WEEK 3- E-A-R-T-H-Q-U-A-K-E-S

If I want to know something about earthquakes, the first websites I go to are: the USGS Real Time Earthquakes Website or the IRIS monitoring website.

This week we are exploring seismicity and what countries do to prevent/mitigate the hazard.

Re: the first issue, the new US map of seismicity (see image from USGS) shows the (obvious, in not pink) ring of fire portion on the West coast but also a central area in the middle of the plate. I’d like to talk a bit more about this non-obvious one. This area, called the New Madrid Zone was shaken by a M8 (!) in 1811. The reason for the activity is a very old intraplate rift placed below the area (see image from http://showme.net)... if the earth shakes in any of those areas, you cannot say you do not know why....tectonics, tectonics, tectonics....

In the last years, a few papers have come out discussing man-made quakes. USGS has great articles about those. The number of earthquakes has increased dramatically over the past few years within the central and eastern United States. Nearly 450 earthquakes magnitude 3.0 and larger occurred in the four years from 2010-2013, over 100 per year on average. USGS scientists have found that at some locations the increase in seismicity coincides with the injection of wastewater in deep disposal wells. Much of this wastewater is a byproduct of oil and gas production and is routinely disposed of by injection into wells specifically designed for this purpose.