HEILAND LECTURE SERIES

Wednesday, January 10, 2018 4:00 p.m. - Coolbaugh 209

“Scalable seismic monitoring with fiber optics beneath our feet”

EILEEN ROSE MARTIN, PH.D. CANDIDATE GEOPHYSICS DEPARTMENT, LAWRENCE BERKELEY NATIONAL LABORATORY

Eileen Martin is a PhD student in Computational and Mathematical Engineering working in the Stanford Exploration Project research group with Prof. Biondo Biondi. She is an a�liate in the Geophysics Department at Lawrence Berkeley National Laboratory, where she collaborates with scientists developing a scalable fiber optic system for monitoring permafrost thaw under infrastructure. During her Ph.D. studies, she has been supported through the DOE Computational Science Graduate Fellowship and the Schlumberger Innovation Fellowship. She earned her M.S. in Geophysics at Stanford, and her B.S. double-majoring in mathematics and computational physics at the University of Texas at Austin.

Continuously recording, dense seismic arrays could help us better understand earthquake and landslide hazards, permafrost thaw, our hydrological cycle, and near surface changes at energy production sites. But such arrays have typically been expensive to maintain long-term and are logistically di�cult to install in populated areas. We combine two methods to make continuous subsurface monitoring significantly cheaper: estimating wave equation Green’s functions from random vibration recordings in the area of interest, and measuring vibrations as meter-scale strain rate profiles along fiber optic cables. In addition, the continuously recorded data from fiber optics can be used to analyze ground motion during earthquakes. These methods can make continuous high-resolution subsurface imaging a possibility where it was previously impossible, but there are several challenges I will address: (i) algorithms must be modified for real-time analysis of streaming data from many sensors, (ii) the theory for Green’s function estimation must be altered to account for new sensors measuring tensor strain rates as opposed to particle velocity vectors or pressure scalars, and (iii) existing Green’s function estimation theory assumes independent, uncorrelated vibration sources (which is far from the reality of urban and infrastructure noise sources). These issues will be shown in the context of two data sets: a buried fiber array near a road in Alaska for monitoring permafrost thaw, and a fiber network in existing telecom conduits under the Stanford campus for earthquake hazard analysis. The fundamental issues behind working with noisy, streaming data for weak signal detection, imaging and inverse problems are common to a wide range of Earth science problems.

Eileen Martinthe Stanford Exploration Project research group with Prof. Biondo Biondi. She is an a�liate in the Geophysics Department at Lawrence Berkeley National Laboratory, where she collaborates with scientists developing a scalable fiber optic system for monitoring permafrost thaw under infrastructure. During her Ph.D. studies, she has been supported through the DOE Computational Science Graduate Fellowship and the Schlumberger Innovation Fellowship. She earned her M.S. in Geophysics at Stanford, and her B.S. double-majoring in mathematics and computational physics at the University of Texas at Austin.

Advanced imaging for practitionersPresented by William W. Symes, Rice University, Houston, TX USA

ABSTRACT Seismic migration has been a core geophysical technology for more than 50 years and continues to evolve in its capacity to reveal detailed quantitative information about the sedimentary earth. Integration of ever more accurate and complete seismic wave physics, more precise numerical methods, and rapidly improving computer hardware and software environments have made formerly “advanced” methods such as prestack reverse time migration (RTM) relatively routine.

This lecture will discuss two variants of RTM aimed at enhancing the significance of image amplitudes. Both true amplitude migration and least squares migration (LSM) are being actively researched; singly and in combination, they have many applications, some surprising. I will describe a number of these applications and illustrate them using synthetic and field data examples.

SM

Sharper Imaging, Angle-Dependent Reflectivity: True amplitude migration modifies RTM by filters and scale factors, producing physically significant amplitudes and more accurate event wavelet for negligible incremental cost. Some variants of true amplitude migration also can produce an extended image volume depending on position in the subsurface and on scattering angle/azimuth. Much additional information can be extracted from such extended images, including estimates of various physical parameters.

Accelerated least squares migration: LSM is iterative linear inversion, requiring repeated RTM application to update a physical model of the subsurface so that data traces are fit, wiggle for wiggle. Therefore, its improved account of the subsurface comes at a fairly high computational price. A properly formulated true amplitude migration can be used to accelerate the convergence of the iteration, reducing the required number of RTM applications by an order of magnitude or more with little additional cost per iteration.

Fast LSM Angle-dependent Reflectivity: Extended images represent the earth as a scattering angle/azimuth dependent reflectivity volume. Extended true amplitude migration accelerates an extended version of LSM also, yielding an extended model volume of calibrated precision at relatively low price.

Irregular Sampling / Missing Data: LSM naturally adapts to irregular acquisition geometry. By treating infill data as additional inversion targets to be determined, it is possible to use true amplitude accelerated LSM with incomplete data as well.

Accelerated FWI: Full waveform inversion (FWI) is the full-physics, nonlinear version of LSM, which is itself a single step in an effective FWI iteration. Acceleration (or even replacement) of this Gauss-Newton step by true amplitude migration results in a very substantial speed-up of FWI, coming much closer to convergence even with the small number of iterations used in typical contemporary FWI exercises.

Velocity Estimation: The velocity field is an essential input to most prestack imaging methods. A reasonably accurate initial estimate of velocity also is essential for reliable FWI. Traveltime tomography is perhaps the most common source of velocity information for these purposes. Wave equation migration velocity analysis (WEMVA) is another. Even though WEMVA is essentially tomographic, aimed at extracting kinematic information from the data, true amplitude migration and accelerated LSM can play a surprisingly constructive role. Use of these inversion methods in constructing image gathers for WEMVA substantially enhances the effectiveness of the WEMVA velocity update, removing some notorious artifacts that can impede convergence, and permitting effective accuracy control.

