Jeroen Tromp - US grants

This award provides one-half the funding required for the purchase of computer equipment to serve the seismology research group in the Department of Earth & Planetary Sciences at Harvard University. Harvard is committed to providing the remaining necessary funds. The equipment includes upgrades of two fileservers to multiprocessor machines, workstation upgrades, acquisition of a color graphics workstation, and the acquisition of a tape archive unit. The seismology research group at Harvard investigates a broad range of problems in seismology including the analysis of very large data sets for the study of earthquake source parameters and the determination of earth structure.

This award will provide partial funding for a systems manager to support the computer system of the geophysics research group in the Department of Geological & Planetary Sciences at Harvard University. The computer facility presently serves 15-20 faculty, postdoctoral research associates, graduate and undergraduate students working in computer-intensive areas of research such as seismic tomography, earthquake seismology, geomagnetics, and other studies of the Earth's deep interior.

This research deals with increasing the resolution of global earth models by extending the inversion theory to account for non- great circle paths taken by surface waves as a result of the earth's lateral inhomogeneity. The basic theory has been developed by the Principal Investigator and the current work will begin its application and investigate the theory's assumption of non- coupling between modes with models of anisotropy, earth rotation, and lateral heterogeneity. Improved velocity models of the upper mantle are expected to result.

9615677 Ekstrom This grant provides $149,829 as partial salary support for a technician responsible for network administration for the seismology computer facility at Harvard University. This is a Phase II technician support proposal under the EAR/IF technician support sub-program and as such, will continue support of this technician for an additional two-years beyond the first three years of technical support (EAR-9219192). The seismology group at Harvard conducts world-class research on global tomographic models, studies of Love and Rayleigh wave propagation in the crust and upper mantle and continues service to the seismological community via their efforts at calculating waveforms, travel times, complete seismograms etc. from data generated from the IRIS Global Seismographic Network (GSN). This grant will provide technical service to a large group (20 faculty, graduate and undergraduate students) of seismologists. Additionally, the University, under the guidelines for a Phase II technician support proposal under the EAR/IF program is committed to support of this position for a minimum of two-years beyond expiration of this Phase II award, ***

9706169 Tromp This research involves the use of a pseudospectral or spectral collocation method with which techniques will be developed to simulate the propagation of elastic and anelastic seismic waves in complex local, regional, and global Earth models. This method requires significantly fewer grid points than spatial finite- differencing techniques to achieve comparable accuracy, exhibits no grid anisotropy and limited grid dispersion, and requires less CPU time because of the use of Finite Fourier Transforms (FFT). On a local scale, it will be used to simulate seismic wave propagation in the Boston, Los Angeles and Tokyo basins based upon detailed geological models. A spherical version will be used to simulate regional wave propagation across Australia where data from the dense SKIPPY array are available for comparison and inversion. On a global scale, the goal is to replace waveforms calculated based upon the path-average approximation with pseudospectral waveforms. These much more accurate waveforms will be used in the Harvard centroid moment-tensor project and in our global tomographic inversions. This research is a component of the National Earthquake Hazard Reduction Program. ***

EAR-0003716
Tromp, Jeroen


The investigator has developed and implemented a spectral-element method (SEM) for the simulation of three-dimensional (3D) seismic wave propagation. The method has been benchmarked against discrete-wavenumber/reflectivity synthetics for layercake models, and it has been demonstrated that the effects of free surface topography, attenuation, anisotropy, and fluid-solid boundaries can be accurately accommodated. The method will be used to assess seismic risk in the L.A. area based upon a 3D basin model. The main objective of this proposal is to extend the SEM to include global wave propagation. The code has been successfully benchmarked against normal-mode synthetics for a 3D Earth model with a size of 1/6th of the mantle by volume and the isotropic, elastic structure of the Preliminary Reference Earth Model PREM. A conforming mesh that enables the modeling of wave propagation in the entire Earth has been constructed. To accurately model 3D global wave propagation the effects of anisotropy, attenuation, self-gravitation, and a stably stratified fluid core need to be incorporated.

0003860
Tromp

This award provides one-half support of the costs of building a cluster of networked PC's (so called Beowulf cluster) for research in theoretical and applied seismology at Caltech. Jeroen Tromp and John Shaw have recently joined the faculty at Caltech after serving for several years on the faculty at Harvard University. They will build a 78 dual-CPU node Beowulf cluster with 78 Gb of RAM. The cluster will be used to run Tromp's spectral element code that has been specifically designed to run on multi-processor machines. The spectral element method represents one of the most comprehensive and robust algorithms for modeling seismic wave propagation though deep sedimentary basins (i.e. the Los Angeles basin) and for predicting the amplitude of strong ground motions that result from varying earthquake source parameters. Beowulf clusters represent a cost effective alternative to expensive shared-memory machines for high resolution modeling of large geophysical data sets.
***

Abstract for proposal EAR0106666 (PH # 53x)

Title: Global Analyses of Body Wave Travel Times and Amplitudes: Whole-mantle Tomography and Simulations of 3-D Wave Propagation

PI's: Jeroen Tromp and Jeroen E. Ritsema, Cal Tech

Seismic tomographic models are beneficial to researchers from a wide variety of disciplines in the Earth Sciences. They provide images of the structure of oceanic and continental lithosphere, and play a central role in constraining the planform of convection in the mantle.

