DISTINCT CRUSTAL STRUCTURE OF THE NORTH AMERICAN MID-CONTINENT RIFT FROM P WAVE RECEIVER FUNCTIONS 

Abstract

Eighty-two broadband seismic stations of the Superior Province Rifting Earthscope Experiment (SPREE) collected 2.5 years of continuous seismic data in the area of the high gravity anomaly associated with the Midcontinent Rift (MCR). Over 100 high-quality teleseismic earthquakes were used for crustal P wave receiver function analysis. Our analysis reveals that the base of the sedimentary layer is shallow outside the MCR, thickens near the flanks where gravity anomalies are low, and shallows again in the MCR's center where the gravity anomalies peak. This pattern is similar to that found from local geophysical studies and is consistent with reverse faulting having accompanied the cessation of rifting at 1.1 Ga. Intermittent intracrustal boundaries imaged by our analysis might represent the bottom of the MCR's mostly buried dense volcanic layers. Outside the MCR, the Moho is strong, sharp, and relatively flat, both beneath the Archean Superior Province and the Proterozoic terranes to its south. Inside the MCR, two weaker candidate Mohos are found at depths up to 25 km apart in the rift's center. The intermediate layer between these discontinuities tapers toward the edges of the MCR. The presence of this transitional layer is remarkably consistent along the strike of the MCR, including beneath its jog in southern Minnesota, near the Belle Plaine Fault. We interpret these results as evidence for extensive underplating as a defining characteristic of the rift, which remains continuous along the Minnesota jog, where due to its orientation, it is minimally affected by the reverse faulting that characterizes the NNE striking parts of the rift.

Joint Inversion of SPREE Receiver Functions and Surface Wave Dispersion Curves for 3‐D Crustal and Upper Mantle Structure Beneath the U.S. Midcontinent Rift

“…We use seismograms from two temporary deployments of seismometers forming two arrays across and around the MCR (Figure 1). The SPREE Flexible Array (FA, supported by the USArray Array Operations Facility) operated for more than 2 years between April 2011 and October 2013 (Bollmann et al., 2019; Ola et al., 2016; Van der Lee et al., 2011; Wolin et al., 2015). The SPREE data set used here consists of 79 broadband seismic stations, with nominal interstation spacing of 30 km, in Minnesota, Wisconsin, and Ontario.…”

“…These IRIS TA data can be accessed at IRIS Transportable Array (2003). The data from the SPREE FA can be obtained at Van der Lee et al (2011).…”

“…

The Superior Province Rifting EarthScope Experiment (SPREE, Figure 1; Van der Lee et al, 2011) was designed to study the seismic structure of the crust and mantle lithosphere of the Midcontinent Rift of North America (MCR) using several seismic methods including receiver function analysis and surface wave tomography. Our study area includes the southern part of the Archean Superior Craton (ASC) (Canadian Shield) and the Paleoproterozoic Yavapai and Penokean orogenic belts to its south.

…”

A Decade of Short‐Period Earthquake Rupture Histories From Multi‐Array Back‐Projection

“…(2016), Institute of Geophysics China Earthquake Administration (IGPCEA) (2007), University of Genoa (1967), MedNet Project Partner Institutions (1988), Lara Wagner (2010), Albuquerque Seismological Laboratory (ASL)/USGS (1994), Oklahoma Geological Survey (1978), Gary Pavlis (2011), Wagner (2012), Charles Langston (2011), William Menke (2012), S. V. D. Lee et al. (2011), University of Oregon (1990), Albuquerque Seismological Laboratory (ASL)/USGS (1992), Simon Klemperer (2010), Kövesligethy Radó Seismological Observatory (Geodetic and Geophysical Institute, Research Centre For Astronomy and Earth Sciences, Hungarian Academy of Sciences (MTA CSFK GGI KRSZO)) (1992), Geoffrey Abers (2010), Leroy et al. (2009), Jim Gaherty (2013), Derek Keir (2014), Barruol et al.…”