Doctor André Rousseau, former researcher in geophysics at CNRS and specialist in sound waves, presents us with the results of his analysis of the seismic signals recorded on September 11, 2001 in New York and gives his point of view as a specialist on the question of the destruction of the three towers at the World Trade Center.

[Translated from the original French by]

Seismic signals were recorded on September 11 2001 during the period when the North and South Towers (respectively WTC1 and WTC2) were penetrated and collapsed, as well as during the collapse of Building 7 of the WTC (also known as WTC7), a building which had not been hit by a plane.

Among the seismic data published on this subject, it is the Palisades recording station, located 34 km north-east of Manhattan, which gives us the data most apt for analysis, particularly for determining their source. These wave graphs are taken from the publications of the Lamont-Doherty Earth Observatory of Columbia University (LDEO), as shown in figure 1 and figure 2.

Seismologists are puzzled in their analysis of signals recorded at this time, as the contradictions are significant. They are particularly intrigued by the presence of seismic “peaks” before the collapses (see figure 4). This text focuses on the study of seismic signals and aims to demonstrate that consistency only appears once we leave the official version of events. It gives rise to a new interpretation that renders the assertions of the “official version” null and void.

Study of the Composition of the Different Wave Graphs

The graphs that we have are the following:
1.The signals in figures 1a & 1b match the moment when the planes hit WTC1 and WTC2 respectively.

2.The signals in figures 2a and 2b match the collapsing of WTC1 and WTC2 respectively.

3.The signal in figure 2e shows the collapse of WTC7.
Determination/indetermination of the Temporal Shocks from the Point of Origin of the Signals.

In the five examples, the origin of the signals was attributed, by the seismologists who published the data, to the impacts of the planes and the collapses of the buildings (Kim et al., 2001; Irvine, 2001; Hoffman, 2006). A study of the propagation of such seismic signals really belongs to applied geophysics, which examines the distance of propagation in relation to the nature of the sources. Normally in this type of study, the time of origin is known with great precision (down to the millisecond), necessary in order to calculate the propagation speed of the different waves. That isn’t the case here. In this case, the video used for the North Tower (WTC1) was from a recording made by CNN with a time stamp on the screen (Hoffman, 2006), and the results were compared with the method utilized by Lamont (Kim et al., 2001). A second method consisted of giving an approximate speed of 2km/s for a Rayleigh wave that traversed several stations (see figure 3) situated at various distances from the point of origin. The major inconvenience of this method is that the stations are not situated on a rectilinear line, that the surface terrain – in which the surface waves move – are different, and, moreover, they don’t have the same speed of propagation. The Hudson River is located on a fault line that separates to the west the sedimentary terrains of the Trias and Jurassic, with intrusions of dolerite, all of which are covered by recent Holocene sediment; and to the east, the crystalline and metamorphic formations of the Proterozoic, the Cambrian, and the Ordovician eras that are found there. These last formations are more rapid than those found to the west, which explains why the path WTC-MANY, the only site to the east of the Hudson, was more rapid than all the other paths, situated to the west. The speed of these formations closely depend upon the sedimentary cover traversed. In other words, it isn’t surprising to find that only the stations at Palisades (34 km), at Arny (67.5 km) and TBR (51 km) provide similar results because they are situated on similar geological formations. Also, the enormous indetermination of 2 seconds in the calculations fixing the time origin of each of the signals, attributed by the authors themselves (Kim et al.), oblige us to take some distance from the official conclusions.

Wave Graphs Attributed to the Planes Crashing Into the Towers

In the first place, we must pose a question about the meaning of such signals’ function with the cause attributed to them. Although the cause of the two signals is similar, the crashing of a plane, the magnitude (reflected by the amplitudes) of the two signals is different and the wave generated by the two do not have the same apparent speed (see figures 1a and 1b), even if the Twin Towers could be considered identical in terms of the spatial origin relative to their distance from the recording sites. The calculation of the propagation speeds, as shown in the graphs of figures 1a and 1b, where the origin was fixed according to the corresponding crash, indicates 2900 m/s for WTC1 and 2150 m/s for WTC2: we are obviously dealing with Rayleigh waves. Even if they were considerably amplified, these signals could not have been generated by the crashes into the Twin Towers – the actual waves generated by the crashes were deadened before hitting the ground (assuming that we were dealing with the same (low) frequencies). Frequencies of waves generated by explosions are on the order of Hertz – which is the case here – while those of crash impacts are above 10 Hertz, often around 100 Hertz. Furthermore, the range of the recording instruments cited does not allow for the recording of such waves. As to the theory of the oscillation of the Towers to explain these signals, as defended by Irvine (2001), it doesn’t hold water because in such a case we would have had a “square” signal of long duration and a constant amplitude, while in actuality we observe a “bell” signal, representing a strong and brief explosion, which is particularly evident in the case of WTC2.

To the degree that it is geophysically impossible to have two different propagation speeds for the same wave at the same frequency – because the surface waves are dispersive, which means that their speed depends upon their frequencies – travelling the same path at a few minutes interval, one must bow to the evidence that the supposed origins of the recorded waves are incorrect, and that they are not linked to the crashes but to another origin, such as an explosion, with a non-identical time displacement for the two towers in relation to the impacts of the two planes. As well, the difference in the magnitude of the two signals can only be linked to different parameters relative to the volume of explosives and/or their distance from the surface.

Wave Graphs Attributed to the Collapse of the Towers (fig. 2a, 2b and 2c)

While the Twin Towers have approximately the same mass, the same height and size, and the same type of internal structure (as well as identical points of origin of the wave in terms of distance to the recording station) the signals attributed to WTC1 (fig 2a) and to WTC2 (fig 2b), instead of being similar as one would suppose from the official thesis which attributes the source of the seismic waves simply to the collapsing of the Towers, they are in fact very different from the point of view of their “form”, their composition and especially their apparent speed.

In fact, the recording for WTC1 demonstrates the three types of wave characteristic of a brief explosive source (“Dirac” type) confined in a compact, solid material: a P wave with a speed of 6000 m/s, the typical value for a very consolidated crystalline or sedimentary terrain (which is the case in the bedrock of Manhattan), an S wave with a speed of 3500 m/s and a surface wave with a speed of of 1800 m/s (Rayleigh wave). These values match with those registered by an earthquake or seismic drilling.

On the other hand, the recording linked to the WTC2 shows none of the type P or S waves observed for WTC1, but only the surface wave, for which the spreading of the amplitudes over the duration is different from that of WTC1. Relative to the determined origin of the signal, the propagation speed of 2125 m/s (Rayleigh wave) is also markedly different from that of WTC1. This wave seems to be followed by a second Rayleigh wave four seconds later.

We find the same thing in the figure for WTC7 where the calculation of the speed of the wave according to the determined point of origin is similar to a Rayleigh wave with a 2200 m/s speed. Note that the amplitudes are comparable to those of the waves emitted at the time of the crashing into the Towers by the airplanes. This wave seems to be followed by a second Rayleigh wave 6.7 seconds later.

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