Week 5: Volcanoes!

 There are about 169 volcanoes in the United States that scientists consider active (source). Most of these are located in Alaska, where eruptions occur virtually every year. Others are located throughout the west and in Hawaii (Ring of Fire anyone?). 

There are several ways we minimize the danger of volcanic activity (apart from the obvious of ‘getting out of the way’…(:

·         Forecasting (earthquakes as early warnings -although in 2014 a Japanese volcano erupted without any previous seismicity (livescience article), land swelling before eruption, gas emissions, etc.)

·         Volcanic Alert Codes (USGS): the levels of alert and the aviation code levels commonly change at the same time (chart on right). A non-erupting volcano will have a green icon, and a red one indicates an imminent eruption (see USGS Alert Codes).

Today the US hazards map (below along with registered earthquakes) shows 6 volcanoes as to be above normal background (elevated unrest):

Kilauea, Semisopochnoi, Great Sitkin, and Pavlof Alert Level=WATCH. Aviation Color Code=Orange.

Davidof, and Mauna Loa Alert Level=ADVISORY. Aviation Color Code=Yellow.

If you want to know more about volcanoes and how we monitor them, there is a MOOC from the University of Iceland that starts in March you might want to enroll into. A short video explanation here. 

Week 3- Earthquakes

Week 3 explores 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 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 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).

The San Andreas Fault System is responsible for most of California natural quakes...Each year the southern California area has about 10,000 earthquakes.!! The latest swarm of quakes in the Salton Sea has been featured in the news often. Earthquakes up to magnitude 4.6 under the Salton Sea are raising concern that a larger quake could be unleashed on the San Andreas fault. The southernmost section of the fault has not ruptured since about 1680.

So, what can we 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. 

There is an Earthquake Tracker all Californians can download to keep informed: try My Shake App.

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)