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Los Angeles Earthquakes

On June 2 a news item in the LA Times described a recent increase in the number of magnitude > 4 earthquakes in the Los Angeles area.  I thought I would take a look at the situation using the hazard viewer on this site.  We can start by defining the circular selection region.

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Today, June 1, is the First Day of Hurricane Season 2014

This is supposed to be an El Nino year, as the forecast below for October-December 2014 shows.  Forecast is from the International Research Institute for Climate and Society of Columbia University.  Wind shear in El Nino years tends to be higher than average, and inhibits the formation of tropical cyclones.

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Earthquake Hazard in the San Francisco Bay, California, Region

Given the recent interest in major earthquakes in the Pacific Northwest, it is interesting to re-examine the earthquake potential of the San Francisco Bay region.  In particular, we examine the probability of earthquakes having magnitude M>6 and M>7 in the most populated region around San Francisco.  The map below shows San Francisco bay, the latest WGCEP/UCERF2 earthquake fault map, and a rectangular selection region.  The figure was produced using the polygon selection with the Hazard Viewer.

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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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