Hello, Pericynthion
QUOTE (Pericynthion @ Apr 5 2008, 02:27 AM)

Your first basic error is that you have completely ignored signal propagation time. The chart above shows the East-West component of ground velocity for the Lamont-Doherty seismometer located at the Palisades, NY station (PAL). It is 34 kilometers north/northeast of the World Trade Center site. According to reference (1) below, the primary signals arriving at PAL during the incidents of 9/11 were short-period Rayleigh surface waves (Rg) which propagate through the local rock structure at 2 kilometers per second:
[indent][/indent]
Your chart shows the seismometer trace beginning at 10:28:30. The collapse begins at 10:28:31, at t=1 second on the chart. With 34 kilometers to travel at 2 km/s, the Rg waves from the START of the collapse don't arrive at the PAL seismometer until about t=18 seconds on that chart, just about where you've drawn your last red line. You're marking off events that can't possibly be seen in the data because the signals haven't yet arrived at the seismometer!
Your first critical error is to presume I ignored the signal propagation time, when in fact it is one of the very first things I considered in marking the graph.
Your second basic error is to assume the time of 10:28:31 is for the initial collapse movement of WTC1. You correctly identify that an event occurring at this time will appear on the graph in the position of my last red line, ie approximately t=18, though this particular event is the main debris field impacting the ground;
not the initial collapse movement. See
NIST NCSTAR 1-6, pg.298, which states at 10:28:
20 “
Tower began to collapse”. Adding a 17s propagation time, readings should then appear on the graph at approximately t=7. The
link you provided states for Palisades, “
Origin times with an uncertainty of 2 s were calculated from the arrival times of Rg waves at PAL using a velocity of 2 km/s.” The line I inserted indicating the initial collapse movement of the upper block is well within t=7±2
Further, if you are still not convinced and believe the first collapse reading does not arrive until t=18, I would very much like to know why there should be so much activity prior to this. We can see here -
http://www.ldeo.columbia.edu/LCSN/Eq/WTC_20010911.html - that the readings from t=6 through to t=18 for the WTC1 collapse are at the approximate M
L (only slightly below) of those for the airliner impacts; highly indicative that the structure is taking damage during this time.
I will add as well that you are the first person I have come across who believes the greatest readings are those of the collapses beginning. All other sources, whether for or against the official story, agree that the largest readings are of the debris impacting the ground – NIST’s FAQ, speaking of the main reading, “
The seismic spikes for the collapse of the WTC Towers are the result of debris from the collapsing towers impacting the ground”, or 911 Research, “
At about 12 seconds into this event [the beginning of collapse]
, this signal is eclipsed by the much larger disturbance of thousands of tons of material impacting the ground.” Therefore, timing backwards from the main debris field impacting the ground to the initial collapse movement also supports that my first line is in the approximate correct position.
It is well worth reading this short section,
The 'Large Spikes' Were Preceded by Smaller Signals, from the 911 Research article I quoted which analyses and confirms the initial collapse readings are shown on the seismograph prior to that of the debris impacting the ground.
QUOTE (Pericynthion @ Apr 5 2008, 02:27 AM)

Your second major error is that you seem to be assuming that a seismometer records a perfect signal in which every squiggle can be traced back to some distinct event at the source. That's just not true. Seismic events generate multiple types of waves which travel at different speeds and will arrive at a distant seismometer at different times. Even waves of the same type can reflect around inside the earth, resulting in multiple arrivals of the same signal at different times, like a voice echoing through a canyon. As flyingswan has been telling you, seismic waves are periodic oscillations and when different signals overlap, they can cancel or enhance each other.
Your third significant error is to suppose I am not listening to and accounting for flyingswan’s input. Although every reading
is in fact a given of a specific occurrence, even if such as from two signals coming together or a form of seismic ‘echo’, I realise due to the complexity involved this cannot always be realistically traced back to a precise event. In summary, I understand there can be a degree of chance or seeming randomness in the seismic readings. In addition to all of this, I also understand that a reduced reading on a seismograph could well indicate the obvious possibility of reduced seismic activity.
The question then is, as I have been discussing with flyingswan, what is the likelihood of a given reading occurring due to chance or design, not once but in the case of both collapses, in conjunction with a specific observable event? The “given reading” referred to is the reduced activity I have highlighted mid-collapse and the “observable event” being the moment the upper block has fallen through its height. If it happened only once I would be content to write this off as chance. When the reduced reading mid-collapse in
both Towers occurs in conjunction with the same observable event in the case of
both Towers, I am more inclined to deduce it is by design, ie due to an event, rather than chance.
Indeed, flyingswan has calculated the probability of the readings coinciding with those events by chance to be approximately 19%. Notwithstanding my belief that this probability is generously high, it still leaves the 81% likelihood that the readings were actually caused specifically by reduced seismic activity at that time.
QUOTE (Pericynthion @ Apr 5 2008, 02:27 AM)

See the comment about constructive interference on the E-W component at PAL? That's the same signal you've been looking at. It's not just a simple, direct record of the collapse. The authors believe it's a mix of at least two overlapping "echoes" of the Rg waves created during the collapse.
Yes, I do see that comment, though there is no indication in the text that it refers to the reduced reading I have highlighted just before 10s. Also here, the authors use terms such as “may well” and “not necessarily”, indicating that discussed above – there is a degree of possibility the readings could be for one reason or another. Anyhow, if you think the comment does refer to the reduced signal I have been looking at, then it contradicts your original assertion that a signal is not received until t=18. Can we have some consistency in your argument please.
QUOTE (Pericynthion @ Apr 5 2008, 02:27 AM)

So, the half-ton truck bomb detonating below the WTC wasn't detectable at any of the seismic stations in the area, yet the individual blasts of your supposed "stealth" demolition charges high in the towers were clearly recorded at a station 34 kilometers away. Is that what you're claiming?
There is a large difference between the pressure blast of a single truck bomb and the force of demolition charges placed directly against the main structural columns. Do you really need me to explain why? As mentioned above, the increased collapse activity I mark out as perhaps indicative of demolition charges is approximately on the level of the impacts which is to be expected, ie both impacts and demolition charges would cause damage/severing of the core columns. In any case, although the increased activity levels during the second phase of collapse (that of the lower blocks commencing from t=10), could possibly indicate explosives, no, that is not my main claim.
The real claim I am making is that the reduced seismic reading mid-collapse may be indicative of reduced activity and further, a reduction of the collapse momentum – in all, constant activity, followed by reduced activity, moving to increased activity. This is not supportive of the official
progressive collapse theory where activity should be at a constant or gradually increasing level throughout. It is though supportive of these two distinct phases of controlled demolition: -
- Thermite/thermate charges (apparent from evidence presented by Professor S Jones and visible flowing from WTC2) initiated the collapse.
- Further conventional demolition charges (evident through explosive ‘squibs’ during collapse) removed remaining resistance from the structure resulting in a symmetrical, near freefall collapse.
Thank you for your comments, Pericynthion. As you admit to not doing so, it may be useful to read the thread carefully and also compare the seismic records to video evidence if you intend to carry on with this discussion.