So far as I can see, it's not relevant to anything that's been stated so far. It is most relevant: it answers all your questions at once.
The Tunguska explosion event does prove that the surface of the Earth is actually flat.
What would be the point of addressing seismic waves?
To tell you that the discontinuities of the seismic waves assumed by modern science to occur at the crust mantle boundary are actually a network of huge caverns and large underground bodies of water and that they would match perfectly the seismic data?
That great masses of water are interpreted as molten rock?
Seismic data which directly refute the claims of a solid Earth (RE) have been ignored by seismologists.
Did you know that seismic waves travel faster north-south than east-west for a full four seconds?
"The S-wave shadow zone is larger than the P-wave shadow zones; direct S waves are not recorded in the entire region more than 103° away from the epicentre. It therefore seems that S waves do not travel through the core at all, and this is interpreted to mean that it is liquid, or at least acts like a liquid. The way P waves are refracted in the core is believed to indicate that there is a solid inner core. Although most of the earth's iron is supposed to be concentrated in the core, it is interesting to note that in the outer zones of the earth, iron levels decrease with depth.
Seismologists sometimes draw contradictory conclusions from the same seismic data. For instance, two groups of geophysicists produced completely different pictures of the core-mantle boundary, where there are believed to be 'mountains' and 'valleys' as high or deep as 10 km. The two groups used virtually the same data but used different equations to process them. Seismologists also disagree on the rate of rotation of the inner core: some say it is rotating faster than the rest of the planet, others that it is rotating more slowly, and yet others that it rotates at the same speed!
It is becoming increasingly evident that the earth model presented by the reigning theory of plate tectonics is seriously flawed. The rigid lithosphere, comprising the crust and uppermost mantle, is said to be fractured into several 'plates' of varying sizes, which move over a relatively plastic layer of partly molten rock known as the asthenosphere (or low-velocity zone). The lithosphere is said to average about 70 km thick beneath oceans and to be 100 to 250 km thick beneath continents. A powerful challenge to this model is posed by seismic tomography, which shows that the oldest parts of the continents have deep roots extending to depths of 400 to 600 km, and that the asthenosphere is essentially absent beneath them. Seismic research shows that even under the oceans there is no continuous asthenosphere, only disconnected asthenospheric lenses.
The more we learn about the crust and uppermost mantle, the more the models presented in geological textbooks are exposed as simplistic and unrealistic. The outermost layers of the earth have a highly complex, irregular, inhomogeneous structure; they are divided by faults into a mosaic of separate, jostling blocks of different shapes and sizes, generally a few hundred kilometres across, and of varying internal structure and strength. This fact, in conjunction with the existence of deep continental roots and the absence of a global asthenosphere, means that the notion of huge rigid plates moving thousands of kilometres across the earth is simply untenable. Continents are about as mobile as a brick in a wall!
The plate-tectonic hypothesis that the present oceans have formed by seafloor spreading since the early Mesozoic (within the last 200 million years) is also becoming increasingly implausible. Numerous far older continental rocks have been discovered in the oceans, along with 'anomalous' crustal types intermediate between standard 'continental' and 'oceanic' crust (e.g. plateaus, ridges, and rises), and the evidence for large (now submerged) continental landmasses in the present oceans continues to mount.
At the Kola hole, scientists expected to find 4.7 km of metamorphosed sedimentary and volcanic rock, then a granitic layer to a depth of 7 km (the 'Conrad discontinuity'), with a basaltic layer below it. The granite, however, appeared at 6.8 km and extends to more than 12 km; no basaltic layer was ever found! Seismic-reflection surveys, in which sound waves sent into the crust bounce back off contrasting rock types, have detected the Conrad discontinuity beneath all the continents, but the standard interpretation that it represents a change from granitic to basaltic rocks is clearly wrong. Metamorphic changes brought about by heat and pressure are now thought to be the most likely explanation.
The superdeep borehole at Oberpfälz, Germany, was expected to pass through a 3-to-5-km-thick nappe complex into a suture zone formed by a supposed continental collision. The borehole reached a final depth of 9101 m in 1994, but no evidence supporting the nappe concept was found. What the scientists did find was a series of nearly vertical folds that had failed to show up on seismic-reflection profiles.
