There has been an increase in the numbers of earthquakes over 6.0, over the last few years. For the first half decade till 2006, there were about 13 earthquakes a year over 6.0 according to statistics at the USGS (13, 13, 13, 12, 13).
After the Haiti earthquake in 2010, followed by one of the largest earthquakes ever recorded in Chile in January, at 7.1, followed by two averaging 6.7 in February, and also in February a 6.3 in February in New Zealand (in a part of the country not prone to earthquakes), now we have the 9.0 mega quake with a 7.2 aftershock in Japan, in March.
At last year’s American Geophysical Union meeting geologists were already questioning whether there was a climate change link underlying the increasing frequency of unusually large earthquakes, according to Mathew McDermott at Treehugger. The Haiti earthquake was then just the latest example.
In the case of regions like Haiti, the deforestation – caused by years of drought, caused by climate change – is rendering the earth’s crust more unstable, posited geologist Shimon Wdowinski at the meeting. Deforestation leads to erosion and mudslides – and Haiti is 98% deforested.
The 2010 disaster stemmed from a vertical slippage, not the horizontal movements that most of the region’s quakes entail, supporting the hypothesis that the movement was triggered by an imbalance created when eroded land mass was moved from the mountainous epicenter to the Leogane Delta.
Other evidence of a deforestation link comes from Taiwan, which also has experienced earthquakes after major storms in Mountain regions.
But other forces are at work as well. As early as 2009, scientists were beginning to develop a theory connecting climate change to earthquakes. (Japan’s Earthquake: The Climate Change Connection)
The theory is that melting glaciers, due to climate change, are now relieving weight on the crust, and beginning to shift the pressures on the earth, and that this could be behind the recent increase in major earthquake frequency. (Which has repercussions for glaciers too: 40 Million Tonne Iceberg Dumped in Lake by NZ Earthquake)
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