Imaging lithospheric structures beneath Connecticut with receiver function and wavefield migration techniques

Abstract:

The geology of southern New England has been shaped by a variety of past tectonic events, including Appalachian orogenesis and continental rifting during the Mesozoic. The U.S. state of Connecticut contains various terranes in a relatively compact area. These include Laurentian (Proto-North American) units in the west and various peri-Gondwanan terranes of various affinities, including Avalonia in the eastern part of the state. How lithospheric structures beneath this region were deformed and modified by past tectonic events is an important scientific question. The Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) project involved the deployment of a dense array with 15 broadband seismometers across northern Connecticut from 2015 to 2019. Data from this experiment provides the opportunity to investigate the lithospheric structures beneath this region in detail. The P-to-S receiver function analysis on SEISConn data shows that the westernmost part of Connecticut has much deeper Moho than central and eastern Connecticut, and the lateral transition is very sharp, with ~20 km Moho depth reduction over ~15 km horizontal distance. The tight station spacing of SEISConn project also enables techniques with higher resolution, including common-conversion-point (CCP) receiver function imaging and generalized Radon transform (GRT) wavefield migration analysis. The sharp “step” in the Moho is prominent in both CCP images and preliminary results obtained using GRT wavefield migration. This sharp transition of Moho depth appears to correspond to the eastern edge of Laurentia, and its characteristics may shed light on the processes involved in the early phases of the Appalachian orogeny.