Swatara Township Tremors

     Residents of Swatara Township, Dauphin County reported several tremors in October, 2011. The dates and times of those reported are:

June 17th at 6:45 a.m.
October 4th at 12:10 p.m.
October 4th at 12:15 p.m.
October 4th at 12:45 p.m.
October 4th at 1:26 p.m.
October 6th at 6:10 p.m.
October 7th at 12:45 p.m.
October 8th at 7:00 a.m.
October 24 - 7:31 a.m.
November 11 at ~12:00 p.m.

A resident in Bressler reported a microquake on October 31, 2012 at 2:54 p.m. Upon checking with the Pennsylvania Geologic Survey, Helen Delano reported that their seismograph did record a tremor at that time. We are looking for others who have felt this quake to report it. Below is a seismogram on the October 31st tremor taken from the Pa. Geologic Survey in Middletown.

     To gather as much information about these tremors and any future tremors, please report them to Jeri Jones by emailing him at jonesgeo@comcast.net or call (717) 887-7103. You may also email Dr. Charles Scharnberger at MIllersville University at scharnbereger@verizon.net to either report a tremor or ask any questions concerning this swarm.

     When you report a tremor(s), please list your address, time tremor(s) was felt, what did it feel like and how long did it last. Building a database with this important information will assist in establishing the number of tremors and center of activity.

     If you felt anything prior to October. including the same activity reported in June, 2011, we would like to hear from you. In addition to reporting tremors, if you notice any abnormal flow of groundwater (springs) and the occurrence of existing or new sinkholes, please report their locations.

     At a Board of Supervisors meeting of Swatara Township on October 12th, Dr. Scharnberger explained that this swarm may last a few days, few weeks or few months. The possibility of a larger earthquake that could cause damage to the infrastructure is quite low, but not out of the question. No swarms known on the East Coast of the United States are known to include a damaging earthquake. A magnitude 4.0 or greater earthquake is usually needed to cause damage to structures.

     Below are two seismograms recorded on the Pennsylvania Topographic and Geologic Survey's seismograph in Middletown, PA. Dr. Charles Scharnberger calculates their magnitudes about a 1.0. Also, from the patterns on the seismograms, these were true tremors caused by slight tectonic movement in the bedrock and not from man-made explosions or any collapse of caves or sinkholes. Each record contains three different movements of the instrument: top line is vertical movement, the middle line is east-west horizontal movement and the bottom line is north-south horizontal movement.

October 6

October 7

October 24

     Additional information will be added here as received or determined by the researchers. This includes a isoseismal map that would show a map with reports and approximate location of the sismic activity.

     The investigators are interested in this small micro-earthquake swarm for two reasons: 1) They are occurring and 2) What relationship do these tremors have with those that occurred in Camp Hill in September, 2010 and the larger swarm in Dillsburg that started in August, 2008.

February 25, 2016

     An Individual reported a loud boom and shook the building at 4316 Derry Street in Swatara Township. On a 1-5 scale (with 5 being the worst), they placed the event as a 3.5. The time of the event was around 12:30 p.m. The event last about 3 seconds. This report sound similar to the pervious reported events, several that were confirmed as tremors based on seismograms as recorded at the Pennsylvania Geologic Survey offices near Middletown, PA.

     We contacted both the Pennsylvania Geological Survey and Dr. Charles Scharnberger at Millersville University to see if anything was recorded around that time. The PA Geological Survey reported that nothing showed up. Dr. Scharnberger did report that the seismograph at Franklin and Marshall College did show something between 12:45-12:50 pm. The Millersville station did have a small bump at 12:49 pm maybe correlating with the F & M station but the bump was too small to draw any conclusions.


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