TY - JOUR
T1 - Shear velocity structure beneath the central United States
T2 - Implications for the origin of the Illinois Basin and intraplate seismicity
AU - Chen, Chen
AU - Gilbert, Hersh
AU - Andronicos, Christopher
AU - Hamburger, Michael W.
AU - Larson, Timothy
AU - Marshak, Stephen
AU - Pavlis, Gary L.
AU - Yang, Xiaotao
N1 - Funding Information:
The National Science Foundation supported the OIINK experiment under grants EAR-1053248 to Purdue University, EAR-1053354 to Indiana University, and EAR-1053551 to University of Illinois. Data from the TA network and permanent stations were accessed from the IRIS Data Management Center. IRIS Data Services are funded by the National Science Foundation through the Seismological Facilities for the Advancement of Geoscience and EarthScope (SAGE) Proposal of the National Science Foundation under Cooperative Agreement EAR-1261681. Thanks to Yingjie Yang and Aubreya Adams for their generous help with the resolution test in this study. The manuscript was greatly improved from thoughtful reviews by three anonymous reviewers and Editor Thorsten Becker.
Publisher Copyright:
© 2016. American Geophysical Union. All Rights Reserved.
PY - 2016/3
Y1 - 2016/3
N2 - We present new estimates of lithospheric shear velocities for the intraplate seismic zones and the Illinois Basin in the U.S. midcontinent by analyzing teleseismic Rayleigh waves. We find that relatively high crustal shear velocities (VS) characterize the southern Illinois Basin, while relatively low crustal velocities characterize the middle and lower crust of the central and northern Illinois Basin. The observed high crustal velocities may correspond to high-density mafic intrusions emplaced into the crust during the development of the Reelfoot Rift, which may have contributed to the subsidence of the Illinois Basin. The low crustal VS beneath the central and northern basin follow the La Salle deformation belt. We also observe relatively low velocities in the mantle beneath the New Madrid seismic zone where VS decreases by about 7% compared to those outside of the rift. The low VS in the upper mantle also extends beneath the Wabash Valley and Ste. Genevieve seismic zones. Testing expected VS reductions based on plausible thermal heterogeneities for the midcontinent indicates that the 7% velocity reduction would not result from elevated temperatures alone. Instead this scale of anomaly requires a contribution from some combination of increased iron and water content. Both rifting and interaction with a mantle plume could introduce these compositional heterogeneities. Similar orientations for the NE-SW low-velocity zone and the Reelfoot Rift suggest a rift origin to the reduced velocities. The low VS upper mantle represents a weak region and the intraplate seismic zones would correspond to concentrated crustal deformation above weak mantle.
AB - We present new estimates of lithospheric shear velocities for the intraplate seismic zones and the Illinois Basin in the U.S. midcontinent by analyzing teleseismic Rayleigh waves. We find that relatively high crustal shear velocities (VS) characterize the southern Illinois Basin, while relatively low crustal velocities characterize the middle and lower crust of the central and northern Illinois Basin. The observed high crustal velocities may correspond to high-density mafic intrusions emplaced into the crust during the development of the Reelfoot Rift, which may have contributed to the subsidence of the Illinois Basin. The low crustal VS beneath the central and northern basin follow the La Salle deformation belt. We also observe relatively low velocities in the mantle beneath the New Madrid seismic zone where VS decreases by about 7% compared to those outside of the rift. The low VS in the upper mantle also extends beneath the Wabash Valley and Ste. Genevieve seismic zones. Testing expected VS reductions based on plausible thermal heterogeneities for the midcontinent indicates that the 7% velocity reduction would not result from elevated temperatures alone. Instead this scale of anomaly requires a contribution from some combination of increased iron and water content. Both rifting and interaction with a mantle plume could introduce these compositional heterogeneities. Similar orientations for the NE-SW low-velocity zone and the Reelfoot Rift suggest a rift origin to the reduced velocities. The low VS upper mantle represents a weak region and the intraplate seismic zones would correspond to concentrated crustal deformation above weak mantle.
KW - Rayleigh wave tomography
KW - cratonic basin
KW - intraplate seismicity
KW - mantle refertilization
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U2 - 10.1002/2015GC006206
DO - 10.1002/2015GC006206
M3 - Article
AN - SCOPUS:84978322308
SN - 1525-2027
VL - 17
SP - 1020
EP - 1041
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
IS - 3
ER -