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	Alison Malcolm amalcolm [at] mit.edu Department of Earth, Atmospheric and Planetary Sciences Massachusetts Institute of Technology 77 Massachusetts Ave, 54-522 Cambridge, MA, 02139 617-324-1974

Check out the Imaging and Computing Seminar
I co-organize with Laurent Demanet

The intro to seismic imaging lectures I gave at MSRI are here and here .

       Research        Students        Publications        Teaching        Personal

Research Overview

Each of my current research projects is described briefly below. If you're interested in my past work, have a look at my CV (pdf), for my guess at what I might be up to in the future, you can check out my research statement.

Collaborators: Oleg Poliannikov, Gabi Melo and Mike Fehler from MIT and Michael Prange and Hugues Djikpesse of Schlumberger

A problem in hydraulic fracturing is estimating where the fractures are after the fracturing process is complete. With Geothermal applications in mind, we are working on using the multiply scattered coda to help monitor and understand these sorts of fracture systems.

As part of this work, my student Gabi is working on estimating Green's functions between microquakes using seismic interferometry as discussed in this paper. By estimating the Green's function between sources we hope to create a denser data set. Because of the sparse receiver coverage in a typical geothermal experiment, Gabi is working on using SVD to improve the recovered Green's function. The picture below shows an example in which the first arrival and the coda are more accurately recovered this way. This is related to the work I am doing with Oleg Poliannikov, Michael Prange and Hugues Djikpesse on using one microseismic event to locate another discussed here and here.

MIT research scientist Oleg Poliannikov and I are working on how to use the muliply scattered coda to estimate changes in Earth structure as discussed in this SEG abstract for CO2 sequestration. Using this technique, along with the data set Gabi is working to construct we hope to be able to improve our understanding of an Enhanced Geothermal site in Indonesia.

Collaborators: Fernando Reitich , in the School of Mathematics at the University of Minnesota and James Greenleaf, Mostafa Fatemi , Thomas Gallot, MIT.

Ultrasound vibro-acoustography is a new imaging modality developed at the Mayo Clinic that combines the high resolution possible with high-frequency imaging methods with the clean (scatter-free) images possible using low-frequency waves. It was first introduced by Fatemi and Greenleaf in 1999; that paper can be found here . We are working to model these experiments with the goal of improving the understanding of the underlying physics which we hope will result in improved images of abnormal tissue. The image below shows the current state of our model, on the left is an experimental image of an aluminum rod submerged in water and on the right is the result of our model for the same configuration. More details can be found in the paper here .

Along with postdoc Thomas Gallot, and a group of MIT researchers, I am working on extending this and similar techniques to borehole imaging. We are looking at both experimental and modeling aspects of these problems.

Collaborators: Bjørn Ursin at the Technical University in Trondheim and Maarten de Hoop in the Center for Computational and Applied Math at Purdue University, Alan Richardson and Henri Calandra.

In typical seismic experiments for oil prospecting sources and receivers are restricted to lie on the Earth's surface. Waves are also typically assumed to reflect only once in the subsurface and to travel primarily downwards into the Earth before reflecting and upwards afterwards. The combination of these restrictions limits the region of the Earth imaged. We are working to extend this region by relaxing the restriction that waves scatter only once in the subsurface. From doubly scattered waves this improves images of steeply dipping structures and from triply scattered waves we are able to image some structures from below. We have published a theoretical paper and a case study on this work, as well as two SEG abstracts. My student Alan is working on a detailed comparison of our method with reverse-time migration. The image below shows an example of imaging a fault, with a standard image on the left and our improved image on the right; this example is similar to that presented by Jin, Xu and Walraven at SEG in 2006, available through the Society of Exploration Geophysicists.

Collaborators: Mike Fehler, Andrey Shabelansky and Di Yang of MIT.

A 4D seismic data are used to monitor changes in a reservoir. A typical 4D data set consists of an initial data set collected before the change is made (baseline data) and one or more data sets collected during or after the induced change (monitor data sets). From these data, two images are typically made, one with the baseline data and the other with the monitor data set. Changes in the Earth are then estimated by subtracting the two resulting images. The changes are usually relatively isolated so this results in the processing of a lot of data that do are not sensitive to the changes we are interested in. We are working on both methods of estimating which parts of the data are most sensitive to changes, as discussed in Andrey's SEG abstract and on focused full-waveform inversion method, as discussed in Di's SEG abstract.

Collaborators: David Nicholls, of the University of Illinois at Chicago

Along with David Nicholls, I am working on methods to rapidly solve the seismic inverse problem for layered media with independent topography on each layer. We (mostly Dave) have done a lot of preliminary algorithmic work available here and here and are hoping to move on to data very soon.

Students

I am currently working with four students:

Gabi Melo is working on seismic interferometry between micro-seismic sources for geothermal energy, with limited receiver coverage.

Alan Richardson is working on combined imaging of multiples and primaries.

Andrey Shabelansky is working with Mike Fehler and I on developing imaging techniques for monitoring Steam Assisted Gravity Drainage.

Di Yang is working with Mike Fehler and I on developing full-waveform inversion methods for CO2 sequestration.

Publications

Journal Articles:

* Where the first author is not the primary or corresponding author of the paper, that author is marked with an asterix.

