The earth spins at 1000 miles per hour or pi/12 radians per hour.
Any surface imbalance of weight will incur drifts in mass within the plastic mantle. Such drifts are most likely diffusion processes and may cause increases in density of heavy radionuclides, verging on critical mass at particular locations within the mantle. That causes an increase in HEAT that rises to the Earth's surface creating seismic disturbances.

Now human migrations to cities along with heavy related infrastructure facilities is more likely to cause such events. Slowly melting ice features at the poles, quickly rebalances itself tidally without seismic changes.

The same concept is also present in solar disturbances. Dramatic, Periodic solar flares are the result.

The bottom line is that human migrations to cities are causing enhanced seismic activity plus large POINT surface ENTROPY gradients that appear as global climate instabilities.

The whole CO2 greenhouse warming puppy appears to be a 'con' job by politicians who wish to control the masses by inventing a theory that necessitates taxation and thus political oligarchy. It won't solve climate change. It just allows economic growth to benefit specific minorities on the back of unwise human overpopulation and overbreeding. This is a short-term strategy. Ultimately the unpredictability of Overpopulation. PEAKOIL &resource WARS will end it around 2030. Expectations of 9 billion people at 2050 are pure nonsense in any THERMODYNAMIC analysis. Meanwhile the Earth's rotation will adjust GEO-Climate and start all over with some dramatically new dominant species.

If Homo Sapiens wish to remain a part of the biosphere then population control and Geothermal heat mining are essential. Not least of all because Geothermal is inexhaustable clean baseload energy that could power sub 6 billion population structures for thousands of years with clean environments that foster creativity over dumb-procreation.

One way or another the Earth's spin will rid the biosphere of DUMB politicians and dumber corporate manipulators and there is nothing they can do about it unless they come up with a power source greater than the Earth spin/Nuclear Heat cycles.

Ce n'est pas possible ca!

As Kaep indicates, our big dynamo has a spin rate of 365 r/p/year, or thereabouts: just about right for its biological development, and a few other things (a rate of only 1 r/p/year would produce a moonscape earth; and also the beauty of an Aurora Australis would be missing).
However, putting a bit of spin on the cause of earthquakes is confusing the issue; confusing it just as much as Fred Pearce has done with Bill Maguire’s information (whatever Maguire may have actually written).

Any number of things might trigger earthquakes. However, their cause is due to the sudden disbursement of energy which had already built up across snagged fault lines in the earth’s crust, as continental plates drift past each other.
There are a several such plates, a dozen or so major ones - Eurasian, Pacific, Indo-Australian, African etc., moving towards, away from, along, or riding over each other at speeds varying from about one to about nine centimeters per year; and some rotate. It’s a wild world down there.
The mass, for example, of the Indo-Australian plate moving north-east at about 7cm a year has a bit of kinetic energy at its disposal. If a corner of the plate were held up for a century, there is the potential for a sudden 7 metre jump. What triggers it is just that - a trigger for an event, no matter how unpleasant, that is about to happen anyway.

Fred Pearce, a self-professed science writer, does his status no favours by ignoring basic fundamentals

All well and good Collinset but you don't explain what makes the plates drift in the first place.

Without Earth spin, like on Venus, there would be NO plate tectonics to begin with.

Understanding this fully gives us an opportunity to prepare *GEOTHERMAL mining as a way to obviate the cruelty that will come with PEAKOIL around 2030. Otherwise we will be locked in false theories like CO2 greenhouse warming when the hammer comes down.