AFTERSHOCK ANALYSIS FROM THE 30 NOVEMBER 2017 DELAWARE EARTHQUAKE

The Mw 4.2 Dover, DE, earthquake in November 2017 represented an opportunity to evaluate seismicity in a passive margin setting, motivating a rapid deployment of instruments in order to record aftershocks. Within 24 hours of the main shock, personnel from the Lamont-Doherty Earth Observatory, the Department of Terrestrial Magnetism of the Carnegie Institution for Science, the University of Maryland, Lehigh University, and the USGS mobilized to install a mix of instruments in the epicentral area.

Using template-matching, we detect several dozen aftershocks, all with magnitudes ≤ 2.0, and locate a subset of them using a site-specific 1D model. The 1D model is based on receiver function modeling refined by modeling waveforms to 5 sec period of the largest aftershock at the closest deployed temporary broadband station. The locations of the aftershocks allow us to identify the fault structures of the immediate region. Using three-component waveforms filtered at 1 – 5 Hz, we perform moment tensor inversion for larger aftershocks to determine moment magnitude and asses focal mechanism variability. We discuss the aftershock productivity and locations in the context of East Coast seismicity.