magnitudes of past seismic events — a statistical system that “works pretty well” for predicting future events, Brodsky says. “But we were trying to put some physics behind that.”

Many studies suggest that aftershocks occur as a result of “static stress,” stress that begins during the main event and remains steady, says Karen Felzer, a geologist at the U.S. Geological Survey (USGS) in Pasadena, Calif. In the lab, she says, putting a rock in a clamp and applying increasing pressure will cause the rock to break at some point. In Earth, she says, a shift in a fault is like tightening the clamp, adding stress to the surrounding rock.

But during an actual earthquake, in addition to static stress, “there’s also a tremendous amount of shaking,” Felzer says. That shaking, or “dynamic stress,” applies a series of brief bursts of pressure to the surrounding rocks rather than the steady, continual push of static stress. While static stresses decrease quickly farther from the mainshock, dynamic stresses propagate over much greater distances. Thus, scientists have proposed that dynamic stresses may cause some aftershocks, particularly those occurring farther from the earthquake’s epicenter, Felzer says.

To better understand which stresses might dominate aftershock triggering in different locations after an earthquake, Felzer and Brodsky analyzed newly revised earthquake catalog data within California to measure how the number of aftershocks changed with distance from the location of the mainshock. The catalog of primarily small- to moderate-sized earthquakes provides the most precise earthquake locations to date, Felzer says.

The researchers found that the frequency of all aftershocks decreased with distance from the mainshock according to a single mathematical law, instead of the dominant triggering mechanism shifting from static to dynamic stress over distance. That suggests that only one mechanism was triggering the aftershocks, and because the decrease in rate was too gradual to attribute to static stress, dynamic stress is the likely culprit, the researchers reported in the June 8 Nature.

USGS is now considering how to incorporate this new information into its aftershock predictions, Felzer says, but much more work is on the horizon. Researchers, for example, still do not understand which physical aspects of the ground-shaking pulses are the actual triggers, she says.

Furthermore, the study does not include large-magnitude quakes, which are much rarer events, making such a statistical analysis far less accurate, Brodsky says. However, as far as the underlying physics that trigger aftershocks, she says, “we see no reason it ought not to apply to big earthquakes.”

That static stress did not appear to trigger any aftershocks after small to medium earthquakes is “surprising, but well-substantiated” by the study, says Ian Main, a seismologist at the University of Edinburgh in the United Kingdom. However, he notes, dynamic stress alone does not account for long delays between quakes and their aftershocks, and studies of some larger earthquakes — such as the 1999 Izmit earthquake in Turkey and its predecessors — suggest that powerful aftershocks tend to occur in increased areas of static stress. “I would say the jury’s still out in terms of triggering after big earthquakes,” Main says.

Carolyn Gramling

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