IDENTIFICATION OF LOW-LEVEL SEISMICITY IN OHIO

OhioSeis records are examined to identify previously undocumented low-level earthquakes in Ohio and surrounding regions. Records are scanned at multiple stations (at least four) to identify peak amplitude arrivals within a time window specified by the lowest likely arrival phase velocity and the maximum inter-station distance. A potential arrival peak must have an amplitude of at least 1.5 times the RMS amplitude over an entire hour containing that peak. The location (epicenter) of the potential earthquake is obtained using a velocity-independent-arrival-order-location (AOL) technique. The event is classified as a probable earthquake if it is similarly identified and located using a different set of four stations.

Five probable earthquakes in 2011 were each identified using at least five combinations of stations of four seismic stations. This includes the documented 2011 New Year’s Eve M4.0 event in Youngstown OH, which was located by this technique within 14 km and 10 seconds of the epicenter and origin time reported by the USGS. An additional three events were identified using at least three sets of four stations, and thirteen possible 2011 earthquakes were identified using two sets of four stations. Most of these locations extend from Lake Erie up the Cuyahoga Valley, through east-central Ohio towards Marietta OH.