Earthquake in Oklahoma!

Seismogram posted this morning by
the Oklahoma State Geological Survey

Late Saturday night, the biggest earthquake in history, magnitude 5.6, hit Oklahoma  about half way between Oklahoma City and Tulsa. It was preceded by a 4.8 earthquake that morning, itself the third-strongest in Oklahoma history. The big earthquake was about the same size as the one that hit the east coast in August.They were a few miles apart and neither caused injuries or death, although some damage is being reported--buckling of roadways, damaged chimneys, interior damage to houses. The quake was felt in nine states. There have been more than seventy aftershocks as of early Sunday morning. The epicenter was four miles east of Sparks. The morning earthquake was shallow, 3.1 kilometers, and the evening earthquake deeper at 5 kilometers.  Both quakes were very near a place where a magnitude 4.3 earthquake occurred on February 27, 2010. They are on the Wilzetta fault, which is also called the Seminole uplift.


The first reported earthquake in Oklahoma occurred in September 1918, according to a USGS summary of earthquake history in the state, and earthquakes have not been uncommon in the state. Earthquakes have increased in frequency from about 2009 to the present and there is speculation, though no agreement, on the cause of this increase. The Seminole Uplift is a broad subsurface feature about 50 miles wide and over 75 miles long. It consists of a number of anticlines and "faulted noses" (oil company jargon) that host oil, and the uplift has been a prolific oil source. Many of the wells drilled in the 1920's to 1940's are still producing today and it is likely that there will continue to be speculation on the role of drilling and oil production in causing shallow earthquakes such as those that occurred this weekend.

Here's a nice article on the history of oil production in Oklahoma. The geology librarian, Lura Joseph, at the University of Illinois has created a resource of earthquake and tsunami information here.

Many of us can't hear the word "Oklahoma" without hearing it as "Oooooooooo-klahoma..." from the great musical by Richard Rogers and Oscar Hammerstein, set outside the town of Claremore in 1906, one year before Oklahoma was granted statehood.  The discovery of abundant oil there in 1889 and successive years contributed significantly to the granting of statehood. It's a great fun musical in case you haven't seen it!

Oklahoma

They couldn't pick a better time to start in life
It ain't too early and it ain't too late
Starting as a farmer with a brand new wife
Soon be living in a brand new state
Brand new state, gonna treat you great!

Gonna give you barley, carrots and pertaters
Pasture fer the cattle, spinach and termayters
Flowers on the prarie where the June bugs zoom
Plen'y of air and plen'y of room
Plen'y of room to swing a rope
Plen'y of heart and plen'y of hope

Oklahoma!
Where the wind comes sweeping down the plain
Where the waving wheat
Can sure smell sweet
When the wind comes right behind the rain

Oklahoma!
Every night my honey-lamb and I
Sit alone and talk
And watch a hawk
Making lazy circles in the sky

We know we belong to the land
And the land we belong to is grand
And when we say Yeeow!
Ayipioeeay! Yeeow!
We're only saying "You're doin' fine Oklahoma"
Oklahoma O-K

O-K-L-A-H-O-M-A
Oklahoma!