Blogs

If you have ever holidayed in Rome, probably you took a side trip to the Alban Hills, 15 miles south of the City.  The Alban Volcano Complex has been a get away spot for Romans for 1000s of years. Emperor Caligula took his mammoth ‘pleasure ship’ out for summer night spins around Nemi Lake in one of the Alban craters.  To escape city heat, Popes have retreated to their summer home at Castel Gandolfo above Albano Lake since 1700.

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.

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.

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:

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:

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:

One February several years ago I was invited to give a presentation at the “Spring Meeting” of a Geological Club in Saint John’s Newfoundland. I arrived to face freezing rain and three inches of ice coating every possible exterior surface. I learn later that the “Spring Meeting” handle was an example of Newfoundland humor. I guess that same humor explains why Newfoundland Standard Time is GMT less  three  --- AND ONE HALF --- hours.

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

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.

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.