James GLANZ - Eric LIPTON, New Data Give Graphic Look at How Trade Towers Fell. There is a computer image that captures the jetliner's nose as it splays open like a log being split, its wings shearing apart, the entire aircraft dissolving into a hail of steel and aluminum buckshot during its deadly plunge through one of the twin towers. There is, too, a meticulously annotated, color-coded map that tracks how the fires in the towers moved on the morning of Sept- 11 - window by window, floor by floor, timed to the minute as they caused trapped office workers. And there is the alien landscape of ground zero - the cliffs of debris, the weird meadows of tumbled columns, and the somehow uncrushed subterranean passageways - that is captured in thousands of never before seen photographs. This trove of material, including videotape, compact discs, witness accounts, mathematical analyses and high-tech imagery, was kept confidential until last week, when a federal judge in the World Trade Center insurance case made it clear that he had no objection to its public release. Taken together, the dozens of boxes represent the largest single repository of raw data and expert analysis on the Sept- 11 attack in Lower Manhattan, dwarfing the analysis compiled by the government in its first examination of how and why the towers collapsed. The expert consultants have gathered this material as part of a $3,5 billion lawsuit to determine how much Larry A- Silverstein, the trade tenter leaseholder, should be compensated for the loss of the towers. Mr- Silverstein says he is owed about $7 billion; the insurance companies say he should only receive half that. The opposing teams of experts also produced completely different answers to the rarely asked question of what might have been the implications for the Trade Center if only one tower had been struck and destroyed. Because the teams were hired either by the insurance companies, or by Mr- Silverstein, they often arrived at different conclusions. One set of experts determined that the damage caused by the one tower's collapse would not have caused serious structural damage, permanent environmental contamination or ignited widespread fires in the other tower. Thes are just a few of the reelations and disagreements that emerge from the thousands of pages of reports by the experts. Despite the disagreements, Jeremy Isenberg, a member of the National-Academy of Engineering. and president of Weidlinger Associates, where some of the work was done said the analysis "represents a milestone in the forensic engineering of a disaster." He believes the information can be used to build safer skyscrapers and to better understand the risks posed by existing ones. "I have never seen this level of technical knowledge and experience brought to bear on a single problem." The Sept- 11 disaster began as two jetliners, each weighing more than 200,000 pounds with their fuel, cargo and doomed passengers, hurtled into the towers and disappeared forever from the view of the outside world. But a powerful computer simulation led by Matthys Levy, an engineer and founding partner at Weidlinger Associates, has created a three dimensional renndition of the mayhem that probably took place in less than a second before most of the plane fragments came to rest inside the towers. The simulation created ultra slow motion movies, each framë separated. from the next by less than a thousandth of a second, as the plane and the structure of the towers broke up. Although the simulation does not include the people who, tragically, were on the floors that were struck, the movies do hold new revelations about their immediate fate. The planes were moving at such great speeds - up to 586 miles an hour in the south tower impact and almost 500 miles an hour in the north - that the aluminum of their wings and fuselage and the steel of their engines passed through the perimeter steel columns of the towers almost without slowing down at all, the simulation shows. "It was able to go through the outer wall quite easily," Mr. Levy said. Once inside, the aluminum of the planes was hacked to pieces by the concrete slabs of the floors, which acted like great axes when struck from the side. The heavier steel of the engines punched ahead until striking sturdy structural elements or plunging all the way through the building and soaring out the other side. As the plane slowed, the concrete floors themselves were pulverized to dust. Whole sections of the light steel support trusses that held up the floors - a web of thin bars and steel strips - were annihilated. The mangled planes finally barreled into a forest of crucial structural columns in the cores of the buildings, the simulations show. In both towers, the damage to those columns was severe - so severe, in fact, that the simulations predict that the south tower should have, by this calculation, collapsed immediately. "A slight change in the direction of the plane could have caused more damage, could have caused immediate collapse," Mr. Levy said. Mr. Levy conceded that the simulations do have some significant limitations. They take into account only the tower's structural steel and rot the partitions and other contents of the offices inside, which must have absorbed some of the plane's impact. So the estimated damage to the structure itself is an upper limit, "the worst thing that could happen in terms of the results," Mr. Levy said. Next, of course, came the fire. By assembling thousands of photographs, videos and witness accounts, Richard L-. P- Custer, the national technical director of ArupFire, a Massachusetts fire science company, prepared a color-coded map of each face of the two towers that shows the spread of fire and smoke from the moment the fireballs erupted until each of the towers collapsed. Either way, said Daniel A- Cuoco, an engineer who is president of the Thornton-Tomasetti Group, "the central portion collapsed on itself and the facade just peeled off," a conclusion he reached after his company, which worked for the city at ground zero beginning on Sept. 11, examined hundreds of photographs of the ghastly patterns of destruction and debris that remained where the giant towers had stood. Those photographs, each annotated to specify where and when it was taken, form perhaps the largest repository of ground zero images ever assembled, "They present a catalog, so to speak, to anyone who has an interest in understanding the disaster," said Richard Tomasetti, co-chairman of the Thornton-Tomasetti Group. A darkened subterranean train station where tumbling debris has ripped open the ceiling and fouled the tracks with twisted bars and pulverized concrete. An abandoned, dust-choked, underground newsstand, gutted duct-work and burned-out wiring dangling over shelves still neatly stocked with candy and magazines. A steel canyon carved into what had been the trade center's plaza, the charred and ruddy steel columns that had help up the towers strewn about like tree branches after a hurricane. It is a world that has now vanished. But through this strange, adversarial court proceeding, its images remain.