continental lithosphere
; geodynamics
; hot spot
; Mesozoic
; numerical model
; rift zone
; seismic wave
; seismicity
; tectonic plate
; wave attenuation
; wave velocity
; waveform analysis
; United States
英文摘要:
Hotspot tracks are thought to be the surface expressions of tectonic plates moving over upwelling mantle plumes, and are characterized by volcanic activity that is age progressive. At present, most hotspot tracks are observed on oceanic or thin continental lithosphere. For old, thick continental lithosphere, such as the eastern United States, hotspot tracks are mainly inferred from sporadic diamondiferous kimberlites putatively sourced from the deep mantle. Here we use seismic waveforms initiated by the 2011 M w 5.6 Virginia earthquake, recorded by the seismic observation network USArray, to analyse the structure of the continental lithosphere in the eastern United States. We identify an unexpected linear seismic anomaly in the lower lithosphere that has both a reduced P-wave velocity and high attenuation, and which we interpret as a hotspot track. The anomaly extends eastwards, from Missouri to Virginia, cross-cutting the New Madrid rift system, and then bends northwards. It has no clear relationship with the surface geology, but crosses a 75-million-year-old kimberlite in Kentucky. We use geodynamical modelling to show that an upwelling thermal mantle plume that interacts with the base of continental lithosphere can produce the observed seismic anomaly. We suggest that the hotspot track could be responsible for late Mesozoic reactivation of the New Madrid rift system and seismicity of the eastern United States.
State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, Hubei 430077, China; Laboratory of Seismology and Physics of Earth's Interior, University of Science and Technology of China, Hefei, Anhui 230026, China; Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, United States
Recommended Citation:
Chu R.,Leng W.,Helmberger D.V.,et al. Hidden hotspot track beneath the eastern United States[J]. Nature Geoscience,2013-01-01,6(11)