Monday, May 27, 2013

Deep earthquakes

(Mobile readers please scroll down to read the post).

This past week, a very powerful deep earthquake of magnitude 8.3 originating 378 miles beneath the Sea of Okhotsk (west of the Kamchatka Peninsula) has scientists wondering whether this is the most powerful deep earthquake ever recorded.

At 3.8 miles deep or 609 kilometers below the surface, it is not quite as deep as the 395-mile deep (631 kilometer) earthquake that occurred below Bolivia in 1994, but at 8.3 it was more powerful than the Bolivia deep earthquake, which was judged to be 8.2.  

Here are two articles describing the recent deep earthquake below the Sea of Okhotsk, one from the "newsblog" of the journal Nature, and one from the website LiveScience.

Deep earthquakes present some challenges to geologists.  In fact, until the Bolivia earthquake, conventional geologists did not believe that deep earthquakes could approach the power of shallow earthquakes.  That's because conventional geologists believe that earthquakes are primarily driven by the engine of heat, primarily by the heat created by the friction and pressure at plate boundaries, which causes rock to suddenly squeeze into a denser form, leading to rapid realignment of material below the surface that creates a chain reaction from the epicenter which is felt as an earthquake.  

Deep earthquakes pose a problem for that theory, in that the heat and pressure so far below the surface are so great that the mechanism used to explain earthquakes at shallower depths would not seem to be a plausible explanation for deep earthquakes.  Whatever caused deep earthquakes, scientists did not believe that deep earthquakes would be as powerful as shallow earthquakes, but the Bolivia quake challenged that view.

As this New York Times Science Page article published in 1995, in the wake of the powerful Bolivia deep quake,  explains:
These upheavals [deep earthquakes], which occur 200 to 400 miles below the earth's surface, are puzzling in that they ought to be impossible. The pressures and temperatures at that depth are so great that rock should undergo no frictional sliding, the mechanism of garden-variety earthquakes near the surface. So most geologists came to believe that the crushing pressures and increasing heat below a certain depth squeezed the rock into forms that were suddenly denser, creating huge cracks that developed into big temblors.

No more. An extraordinarily big earthquake 395 miles beneath Bolivia last June not only shattered records by jolting cities as far away as Toronto but also left the squeeze theory shaken.

A new analysis of shock waves from that earthquake show its fault zone was 30 miles long and 20 miles wide, too big to be explained by the leading theory. In fact, experts say, the quake bears a disturbing resemblance to big ones that occur near the earth's surface.

"It's embarrassing," said Dr. Paul G. Silver, a geologist at the Carnegie Institution of Washington who questions the old theory. "It looks and acts and talks like these shallow earthquakes. But it shouldn't exist."

As the article goes on to explain, "The mystery is how earthquakes happen at all at remote depths where temperatures may exceed 2,900 degrees Fahrenheit and pressures are 240,000 times greater than those at the surface of the earth. In theory, any rock there should have the consistency of putty, ruling out the brittle fracture and frictional sliding found in faults near the surface."

In spite of the embarrassment of the "experts," that article reassures the reader that: "No matter who wins the intellectual battle, experts agree that deep earthquakes are a general expression of plate tectonics."

Well, that's comforting.

Except that proponents of plate tectonics still have a king-sized problem providing valid explanations for the characteristics of deep earthquakes, as Dr. Walt Brown -- the originator of the hydroplate theory -- explains in great detail in his discussion of the phenomenon.  Here is the beginning of an extended section of his book (the entirety of which can be read online here, or purchased to read in hardcover from his site or from Amazon) dealing with the phenomenon of earthquakes, and discussing the importance of deep earthquakes.

According to the hydroplate theory's model, the reason conventional geologists have a hard time explaining deep earthquakes is that their explanation of all earthquakes is incorrect.  On this page of his book (and the one that follows it), Dr. Brown presents an extended chart that lists features of earthquakes and then compares the hydroplate theory explanation to the tectonic theory explanation for each.  

