ORCID Profile
0000-0002-1402-5669
Current Organisation
Nanyang Technological University
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Publisher: Geological Society of America
Date: 03-01-2023
DOI: 10.1130/G50656.1
Abstract: The recycling of oceanic lithosphere into the deep mantle at subduction zones is one of the most fundamental geodynamic processes on Earth. During the closure of an ocean, ancient oceanic slabs are thought to be consumed entirely in subduction zones due to their negative buoyancy. Yet, it is recently suggested that small pieces of oceanic slabs could be trapped along paleo-subduction zones. What remains far more enigmatic is whether significant portions of paleo-oceanic lithosphere could eventually avoid the fate of subduction and be accreted to continental lithosphere, thus contributing to continental growth through time. We present seismic evidence for a preserved paleo-oceanic lithosphere beneath the Junggar region in northwestern China. We show that unsubducted oceanic lithosphere in the West Junggar has been preserved beneath the Junggar Basin, becoming a piece of the Eurasian continent. This scenario is likely to have occurred in other continents throughout Earth’s history, providing an additional and commonly underestimated contribution to the growth of continental lithosphere.
Publisher: Elsevier BV
Date: 03-2022
Publisher: Seismological Society of America (SSA)
Date: 28-03-2022
DOI: 10.1785/0220210292
Abstract: Myanmar occupies a complex region in the active Indo-Burma subduction system. To illuminate the upper 10 km crustal structure of central Myanmar and obtain new insight into the subduction system, we jointly use P-wave polarizations and receiver functions (RFs) to construct a high-resolution VS profile based on a Bayesian Markov chain Monte Carlo approach. This obtained profile clearly delineates six tectonic units and their boundaries, including the Indo-Burman ranges (IBR), the IBR-fore-arc basin boundary, the fore-arc basin, the volcanic arc, the back-arc basin, and the Sunda plate. The Sunda plate has relatively higher upper crustal VS (& .0 km/s) and thinner sedimentary cover (∼1 km) compared with the Central Myanmar basin in the Burma plate. The fore-arc basin, containing thick sediments (& km), and the back-arc basin, with thinner sediments (∼1–6 km), are separated by a region with higher VS (∼3.0 km/s), which represents crystallized magma beneath the volcanic arc. A narrow zone of relatively high-VS (∼2.6–2.7 km/s) ophiolites is situated between the fore-arc basin and the IBR. We also find a narrow zone of high-VS (∼2.9 km/s) metamorphic rocks contained within the low-VS (≲2.3 km/s) IBR. This study suggests that the proposing joint inversion of two types of single-station measurements, that is, P-wave polarizations and RFs, can robustly and computationally efficiently image the shallow VS structure and provide a reliable uncertainty estimation.
Publisher: Elsevier BV
Date: 05-2021
Publisher: American Geophysical Union (AGU)
Date: 11-2019
DOI: 10.1029/2019JB018302
Publisher: American Geophysical Union (AGU)
Date: 12-08-2022
DOI: 10.1029/2022GL100233
Abstract: We present a high‐resolution P ‐wave azimuthally anisotropic velocity model for the upper and middle crust beneath southern California by a novel adjoint‐state traveltime tomography technique. Our model reveals significant anisotropy variations between tectonic blocks that clearly reflect both past and current plate boundary deformation. In the shallow crust, seismic anisotropy is mostly controlled by the preferred alignment of microcracks related to the present N‐S compressive stress while at deeper depths ( ∼6 km), seismic anisotropy mainly records paleofabrics formed during the long‐lived Farallon subduction and later extension that have not been fully reset by the present transform motion. Interestingly, our model demonstrates distinct fast axes beneath the western Transverse Ranges from its neighboring blocks, probably reflecting the large‐scale vertical axis clockwise rotation of the block. In addition, we identify layered structures with distinct anisotropy features beneath the Salton Trough, which could be a result of the current transtension.
Publisher: Elsevier BV
Date: 05-2022
Publisher: American Geophysical Union (AGU)
Date: 02-2022
DOI: 10.1029/2021JB023033
Abstract: The Moho discontinuity plays an important role in crustal growth and evolution. In this study, we delineate the Moho geometry in southern California by jointly using local Moho‐reflected waves PmP and teleseismic Moho‐converted waves Ps. To well constrain the Moho geometry, we have developed a two‐stage process to pick PmP waves and have created a reliable PmP travel time data set with a total of 10,192 picks. We have also extracted 38,648 high‐quality P‐wave receiver functions (RFs). The Moho depth is initially estimated via the common conversion point (CCP) stacking of RFs and then refined by inverting the PmP travel time data in a community velocity model (CVM‐H, version 15.1.1). The newly built Moho geometry is generally consistent with the California Moho Model version 1.0 (CMM‐1.0), that is, a shallow Moho beneath the Salton Trough (23 km), a uniformly shallow Moho beneath the Mojave Desert and the Basin and Range ( km), and a sliver of deep Moho under the western Peninsular Ranges, the eastern Transverse Ranges, and the western Sierra Nevada ( km). However, our Moho model reveals some new features different from the CMM–1.0, such as a deep Moho (∼34 km) beneath the northern end of the central and western Transverse Ranges, consistent with the observation of deep seismicities due to a thick brittle crust there. We also find a gradual transition from the lower crust to the uppermost mantle beneath the western Peninsular Ranges, leading to the rareness of pickable PmP waves as well as weak Moho‐converted signals there.
