SEISMICITY IN PENNSYLVANIA AND THE PENNSYLVANIA STATE SEISMIC NETWORK

Seismicity in Pennsylvania results from natural earthquakes, mining blasts, and other induced events. Earthquakes occur primarily in the northwestern and southeastern portions of the state, and while the majority of the earthquakes are small, there have been moderate size earthquakes in the past, such as the September 25, 1998 magnitude 5.2 Pymatuning earthquake. Seismic events caused by mine and quarry blasts occur throughout the state, mainly in the bituminous and anthracite coal mining regions, and although rare, there have been seismic events associated with hydraulic fracturing. However, to date there are no known seismic events linked to wastewater injection.

In 2006, The Pennsylvania State University, in collaboration with the Bureau of Topographic and Geologic Survey within the Pennsylvania Department of Conservation and Natural Resources (DCNR), began constructing a network of seismic stations to detect and locate seismicity in the state. Between 2006 and 2013, the network grew to a total of 10 seismic stations providing near real time, open access seismic data for use by government agencies, academic institutions, industry, and the public. In late 2015, an expansion of the network to 30 seismic stations began with funding from the DCNR and the Pennsylvania Department of Environmental Protection (DEP). Construction of the 30-station network was completed in August 2016.

The 30 stations in the network plus another 13 stations operated by other organizations provide fairly even data coverage across the Commonwealth. Data from these stations, in addition to data from 28 stations in neighboring states, are used to monitor seismicity within Pennsylvania. Data from the 71 stations are fed into an EarthWorm system at Penn State for automatic event detection and location. To improve the automatic locations, the arrival times of P and S waves are repicked by hand and then used with the HYPOINVERSE code to obtain a refined location. Station and event information for the network can be found at www.paseis.geosc.psu.edu.