Lele Zhang
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SEG J. Clarence Karcher Award 2024
Lele Zhang developed a revolutionary internal multiple elimination method that has been verified on synthetic and real data sets and resulted in an Honorable Mention for Best Paper in Geophysics in 2019. He conceived and derived an unsupervised method of multiple suppression that simultaneously eliminates free-surface and internal multiples without requiring adaptive subtraction. Zhang’s work on these original methods was showcased in the Bright Spots department in The Leading Edge in 2021 and 2022. He has consistently moved ideas from concept to peer acceptance, resulting in 24 peer-refereed journal articles, 13 of which list him as senior author. Many of Zhang’s groundbreaking innovations are a result of curiosity-driven research, targeting major obstacles encountered by his peer community, which ultimately resulted in a network of researchers/cohort addressing the most challenging problems in multiple suppression and full-wavefield migration. His connections and respect within his research community has made him an extremely successful associate editor of Geophysics and the Journal of Seismic Exploration.
Biography Citation for the J. Clarence Karcher Award
by Evert Slob and Kees Wapenaar
It was just 10 years ago that our applied geophysics group in Delft had published several papers showing how complex wavefields recorded at an acquisition surface can be organized to focus at a chosen location in the subsurface where no source or receiver was present. This could be done with only traveltime knowledge of the direct wave through the medium from acquisition surface to said subsurface focus point, and yet it accounted for all internal multiples. We showed that the required equations can be derived from representation theorems and had general applicability in 3D media. In the summer of 2015, we advertised two PhD positions on this new Marchenko-type method. In Lele Zhang we found the ideal candidate who had demonstrated excellence in physical and mathematical thinking with a broad interest, who is a good communicator, and who is able to learn quickly. Lele applied for the electromagnetic position of the two advertised jobs while coming from a purely seismic background. Interestingly, within the first year of his appointment, Lele convinced us that this method was not the most suitable for electromagnetic waves in the subsurface because we usually collect data at the ground surface and that is not sufficient for applying the method in lossy media. He had very good ideas to focus on the elimination of interbed multiples in seismic reflection data, which he later extended to include elimination of surface multiples. We were happy to give him the space to develop these ideas. This culminated in the PhD thesis titled “Acoustic multiple reflection elimination in the image domain and in the data domain,” which he successfully defended on 19 December 2019.
Lele has a gift for doing independent scientific research, identifying open questions for which finding the solution is urgent and important. With his work, he introduces theory for new acoustic internal multiple elimination methods. He applies them to and analyzes the results on synthetic, laboratory, and field data. When Lele started his research, no operational data-driven scheme was known with demonstrated theoretical and numerical capability to eliminate all orders of internal multiple reflections correctly from seismic reflection data without the need for adaptive subtraction. Lele started with a method derived from Marchenko imaging and introduced a variant that removes artifacts caused by internal multiples from a reverse time migration (RTM) image. His scheme is straightforward to include in industry routine RTM imaging. With this work as a basis, he was able to isolate the multiple elimination process from the migration process. In practice, the redatuming step requires subsurface information, which Lele avoided by developing a scheme that eliminates internal multiple reflections from the data at the surface. This method has become known as Marchenko multiple elimination (MME). Lele extended this method to a version that compensates for two-way transmission effects in the primary reflections, which is named transmission-compensated MME (T-MME). In a paper on the comparison of strategies, he showed that his method outperforms the existing method in a model where primaries are masked by overlapping multiples and in a complex model. This paper was featured in the Bright Spots department of The Leading Edge and received an Honorable Mention in the 2019 Best Paper in Geophysics voting. Lele then moved on to develop a method that solves the problem of eliminating free-surface and internal multiples simultaneously. Two important features were introduced: the method does not require adaptive subtraction techniques that are often used in free-surface multiple elimination schemes, and the elimination process runs fully unsupervised. Lele published his methods and illustrated them with papers on synthetic data from simple to complex models, to ultrasonic data measured in the laboratory, and on seismic field data.
Lele is one of few in our group who was able to graduate with his PhD within the time frame of four years. During this period, he surprised us time and again with his creativity to come up with ideas for novel methodologies and to turn them into working algorithms and computer codes. He has demonstrated his ability to turn these ideas and the corresponding results into numerous scientific communications in the form of journal articles and conference abstracts. His productivity can be said to be high, and even though high productivity in itself is not a quality, each of his journal papers brings an important advance in one of his methods or demonstrates their performance on simulated or measured data. He is first author on 13 journal papers, and coauthor on another 11.
The performance of his methods has also been noticed by industry. This has given him the opportunity to do internships at companies just after graduating. It has also enabled him to co-organize two workshops for the European Association of Geoscientists and Engineers and to be an invited speaker in an SEG workshop on multiples. After finishing his PhD work, he joined the Delphi consortium as a researcher, which helped him further expand his international network in industry. He was the initiator of the “Advances in seismic multiple reflection processing” special section that was published in the September/October 2021 issue of Geophysics. Lele formed a team of guest editors from academia and industry to attract contributions from as wide an authorship as possible to the special section, which resulted in a special section of 16 papers. In 2021, Lele became a member of the editorial board of the Journal of Seismic Exploration and an associate editor of Geophysics. Since November 2021, Lele has been an associate professor in the China University of Geosciences in Wuhan, China, in the Institute of Geophysics and Geomatics.
In our opinion, Lele Zhang rightfully receives the J. Clarence Karcher Award because of the highly innovative character of his research, the high quality of his scientific output, his enthusiastic support of a new generation of geophysicists, his community service, and, last but not least, the international recognition of his work.