To improve these models, we will construct new tomographic models in which we will take advantage of the extensive seismic data set that we have compiled in the past several years. It includes unique data types, such as higher-mode Rayleigh wave phase-velocity measurements and travel times of converted body-wave phases (e.g., SP, SKP), which have not been fully exploited in tomography.

In a parallel research effort, we apply the new Spectral Element Method of Komatitsch and Tromp [1999] to study the effects of 3-D mantle structure on long-period body-wave propagation. Specifically, we will test the applicability of ray theory to wave propagation in `low-degree' seismic models, whether small-scale structure in the deep mantle, such as plumes, produce characteristic, observable travel-time or waveform variations, and whether the large-scale pattern of long-period body-wave amplitude anomalies can be explained by large-scale variation of seismic velocity in the mantle. These analyses provide insight into the quality of present-day tomographic models and help us design the next generation of tomographic inversions when fully 3-D forward theories can be incorporated.

0205653
Gurnis

This is a project to develop a suite of tools to model multi-scale deformation for Earth Science problems. This effort is motivated by the need to understand interctions between the long-term evolution of plate tectonics and shorter term processes such as the evolution of faults during and between earthquakes. Several major data acquisition efforts within the Earth Sciences community are underway or at an advanced planning stage (EarthScope including PBO - Plate Boundary Observatory, InSAR - Satellite based Interferometric Synthetic Aperture Radar, USArray - a 400 element moveable seismic array, GPS - continuous Global Positioning System measurements). These observational programs will rapidly produce vast, high-quality data sets which record deformation of the Earth's surface on multiple time scales, from co-seismic and post-seismic to long term tectonic time scales, and on multiple spatial scales, from centimeters to thousands of kilometers.

The Principal Investigators will produce a modeling package, usable by the entire Earth sciences community, that addresses the limitations of what is currently feasible and that is engineered with software evolution and growth as design requirements. Their efforts will extend the capabilities of the PYRE framework, an object-oriented environment capable of specifying and launching numerical simulations on multiple platforms, including Beowulf class parallel computers, that can function with grid-computing systems. Specifically, the community needs fexible modeling tools that incorporate complex rheologies, e.g., temperature-dependent, non-Newtonian, visco-elasto-plasticity with discrete failure planes and dynamic re-gridding to resolve evolving regions of high strain. From a computational perspective, this is an excellent time to pursue these objectives. Major advances in the PC industry enable scientists to build massively parallel PC cluster computers that facilitate realistic 3-D simulations at reasonable computational and monetary costs. Complimenting these hardware advances are major architectural solutions allowing more traditional codes to be bound together to solve complex, multi-scale, multi-physics problems.

This will be a collaborative project between two Caltech units; The Center for Advanced Computer Research (CACR) and the Seismological Laboratory. After about eighteen months into the project, beta versions of the software will be made available to the community and final versions will be available without restrictions, installed on NSF PACI computing facilities, for example. The new geodynamics modeling framework will easily allow one to launch 2-D AND 3-D simulations on platforms ranging in scale from uniprocessors to the TerraGrid, making the code useful to a wide range of users from individual scientists and educators to inter disciplinary teams working on state of the art calculations posed within EarthScope.
***

Tromp
EAR-0309576

The investigators will use and extend a numerical technique called the `spectral-element method' (SEM) to model seismic wave propagation. The method incorporates complications due to lateral variations in compressional-wave speed, shear-wave speed and density, a 3D crustal model, ellipticity, topography and bathymetry, the oceans, attenuation, anisotropy, and, at long periods, rotation and self-gravitation. They propose to use these capabilities to investigate tradeoffs between isotropic and anisotropic structure in surface-wave modeling, and to analyze long-period PKIKP waveforms associated with an anisotropic inner core. They will also implement fully 3D centroid-moment tensor (CMT) inversions based upon numerically calculated Frechet derivatives. The SEM can handle finite rupture models, which turns out to be quite important for several large recent events that exhibit strong directivity. When modeling amplitude anomalies there exist significant tradeoffs between elastic focusing and attenuation. The SEM can accommodate lateral variations in both elastic and anelastic structure, which provides a quantitative means of assessing this tradeoff. The investigators will extend the SEM to simulate seismic wave propagation in sedimentary basins. Based upon a detailed 3D Los Angeles basin model developed by Prof. John Shaw and his co-workers at Harvard, they are embarking on waveform modeling of TriNet data. At the end of the proposed research period the basin software package will be made available for use by other research groups. Finally, the investigators have established a collaboration with Dr. Seiji Tsuboi of JAMSTEC (Japan), which involves SEM simulations on the Earth Simulator, the world's largest and fastest computer.