At the heading of the two columns (hydroplate and tectonic), he explains the two different explanations that the two theories provide for the phenomenon of earthquakes (and the related phenomena of the Pacific basin, including the "Ring of Fire" and the deep Pacific trenches).  

The tectonic model explains earthquakes, deep Pacific trenches, and the "Ring of Fire" (surrounding the Pacific basin) as the product of "subducting plates that have been diving into the mantle for hundreds of millions of years."  As noted above, this explanation sees earthquakes and the related phenomena as primarily driven by heat.

In contrast, the hydroplate theory has a very different explanation.  According to Dr. Brown, "Trenches, earthquakes, and the Ring of Fire are a result of shifts inside the earth during the flood, including the rising of the Atlantic floor and the subsidence of the Pacific floor."  Rather than being driven by heat, these phenomena are primarily driven by gravity, according to the hydroplate theory.

You can explore the list of geological evidence in the two columns and decide for yourself which of the two explanations explains the evidence more satisfactorily.

According to the hydroplate theory, earthquakes today are the result of a cataclysmic event that took place at the time of a global flood.  The initial eruption of floodwaters from under the crust removed the weight of the continents above and led to an upward bulge of the basement rock beneath.  This series of events caused the mid-Atlantic ridge, and led to tremendous friction and melting inside the earth, in a widening cone whose base on the other side of the earth corresponds today (roughly) to the edge of the Pacific basin and the Ring of Fire.

In figure 95, found in note 37 on this page of Dr. Brown's online book, he presents a simplified diagram showing the effect on the inner earth of the proposed upward springing of the floor of the Atlantic after the release of the floodwaters and the erosion of the sides of the continents, which removed weight above the basement rock that forms today's Atlantic floor (this event was discussed in some detail in this previous post). The caption accompanying the image at figure 95 explains:
The mass rising to fill in the blue region of the top cone (the new Atlantic floor) would, as a first approximation, equal the mass passing through the center of the earth. The rock in the yellow cone would experience extreme shearing stresses and deformations, so rock first melted as it approached (and was extruded through) the constriction at the center of the earth. (This is how the earth’s core, shown in red, began.) As the extruded rock melted, it also shrank, by about half, because it was far below the crossover depth. That, in turn, collapsed the deepest foundations on the Pacific side of the earth and produced more shearing deformations and melting immediately above. A runaway situation quickly developed which formed the ring of fire (shown in green), and produced a myriad of fractures in and below the Pacific plate [to see the different colored areas he is describing, visit figure 95 in his book].
(This same sequence of events was also responsible for the creation of our planet's very strong magnetic field, as discussed in this previous blog post). 

Figure 86 (located almost halfway down this page discussing earthquakes, trenches, and the Ring of Fire) shows that earthquakes with magnitudes of 5.0 or greater have a distribution with two peak depths -- one at 22 miles and one at 370 miles beneath the surface.  The distribution chart shows that very few earthquakes originate at 222 miles -- the distribution curve has two distinct groupings of shallow earthquakes and deep earthquakes, with very few at the "crossover point" in between the two groups.  It also shows that earthquakes do not originate at depths greater than 410 miles.  

Dr. Brown's theory has an explanation for this surprising evidence.  His theory argues that earthquakes are caused when rock converges upon a point beneath the surface.  But how could rock converge on a point, unless rock that had been at that point were to somehow disappear to allow the surrounding rock to rush in?  Dr. Brown explains that due to the principles of physics, magma (molten rock) will expand and move upwards (towards the earth's surface) if it is above the crossover depth (of 222 miles), and that it will contract and move downwards (towards the earth's core) if it is below the crossover depth.

Shallow earthquakes are often caused when molten rock expands and moves upwards -- like a beach ball being held under the surface of the water, it wants to get up and eventually paths will open up for it to do so, often quite suddenly and with a chain reaction of further melting of the rock around them.  As this takes place, rock in the area will rapidly rearrange and cause an earthquake.

Deep earthquakes are caused by the same process, except that below the crossover depth the magma contracts and seeks to sink down to the core.  When it manages to do so, the rearrangement of rock that takes place creates a deep earthquake.