Things to Come: Much of the theory and practice for both true amplitude migration and LSM rests on the simplest acoustic wave equation. Recent work focuses on incorporating more accurate seismic physics, particularly elastodynamics and attenuation, and on reducing the computational expense of angle-dependent reflectivity estimation.

2018 SPRINGDISTINGUISHED LECTURER

Supported through the SEG Foundation by

William W. Symes graduated with honors from the University of California--Berkeley in 1971 and received a PhD in mathematics from Harvard University in 1975. After research and teaching positions at University of British Columbia, University of Wisconsin, and Michigan State University, in 1983 he joined the faculty of Rice University, where he currently is Noah G. Harding Professor Emeritus and Research Professor in Computational and Applied Mathematics. He also has been a faculty member in Rice’s Department of Earth Science. He has worked in many areas of applied and numerical mathematics, including numerical methods for wave modeling, scientific software engineering, and theory of, and algorithms for, seismic inversion. He has developed grid-based eikonal solvers, data compression and multi parameter inversion algorithms, efficient viscoelastic modeling methods, QC methods for finite difference modeling (as part of the SEG’s Phase I SEAM project), optimal check-pointing for RTM and FWI gradient calculation, wave equation based acceleration of iterative least squares migration, and the extended modeling / differential semblance concept for seismic velocity estimation. To better explore these topics in an industrial context, Symes founded a research consortium, The Rice Inversion Project, which has been sponsored for more than 25 years by firms in the oil and computer industries, and has supported the studies of more than 40 MA, PhD, and postdoctoral students. Among other honors and awards, Symes has received the Ralph E. Kleinman and Geoscience Career awards from SIAM and is a SIAM Fellow (inaugural class) and Fellow of the Institute of Physics. In 2015, he received the Desiderius Erasmus prize from the European Association of Geoscientists and Engineers for his “seminal contributions to methods, analysis, algorithms, and software for seismic inversion and wave propagation…”

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The Society of Exploration Geophysicists is a not-for-profit organization committed to connecting the world of applied geophysics. With more than 27,000 members in 128 countries, SEG provides educational and technical resources to the global geosciences community through publications, books, events, forums, professional development courses, young professional programs, and more. Founded in 1930, SEG fosters the expert and ethical practice of geophysics in the exploration and development of natural resources, characterization of near surface, and mitigation of earth hazards. For more information visit seg.org.

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To see William W. Symes’ full itinerary or to view previous Honorary and Distinguished Lecturer presentations, visit: ”It’s up to you to make sure that you remain very well informed, and you will be a valuable

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HEILAND LECTURE SERIES

Wednesday, January 31, 2018 4:00 p.m. - Coolbaugh 209

“New Frontiers of Planetary Seismology”

PROFESSOR PHILIPPE LOGNONNÉ INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

UNIVERSITÉ PARIS DIDEROT-SORBONNE PARIS CITÉ, FRANCE

Dr. Philippe Lognonné is a Professor at University of Paris Diderot-Sorbonne Cité and Planetary geophysicist at the Institut de Physique du Globe de Paris. His background is seismology and planetary sciences. He is Principal Investigator of the SEIS experiment onboard NASA 2018 InSIght mission, which will be launched on May, 5th, 2018 and will land on Mars on November, 26th, 2018.

He also contributed to several projects in ionospheric seismology, including NASA Concept Study VAMOS, which is aiming to perform remote sensing of seismic waves on Venus.. He is Director of the Planetary Space Science Laboratory at the Institut de Physique du Globe de Paris, Senior Member of the Institut Universitaire de France.

About 45 years ago seismology started its escape from Earth, with not only the first successful installation of a seismometer on the Moon by the Apollo missions but also with the first observations of seismic waves in the ionosphere, 250 km or more above Earth surface.Our journey to today’s research at these frontiers of seismology will start with the Moon and the 40 years old Apollo data and will then move to Mars and finally Venus or Europa, both targets of concept studies for the 2020-2030.We first present the most recent results obtained in the re-processing of the Apollo data since 2000: re-estimation of the lunar crustal thickness, discovery of the Lunar core reflected seismic waves, characterization of the dynamics of the deep moon quake and impacts.We then move to Mars, where data will wait for the launch in May 2018 of the NASA InSight mission, which will carry to the Martian surface a 3 axis Very Broad Band and a 3 axis Short Period seismometer. We present the scientific perspectives of the mission and the technical challenges associated to the robotic installation of VBB instruments in an hostile and windy environment.We then conclude with possible future missions in planetary seismology, which concepts are presently worked by the international Planetary seismology. These might either enable the seismic discovery of new bodies, like Euopa, one of the icy moon of Jupiter with an underground ocean, Venus, with remote sensing perspectives based on airglow observations, asteroides or might lead to the deployment of a new seismic network on the Moon.

Dr. Philippe Lognonnéand Planetary geophysicist at the Institut de Physique du Globe de Paris. His background is seismology and planetary sciences. He is Principal Investigator of the SEIS experiment onboard NASA 2018 InSIght mission, which will be launched on May, 5th, 2018 and will land on Mars on November, 26th, 2018.

He also contributed to several projects in ionospheric seismology, including NASA Concept Study VAMOS, which is aiming to perform remote sensing of seismic waves on Venus.. He is Director of the Planetary Space Science Laboratory at the Institut de Physique du Globe de Paris, Senior Member of the Institut Universitaire de France.