A groundbreaking study led by Professor ZHANG Haijiang from the University of Science and Technology of China (USTC), in collaboration with Dr. Robert Myhill from the University of Bristol, has unveiled new insights into the deep Earth processes beneath Northeast China. Utilizing advanced tele-seismic double-difference tomography, the research team constructed a high-resolution, three-dimensional velocity model that reveals the intricate morphology of the Pacific tectonic plate’s subducting slab within the mantle transition zone. Their findings have profound implications for understanding the interconnected dynamics of deep-focus seismicity and volcanism, particularly concerning the enigmatic Changbaishan volcanic field (CVF). This research, published in the prestigious journal Nature Communications, reshapes our comprehension of the physical mechanisms driving both seismic and volcanic phenomena in this geologically complex region.
Northeast China hosts a notable distribution of Cenozoic volcanoes, with the Changbaishan volcanic field standing as the largest and most prominent example. Despite its significance, the geological mechanisms underpinning the formation and enduring activity of CVF have long been the subject of debate. Traditional models struggled to reconcile the presence of this intraplate volcanic field with regional tectonic settings. Moreover, a deep earthquake cluster situated approximately 300 kilometers east of the CVF adds further complexity. These deep-focus earthquakes, which occur at depths considered typical of the mantle transition zone, challenge existing hypotheses about seismicity generation, as their mechanisms are thought to be influenced by thermomechanical conditions remaining relatively consistent throughout Northeast Asia.
The prevailing theories surrounding deep-focus earthquake genesis include processes such as dehydration embrittlement, where fluids released from subducted minerals weaken the slab, and adiabatic shear instability, a dynamic structural failure under rapid deformation. However, these explanations hinge heavily on thermal parameters, which appear uniform along the strike of the subduction zone within Northeast Asia. This uniformity raises a perplexing question: why do these deep earthquakes concentrate so distinctly near the Changbaishan region? The existing models proved insufficient to fully explain this localized seismicity, underscoring the need for detailed subsurface imaging and mechanical interpretations.
To tackle this challenge, the researchers harnessed seismic arrival records collected from a network of global stations monitoring seismic activity across Northeast Asia. Employing multi-scale double-difference tomography — a technique that refines the relative arrival times of seismic waves to improve spatial resolution — they meticulously reconstructed a three-dimensional velocity model extending over 1000 kilometers in depth. This high-fidelity model captures subtle variations in seismic wave speeds, allowing for unprecedented visualization of the subducting Pacific slab’s geometry as it interacts with the mantle transition zone’s seismic discontinuities.
Their analysis reveals a striking morphological feature beneath the CVF: the Pacific slab exhibits a localized penetration, descending from the mantle transition zone into the lower mantle. Intriguingly, the slab is not uniformly subducted; its northern and southern extremities remain stagnant within the transition zone, adopting a flattened configuration. This complex three-dimensional geometry indicates that the slab transitions from lying flat against the mantle discontinuities to sharply diving into the lower mantle before flattening again, creating a curved and regionally variable subduction pattern.
Correlating these morphological features with receiver function imaging, the research identified coincident localized depressions along the 660-kilometer seismic discontinuity interface — a boundary marking the transition between the upper and lower mantle. Such depressions align precisely with the regions where the Pacific slab dips into the lower mantle, suggesting a dynamic interaction where slab morphology influences mantle discontinuity topography. This interaction likely affects mantle flow patterns, mechanical stresses, and thermal structures crucial to understanding both seismic and volcanic phenomena.
The undulating slab geometry creates localized cavities beneath it, which, according to the study, permit the ascent of hot mantle materials from deeper regions. This upwelling provides an essential mantle heat and material source that fuels the volcanism observed at the CVF. It essentially bridges the deep mantle dynamics with surface geological expressions, offering a comprehensive explanation for the volcanic field’s sustained activity and its unique intraplate setting.
The study also sheds light on the deep earthquake cluster to the east of CVF. These earthquakes concentrate along the curved segment of the Pacific plate where it pierces through the 660-kilometer boundary. The researchers propose that this localized strong deformation, induced by the slab’s penetration into lower mantle depths, acts as a catalyst for seismicity. The process likely intensifies strain accumulation and stress localization, facilitating the conditions necessary for deep-focus earthquakes to nucleate within this otherwise mechanically stable environment.
By elucidating the relationship between slab morphology and the distribution of both deep earthquakes and volcanism, this research unifies two previously disparate geological processes under a single dynamic framework. It emphasizes how the mechanics of slab subduction through the mantle transition zone play a pivotal role in shaping the tectonic and volcanic landscape of Northeast China. This unifying perspective represents a vital advancement in geodynamics, highlighting that deep Earth processes reverberate through the lithosphere to influence surface geology in profound ways.
This work also challenges earlier assumptions which treated volcanic and seismic activity in the region as independent phenomena with separate causes. Instead, it firmly establishes that the partial subduction and slab morphology control a spectrum of dynamical processes, from mantle material upwelling driving volcanism to stress concentration facilitating deep seismicity. Through this lens, the CVF and the associated deep-focus earthquakes emerge as interconnected manifestations of the deep Earth’s complex convective and mechanical behaviors.
Beyond the regional implications, the methodological approach pioneered here — integrating tele-seismic double-difference tomography with detailed receiver function analysis — sets a new standard for imaging slab geometries and their relationship to mantle boundaries worldwide. It opens avenues for investigating other subduction zones characterized by comparable volcanic and seismic patterns, potentially transforming our understanding of Earth’s interior dynamics and their surface expressions.
The implications of this research extend towards improved seismic hazard assessment in Northeast Asia. Understanding the precise mechanisms controlling deep-focus earthquakes enables better prediction models and risk mitigation strategies. Moreover, by illuminating the mantle heat sources driving intraplate volcanism, it contributes to broader geological and geothermal energy resource perspectives, underpinning the societal relevance of deep Earth studies.
In sum, this pioneering study delineates an intricate narrative of tectonic slabs navigating mantle boundaries, giving rise to the deep-focus seismicity and persistent volcanism typified by the Changbaishan volcanic field. It exemplifies scientific synergy — bridging observational seismology, geodynamic modeling, and geological interpretations — propelling our knowledge of Earth’s subsurface architecture to new heights. As we continue to probe the enigmatic depths below, such discoveries will be key to unlocking the secrets of our ever-changing planet.
Subject of Research: The dynamic interactions between subducting Pacific tectonic slabs in the mantle transition zone and their impact on deep-focus seismicity and intraplate volcanism in Northeast China.
Article Title: Local slab penetration into lower mantle controls deep-focus seismicity and Changbaishan volcanism in northeast China
News Publication Date: 21-Mar-2025
Web References:
https://www.nature.com/articles/s41467-025-58053-5
http://dx.doi.org/10.1038/s41467-025-58053-5
Image Credits: USTC
Keywords: Earth sciences, Geophysics, Seismology
