I am currently a 5th-year PhD student at the University of California, Los Angeles, in the Department of Earth, Planetary, and Space Sciences. My research focuses on understanding global devastating earthquakes. I utilize multi-geophysical data and advanced observation and modeling techniques to explore earthquake mechanisms, rupture propagation, fault unzipping, and their associated hazards. My work spans both continental and oceanic earthquakes, covering continental faults, subduction zones, and oceanic transform boundaries.
A significant focus of my research is on supershear earthquakes, where fault rupture speeds exceed the shear wave velocities in rock materials. I have also explored the critical role of fault asperities in the rupture process, from the pre-seismic to the co-seismic stages. My work spans from detailed case studies of individual earthquakes, such as the 2021 Mw 7.4 Maduo earthquake and the 2023 Mw 7.8 and Mw 7.5 Turkey earthquake doublet, to the development of innovative techniques for earthquake imaging.
One of my current projects focuses on improving observational methods for global earthquakes, specifically through the development of a “core phase Back-Projection” method, which uses seismic waves traveling through Earth’s core to enhance the imaging of earthquake ruptures on a global scale. In addition, I conduct interdisciplinary research that bridges natural earthquake observations with dynamic simulations, offering new insights into the rupture dynamics of large, destructive earthquakes.
For more information about my research, publications, and ongoing projects, please explore the rest of my website. You can also find my CV here: Liuwei Xu’s Curriculum Vitae. My current email address is xuliuw1997@ucla.edu.
🔥 News
- 2024.08: 🎉🎉 Our paper on the 2024 Noto earthquake in Japan has been published and featured as the cover article in Science.
- 2024.05: 🎉🎉 I have been selected as a recipient of the UC President’s Dissertation Year Award.
📝 Publications
Dual-Initiation Ruptures in the 2024 Noto Earthquake Encircling a Fault Asperity at a Swarm Edge
Citation: Xu, L., Ji, C., Meng, L., Ampuero, J.-P., Yunjun, Z., Mohanna, S., Aoki, Y. (2024). Dual-Initiation Ruptures in the 2024 Noto Earthquake Encircling a Fault Asperity at a Swarm Edge. Science, (on cover), 385,871-876(2024). https://doi.org/10.1126/science.adp0493
Citation: Xu, L., Yunjun, Z., Ji, C., Meng, L., Fielding, E. J., Zinke, R., & Bao, H. (2023). Understanding the rupture kinematics and slip model of the 2021 Mw 7.4 Maduo earthquake: A bilateral event on bifurcating faults. Journal of Geophysical Research: Solid Earth, 128, e2022JB025936. https://doi.org/10.1029/2022JB025936
Citation: Xu, L., Mohanna, S., Meng, L. Ji, C., Ampuero, J.-P., Yunjun, Z., Hasnain, M., Chu, R., Liang, C. (2023). The overall-subshear and multi-segment rupture of the 2023 Mw7.8 Kahramanmaraş, Turkey earthquake in millennia supercycle. Communications Earth & Environment, 4, 379. https://doi.org/10.1038/s43247-023-01030-x
Global frequency of oceanic and continental supershear earthquakes
Citation: Bao, H.,† Xu, L.,†(co-first author), Meng, L., Ampuero, J.-P., Gao, L., Zhang, H. (2022). Global frequency of oceanic and continental supershear earthquakes. Nature Geoscience, 15, 942–949. https://doi.org/10.1038/s41561-022-01055-5
Citizen seismology helps decipher the 2021 Haiti earthquake
Citation: Calais, E., Symithe, S., Monfret, T., Delouis, B., Lomax, A., Courboulex, F., … & Xu., L., Meng, L. (2022). Citizen seismology helps decipher the 2021 Haiti earthquake. Science, eabn1045. https://www.science.org/doi/full/10.1126/science.abn1045
Citation: Xie, Y., Meng, L., Zhou, T., Xu, L., Bao, H., & Chu, R. (2022). The 2021 Mw 7.3 East Cape earthquake: Triggered rupture in complex faulting revealed by multi-array back-projections. Geophysical Research Letters, 49, e2022GL099643. https://doi.org/10.1029/2022GL099643
🎖 Honors and Awards
- 2024.09, John W. West Research Award of UCLA
- 2024.05, UC President’s Dissertation Year Award
- 2024.01, Seismological Society of America (SSA) Travel Grant for Graduate Students
- 2023.07, School on Subduction Zone Processes 2023 Travel Grant
- 2019.10, Shizhe-Suya Award, School of Earth Sciences, Zhejiang University
- 2019.09, 3rd Prize of National Mathematics Competition for College Students
- 2018.09, Outstanding Student Scholarship for Second Prize in Academic, Zhejiang University
📚 Research
- Fault asperity controls the swarm activity and rupture development
During the 2024 Mw 7.5 Noto earthquake in Japan, we found notable complexity in the early stage of the rupture. A strong fault asperity, which remained unbroken in preceding seismic swarms, slowed down the rupture in the first 10 s. Then, a second rupture initiated at the opposite edge of the asperity at 12 s, and the asperity succumbed to double-pincer rupture fronts during 12-20 s. The failure of this high-stress drop asperity drove the earthquake into a large-scale event. Interestingly, we observed a lack of swarm seismicity before 2024 within the asperity, indicating that its behavior as a fault barrier was already apparent during the preceding swarm. Our observations help unravel the crucial role of fault asperities in controlling swarm migration and rupture propagation and underscore the need for detailed seismological and interdisciplinary studies to assess seismic risk in swarm-prone regions. See Xu et al. (2024), Science for more details.