The broader impacts of the proposal include open-source software packages for the simulation of seismic wave propagation in sedimentary basins and the entire globe. Simulations based upon these packages can be used to investigate seismic hazard and aid in the determination of earthquake source parameters. The SEM can also be used to assess and improve the quality of tomographic models of the mantle, an endeavor that will enhance our understanding of the physics of the Earth's interior. Finally, the proposal would support the education and training of two graduate students and one postdoc.

EAR-0521699
Tromp

Caltech's Division of Geological & Planetary Sciences will construct an 864-node PC cluster computer that will be combined with an existing 160-node cluster. The resulting supercomputer will have 1024-nodes (2048 processors) and will be dedicated to a wide spectrum of geoscience research and education. The NSF Award provides an important component of the funding for a partnership between Dell, Intel, and Caltech. NSF, Dell, and Intel have provided the funds for the computer while Caltech renovated 1750 square feet of space with advanced cooling and uninterruptible power.

The computational facility will be used for research in the solid-earth sciences (including seismology, geodynamics, and geodesy), atmospheric sciences (including climate dynamics), and planetary sciences (including planetary atmospheres). The project spans a wide range of topics in basic research as well as work that will have a substantial benefit to society (such as work related to earthquake shaking and climate change). For example, in seismology, the infrastructure will lead to dramatically improved images of earth structure, globally and locally, as well as images of the rupture of large, destructive earthquakes. In geophysics, simulations tied to observations will lead to a fuller understanding of the forces driving plate tectonics and the rupture of earthquakes. In atmospheric sciences, simulations will be used to demonstrate how water vapor is maintained, how it varies, and how it may cause rapid climate change. In planetary sciences, the mechanisms of the most dramatic weather events in the solar system, the Martian global dust storms, will be investigated.

Since many of the scientific challenges facing geoscientists today transcend disciplinary boundaries, and many of the computational challenges involve common issues related to algorithms, visualization, and data assimilation, the single computer system will enable cutting-edge simulations while promoting and fostering cross-fertilization of ideas. The facility will generate a learning environment that fosters interdisciplinary interactions and integrates research with education, thereby educating and training the next generation of academic and industry computational scientists and engineers.

Intellectual Merit
Seismologists have known for many years that the lowermost mantle is complex.
Attempts at modeling seismic waveforms sampling this region produced ultra-low velocity zones, sharp horizontal discontinuities, strong zones of anisotropy (SH>SV), and in some cases near vertical walls. It now appears that this myriad of fine structure is beginning to be understood in terms of mineral physics with dense melts from hot perovskite and a new post-perovskite structure. These new discoveries can explain many of the above features. In particular, the investigators earlier dynamic 2D model of slabs folding at the CMB generates a strong positive velocity gradient, which in turn produces synthetic seismograms containing a small triplication, if a 1% velocity jump is allowed. Assuming that this jump results from a phase-change with a positive Clapeyron slope, and transforming tomographic images through such a hybrid global model, generates some of the geographic behavior of the observed S-wave triplication: where the post-perovskite layer is thickest beneath fast regions and disappears beneath slow regions. The team's latest 3D dynamic models explain the locations of the fastest regions based on the history of plate subduction. Results from 3D dynamics are significantly different from those in 2D, and may help us explain more of the variability in seismic waveform data sampling the lower mantle when seismic and dynamic models are merged. In order to make accelerated progress toward understanding the lower mantle and D" propose research to resolve the 3D nature of these structures. They will address the following questions:
o How compatible are 3D dynamic predictions of slab histories with lower mantle
structure?
o Can we separate velocity gradient effects caused by subduction from the phase-boundary effects and update a global map?
o How different is the mid-Pacific lower mantle structure compared to the African
structure and what does this imply in terms of the stability of upwelling?
o What dynamic models of thermo-chemical boundary layers are consistent with the proposed post-perovskite structure and seismic data?

Broader Impact
Answers to the above questions will be of great use to the entire Earth Science community, especially mineral physicists who need fundamental seismic information about the global properties of the newly discovered phase boundary. Making the direct connection between the detailed fast structures in the lower mantle with respect to the history of subduction will answer a key question in plate tectonic dynamics. These multi-disciplinary efforts should help the involved students become leaders in future CSEDI developments.

0606901
Tromp

Many fundamental questions related to the physics of earthquakes still evade understanding or consensus. How do earthquakes nucleate and arrest? What are the appropriate descriptions and parameters of fault friction? How do thermal effects, such as flash heating, pore-fluid pressurization, and melting, influence dynamic rupture propagation? What governs post-seismic creep? What is the stress state on faults and the surrounding crust? How can crustal deformation and tectonic loading be realistically described and incorporated into models of earthquake cycles? This rich and very active area of seismology involves laboratory experiments, numerical modeling, and theoretical investigations.

This award will help support a symposium focused on the Physics of Earthquakes. This symposium is organized in honor and recognition of Professor Hiroo Kanamori's recent retirement. Its aim is to bring together Hiroo's closest colleagues, students, posdocs, and friends for a two day in-depth discussion of the current state of knowledge with regards to earthquake physics. Earthquake early warning has long been one of Hirroo's research interests and will be another theme of the meeting. Hiroo has been a leader in earthquake seismology for decades. He has received numerous awards for his work including the Medal of the Seismological Society of America, the Arthur L. Day Prize and Lectureship of the National Academy of Sciences, the Walter H. Bucher Medal of the American Geophysical Union, and the Japan Prize.

