by André Rousseau
04 June 2010

translated from french by SOTT

from SOTT Website

Original source


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.

André Rousseau, Docteur d'État, is a retired researcher at CNRS where he studied the relations between the characteristics of progressive mechanical waves and geology. He published numerous peer-reviewed articles on geophysics and participated in numerous conferences, including selection committees.

In this article he puts forward evidence that the seismic waves recorded on September 11, 2001 in New York are the result of subterranean and subaerial explosions that were part of the controlled demolition of the Twin Towers and WTC7.

Curriculum Vitae
André Rousseau

* Faculté des Sciences de Paris:

- Second cycle en Sciences de la Terre, Géophysique interne et externe,
- DEA de Tectonophysique-Océanographie,
- DEA de Géophysique Appliquée

* Université de Rennes 2 : thèse de 3ème cycle
* Université de Bordeaux 1 : thèse d'Etat (voir ci-après). Ancien Chercheur titulaire au CNRS

Collapse of WTC
Seismic Signals Reveal Explosives Were Used at the WTC on 9/11,

according to geophysicist André Rousseau (*)

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 (bottom page.)

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 - traveling 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.



The problem of the above-named "displacements" between the time of origin of the seismic waves and the times that the planes crashed into the Towers, particularly that for WTC1, is certainly the key question which is emblematic of all the contradictions of the official version of September 11, 2001.


In their publication on the Web (Kim et al., 2001), the LDEO published two different timetables of sources, which are indicated in the table below. The first timetable (LDEO [1]) is that furnished without the published graphs, then the LDEO modified them (LDEO [2]) to obtain coherent seismic speeds. What is the indisputable data here?


There are two: the time that the waves reached the Palisades station, which is relatively easy to determine, and the distance from the WTC to Palisades (34 km).


If the recorded wave is actually a Rayleigh wave, its speed is around 2000 m/s. Therefore, this wave was created 17 seconds before its arrival at Palisades. Where the problem deepens for the adepts of the official version is that the time for the source of the Rayleigh wave attributed to the crash into WTC1, which officially arrived at Palisades at 8.46.42±1, must in fact be 8.46.25±1!


Compare that time with the times given in the first column of the table below.

9/11 Seismic Study - Table 1

The data given by the NTSB (National Transportation Safety Board) comes from radars at ground level and are reliable to one second.


If we consider the time of the impact of the plane into WTC1 furnished by the NTSB, 8.46.40 (Ritter, 2002), the only reliable data because it doesn't come from any hypothesis, there is a hiatus of 15 seconds between the plausible time of the origin of the Rayleigh wave and the time - afterwards - of the crash of the plane into WTC1. What else but an explosion could be the origin for this seismic wave in the absence of an earthquake?

Concerning the generation of the seismic waves following the crash into the Towers by a Boeing, the transformation of the kinetic energy into seismic waves would only make sense if we were dealing with a crash between two full, solid, and in-deformable objects. In this case, the kinetic energy of a moving body would in part be transformed into heat and the rest would be transmitted to the pierced object in the form of vibrations, that is, seismic waves.


However that is not the case here because we have two hollow and deformable objects. During the crash, the whole of the energy is transformed into heat and the deformation of the envelopes (exterior walls). In the case where a little mechanical energy would remain, the waves created in the pierced envelope would be quickly dispersed because of the absence of continuity in this alveolar envelope.


The necessary condition for the creation of seismic waves by such a crash would be the direct impact of the central columns by a full body.


Even if a Boeing engine had succeeded in hitting a central column, it would have been with an energy lessened by the envelope. In conclusion, even if a seismic wave could be created in a metallic column, it would hit the ground in the form of a sound, and as the passage from metal to rock is a refraction that absorbs energy, there wouldn't be much left to propagate in the ground.

Could the collapse of the towers be the source of these seismic waves?


In the case of a crash on the ground that generates seismic waves, the enormous mass of the Twin Towers could hypothetically be taken into account if the Towers had fallen in a compact block, like a meteorite. But in the present case, it was scattered remains that fell, largely transformed into dust, and the fall lasted several seconds.


We are far from a Dirac-type force that can create seismic waves; in this case, the magnitudes simply don't add up.

Given that neither the crash into the tower nor its vibration, nor the fall of debris can be the source of the seismic waves registered 34 kilometers away, and that the low frequencies could not have been provoked other than by explosions, we must research why the wave graphs are different. Various things must be considered.


We must distinguish between subterranean explosions, subaerial explosions (close to the ground without touching it) and aerial explosions.

  • Subterranean explosions are similar to earthquakes in that mechanical energy is transmitted to the earth in the form of volume waves (P and S) - either directly in the latter case, or by conversion of the waves due to a cavity in the former case - and surface waves (Rayleigh and Love), when the signal reaches a solid-fluid interface (in the case of the atmosphere, for example) (Case 1).