Rock density is generally expected to increase with depth, as pressures rise. Results from the Kola hole indicated that densities did increase with depth initially, but at 4.5 km the drill encountered a sudden decrease in density, presumably due to increased porosity. The results also showed that increases in seismic velocity do not have to be caused by an increase in rock basicity. The Soviet Minister of Geology reported that 'with increasing depth in the Kola hole, the expected increase in rock densities was therefore not recorded. Neither was any increase in the speed of seismic waves nor any other changes in the physical properties of the rocks detected. Thus the traditional idea that geological data obtained from the surface can be directly correlated with geological materials in the deep crust must be reexamined.'
The results of superdeep drilling show that seismic surveys of continental crust are being systematically misinterpreted. Much of the modelling of the earth's interior depends on the interpretation of seismic records. If these interpretations are wrong at depths of only a few kilometres, how much reliance can be placed on interpretations of the earth's structure at depths of hundreds or thousands of kilometres beneath the surface?!
Contrary to expectations, signs of rock alteration and mineralization were found as deep as 7 km in the Kola well. The hole intercepted a copper-nickel ore body almost 2 km below the level at which ore bodies were thought to disappear. In addition, hydrogen, helium, methane, and other gases, together with strongly mineralized waters were found circulating throughout the Kola hole. The presence of fractures open to fluid circulation at pressures of more than 3000 bars was entirely unexpected. The drillers at Oberpfälz discovered hot fluids in open fractures at 3.4 km. The brine was rich in potassium and twice as salty as ocean water, and its origin is a mystery.
Another surprise at the Kola hole was that lifeforms and fossils were discovered several kilometres down. Microscopic fossils were found at depths of 6.7 km. 24 species were identified among these microfossils, representing the envelopes or coverings of single-cell marine plants known as plankton. Unlike conventional shells of limestone or silica, these coverings were found to consist of carbon and nitrogen and had remained remarkably unaltered despite the high pressures and temperatures to which they had been subjected.
The oceanic crust is commonly divided into three main layers: layer 1 consists of ocean-floor sediments and averages 0.5 km in thickness; layer 2 consists largely of basalt and is 1.0 to 2.5 km thick; and layer 3 is assumed to consist of gabbro and is about 5 km thick. A drillhole in the eastern Pacific Ocean has been reoccupied four times in a 12-year span, and has now reached a total depth of 2000 m below the seafloor. Seismic evidence suggested that the boundary between layers 2 and 3 would be found at a depth of about 1700 m, but the drill went well past that depth without finding the contact between the dikes of layer 2 and the expected gabbro of layer 3. Either the seismic interpretation or the model of layer 3's composition must be wrong.
If the earth's interior were homogeneous, consisting of materials with the same properties throughout, seismic waves would travel in a straight line at a constant velocity. In reality, waves reach distant seismometers sooner than they would if the earth were homogeneous, and the greater the distance, the greater the acceleration. This implies that the waves arriving at the more distant stations have been travelling faster. Since seismic waves travel not only along the surface but also through the body of the earth, the earth's curvature will clearly result in stations more distant from an earthquake focus receiving waves that have passed through greater depths in the earth. From this it is inferred that the velocity of seismic waves increases with depth, due to changes in the properties of the earth's matter.
Seismic velocity in different media depends not just on the substance's density but also on its elastic properties (i.e. rigidity and incompressibility). In the case of solids and liquids, for instance, there is no correlation between sound-wave velocity and density. Here are some examples involving metals:
Substance Density (g/cm³) Velocity of longitudinal waves (km/s)
aluminium 2.7 6.42
zinc 7.1 4.21
iron 7.9 5.95
copper 8.9 4.76
nickel 8.9 6.04
gold 19.7 3.24
There is a correlation between density and seismic velocity in the case of gases: velocity decreases with increasing density due to the increased number of collisions.
According to the relevant equations, the velocity of seismic waves will become slower, the denser the rocks through which they pass, if the rocks' elastic properties change in the same proportion as density. Since seismic waves accelerate with depth, this would imply that density decreases. However, scientists are convinced that the density of the rocks composing the earth's interior increases with depth. To get round this problem, they simply assume that the elastic properties change at a rate that more than compensates for the increase in density. As one textbook puts it:
Since the density of the Earth increases with depth you would expect the waves to slow down with increasing depth. Why, then, do both P- and S-waves speed up as they go deeper? This can only happen because the incompressibility and rigidity of the Earth increase faster with depth than density increases.Thus geophysicists simply adjust the values for rigidity and incompressibility to fit in with their preconceptions regarding density and velocity distribution within the earth! In other words, their arguments are circular.