The symposium will be held on February 23 & 24, 2006 at the Beckman Institute Auditorium on the Caltech campus. The program for the symposium reflects Hiroo's broad research interests ranging from the interaction of atmosphere and lithosphere to real-time seismology for hazard mitigation to long-term crustal processes associated with earthquakes. Speakers at the symposium will be a balance of junior and senior scientists, including some of Hiroo's most recent students and postdocs.

0620203
Tromp

This award will help support a symposium focused on Planetary Impacts and the Physics of Planetary Interiors. The symposium is organized in honor and recognition of Prof. Tom Ahrens' retirement from Caltech and his many and varied contributions to the field of mineral physics. Prof. Ahrens, with his students and colleagues in the Lindhurst Laboratory of Experimental Geophysics, has been actively conducting research on the high-pressure properties of minerals of the Earth and planetary interiors, as well as impact effects on planetary surfaces, such as production of craters, accretion of the planets, and formation of magma oceans overlain by primitive atmospheres. Ahrens' group has pioneered the use of optical radiation versus time at a series of wavelengths to directly determine shock temperatures. The recent detection of the postperovskite phase in the lowermost mantle has generated a lot of excitement within the mineral physics and the seismological communities, and the symposium should bring about much lively and interesting discussion.

The program for the symposium reflects Prof. Ahrens' broad research interests ranging from the origin, differentiation and evolution of the Earth and planets to laboratory and spacecraft-based measurements of the physical properties of planetary materials to impact processes on planetary surfaces and atmospheres. The symposium features a balance of junior and senior speakers, including some of Prof Ahrens' most recent students and postdocs.

The increasing availability of large numbers of high-quality digital records from the global seismic networks has made possible a variety of new ways to study earthquakes and deep Earth structure. By analyzing hundreds or thousands of seismograms, it is often possible to resolve new features in the data, or to perform more comprehensive analyses of problems that were previously addressed on smaller scales. This project will continue analyses of global seismic data at U.C. San Diego to examine a variety of geophysical issues. These include: (1) Study of seismic discontinuities in the upper mantle using reflected and converted seismic phases. Resolving details of mantle discontinuity properties is important, both for modeling of mantle composition and for understanding the effect that the discontinuities can have on mantle convection. (2) Imaging earthquake rupture using back-projection methods. These methods have the potential to provide near-real-time images of the rupture extent of large earthquakes, which will help in planning disaster relief operations. (3) Analyses of earthquake spectra to resolve directivity and stress drop. This will help determine whether large, damaging earthquakes are simply "scaled up" versions of smaller earthquakes, in which case strong ground motions could be predicted for future large quakes by studying records of the much more numerous smaller earthquakes that are detected instrumentally. (4) Study and modeling of high-frequency waves scattered from small-scale mantle and core structure. This will provide information on compositional variations in the mantle at much finer scales than are possible from other seismic methods and will provide constraints on geochemical models of the mantle. (5) Development and application of waveform cross-correlation and cluster analysis techniques to long-period waveforms. This provides a practical way to process the large volumes of seismic data that are currently available and will lead to improved models of three-dimensional seismic velocity variations. (6) Observing and modeling lateral variations of seismic attenuation in the mantle, which will provide valuable constraints on mantle temperatures and chemistry. This project supports the educational program at U.C. San Diego by providing funds for graduate and postdoctoral students. This research will lead to improved models of Earth structure and earthquake rupture processes, which will be of interest to the tectonics, geodynamics and mineral physics communities. Results will be widely disseminated through publications, conference presentations, and material provided to education and outreach programs.

The focus of this project is on inverse problems in seismography.
Inferring undergound structure from seismic measurements is a nonlinear problem that is also notoriously ill-posed. The PIs will tackle this problem in its full nonlinearity via the adjoint method, by iteratively minimizing a variational functional in which, at each iteration step, the nonlinear effects of the approximate solution are fully taken into account for the computations in the next iteration.
To deal with the ill-posedness of the problem, they will use a regularization method that incorporates efficient modeling of spatial distributions that can exhibit discontinuities as well as smooth behavior between discontinuous transitions. More precisely, they will model the distribution as a sparse superposition of wavelets and curvelets, and add the sum of the absolute values of the corresponding expansion coefficients as a penalty term to the variational functional to be minimized. The inclusion of such a term enforces the sparseness of the expansion, thus expressing the smoothness of the model between discontinuous transitions, and has been proved to be regularizing. Computational resources have reached the speed and scale at which it is now feasible to use this approach for realistic problems.

