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Earthquakes in Oklahoma

The Oklahoma Geological Survey and the US Geological Survey recently released a statement on the ongoing earthquake activity in that state.  They noted that the rate of earthquake activity has increased remarkably in the state, with 145 earthquakes having magnitude M>3 since January, 2014.  That currently makes Oklahoma the most seismically active state in the US.  Below we reproduce an image from that report.

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Magnitude 6.7 Earthquake Vancouver Island, April 23, 2014

The earthquake was near the Haida Gwai area, that has been the site of several large earthquakes recently.  A map of the region with the earthquake and a selection circle is below:

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Magnitude 7.5 Earthquake near Papua, New Guinea April 19, 2014

A strong earthquake occurred near Papua New Guinea a few hours ago on Saturday Apr 19 2014 at 06:27:59 GMT-0700 (PDT).  From the Hazard Viewer we can do a simple but rapid analysis.  The forecast from the Hazard Viewer was computed last night at midnight, a few hours prior to the earthquake.  The earthquake locations are shown below, with the bright red event being the M7.5 mainshock:

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Mexico Earthquake Magnitude 7.2, April 18, 2014

Two hours ago a magnitude 7.2 earthquake struck near Galeana, Mexico.  It shook both the nearest city of substantial size, Tecpan, as well as the capital of Mexico city.  The latter is located on an old lake bed and is subject to amplified shaking due to the thick layer of sediments.

From the Hazard Viewer, it can be seen that the earthquake struck in an area of elevated probability:

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Oklahoma is the most Seismically Active State in the USA

To those of us studying California earthquakes during the last 30 years, this is really weird.

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Fracking, Wastewater Injection, and Earthquakes

I was just reading an interesting article on wastewater injection and earthquakes.  The process of fracking, that is fracturing tight shales to allow hydrocarbon production, can involve the production of large volumes of waste fluids.  These are then typically re-injected into the ground.  The injected fluid has been shown in some areas to lead to increases in the number of earthquakes.  Examples are the Rocky Mountain arsenal in February 1966, and Basel Switzerland in 2009.

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Chile Earthquake Magnitude M7.8 Aftershock

Some computations from the hazard viewer.  This event is much closer to Iquique than the mainshock, probably more damage.

(Update  21:29 PDT: Magnitude now downgraded to 7.6)

Events and forecast map, together with selection circle.

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Chile Tsunami Should be Approaching Taiwan Now

From NOAA.  Posted at 15:33 on 4/2/2014

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Chile Earthquake filled an Old Gap

This slide is from a compilation by the IRIS consortium


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Chile Earthquake Seismic Gap

One of the theories about earthquake occurrence over the years is that seismic gaps develop between major and great earthquakes, and are eventually filled.  With that in mind, it is interesting to plot the approximate slip planes for both the M8.8 earthquake of 27 February, 2010, and today's M8.2 earthquake of April 1, 2014.


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