Friday, June 11, 2010

Is the New Madrid Fault at Fault?

Was the source of what are commonly refered to as the New Madrid Earthquakes of 1811 and 1812 really in the Wabash Seismic zone of Southern Illinois? This was indeed initially reported on our local NPR station, WKMS.

WKMS, along with other news outlets on "the wire" reported:

New research by U.S. Geological Survey scientists is casting doubt on the long-held idea the New Madrid Fault Zone in Missouri's Bootheel unleashed a series of devastating earthquakes in 1811 and 1812. In a new study, the researchers say the culprit may have instead been the Wabash Valley Fault Line that runs through southern Illinois."

Later, WKMS updated the story with a correction. In the updated story, Dr. Susan Hough, a seismologist with the U.S. Geological Survey states that in actuality, her
article introduces evidence that the smallest of the three New Madrid earthquakes might have come from the Wabash Valley zone of Southern Illinois and Indiana. She states, "...which would sort of make it a triggered earthquake, triggered by the New Madrid activity. But there's no question that the sequence was overwhelmingly in the New Madrid seismic zone. So the idea that, 'Oh we were wrong and the activity was in Illinois', that's just not what the study ever said."

Thus, from this statement, Dr. Hough clarifies that her report did not imply that the 1811/12 New Madrid quakes really occurred in the Wabash Valley, but that the Wabash Valley quake was perhaps triggered by the New Madrid quake.

At this point, I thought that the misunderstanding had been clarified but the report goes on to quote retired Murray State University professor Lynne Leasure who says, "That's one of the relatively newer ideas, that it might be remotely triggered. There was a possibility that one of the earthquakes in this series might have occurred in Southern Illinois. They do have surface evidence of sandblows. And the sandblows are very common in southeast Missouri from this event."

She seems to be saying that one of the earthquakes in "this series", that series being the New Madrid series, might have occurred in Southern Illinois. What does the "it" refer to in "it might be remotely triggered"? The New Madrid quakes or the Wabash Valley quake?
It is not clear but let's assume that she is referring to the Wabash Valley quake.

Now the report goes back to Dr. Hough, who states, "The January main shock... I can present evidence for why the Wabash valley is a plausible source. But the truth is that we really can't constrain the location of that event. It could have been in Western Kentucky. It could have been in New Madrid. But the observations just aren't as strong."

Huh? So now Dr. Hough does indeed suggest that the source (trigger) of the main January shock commonly attributed to the New Madrid Fault was actually in the Wabash Valley...or even possibly in Western Kentucky! I am confused. What triggered what?

The problem here does not lie in the uncertainty of Dr. Hough. Developing theories on what happened in 1811 from current data and analysis with something as complex as the inter-relationships between adjacent geological faults and seismic zones is challenging scientific work. Further, I honestly do not believe that either Dr. Leasure or Dr. Hough were as unclear as this report suggests. I think it is really just a case of sloppy reporting. Here is a suggestion for all of you budding journalists. If you initially release a story with incorrect information. Please be sure that your correction is does not further muddy the waters.

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