  • Aerial explosions give off all of their energy in the air (P waves, or sound waves), and what remains upon hitting the ground - if it hits it - is thus too weak to create volume waves (although there can be surface waves over a small distance) (Case 2).


  • Subaerian explosions give off an energy that splits into sound waves, mainly in the air, and surface waves on the ground. The volume waves dispersed in the air don't end up lessened on the ground, but surface waves are certainly present (Case 3).

In brief, a subterranean explosion would not be heard in the air, but the ground would shake and initiate a series of waves (volume and surface waves), while if we hear an explosion, it is because it is either "aerial" and doesn't give a seismic signal, or it is subaerial and surface waves could be generated.

Therefore we can affirm that explosions qualified as "subaerial" were set off close to the base of the Towers simultaneously with the crashes into each by the planes.


The sound coming from these explosions would have been mixed with the sounds generated by the impacts of the planes (Case 3). The Towers were thus weakened by the breaking of the load-bearing columns. The explosion at the base of WTC1 was heard by eyewitness Walter Rodriquez (2006) (see also Spingola (2005)).

As to the collapse of the Towers, we must distinguish between WTC1 and those of WTC2 and WTC7. Based upon the tips of waves coming from these last two towers, they underwent a very large "subaerial" explosion (Case 3), heard by witnesses.


For example, regarding WTC2, a fireman witnessed an explosion before the building collapsed into an enormous cloud of dust (See [1]), apparently not too far from the base of the tower accompanied by flashes of light and noise, according to an "Assistant Commissioner" (see [2]).


Another fireman, present at the base of WTC2, stated there was a large explosion about 20 floors below the impact zone of the plane just before the summit of the Tower collapsed (see [3]).


These explosions were too high to generate volume waves in the ground, and the Rayleigh wave recorded probably comes only from the explosion closer to the ground. Among the other explosions heard at the base of WTC2 (Anonymous, 209), one of them generated the second Rayleigh wave four seconds after the first. The same thing happened at WTC7.


A witness watching this tower heard something like a "thunderclap" that caused the windows to explode outwards, while the base of the burning building gave way a second later, before the whole building followed the movement (see [4]), aided by a second explosion that generated the second Rayleigh wave 6.7 seconds later.

As for WTC1, the collapse of which began after that of WTC2 in spite of the fact that it had been hit earlier, it was a subterranean explosion (Case 1) that preceded its collapse. This explosion was thus logically not heard by the witnesses outside at 10:28 EDT, except for those located next to the tower (see [5]), but it was "felt" by a camera filming the tower that was solidly on the ground and was shaken by the vibration of the ground at the moment of the explosion (see [6]).


On the other and, it is also logical that the many explosions shown in videos in the upper floors before and during the collapse didn't provoke any seismic waves (Case 2) because of the fragmentation in time of the detonated energy with the multiplication of successive sources, each of which had only a limited force, insufficient to generate seismic waves in the ground.

Even if controlled demolitions do not create seismic waves (aerial explosions), it is useful to compare these observations with seismic data obtained during the controlled demolition of the Kingdome in Seattle (see Anonymous, 2009) and at Oklahoma City (US) (Holzer et al., 1996).


The case of the Kingdome is particularly interesting because seismologists expressly asked that the explosions be measured (they wanted to take advantage of the occasion), and those in Oklahoma City were part of a reconstruction using explosives of the bombing of the Alfred P. Murrah building. These two examples fit into Case 3 cited above, with a powerful subaerian explosion and the emitting of Rayleigh waves, and where the falling of the debris had no seismic consequences, even at distances under 34 km (less than 7 km and 26 km respectively).


Only the seismic equipment situated close to the source during the reconstruction of the bombing in Oklahoma City reacted to the seismic energy created by the collapse of the building.

The local magnitudes (LM) that the seismologists calculated from the surface waves gave results that consolidate our analysis. Effectively, on the Richter scale, they were higher than 2 for the waves emitted at the moment of the collapse. It is impossible to get such a magnitude only from the falling of the debris, more especially over a duration of ten seconds!!


Even if the entire tower had been compacted into a tight ball, it would have necessitated the speed of a meteorite, in any case, more than that caused by the Earth's gravity, to even approach such a magnitude!! Moreover, we must note that the magnitude attributed to the subterranean explosion at the WTC1 is LM=2.3 - comparable to the earthquake that hit New York January 17, 2001 (LM=2.4) - while the magnitude coming from the WTC2 explosion is LM=2.1, thus weaker, and this disparity - consistent with the explosions described - is particularly appreciable in this logarithmic scale.