- Global frequency of oceanic and continental supershear earthquakes
Earthquakes are supershear when their rupture speed is faster than the shear wave speed. These events are rare but highly destructive owing to the associated strong ground shaking. Only a few supershear earthquakes have been reported previously, most of which were continental. We performed a systematic global search for supershear earthquakes by analysing seismic data from all large shallow strike-slip earthquakes occurring between 2000 and 2020. We found that at least 14.0% of large earthquakes during the study period were supershear, with oceanic events occurring as frequently as continental ones. The transition to and propagation of supershear earthquakes may be promoted in oceanic settings due to the thicker crustal seismogenic zones and the material contrast at oceanic–continental boundaries. See Bao & Xu et al. (2022), Nature Geoscience for more details.
- Observations on large continental earthquakes
Continental earthquakes are dangerous and destructive, especially when they strike near densely populated areas. My research integrates multi-geophysical data, including near-fault strong motion recordings, GPS measurements, and satellite imagery, with cutting-edge source imaging techniques to analyze the rupture processes of these earthquakes. One example is the 2021 Mw 7.4 Maduo, China earthquake (upper figure), where our study revealed a left-lateral strike-slip rupture that propagated bilaterally along a 160 km north-dipping, sub-vertical fault system, which bifurcates near its eastern end. Approximately 80% of the total seismic moment (energy) was released on faults shallower than 10 km, with a peak slip of 5.7 meters. Another example is the 2023 Mw 7.8 and Mw 7.5 earthquake doublet (lower figure). The Mw 7.8 event ruptured a fault extending over 300 km at an average speed near the Rayleigh wave speed (indicated by diamonds in the figure), while the Mw 7.5 event ruptured a 130 km fault at supershear speed (indicated by circles in the figure). Please see our papers (Xu et al., 2023, JGR: Solid Earth, and Xu et al., 2023, CEE) for more details.
- Core-phase Back-Projections
Standard Back-Projections (BPs) utilize P-phase recordings from large aperture arrays located at teleseismic distances (30°-90°) to image earthquake sources. However, the majority of sizable arrays are in the northern hemisphere, leaving many southern hemisphere earthquakes beyond the teleseismic range. To address this gap, we used core phases—specifically PKIKP and PKPab—that travel through the Earth’s core to track rupture propagation during large earthquakes. Our results from core phase BPs applied to three well-studied events—the 2010 Mw 8.8 Chile, 2015 Mw 7.1 Southeast Indian Ridge, and 2021 Mw 7.2 Haiti earthquakes—were consistent with published BPs and/or slip models, confirming the feasibility and reliability of this method. Core phase BPs are particularly valuable when teleseismic arrays are unavailable and have proven effective in imaging bilateral rupture. See Xu & Meng (2023) for more details.
📖 Educations
- 2020.09 - Present, PhD student, Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, USA.
- 2016.09 - 2020.06, BS, School of Earth Sciences, Zhejiang University, Hangzhou, China.
💬 Invited Talks
- 2024.09, Youth Forum, China Earthquake Administration.
- 2023.11, Lithospheric Dynamics Seminar Series, University of Southern California.
- 2023.08, School of Earth Sciences Seminar, Zhejiang University.
- 2023.08, School of Earth and Ocean Sciences Seminar, Tongji University.
🧑🎨 Services
- Teaching Fellow: Remote Sensing in Earth Science (EPS-SCI 150, UCLA, Fall 2024)
- Teaching Associate: Introduction to Earth Science (EPS-SCI 1, UCLA, Fall 2023), Earthquake (EPS-SCI 8, UCLA, Spring 2023)
- Teaching Assistant: Earthquake (EPS-SCI 8, UCLA, Winter 2021 and Fall 2022)
- Reviewer: NSF proposals, GRL, JGR, GJI, Seismica, and many others.