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OFR 01-0429: World Trade Center USGS Vibrational Processes Map
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Images of the World Trade Center site show patterns of materials with spectral absorptions due to vibrational processes

The map on this page (Vibrational Figure 1) shows locations of materials with vibrational absorption features commonly found in clays and other phyllosilicates (like muscovite), carbonates, and water-bearing sulfates. Such minerals are commonly found in building materials. For example, walls are often constructed with a board containing gypsum, a sulfate. Gypsum has been identified in samples from the WTC area (see sample analysis section). Muscovite, carbonates, and other hydroxyl-bearing minerals have also been identified in the WTC samples (see the Integration of Results section).

The debris contains common building materials, therefore, the map also shows these materials in other buildings not associated with the World Trade Center (WTC) collapse. While the minerals mapped in any one location may or may not be associated with the WTC event, a pattern is seen that shows the distribution of materials related to the WTC collapse. This pattern matches the pattern from the ferric and ferrous absorption features map.

The spectral absorptions due to vibrational processes are normally diagnostic of mineralogy or material type. The spectral signatures in the WTC debris are, however, quite weak (see laboratory spectroscopy of field samples, below). Because of their weak strength, and influences of the spectral signatures of other materials, including organics, definitive identifications could not be made in this case. Definitive identifications might be made on such samples if the sensor had a higher signal to noise.

Both the iron maps, dust/debris maps, asbestiform mineralogy maps, and vibration absorption maps show a pattern of materials suggesting asymmetric distributions to the composition of the debris/dust.

Again, at any one location in the image, the mapped materials may be unrelated to the WTC debris because they may be common building materials used in the area. However, if a certain type of debris must be cleaned up, this and the other maps indicate the locations to investigate on the ground where similar compositions occur.

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Vibrational Figure 1a. Vibrational absorption features map.

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Vibrational Figure 1b. Vibrational absorption absorption features map, same as at right, but zoomed in to lower Manhattan.

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