Drilling results at the Kola borehole revealed significant heterogeneity in rock composition and density, seismic velocities, and other properties. Overall, rock porosity and pressure increased with depth, while density decreased, and seismic velocities showed no distinct trend. In the Oberpfälz pilot hole, too, density and seismic velocity showed no distinct trend with increasing depth. Many scientists believe that at greater depths, the presumed increase in pressures and temperatures will lead to greater homogeneity and that reality will approximate more closely to current models. But this is no more than a declaration of faith.
Scientists' conviction that density increases with depth is based on their belief that, due to the accumulating weight of the overlying rock, pressure must increase all the way to the earth's centre where it is believed to reach 3.5 million atmospheres (on the earth's surface the pressure is one atmosphere). They also believe that they know by how much rock density increases towards the earth's centre. This is because they think they have accurately determined the earth's mass (5.98 x 1024 kg) and therefore its average density (5.52 g/cm³). Since the outermost crustal rocks -- the only ones that can be sampled directly -- have a density of only 2.75 g/cm³, it follows that deeper layers of rock must be much denser. At the centre of the earth, density allegedly reaches 13.5 g/cm³.
Pari Spolter casts doubt on this model:
About 71% of the earth's surface is covered by oceans at an average depth of 3795 m and mean density of 1.02 g cm-3. The average thickness of the crust is 19 km and the mean crustal density is 2.75 g cm-3. From studies of seismic wave travel time, geophysicists have outlined a layered structure in the interior of the earth. There is no accurate way currently known of estimating the density distribution from seismic data alone. To come up with a mean density of 5.5, earth models assuming progressively higher density values for the inner zones of the earth have been devised. . . .
Except for the ocean and the crust, direct measurements of the density of the inner layers of the earth are not available. This currently accepted Earth Model is inconsistent with the law of sedimentation in a centrifuge. The earth has been rotating for some 4.5 billion years. When it was first formed, the earth was in a molten state and was rotating faster than today. The highest density of matter should have migrated to the outer layers. Except for the inner core, . . . the density of the other layers of the earth should be less than 3 g cm-3.
Also, heavy elements are rare in the universe. How could so much of materials with such low stellar abundances have concentrated in the earth's interior?
The seismic radiation of deep earthquakes is similar to that of shallow earthquakes. It used to be said that deep-focus earthquakes were followed by fewer aftershocks than shallow ones, but there are indications that many of the aftershocks are simply difficult to detect, and that there is much more activity at such depths than is currently believed. The fact that deep earthquakes share many characteristics with shallow earthquakes suggests that they may be caused by similar mechanisms. However, most earth scientists are incapable of entertaining the notion that the earth could be rigid at such depths. One exception is E.A. Skobelin, who draws the logical conclusion that since deep-focus earthquakes cannot originate in plastic material but must be linked to some kind of stress in solid rock, the solid, rigid lithosphere must extend to depths of up to 700 km.
On 8 June 1994, one of the largest deep earthquakes of the 20th century, with a magnitude of 8.3 on the Richter scale, exploded 640 km beneath Bolivia. It caused the whole earth to ring like a bell for months on end; every 20 minutes or so, the entire planet expanded and contracted by a minute amount. A significant feature of the Bolivian earthquake was that it extended horizontally across a 30- by 50-km plane within the 'subducting slab'. This undermines the hypothesis that such quakes are caused by olivine within the 'cold' centre of a slab suddenly being transformed into spinel in a runaway reaction when the temperature rises above 600°C. It also undermines the theory that gravity increases with depth; if this were true, the motion of earthquakes at such depths should be nearly vertical. There appears to be something very wrong with scientific theories about what exists and what is happening deep within the earth.
The acceleration due to gravity is 9.8 m/s² at the earth's surface and the prevailing view is that it rises to a maximum of 10.4 m/s² at the core-mantle boundary (2900 km), before falling to zero at the earth's centre. But not all earth scientists agree. Skobelin argues that the normal, downwardly-directed gravitational force may be replaced by a reversed, upwardly-directed force at depths of 2700 to 4980 km, and that the widely-accepted figure of 3500 kilobars for the pressure at the earth's centre, may be an order of magnitude too high."
David Pratt
see also:
http://davidpratt.info/inner1.htm#s5