9/5/2016- EARTHQUAKES IN THE USA

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 natural seismicity and what countries do to prevent/mitigate this hazard.

Re: the first issue, the new US map of seismicity (see image from USGS) shows the (obvious, in 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.

Re: the second issue, I want to focus on the USGS ShakeAlert system, developed for the West coast using some of the existing systems. Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of an EEW (Earthquake Early Warning) system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds, depending on the distance to the epicenter of the earthquake. 

 A few seconds of warning might make all the difference (enough to stop transit/elevators and to drop, cover, hold on). All, watch out for thsi year's ShakeOut on October 20th.

NOTE- Of course the news of a 5.6 quake in the middle of the USA –OK- was news this week, as it was also felt in seven surrounding states. After that event, there was a shutdown of gas-linked wells. The issue of possible man-made or induced quakes once more resurfaces…for more information on those the USGS website is useful.

All for now-