Seismology seeks to gain insight into underground geological structure by measurements done at the surface. When vibrational signals are sent into the ground (whether by earthquakes, carefully tailored explosions or specially constructed vibrators), they propagate at different speeds through layers of different constitution, and are reflected at the often abrupt transitions between different layers. The goal of seismology is to reconstruct the underground structure traversed by these seismic waves from the complex signals, registered by seismographs, that result from the multiple reflections and their interaction. The corresponding numerical problem is of such great complexity that it has been necessary, in the past, to simplify it so as to keep the problem feasible; this led, of necessity, to approximate solutions. The PIs will make use of recent mathematical advances that make it possible to model more effectively heterogeneous underground structures, and of the continuing progress in speed of computational resources to tackle the problem without having to introduce some of the restrictive simplifications used previously. This is expected to result in more accurate maps of underground structure.

This NSF award to Princeton University funds U.S. researchers participating in a project competitively selected by the G8 Research Councils Initiative on Multilateral Research through the Interdisciplinary Program on Application Software towards Exascale Computing for Global Scale Issues. This is a pilot collaboration among the U.S. National Science Foundation, the Canadian National Sciences and Engineering Research Council (NSERC), the French Agence Nationale de la Recherche (ANR), the German Deutsche Forschungsgemeinschaft (DFG), the Japan Society for the Promotion of Science (JSPS), the Russian Foundation for Basic Research (RFBR),and the United Kingdom Research Councils (RC-UK), supporting collaborative research projects selected on a competitive basis that are comprised of researchers from at least three of the partner countries.

The primary goal of this international project involving collaborating researchers in three countries is the development of sophisticated 3D seismic imaging tools for the characterization of earthquakes, Earth 'noise', and mapping of Earth's interior on all scales. The research affects the fields of exploration geophysics, regional and global seismology, and even helioseismology. The proposed research ensures that seismologists will be able to effectively and efficiently harness future high performance computers. The project will develop and enhance open-source software for the simulation of 3D seismic wave propagation in acoustic, (an)elastic and poroelastic media on hierarchical computer architectures. These simulations account for heterogeneity in the crust and mantle, topography, anisotropy, attenuation, fluid-solid interactions, self-gravitation, rotation, and the oceans. A major goal is to be able to routinely and efficiently reach a shortest period of 1 s in global simulations, the shortest period signal that propagates across our planet.

This NSF award supports the education and training of a postdoc. Software developed during the course of the proposed research period will be made freely available via the Computational Infrastructure for Geodynamics (CIG). The award also supports the further development and enhancement of the southern California and global ShakeMovie web sites.

The primary goal of this project is to use seismic data to image Earth
structure and seismic sources based on modern numerical methods and
imaging techniques. We will further develop and enhance software for the
simulation of 3D seismic wave propagation, with a particular emphasis on
computing on Graphics Processing Units, rather than traditional Central
Processing Units, potentially providing an order of magnitude increase
in simulation speed. The broader impacts of the proposal include
open-source software packages for the simulation of seismic wave
propagation. Simulations based on these packages may be used to
investigate seismic hazard and aid in the determination of tomographic
images of Earth's interior and earthquake source parameters. All
software developed during the course of the proposed research period
will be made freely available via the Computational Infrastructure for
Geodynamics (geodynamics.org).

The simulations of seismic wave propagation account for heterogeneity in
Earth's crust and mantle, topography& bathymetry, seismic anisotropy,
attenuation, fluid-solid interactions, self-gravitation, rotation, and
the oceans. The main intellectual merit of this project revolves around
harnessing the power of the forward modeling tools to enhance the
quality of images of Earth's interior and the earthquake rupture
process. The approach is to minimize remaining between simulated and
observed seismograms based on so-called adjoint techniques in
combination with conjugate gradient methods, an approach we refer to as
"adjoint tomography". Specifically, following a successful application
in southern California, we will 1) develop open-source GPU-based forward
and adjoint spectral-element solvers, 2) perform adjoint tomography of
Europe, 3) further develop noise cross-correlation tomography based on
adjoint methods, 4) move towards adjoint tomography of the entire
planet, and 5) extend the southern California and global "ShakeMovie"
cyber infrastructure.

This is an Institutional Infrastructure proposal to build a GPU cluster to support research in data-parallel code development and optimization, as well as research applications, in three scientific domains, namely, seismology, biology and astrophysics. These goals build on a close collaboration with an expert team in GPU computing from computer science. The proposed cluster will serve not only as an invaluable resource for computation, but will also aid cross-fostering of techniques and concepts between disciplines and will be used to stimulate collaboration and synergistic research activity in a wide range of areas.

Even though domain scientists are increasingly dependent on computation to achieve their research goals, most are not experts in parallel programming or GPU architectures. The difficulty of parallel programming for GPU clusters is an impediment to scientific progress. In order to relieve scientists of the burdens of parallel programming, computer scientists at Princeton have developed systems for automatically parallelizing programs for GPU. Building on this success, the PIs plan to extend these techniques to GPU clusters and work closely with the seismologists, biologists and astrophysicists to accelerate the pace of science.

