It seems like there are more big earthquakes than ever before.
Some people are calling foul play. For example, some point to the fact that former secretary of defense William Cohen told a conference on terrorism on April 28, 1997 that people can:
Alter the climate, set off earthquakes, volcanoes remotely through the use of electromagnetic waves.
Secretary Cohen might be right. Does that mean that hostile governments or terrorists are using electromagnetic weapons to cause earthquakes?
Others claim that climate change or an approaching celestial event having to do with the year 2012 are causing the earthquakes. Are they right?
Well, the United States Geological Survey explains that - contrary to appearances - we really don't have more earthquakes than normal:
Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant throughout this century and, according to our records, have actually seemed to decrease in recent years.
There are several reasons for the perception that the number of earthquakes, in general, and particularly destructive earthquakes is increasing.
1) A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications.
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2) The population at risk is increasing. While the number of large earthquakes is fairly constant, population density in earthquake-prone areas is constantly increasing. In some countries, the new construction that comes with population growth has better earthquake resistance; but in many it does not. So we are now seeing increasing casualties from the same sized earthquakes.
3) Better global communication. Just a few decades ago, if several hundred people were killed by an earthquake in Indonesia or eastern China, for example, the media in the rest of the world would not know about it until several days, to weeks, later, long after such an event would be deemed “newsworthy”. So by the time this information was available, it would probably be relegated to the back pages of the newspaper, if at all. And the public Internet didn't even exist. We are now getting this information almost immediately.
4) Earthquake clustering and human psychology. While the average number of large earthquakes per year is fairly constant, earthquakes occur in clusters. This is predicted by various statistical models, and does not imply that earthquakes that are distant in location, but close in time, are causally related. But when such clusters occur, especially when they are widely reported in the media, they are noticed. However, during the equally anomalous periods during which no destructive earthquakes occur, no one deems this as remarkable.
The USGS provides the following charts on large earthquakes:
Note that many people have seen strange lights in the sky prior to or during recent earthquakes.
However, strange lighting phenomenon has been observed in connection with earthquakes throughout history.
For example, "immense columns of flame" were reported by Greek writings prior to the giant earthquake in 373 BC in which destroyed the cities of Helike and Bura.
And the New England Earthquake of 1727 was preceded by strange lighting phenomena:
People that were awake when the earthquake came said that a flash of light preceded it. It was seen as it passed the windows, and a blaze seemed to run along the ground, dogs that saw it giving a sudden bark as if frightened. Before they had time to consider the source or cause of the light a sound like a gentle murmur floated to them on the still evening air, followed by a slight ruffling wind. Then came a rumbling as of distant thunder, which approached nearer and nearer and grew louder and louder till it sounded as if innumerable heavy carriages were being rapidly driven over pavements, or like the roaring of a great furnace, but incomparably fiercer and more terrible, having a hollow sound as if it came from under the earth. Then the shock came suddenly and severely and the houses were felt to totter and reel with the trembling and heaving of the ground.See this and this.
There are numerous theories about the cause of "earthquake lights", including:
- Sparks or gas ionisation due to a piezoelectric effect in quartz-bearing rock
- Frictional heating
- Exoelectron emissions
- Sonoluminescence
- Triboluminescence
- Generation and ignition of flammable gases either from pockets of natural gas or from rocks under enormous stress.
- Gas ionisation or electrical effects due to electrokinetics
- Separation of positive hole charge carriers that turn rocks momentarily into p-type semiconductors
