Dongdong Tian

田冬冬

Postdoctoral Research Associate

Michigan State University

Dongdong Tian is a seismologist. His research is directed toward understanding the structure of the Earth’s deep interior, mechanisms of seismic sources (e.g., microseismic, explosions, and collapse), and seismic wave propagation in complex media.

He received his Ph.D. degree in Geophysics from University of Science and Technology of China in 2018, advised by Prof. Lianxing Wen. Currently, he is a Postdoctoral Research Associate at Michigan State University, collaborating with Prof. Songqiao Shawn Wei.

He is also a big fan of open-source and serves as a core developer of the Generic Mapping Tools (GMT), a widely-used software for processing and visualizing geophysical data in Earth Science, and its Python wrapper, PyGMT.

Interests

Structure of the Earth’s deep interior
Mechanisms of seismic events
Seismic wave progration in complex media

Education

Ph.D. in Geophysics, 2018
University of Science and Technology of China
BSc in Geophysics, 2012
University of Science and Technology of China

Recent News

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2020-10-22: Dongdong, collaborating with Jiayuan Yao, Li Sun, and Lianxing Wen, make a comment on the paper “Origin of temporal changes of inner-core seismic waves” by Yang and Song (2020). The comment is published on Earth and Planetary Science Letters. Jiayuan Yao is the first author.
2020-10-02: Our new global survey of the 520- and 560-km mantle discontinuities, based on seismic observations (SS precursors) and thermodynamic modeling, is published on Earth and Planetary Science Letters.
2020-06-20: Dongdong serves as an instructor of the 2020 UNAVCO Short Course “The Generic Mapping Tools for Geodesy”, online via Zoom.
2019-07-29: Dongdong particats the GMT Developer’s Summit at Scripps Institution of Oceanography, La Jolla, USA, Jul. 29–Aug. 2, 2019.
2019-07-22: Dongdong serves as an instructor of the 2019 UNAVCO Short Course “The Generic Mapping Tools for Geodesy”, at Scripps Institution of Oceanography, La Jolla, USA, Jul. 22–23, 2019.

Research

Inner Core Boundary

The Earth’s solid inner core grows from the solidification of the liquid outer core. The solidificaiton process releases latent heat and expels light elements, providing driving forces for the outer core convection and the geodynamo which generates the Earth’s magnetic field. The information of the Earth’s inner core boundary (ICB) is important for our understanding of the thermo-compositional state of the Earth’s core. We use seismic waves reflected from the Earth’s ICB to study the spatial and temporary changes of ICB.

North Korea Nuclear Tests

North Korea has conducted six nuclear tests since 2006. Using seismological techniques, we determine their high-precison locations, yields, and source characteristics of the six nuclear tests and associated small seismic events.

Mantle Discontinuities

Seismic discontinuities in the mantle provide critical insight into thermal and compositional states of Earth’s mantle and its dynamics. The 410- and 660-km seismic discontinuities are observed globally, and are generally linked to phase transformations of olivine → wadsleyite and ringwoodite → bridgmanite + ferropericlase. The 520- and 560-km discontinuities are usually less observed and studied, and are caused by phase transformation of wadsleyite → ringwoodite, and exsolution of Ca-pv from garnet. We analyze waveforms of SS precuros recorded by global stations to investigate global variations of the 520- and 560-km discontinuities.

Featured Publications

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Dongdong Tian, Mingda Lv, S. Shawn Wei, Susannah M. Dorfman, Peter M. Shearer

Oct 2, 2020 Earth and Planetary Science Letters

Global variations of Earth's 520- and 560-km discontinuities

We perform a global survey of the 520- and 560-km mantle discontinuity by analyzing SS precursors.
Our observations confirm the global existence of the 520-km discontinuity.
Depth variations of the 520-km discontinuity correlate with the mid-MTZ temperature.
Compositional heterogeneity also contributes to the 520-km discontinuity topography.
A 560-km discontinuity is sporadically detected in subduction zones and mantle upwells.
The existence of the 560-km discontinuity may imply localized Ca-enrichment in the mid-MTZ possibly related to the recycling of oceanic crust.

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Dongdong Tian, Jiayuan Yao, Lianxing Wen

Apr 27, 2018 Geophysical Research Letters

Collapse and earthquake swarm after North Korea's 3 September 2017 nuclear test

We present high-precision locations and detailed source information of four small seismic events following North Korea’s 2017 nuclear test.
The first event is an on-site collapse 440 m northwest of the test site and best explained by a near vertical single force.
The later events are an earthquake swarm located 8.4 km north of the test site with a focal depth of at least 2.4 km.

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Dongdong Tian, Lianxing Wen

Aug 1, 2017 Nature Communications

Seismological evidence for a localized mushy zone at the Earth’s inner core boundary

Although existence of a mushy zone in the Earth’s inner core has been hypothesized several decades ago, no seismic evidence has ever been reported. Based on waveform modeling of seismic compressional waves that are reflected off the Earth’s inner core boundary, here we present seismic evidence for a localized 4–8 km thick zone across the inner core boundary beneath southwest Okhotsk Sea with seismic properties intermediate between those of the inner and outer core and of a mushy zone. Such a localized mushy zone is found to be surrounded by a sharp inner core boundary nearby. These seismic results suggest that, in the current thermo-compositional state of the Earth’s core, the outer core composition is close to eutectic in most regions resulting in a sharp inner core boundary, but deviation from the eutectic composition exists in some localized regions resulting in a mushy zone with a thickness of 4–8 km.