Friday, October 16, 2009

Report on the Dillsburg earthquake swarm

A new Open-File report presents information on the earthquake swarm in Dillsburg, York County, which began in October 2008. Data on microearthquakes were collected by an array of portable seismographs placed and operated by Lamont-Doherty Geological Observatory of Columbia University from October 24 to December 11, 2008. Results and interpretations based on this data are presented here. The Pennsylvania Geological Survey assisted in placement and monitoring of a later array from May to September, 2009. Data from that installation are still in processing and interpretation. A follow-up study, conducted by the Pennsylvania Geological Survey, Penn State University, Charles Scharnberger and Jeri Jones, will investigate the spatial and temporal distribution of seismic events during the summer of 2009, based upon the small array of seismographs that were in place during that period.

similar swarms in Pennsylvania, Maryland, Connecticut, South Carolina, Maine, Ontario, and elsewhere, have not led up to a big earthquake.  Rather, the activity has died away after several months.  Thus, it seems most likely that this is what will also happen with the Dillsburg swarm.
Full disclosure: I was the outside reviewer for this report.


  1. We live west of Dillsburg Boro along the base of the mountains west of town and last nite we had our alarm system go off for what our system catagorized as a "sonic event". This occured between 0330 and 0400. Was there any seismic activity west of the swarm area last nite?

  2. The best place to check for this is at
    The one problem is that this will give quakes picked up by the permanent seismographs that are part of the LCSN nework. The smaller quakes that were picked up when the portable seismogarphs were deployed in the Dillsburg area would not necessarily show up here, and it is possible that one of these smaller events is what you felt. But you could perhaps check with the local officials or the newspaper, because they usually get a number of calls, even for the smaller localized events.


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