Given the Twin Towers were of similar height and mass, the falling debris should have generated similar magnitudes, if they were the source of the waves...

Note that applied geophysics knows how to generate seismic waves in the ground, using non-explosive sources such as "weight dropping" - which consists of letting a three ton weight fall to earth - or else using "vibrators" attached to the ground.


But the energy of the waves developed in the ground are too weak for the waves to go further than several hundred meters.


The Relation between the Seismic Waves/Process of Collapse

Observation of the collapse of each tower shows they were each different, and this correlates with the corresponding measures of the seismic waves.

The collapse of WTC7 is the one that comes closest to a classic controlled demolition, with the successive collapsing of the floors starting from the base which had been weakened by a subaerial explosion. As for the Twin Towers, they were first weakened by explosions at their base at the moment the airplanes crashed into them.


After that we must distinguish between the parts of the building above the impact zone of the planes and those located below. If the seismic waves couldn't have been generated by the small explosions visible in the floors (which allowed for the gradual collapse from the bottom up to the impact zone) then only a powerful explosion at the base of both buildings could have accelerated the process of total ruin and produce the observed seismic waves.

In the case of WTC1, FEMA (Federal Emergency management Agency) implicitly confirms this scenario.


They note that,

"Review of videotape recordings of the collapse taken from various angles indicates that the transmission tower on top of the structure began to move downward and laterally slightly before movement was evident at the exterior wall. This suggests that collapse began with one or more failures in the central core area of the building."

(FEMA, World Trade Center Building Performance Study, chapter 2).

As this transmission tower was a lattice of I Beams posed diagonally, called a "hat stress", it connected the walls of the edge to the central structure between the 107th stage and the roof and therefore reinforced the centre structure. It also supported the tower installed on the top of the building.


Contrary to the official version which declared that it was the hat stress that transferred the instability of the central columns to those of the perimeter, which then gave out after they were deformed because of the pulling of the floors, the logic of the events forces us to consider that the "rupture" of the central columns came from an explosive "cutting" prior to the collapse of the building.



At the moment of the impact by the planes on the Twin Towers and their collapse, as well as that of WTC7, seismic waves were generated.


To the degree that:

  1. seismic waves are only created by brief impulses

  2. that low frequencies are associated with an energy (magnitude) that is comparable to a seismic event, these waves undeniably have an explosive origin

Even if the planes' impact and the fall of the debris from the Towers onto the ground could have generated seismic waves, their magnitude was insufficient to be recorded 34 km away, and they should have been similar.

However, the composition and magnitude of the seismic signals show significant differences, above all in their propagation speed, even though their paths were identical under identical conditions. This last difference being physically unexplainable in the official version, we must put into question the calculation of the speeds effectuated from the origin shown on the video images. We can only conclude that in reality, the (explosive) source was manually detonated, thus accounting for the variable shift for each origin in relation to the videos.

The composition of the waves is revealing both in terms of the location of the source and the magnitude of the energy transmitted to the ground. The subterranean origin of the waves emitted when WTC1 collapsed is attested by the presence of the P and S volume waves along with the Rayleigh surface waves, which are present in all five explosions.


The placement of the source of the four other explosions is subaerial, attested by the unique presence of Rayleigh waves. The aerial explosions visible on the videos of the upper floors of the Twin Towers do not produce seismic waves 34 km from the source.

There is a factor of ten between the power of the explosions at the time of the impacts on the twin Towers (as well as at the time of the collapse of WTC7) and the strength of those more powerful ones at the time of their collapse, the subterranean explosion under WTC1 being the one that transmitted the most energy to the ground.

Note as well that the degree to which the surface waves disperse (their speed depends upon their frequency), the duration of the recorded signal is not representative of the duration of the signal at the source.

Finally, the controlled demolition of the three towers, suggested by the visual and audio testimony, as well as by observations of their collapse, is thus demonstrated by the analysis of the seismic waves emitted at the moments of the plane impacts and at the moments of the collapse.




Note that for reasons of readability, these figures are shown without modification of their scales, which have a relation of one to ten between the recording at the moment of the collapse of WTC1 and WTC2 and those at the moment of the impacts, as well as for the recording of the collapse of WTC7.


Figure 1a:

Signal recorded at Palisades during the impact on WTC1.

Figure 1b:

Signal recorded at Palisades during the impact on WTC2.

Figure 2a:

Signal recorded at Palisades during the collapse of WTC1.

Figure 2b:

Signal recorded at Palisades during the collapse of WTC2.

Figure 2c:

Signal recorded at Palisades during the collapse of WTC7.

Figure 3:

Shift of origin time of WTC1.

Figure 4:

Seismic 'peaks'.


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