Some buildings constructed of reinforced concrete that were atthe epicenter of the April 6 earthquake in Italy's Abruzzo regionsurvived gravitation forces that were off the chart, a survey hasfound.

That discovery was made by a damage reconnaissance teamassembled by the Earthquake Engineering Research Institute and thePacific Earthquake Engineering Center led by Paolo Bazzurro, AIRWorldwide director of engineering analysis, Boston-based AIRsaid.

"Several identical six-story reinforced concrete structuresbuilt in the late 1980s to early 1990s, which were located at thesite where the recording station went off scale at 1g, showed noapparent structural damage, only moderate cracking to the infillwalls," said Mr. Bazzurro.

"A three-story reinforced concrete frame building, which wasrecently remodeled, located across the street from the recordingstation remained completely untouched," he noted.

Mr. Bazzurro said, "This finding will likely prompt thoroughinvestigation in the engineering community to better understand howthese buildings could survive relatively unscathed under suchsevere ground motion."

The earthquake had magnitude of 6.3 and AIR has estimated thatinsured losses would range between EUR200 million ($263 million)and EUR400 million ($525 million)--with low penetration ofearthquake insurance serving to limit losses to the industry.

AIR estimated damage to buildings and contents (exclusive ofinfrastructure), or "ground up" loss, at between EUR2 billion ($2.6billion) and EUR3 billion ($3.9 billion)

Mr. Bazzurro said the quake "was a shallow event, whichundoubtedly concentrated the damage in the provincial capital ofL'Aquila and surrounding villages. Damage to unreinforced masonrybuildings has been severe. Even in cases where a building looksrelatively intact from the outside, the inside may reveal severe tototal destruction."

"The large majority of reinforced concrete buildings in theepicentral region fared well, particularly since they weresubjected to a ground motion equal to or greater than that forwhich they were designed," he added.

These buildings, he explained, were designed for a horizontalacceleration of 0.25g. Mr. Bazzurro said in the epicentral region,maximum gravitational force accelerations up to 0.67g weremeasured, "and one recording station went off scale at 1g."

"Among the construction classes, modern reinforced concreteframe buildings--designed after 2003 when the last building codewas issued--performed much better than those built in the 1960sthrough the 1990s," he reported.

"Modern RC frame buildings typically suffered no exteriordamage, or perhaps minor to moderate damage to exterior andinterior clay brick partitions. Only very rarely negligible damagewas observed to structural elements," Mr. Bazzurro noted.