Precise information about the structure of the solid Earth comes from seismograms recorded
at the surface of a highly heterogeneous lithosphere. Full-3D tomography based on adjoint and
scattering-integral methods can assimilate this information into three-dimensional models of elastic and
anelastic structure. These methods fully account for the physics of wave excitation, propagation, and
interaction by numerically solving the inhomogeneous equations of motion for a heterogeneous anelastic
solid. Full-3D tomography using adjoint and scattering-integral methods requires the execution of
complex computational procedures that challenge the most advanced high-performance computing
(HPC) systems. Current research is petascale; future research will require exascale capabilities.

This project will establish an interoperable set of community computational platforms?vertically
integrated systems of hardware, software, and wetware that will allow a significant community of
investigators to employ the techniques of full-3D tomography to refine Earth structures. Two tomographic
platforms will be built on highly scalable codes for solving the forward problem: the AWP-ODC 4th-order,
staggered-grid, finite-difference code, which has been widely used for regional earthquake simulation and
physics-based seismic hazard analysis, and the SPECFEM3D spectral element code, which is capable of modeling wave propagation through aspherical structures of essentially arbitrary complexity on scales ranging from local to global. A third platform, based on the Unified Community Velocity Model (UCVM) software developed by the Southern California Earthquake Center (SCEC), will provide a common framework for comparing and synthesizing Earth models and delivering model products to a wide community of geoscientists. These platforms will be deployed at the NCAR-Wyoming Supercomputing Center (NWSC).

The core of this project is the development of a methodology (software
and hardware) to produce synchronized visual and sonic representations
of seismic wave fields in the Earth. Coupling these senses enables
people, from the general public to seasoned seismologists, to
appreciate and perceive an enormous richness in the patterns of
seismic wave fields. The aim is not to simulate the experience of an
earthquake, but to render the physics of wave propagation in the globe
and the nature of earthquake physics into a completely tactile
experience, unlike anything anyone has ever perceived. The working
group is comprised of earth scientists, astrophysicists, sound and
graphics engineers and educators, from the Lamont Doherty Earth
Observatory (LDEO), Princeton University, and the American Museum of
Natural History (AMNH).

The images and sounds are generated from both USArray and GSN data, as
well as from simulations generated with the spectral element method
(SEM), using the SPECFEM3D software. Sounds are generated by shifting
the frequency of the seismic signal into the range of human hearing,
and are filtered and stretched in time to optimize the coupled visual
and sonic effects. Once the methodology is in place, it will take two
general forms:

First, a web-based format that allows people to choose earthquakes and
seismic data to listen to, with images produced by either a dense
array of seismometers (i.e. the ground motion visualizations (GMVs)
produced by IRIS of the Transportable Array data) or a simulation of
the seismic wave field (i.e. by SPECFEM3D). This format will be useful
for classroom and laboratory purposes, and interactive museum
exhibits, as well as for exploratory observation of raw data by
seismologists.

Second, a version will be developed for the Hayden Planetarium at the
American Museum of Natural History, in New York City. The images,
projected on the planetarium dome, will include the surface of the
Earth rendered as a membrane and also a volumetric rendering in which
the observer will see 3D wave fronts propagating throughout the globe.
The sounds will be tuned to the large speaker array in the
Planetarium. Within the context of this project, several Public
Programs will occur in the Planetarium, in which the immersive
experience of listening to the Earth will be guided by the production
team. These Public Programs are the essential first step towards
developing a full planetarium show on the dynamics of the Earth at
AMNH.

The principal investigators of this proposal are a collaboration of seismologists, computer scientists, and structural geologists who are developing computational platforms that can combine seismological and geological information into three dimensional (3D) representations of Earth structure. They derive the seismological information from earthquakes, controlled-source experiments, and observations of the ambient seismic field generated by ocean waves and other near-surface disturbances. They derive the geological information from an even wider variety of sources: field mapping, electromagnetic remote sensing, geotechnical measurements, drilling and well-logging, fault trenching, and laboratory measurements of material properties.

The systematic integration of such diverse datasets into unified structural representations (USRs) is a key problem of geoinformatics. The goal of this project is to develop for community use the complex cyberinfrastructure needed to manage the ?USR lifecycle?, including the effective application of high performance computing (HPC) to invert joint datasets in the iterative improvement of USRs. The lifecycle is initiated by the integration of several components into a starting model; the starting model is refined by full-3D tomographic inversion of seismic waveform data; the refined model is validated for its proposed applications and then disseminated to user communities. This new model becomes the main component of the starting model for the next lifecycle.

The study of hazards and renewable energy are paramount for the development and sustainability of society. Similarly, the emergence of new climatic patterns pose new challenges for future societal planning. Geospatial data are being generated at unprecedented rate exceeding our analysis capabilities and leading towards a data-rich but knowledge-poor environment. The use of advanced computing tools and techniques are playing an increasingly important role in contributing to solutions to problems of societal importance. This project will create specialized computational tools that will enhance the ability of scientists to effectively and efficiently study natural hazards and renewable energy. The use of these tools will support novel methods and the use of powerful computing resources in ways that are not currently possible.

