Earthquake Hazards in the States

This week we are exploring earthquakes and what countries do to prevent/mitigate the hazard. If I want to know something about earthquakes in a place, the first websites I go to are: the USGS Real Time Earthquakes Website or the IRIS monitoring website.

Regarding where quakes are located in the US, this seismicity map (see image below from USGS) shows the (obvious, in hot 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 MadridZone 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).

The San Andreas Fault System is responsible for most of California natural quakes...we had over 550 in the last month...up north, the Cascadia Subduction Zone will be responsible for next big one that area has. So, at least we start to knwo the 'why' of these quakes.

Re: the 'what to do about it', apart from the obvious need for education, 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 could make all the difference (enough to stop transit/elevators and to drop, cover, hold on).

Being aware of the risk and know what to do when the shaking starts is very important. We know that earthquakes cannot be predicted [I recommend Dr. Jones’ book called the big ones’ if you want more information about that]

All for now-