The Search for Non-volcanic Tremor on the Reelfoot Fault, Northern Tennessee
Abstract
In an attempt to detect non-volcanic tremors near Mooring, TN, a phased array of 19 broadband seismometers has been deployed since November of 2009. The array has a section 600 meters in a northern direction and 600 meters in an eastern direction, forming an “L”-shape. The array has been deployed as a result of unusual microtremors that were detected during an active source experiment in November 2006 near the current array location. It has been hypothesized that these events are similar to the non-volcanic tremors seen on the San Andreas fault in central California. The frequency band seen in the 2006 events is between 8 and 15 Hz, therefore the data from the array are analyzed using a beamforming technique with that same frequency band. To date, one month’s data has been analyzed using a 6 second time period looking for the azimuth and horizontal slowness of the peak signal in the 6 second time period. A Matlab user interface has been written that displays the three components of all 19 stations and allows the user to create the FK graph for each component. A time shifting option has been added that aids in determining which peak in the FK graphs corresponds to which signal in waveform data. According to the data from the 2006 experiment, it is estimated that the signals seen in that data set were arriving with high velocities, between 3 and 25 km/s, therefore, we are searching for signals that are arriving within that range. We are also looking for signals with a preferred western azimuth. Different ambient noise patterns such as well pumping and passing trains have been detected in the data along with earthquakes with complex interference patterns which could be a result of scattering of the P and S waves at the near surface. Small events similar to those seen in 2006 show up as high phase velocity arrivals that imply a source region directly below the array on the Reelfoot fault. However, we have not yet seen the intense swarm-like activity in the array data set that was seen in the active source data set of 2006. Amplitudes for these small events are consistent with microearthquakes of M-1 to M0, again similar to those seen in the 2006 data set.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.S23A2094B
- Keywords:
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- 7200 SEISMOLOGY