Complicated lithospheric structure beneath the contiguous US revealed by teleseismic S reflections

Tianze Liu

Scripps Institution of Oceanography, UC San Diego

2021.03.24 （星期三）09:00，腾讯会议ID：988 351 744

https://meeting.tencent.com/s/vfdMmmBrPQgv

Abstract

Lithospheric discontinuities, including the lithosphere-asthenosphere boundary (LAB) and the enigmatic mid-lithospheric discontinuities (MLDs), hold important clues about the structure and evolution of tectonic plates. However, P- and S-receiver-function techniques (PRF and SRF), two traditional techniques to image Earth's deep discontinuities, have some shortcomings in imaging lithosphere discontinuities. Here, we propose a new method using reflections generated by teleseismic S waves (hereafter S reflections) to image lithospheric discontinuities, which is less affected by multiple phases than PRFs and has better depth resolution than SRFs. We apply this method to data collected by the Transportable Array and other regional seismic networks and obtain new high-resolution images of the lithosphere below the contiguous US. Beneath the tectonically active Western US, we observe a negative polarity reflector (NPR) in the depth range of 60–110 km, with greatly varying amplitude and depth, which correlates with active tectonic processes. We interpret this feature as the lithosphere-asthenosphere boundary below the Western US. Beneath the tectonically stable Central and Eastern US, we observe two NPRs in the depth ranges of 60-100 km and 100-150 km, whose amplitude and depth also vary significantly, and which appear to correlate with past tectonic processes. We interpret these features as mid-lithospheric discontinuities below the Central and Eastern US. Our results show reasonable agreement with results from PRFs, which have similar depth resolution, suggesting the possibility of joint inversion of S reflections and PRFs to constrain the properties of lithospheric discontinuities.

Biography of the speaker

Tianze Liu

Education

PhD,     Jan 2020,     Stanford University, Geophysics. Advisor: Simon Klemperer;

BS,       Jul 2013,     Peking University, Geophysics.

Honors and Awards

Green Postdoctoral Fellowship                                                                      2019

AGU Outstanding Student Paper Award (Poster presentation)                     2019

AGU Outstanding Student Paper Award (Oral presentation)                       2015

Stanford Graduate Fellowship                                                                       2014-2017

Research Projects

Imaging the lithosphere-asthenosphere system with scattered waves.                             2020–present

Post-critical SsPmp and its applications in imaging lithospheric structure.                    2013–2020

InSAR study of seismic “bright spots” beneath the Yadong-Gulu Rift, Tibet Plateau.    2016–present

Helium isotope signature of hydrothermal systems in the Tibet Plateau.                         2014–present

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