Many scientific applications in the geosciences are increasingly reliant on "ensemble-based" methods to make scientific progress. This is true for applications that are both net producers of data, as well as aggregate consumers of data. In response to the growing importance and pervasiveness of ensemble-based applications and analysis, and to address the challenges of scale, simplicity and flexibility, the research team will develop the Ensemble Toolkit for Earth Sciences. The Ensemble Toolkit will provide an important addition to the set of capabilities and tools that will enable the geosciences community to use high-performance computing resources more efficiently, effectively and in an extensible fashion. This project represents the co-design of Ensemble Toolkit for Earth Sciences and is a collective effort of an interdisciplinary team of cyberinfrastructure and domain scientists. It will also support the integration of the Ensemble Toolkit with a range of science applications, as well as its use in solving scientific problems of significant societal impact that are currently unable to utilize the collective capacity of supercomputers, campus clusters and clouds

This research involves the development of open-source software for simulations of seismic wave propagation inside the Earth. Such simulations may be used for quantitative seismic hazard assessment, visualizations for outreach and educational activities, as well as a basis for seismic tomography. Like medical tomography, the goal of seismic tomography is to image the Earth's interior on all scales, from hydrocarbon fields in exploration seismology to Earth's mantle in global seismology, to help us understand our planet's inner workings and evolution. As a broader impact this project will publish earthquake wave animations online in near real-time for events with magnitudes of 5.5 and greater at Princeton University's Near Real Time Seismicity Portal (GlobalShakeMovie) .

The main goal of this research is to further develop global seismic tomography using complete seismic waveforms and adjoint-state methods by enabling massive data assimilation and harnessing the largest and fastest available computers. Using a pilot dataset of 253 earthquakes, a first-generation global tomographic model based on "adjoint tomography", an iterative full-waveform inversion technique was built. Based on this experience, a next-generation global model will be constructed by assimilating full waveform data from thousands of earthquakes that were well recorded by broadband global and regional seismographic networks. Prior NSF support demonstrated the feasibility of regional adjoint tomography for isotropic heterogeneity, anelasticity, and azimuthal anisotropy. Similar inversions on a global scale will be done through secured access to the necessary computational hardware through the Department of Energy INCITE program. This research supports a portion of the required human resources, where the rate-limiting steps in this ambitious endeavor are data quality control, I/O, and workflow management. Four main tasks will be tackled bearing these obstacles in mind: 1) prepare and further develop the open source spectral-element seismic wave propagation solvers SPECFEM3D and SPECFEM3D_GLOBE for exascale simulations; 2) further develop the Adaptable Seismic Data Format (ASDF) for fast I/O; 3) further develop the inversion & migration toolkit SeisFlows by taking advantage of the open source Structured Query Language database engine SQLight and existing workflow management tools, such as Pegasus; and 4) perform global adjoint seismic tomography with a database of thousands of earthquakes at a shortest period of 9 s. Task 4 encompasses the main goal of the proposal, but it cannot be completed without simultaneously addressing the other tasks.

The broader impact/commercial potential of this I-Corps project is the development of a next-generation, high-resolution ultrasonic imaging technique for medical and non-destructive testing applications. This technique will improve on existing imaging technologies by enabling highly detailed physical and spatial properties of the imaged material to be determined, beyond what is currently capable from ultrasound, X-Rays or MRI. This will enhance the capability of medical and non-destructive imaging technologies, for example, by allowing more accurate identification and diagnoses of tumor tissues in medical scans, or improving the identification of defects in manufactured parts. Combined with the benefits of ultrasound, in particular, safety, speed, portability, patient comfort, and cost, this technology has potential for broad impact. Commercially, the technology will enable medical practitioners to make diagnoses faster and with higher accuracy. This will allow earlier and more precise identification of tumors, reducing the number of false positives and follow-up procedures. This will ultimately increase diagnostic efficiency, reduce costs and improve patient outcomes. In a non-destructive testing application, this technology will enable imaging detail that was previously only available with more expensive and time-consuming techniques such as X-Rays.

