Jian Hanchao

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Last Name
Jian
First Name
Hanchao
ORCID
0000-0002-8062-2082

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  • Article
    New insights into the rift to drift transition across the northeastern Nova Scotian margin from wide-angle seismic waveform inversion and reflection imaging
    (American Geophysical Union, 2021-11-17) Jian, Hanchao ; Nedimovic, Mladen R. ; Canales, J. Pablo ; Lau, K. W. Helen
    Sparse wide-angle seismic profiling supported by coincident reflection imaging has been instrumental for advancing our knowledge about rifted margins. Nevertheless, features of critical importance for understanding rifting processes have been poorly resolved. We derive a high-resolution velocity model by applying full waveform inversion to the dense OETR-2009 wide-angle seismic profile crossing the northeastern Nova Scotian margin. We then create a coincident reflection image by prestack depth migrating the multichannel seismic data. This allows for the first detailed interpretation of the structures related to the final stages of continental breakup and incipient oceanic accretion at the Eastern North America Margin. Our interpretation includes a hyperextended continental domain overlying partially serpentinized mantle, followed by a 10-km-wide domain consisting of a continental block surrounded by layered and bright reflectors indicative of magmatic extrusions. A major fault, representing the continent-ocean boundary, marks a sharp seaward transition to a 16-km-wide domain characterized by smoother basement with chaotic reflectors, where no continental materials are present and a 3-km-thick embryonic oceanic crust overlying partially serpentinized mantle is created by the breakup magmatism. Further seaward, thin oceanic crust overlies the serpentinized mantle suggesting magma-poor oceanic spreading with variable magma supply as determined from variable basement topography, 2–4 km thick volcanic layer, and magnetic anomalies. Our results demonstrate that magmatism played an important role in the lithospheric breakup of the area crossed by the OETR-2009 profile. Considering that the northeastern Nova Scotian margin has been classified as amagmatic, large margin-parallel variations in magma supply likely characterize a single rift segment.
  • Article
    Subducting plate structure and megathrust morphology from deep seismic imaging linked to earthquake rupture segmentation at Cascadia
    (American Association for the Advancement of Science, 2024-06-07) Carbotte, Suzanne M. ; Boston, Brian ; Han, Shuoshuo ; Shuck, Brandon ; Beeson, Jeffrey ; Canales, J. Pablo ; Tobin, Harold ; Miller, Nathan ; Nedimovic, Mladen R. ; Trehu, Anne M. ; Lee, Michelle ; Lucas, Madelaine ; Jian, Hanchao ; Jiang, Danqi ; Moser, Liam ; Anderson, Chris ; Judd, Darren ; Fernandez, Jaime ; Campbell, Chuck ; Goswami, Antara ; Gahlawat, Rajendra
    The origin of rupture segmentation along subduction zone megathrusts and linkages to the structural evolution of the subduction zone are poorly understood. Here, regional-scale seismic imaging of the Cascadia margin is used to characterize the megathrust spanning ~900 km from Vancouver Island to the California border, across the seismogenic zone to a few tens of kilometers from the coast. Discrete domains in lower plate geometry and sediment underthrusting are identified, not evident in prior regional plate models, which align with changes in lithology and structure of the upper plate and interpreted paleo-rupture patches. Strike-slip faults in the lower plate associated with oblique subduction mark boundaries between regions of distinct lower plate geometry. Their formation may be linked to changes in upper plate structure across long-lived upper plate faults. The Juan de Fuca plate is fragmenting within the seismogenic zone at Cascadia as the young plate bends beneath the heterogeneous upper plate resulting in structural domains that coincide with paleo-rupture segmentation.