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Low Aftershock Productivity of the 2017 Delaware Earthquake

Description: 

The Mw 4.2 earthquake near Dover, Delaware, in November 2017 represented an opportunity to evaluate seismicity in a passive margin setting, motivating a rapid deployment of temporary instruments to record aftershocks. Within 24 hours of the main shock, personnel from the Department of Terrestrial Magnetism of the Carnegie Institution for Science, the University of Maryland, and the USGS mobilized to install a mix of instruments in the epicentral area for one month.

Using template matching, we detect several dozen aftershocks with magnitudes ≤ 2.0 and locate a subset of them using a site-specific 1D velocity model. The local magnitudes reveal unusually low aftershock productivity, with a notable departure from Båth’s Law for the typical magnitude of the largest aftershock. We investigate stress drop and fault orientation with respect to the regional tectonic stress as potential explanations for the earthquake’s unusually low aftershock activity. We then place the event in the context of other low magnitude events across the stable United States in order to better understand potential drivers of aftershock productivity. Finally, we discuss implications for predictions of aftershock productivity and largest aftershock magnitude based on the earthquake location and mechanism.

Session: Unusual Earthquakes and Their Implications - I

Type: Oral

Date: 4/16/2025

Presentation Time: 02:30 PM (local time)

Presenting Author: Karen

Student Presenter: No

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