Publisher: American Geophysical Union (AGU)
Date: 06-2022
DOI: 10.1029/2021JB023582
Abstract: The magma plumbing in the lower crust beneath the Coso volcanic field (CVF) remains controversial, largely because of the absence of high‐resolution lower crustal velocity models. For the first time, we develop a high‐resolution crustal P‐wave velocity model for the Coso‐Ridgecrest region by jointly inverting 137,992 first P and 8,636 PmP travel‐time data using an eikonal equation‐based seismic reflection tomography method. More than half of the PmP travel times are picked from earthquakes after the 2019 M w 7.1 Ridgecrest earthquake. Such abundant PmP travel times significantly improve the resolution of the lower crust. Our final velocity model reveals a prominent low‐velocity body sitting right beneath the CVF at 5–20 km depths, which we interpret as a rhyolite magma reservoir that supplies heat flux to the hot springs and also feeds the volcanic activities at Coso. We find that the upper‐middle crustal low‐velocity body dips southwards into the lower crust, extending to regions beneath the Indian Wells Valley and the Garlock Fault at depth greater than 20 km. We ascribe the lower crustal low‐velocity body (more than 4% Vp reduction) to a basaltic magma reservoir that connects the melts in the uppermost mantle with the eruptible rhyolitic reservoir at shallower depths. The basaltic magma reservoir constitutes an important part of a continuous N‐S elongated crustal magma plumbing system beneath the CVF, formed as a combined result of local extension, faulting, and stress distribution.
Publisher: American Geophysical Union (AGU)
Date: 07-02-2021
DOI: 10.1029/2020GL090853
Abstract: P‐wave azimuthal anisotropic tomography reveals that the July 6, 2019 M w 7.1 Ridgecrest earthquake occurred in a region with clockwise crustal rotation. The rotation together with the sinistral slip on the Garlock Fault is a response to the northwest‐trending, dextral shear within the Eastern California Shear Zone due to the relative motion between the Pacific and North America Plates. The hypocentral area of the Ridgecrest mainshock is characterized by a sharp lateral velocity contrast which has a reversal in contrast polarity at about 5 km depth. We find high Vp/Vs ratio structures covering the rupture zones of the M w 6.4 foreshock and the M w 7.1 mainshock, which may indicate the existence of fluids in the fault zones. We speculate that fluids and crustal rotation may have played important mechanical roles in causing the 2019 Ridgecrest earthquake sequence.
Publisher: Elsevier BV
Date: 05-2023
Publisher: American Geophysical Union (AGU)
Date: 05-2018
DOI: 10.1029/2017JB015332
Publisher: Geological Society of America
Date: 13-12-2022
DOI: 10.1130/GEOL.S.21644651.V2
Abstract: Detailed description of the seismic imaging methods and resolution analyses.
Publisher: Geological Society of America
Date: 29-11-2022
DOI: 10.1130/GEOL.S.21644651.V1
Abstract: Detailed description of the seismic imaging methods and resolution analyses.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Geological Society of America
Date: 13-12-2022
Abstract: Detailed description of the seismic imaging methods and resolution analyses.
Publisher: Wiley
Date: 07-09-2021
Publisher: Geological Society of America
Date: 06-02-2020
DOI: 10.1130/G47053.1
Abstract: Because an oceanic plate colliding with a continental plate will usually be subducted and recycled into the deep mantle, a fossil oceanic plate after the closure of an ancient ocean has rarely been imaged in the subcontinental lithospheric mantle. This has led to a long-standing debate about the fate of subducted ocean plates. The problem can be addressed by imaging the lithosphere in a continental accretion zone with past ocean subduction. We present a study using long-period magnetotelluric data that reveals a large shallow-mantle conductor in a Phanerozoic accretion area in northwestern Xinjiang, China. This conductor extends & km laterally at depths from 120 to 220 km and resembles a segment of a fossil oceanic plate. The reduced resistivity is ascribed to the volatile-bearing metasomatic minerals, based on its relatively fertile nature and low temperature. Our results demonstrate that an oceanic plate can be trapped in continental lithosphere, underscoring the significance of oceanic plate subduction to continental accretion, and shedding new light on our understanding of continental formation and evolution.
Publisher: Wiley
Date: 19-12-2021
Publisher: American Geophysical Union (AGU)
Date: 12-2022
DOI: 10.1029/2022JB024554
Abstract: Crustal deformation in the Sierra Nevada and Walker Lane is mainly investigated by geologic and geodetic constraints which suffer from a lack of depth information. In this study, we construct a new depth‐dependent azimuthally anisotropic P‐wave velocity (Vp) model of this area to investigate regional deformation regimes in the upper and middle crust. The model is built based on adjoint‐state traveltime tomography of ∼650,000 local direct P arrivals collected from 1967 to 2021. The average Vp structure agrees well with previous tomographic models with refined velocity features benefiting from the ray‐free adjoint‐state tomography and more arrival time data. The azimuthal anisotropy of Vp reveals distinct differences between the rigid Sierra Nevada block and the Walker Lane shear zone: (a) The western Sierra Nevada shows weak anisotropy ( %) and NW‐SE oriented fast velocity directions that are parallel to the Pacific‐North American plate boundary, mainly reflecting preserved paleofabrics developed in past subduction processes. (b) In the shallow Walker Lane ( km), the orientation of fast‐velocity directions is NNE controlled by regional compressive stress, and changes to NNW at greater depths in the north under shear deformation regimes. (c) In the central Walker Lane, strong anisotropy with ENE‐oriented P fast axes is imaged at 6–16 km from the area south of Lake Tahoe (2%–4%) to the Long Valley volcanic area (4%–8%) because of clockwise crustal block rotations and crustal fluids. The proposed anisotropic Vp model provides new insight into how past and present‐day deformation is accommodated in this tectonic complex plate boundary region.
Publisher: Wiley
Date: 22-03-2022
No related grants have been discovered for Shucheng Wu.