These are very broad outlines of the forces involved; for a more complete explanation, the reader is invited to examine the several pages of detailed discussion and diagrams in Dr. Brown's book on this topic.  However, it is important to point out that Dr. Brown's theory links deep earthquakes, the Ring of Fire, and the deep ocean trenches to a single originating event that connects all of them.  As you can see from the maps of this recent powerful deep earthquake, it originated in the vicinity of the Kuril-Kamchatka Trench (see map above from the USGS, with last week's earthquake location pointed out by a black arrow that I added based on the USGS report here).

The conventional explanation for the origin of these trenches, as well as the deep earthquake that took place last week, is that the Pacific plate is subducting or diving underneath another plate along these trenches, and that this subduction creates the trenches and the earthquakes.  As the article linked above from the journal Nature explains, the conventional view is that, "The crust is descending fast enough — about 8 centimetres per year — to remain cool enough to rupture even at great depths. The diving plate is thus seismically active down to 650 kilometres or greater."

Never mind the fact that a thirty-to-sixty mile thick plate diving beneath another plate would create intense pressure and intense heat, which would increase dramatically the deeper the plate went (making the above explanation somewhat problematic), the very idea that subduction is responsible for the deep ocean trenches is fraught with problems.  

One of the biggest of these, as Dr. Brown points out, is the shape of the ocean trenches -- they are frequently arcs, and sometimes they have dramatic cusps.  How could a diving plate create an arc?  As Dr. Brown points out, if you bend a thick paperback book in half (to simulate a plate that is subducting), you will have a very difficult time making that bend resemble an arc (in fact, you won't be able to do it).  

The cusps create an even bigger problem.  In the map above, you can see that the recent deep earthquake near the Kuril-Kamchatka Trench was located almost due west of a point where the trench takes a dramatic 90-degree turn.  What kind of subducting plate could create a trench shaped like that?

There are numerous other problems with the tectonic explanation for the deep ocean trenches (including the fact that almost all of them are located along the western portions of the Pacific basin).  Some of those are discussed in previous blog posts, such as this one and this oneMany more are discussed in detail in Dr. Brown's book.

On the other hand, the mechanism proposed by the hydroplate theory explains the shape and distribution of the deep Pacific ocean trenches very comprehensively, as part of the events of the catastrophic global flood, when the inner earth rose towards the Atlantic and "sucked" the Pacific basin towards the center of the earth.  The evidence supporting this explanation is detailed in Dr. Brown's discussion in points 43 through 56 towards the end of this page in his book.

All of this discussion is not a mere academic argument with no real consequence to our day-to-day lives.  According to Dr. Brown's theory, there could be reasons that powerful and deep earthquakes are becoming more common, and if his theory is correct we could see a tremendous increase in earthquakes at some point in the future.  At the end of the discussion accompanying Figure 87 on this page of his book, Dr. Brown writes:

Drainage into the outer core continues today, releases gigantic amounts of heat throughout the mantle and core,31 and will eventually produce many powerful earthquakes.  When this will happen is uncertain.32
In the footnote at the end of that statement (footnote 32), he restates the same disturbing conclusion:
Nevertheless, earthquakes will someday increase substantially, because heat is building up inside the earth and the shrinkage of rock that melts below the crossover depth increases stresses in the crust and upper mantle. Also, these microscopic movements inside the earth generate heat thousands of times faster than heat escapes at the earth’s surface. This increasing heat melts rock, especially along the relatively hot walls of faults extending from trenches down to the liquid outer core. That melt then lubricates and facilitates further internal movements. [See Endnote 31.]
This prospect for earthquakes increasing "substantially" someday is not exactly comforting.  However, it points to the importance of maintaining the ability to critically examine and question the dominant geological paradigms that inform our understanding of the world around us.  Powerful deep earthquakes such as the one that originated below the Sea of Okhotsk last week expose the weaknesses of the conventional models.  

Events such as this one should cause scientists to consider alternative explanations, such as the theory offered by Dr. Walt Brown, which has a lot of evidence to support it.