This I-Corps project combines techniques from the fields of ultrasonic imaging and the geosciences to significantly improve existing mm- to cm-scale imaging technologies. The technology adapts an advanced geophysical imaging method known as full waveform inversion (FWI) for medical and non-destructive testing purposes. Full waveform inversion is conventionally applied for imaging the earth?s structure and to discover oil and gas reservoirs. Instead of applying the technique at seismic scales (m to km), the company applies it at the ultrasonic scale (mm to cm) to generate high-resolution 3-dimensional images with embedded physical properties. Research is focused on both software and hardware development. Software algorithms are being developed which construct images from ultrasonic measurements within seconds to minutes. This is enabled through the use of cutting-edge, highly efficient algorithms and high-performance computing infrastructure. Research and development of prototype hardware is also being undertaken, necessary for generating high-quality ultrasonic data for input into the imaging algorithms. To-date, rapid, high-resolution 2- and 3-dimensional image construction using full waveform inversion techniques has been demonstrated on a range of ?synthetic? ultrasonic-scale objects. This demonstrates that images can be quickly generated, containing a full range of material properties including material density, stiffness and attenuation.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Earth?s mantle thermal convection drives plate tectonics. It is at the origin of numerous risks for populations (e.g., earthquakes, volcanic eruptions, tsunamis). This process extracts Earth?s internal heat, notably produced by the crystallization of its core. The core is ~3,500 km (~2,200 mi) in radius and consists mostly of iron with some nickel. Its liquid outer shell, the outer core, generates the Earth?s magnetic field. Above the core lies the rocky mantle, a hot layer of mostly solid silicates wrapped into the planet?s crust. The core-mantle boundary (CMB) is located ~2,900 km (1800 mi) beneath the Earth?s surface. It is a complex and critical boundary. There, heat transfer, from the core to the mantle, constrains the geodynamo and powers mantle convection. Deep patterns of mantle flow are observed by refined seismic imaging above the CMB. These structures still challenge interpretations in terms of mineralogy and thermodynamical state. Here, researchers focus on the mantle system. The multidisciplinary team of computational scientists consists of a mineral physicist, two seismologists, an applied mathematician, and a geodynamicist. It introduces innovative approaches to analyze the origin of mantle structures, including machine learning algorithm. The models are constrained with the latest mineral physics data, obtained at the extreme pressures and temperatures prevailing in Earth?s interior. Gradually, the scientists unveil the origins, compositions, and temperatures of the deep mantle structures. Outcomes of the project, i.e., state-of-the-art methods, software, and databases, will benefit the Earth Science community. The project also provides support for an early career female scientist, and training for four graduate students at Columbia University and Princeton University.

Here, the researchers use the latest shear (S-) and compressional (P-) wave models obtained by global adjoint tomography, without reference to a 1D spherical model or assumptions of correlations between compressional (VP) and shear velocity (VS) heterogeneities. They also use direct inversion, machine learning algorithms, and the latest mineral physics results on thermoelastic properties of mineral phases undergoing iron spin crossover (ISC). They pay particular attention to the effect of the ISC which disrupts the usual correlation between VS and VP heterogeneities caused by lateral temperature or composition variations. They focus on lower mantle structures, mainly plumes rooted at the CMB and possibly slabs in this region. In the process, they are formatting the mineral physics data on ISCs to make it available through two popular thermochemical and thermoelasticity software/database frameworks ? BurnMan and Perple_X ? that couple with geodynamic codes. With this software/data infrastructure in place, they run geodynamic simulations to understand the effect of ISC on mantle dynamics. Conversely, results of geodynamic modeling coupled to thermoelasticity data are used to synthesize tomographic images to be compared with observed mantle structures. The know-how generated by this project, i.e., methods, software, databases, and results will be made available through peer-reviewed journals and in specialized web sites, e.g., BurnMan, Perple_X, IRIS, github.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

This research will lay the groundwork for improvements in the scientific description of earthquakes, benefitting researchers in earthquake statistics, seismic tomography, seismic hazard, and seismic discrimination, as well as tectonic interpretation and analysis. This is the first step towards making the results of complex and expensive numerical calculations available for multiple applications and a wide range of users. This work focuses on demonstrating the feasibility of the methodology, but the database and method will be valuable for any research requiring accurate predictions of the global seismic wavefield from an arbitrary earthquake at any location without expensive computation. Two graduate students will be trained in research at the nexus of earthquake science, theoretical seismology, and computational Earth science.<br/><br/>This two-year, focused effort will (1) develop a new method for calculating, storing, and accessing high-fidelity long-period synthetic seismograms for state-of-the-art 3D tomographic models of the Earth, and (2) incorporate these seismograms in the earthquake analysis of the Global Centroid-Moment-Tensor (CMT) Project. Currently, the CMT synthetic seismograms are calculated using modern 3D Earth models, but accuracy is limited by the validity of the path-average approximation for mode summation and surface-wave ray theory, inexact predictions of the amplitude and polarization of ground motion, and other unmodeled effects, bias retrieved earthquake parameters. The incorporation of higher-fidelity synthetic seismograms in the CMT analysis will improve the characterization of seismic sources and remove concerns about a key source of uncertainty and bias. The team will adapt the spectral-element wave-equation solver SPECFEM3D_GLOBE to generate a database of kernel seismograms on a global grid of hypocenters, for a large set of station locations, using source-receiver reciprocity to speed up the calculation. Kernel seismograms on the grid will be organized and stored in a format that facilitates rapid access to a particular source region and the stations of the Global Seismographic Network. Kernel seismograms for an arbitrary centroid location will be efficiently calculated by spatial interpolation, in a manner that matches the accuracy of the full forward calculation. The CMT code will be modified to ingest the interpolated SPECFEM3D_GLOBE seismograms and testing will allow the assessment of success of the approach and method. The Princeton numerical seismology group and Lamont earthquake-analysis group will jointly evaluate the approach and fidelity of the waveform interpolation, develop practical formats for accessing the (massive) database of global waveforms, and assess the success of these developments.<br/><br/>This project is jointly supported by the Geophysics and Instrumentation and Facilities programs in the Division of Earth Sciences. It is also co-funded by a collaboration between the Directorate for Geosciences and Office of Advanced Cyberinfrastructure to support AI/ML and open science activities in the geosciences.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.