Abstract Several earthquake swarms in Maine and nearby New Brunswick are analyzed to look for common features among the swarms. The swarms took place at Bar Harbor, Maine, in 2006–2007, at Searsport, Maine, in 2011, at McAdam, New Brunswick, in 2012 and 2015–2016, at Jonesboro, Maine, in 2022, at Dedham, Maine, in 2022–2023, and at Millinocket, Maine, in 2022–2023. The six earthquake swarms all had focal depths of 4 km or less, appear to have taken place within or at the edges of Devonian granitic plutons, and with one exception show spatial distributions that are parallel to trends in the local geology. The swarms all had spatial extents of 3 km or less. The time histories of most of the swarms in Maine and New Brunswick are generally consistent with the main part of the swarm being controlled by aseismic creep rather than by fluid diffusion. Modeling of a rock inclusion that is stiffer than the surrounding rock mass in a regional stress field shows that stress will concentrate within the rock inclusion as well as along some of its edges. This modeling suggests that granitic rock bodies in eastern North American could have stress concentrations that fail in earthquakes, although the size of the largest earthquake in any single granitic rock body cannot be assessed by the results of this study.
John E. Ebel (Tue,) studied this question.