Deep Observation Borehole into the Earthquake Source

A representative from the Illinois State Geological Survey participated in the first meeting concerning a deep borehole observatory project for the New Madrid Seismic Zone. Held in Memphis, Tennessee, May 3-4, 2007, the meeting informed interested scientists, engineers, and institutions about the working group and provided a forum for discussing relevant issues. The workshop defined scientific targets and priorities and developed some strategies to best implement the work. The project is similar to the deep borehole project in Southern California which has drilled through the San Andreas fault and resulted in a new understanding of the fault environment. During the New Madrid Seismic Zone project, instruments will be placed where the earthquakes take place, in the bedrock deep below the thick overlying sediments. Instruments in the bedrock, about a mile below the ground surface, will directly measure many parameters of the earthquakes, which are modified by the overlying sediments. Instruments installed within the seismic activity at depth could produce a better picture of the active faults which produce 100 to 200 small earthquakes each year. Monitoring of instruments in the bedrock could provide a better understanding of the fault location and extent. Samples of the deep bedrock in the seismic zone along with the direct measurements of the physical properties of the thick overlying sediments will produce a better understanding on how the materials will behave in transmitting large earthquake ground motions to the surface, leading to better estimates of damage on the ground surface and better designs to mitigate damage