At last week's American Geophysical Union (AGU) meeting last week in San Francisco, Shimon Wdowinsky of the University of Miami proposed a different method whereby unusual strains on the crust might trigger an earthquake. In a talk titled, Triggering of the 2010 Haiti earthquake by hurricanes and possibly deforestation , Wdowinsky studied the stresses on Earth's crust over the epicenter of the mighty January 12, 2010 Haiti earthquake that killed over 200,000 people. This quake was centered in a mountainous area of southwest Haiti that has undergone severe deforestation—over 98% of the trees have been felled on the mountain in recent decades, allowing extreme erosion to occur during Haiti's frequent heavy rainfall events. Since 1975, the erosion rate in these mountains has been 6 mm/year, compared to the typical erosion rate of less than 1 mm/yr in forested tropical mountains. Satellite imagery (Figure 2) reveals that the eroded material has built up significantly in the Leogane Delta to the north of the earthquake's epicenter. In the 2008 hurricane season, four storms--Fay, Gustav, Hanna, and Ike--dumped heavy rains on the impoverished nation. The bare, rugged hillsides let flood waters rampage into large areas of the country, killing over 1,000, destroying 22,702 homes, and damaging another 84,625. About 800,000 people were affected--8% of Haiti's total population. The flood wiped out 70% of Haiti's crops, resulting in dozens of deaths of children due to malnutrition in the months following the storms. Damage was estimated at over $1 billion, the costliest natural disaster in Haitian history. The damage amounted to over 5% of the country's $17 billion GDP, a staggering blow for a nation so poor. Tragically, the hurricanes of 2008 may have set up Haiti for an ever larger disaster. Wdowinsky computed that the amount of mass eroded away from the mountains over the epicenter of the 2010 earthquake was sufficient to cause crustal strains capable of causing a vertically-oriented slippage along a previously unknown fault. This type of motion is quite unusual in this region, as most quakes in Haiti tend to be of the strike-slip variety, where the tectonic plates slide horizontally past each other. The fact that the 2010 Haiti quake occurred along a vertically moving fault lends support to the idea that the slippage was triggered due to mass stripped off the mountains by erosion over the epicenter, combined with the extra weight of the extra sediment deposited in the Leogane Delta clamping down on the northern portion of the fault. Wdowinsky gave two other examples in Taiwan where earthquakes followed several months after the passage of tropical cyclones that dumped heavy rains over mountainous regions. His theory of tropical cyclone-triggered quakes deserves consideration, and provides another excellent reason to curb excessive deforestation!
Interesting point of view in today's commentary from Dave Ross on CBS Radio:
. . . I happened to see the AP's annual catalog of disaster and realized that the greatest terrorist of all...isn't some radical bomb-thrower. It's The Planet.
In the year 2010, earthquakes, heat waves, floods, mega-typhoons, blizzards, landslides and droughts killed a quarter of a million people - most of them in January's earthquake in Haiti.
By the AP's calculations, that's more than TWICE the number of people who died in terrorist attacks in the last 25 years, COMBINED. . .
More audio at MyNorthwest.com
This is particularly relevant given the 4 solid pages of prime A-section real estate in today's high-fiber WaPo devoted entirely to analyzing the hundreds of billions being spent annually on "public safety." Apparently we can't afford to spend even a small fraction of that on the much deadlier threat from Momma Nature's attempts to kill us.