Poliannikov, O., Malcolm, A., Djikpesse, H. and Prange, M., Interferometric hydrofracture microseism localization using neighboring fracture, Geophysics 76 WC27 DOI:10.1190/geo2010-0325.1

Malcolm, A. E. and Nicholls, D. P.* (2011) A Boundary Perturbation Method for Recovering Interface Shapes in Layered Media, Inverse Problems 27 095009.

Poliannikov, O., Malcolm, A., Djikpesse, H. and Prange, M. (2011), How can we use one fracture to locate another? , The Leading Edge 30 (5) p 551.

Melo, G. and Malcolm, A. (2011), Microquake seismic interferometry with SVD enhanced Green's function recovery The Leading Edge 30 (5) p 556.

Malcolm, A. E., and Trampert, J. (2011), Tomographic Errors from Wavefront Healing: more than just a fast bias, Geophysical Journal International 185 (1), p 385-402.

Malcolm, A. E., and Nicholls, D. P. (2011), A Method of Field Expansions for Scattering by n Periodic Layers, The Journal of the Acoustical Society of America, 129 (4) p 1783.

Malcolm, A. E., de Hoop, M. V., and Ursin, B. (2011) Recursive Imaging with Multiply Scattered Waves using Partial Image Regularization: A North Sea Case Study, Geophysics, 76 B33-B42.

Malcolm, A. E., Ursin, B. and de Hoop, M. V. (2009) Seismic imaging and illumination with internal multiples, Geophysical Journal International, 176 847-64.

Malcolm, A. E., Reitich, F., Yang, J., Greenleaf, J. F. and Fatemi, M. (2008) A combined parabolic-integral equation approach to the acoustic simulation of vibro-acoustic imaging, Ultrasonics, 48 p553-558.

Malcolm, A. E. & Guzina, B. (2008) On the Topological Sensitivity of Transient Acoustic Fields, Wave Motion, 45 821-34.

Malcolm, A. E., de Hoop, M. V., & Calandra, H. (2007), Identifying imaging artifacts from internal multiples, Geophysics, 72 S123.

Malcolm, A. E., & de Hoop, M. V., (2005), A method for inverse scattering based on the generalized Bremmer coupling series, Inverse Problems 21 No. 3 pp 1137-1167.

Malcolm, A. E., de Hoop, M. V., & Le Rousseau, J. H. (2005), The applicability of DMO/AMO in the presence of caustics, Geophysics 70 S1.

Malcolm, A. E., Scales, J. A. & van Tiggelen, B. A. (2004), Retrieving the Green function from diffuse, equipartitioned waves , Phys. Rev. E. 70.

de Hoop, M. V., Malcolm, A. E., & Le Rousseau, J. H. (2003), Seismic wavefield `continuation' in the single scattering approximation: A framework for dip and azimuth moveout,Can. Apply. Math. Q. 10 199-238.

Scales, J. A. & Malcolm, A. E. (2003), Laser characterization of ultrasonic wave propagation in random media , Phys. Rev. E. 67.

Book Chapter:

A. Malcolm, F. Reitich, J. Yang, J. F. Greenleaf, M. Fatemi (2007) "Numerical Modeling for Assessment and Design of Ultrasound Vibroacoustography Systems" in "Biomedical Applications of Vibration and Acoustics in Imaging and Characterisations" editors: M. Fatemi, A. Al-Jumaily and A. Alizad.

SEG Abstracts:

Yang, D., Fehler, M., Malcolm, A. and Huang, L. (2011), Carbon sequestration monitoring with acoustic double-difference waveform inversion: A case study on SACROC walkaway VSP data, SEG Expanded Abstracts 30, 4273, DOI:10.1190/1.3628099

Poliannikov, O., Malcolm, A., Djikpesse, H., and Prange, M., (2011), Interferometric microseism localization using neighboring fracture, SEG Expanded Abstracts 30, 4263, DOI:10.1190/1.3628449

Shabelansky, A. H., Malcolm, A., and Fehler, M. (2011) Visibility analysis using reverse time wave sensitivity for time-lapse target-oriented imaging, SEG Expanded Abstracts 30, 4155, DOI:10.1190/1.3628074

Melo, G. and Malcolm, A. (2011) SVD enhanced seismic interferometry for traveltime estimates between microquakes, SEG Expanded Abstracts 30, 1608, DOI:10.1190/1.3627510.

Poliannikov, O. V. and Malcolm, A. (2010) Detecting medium changes from coda by interferometry, SEG Expanded Abstracts 29, 4227, DOI:10.1190/1.3513751

Melo, G., Malcolm, A., Mikesell, D. and van Wijk, K. (2010) Using SVD for improved interferometric Green's function recovery, SEG Expanded Abstracts 29, 3986, DOI:10.1190/1.3513688

Malcolm, A. and de Hoop M. (2010) Interferometric imaging of multiples in an RTM approach, SEG Expanded Abstracts 29, 3327, DOI:10.1190/1.3513539

Malcolm, A. E., Ursin, B. and de Hoop, M. V. (2008), Subsalt imaging with internal multiples, SEG Expanded Abstracts 27, 2461, DOI:10.1190/1.3063855

Malcolm, A. E., de Hoop, M. V. and Calandra, H. (2005), Estimating imaging artifacts caused by internal multiples, SEG Expanded Abstracts 24, 2111, DOI:10.1190/1.2148129

Malcolm, A. E. and de Hoop, M. V. (2004), Data continuation in the presence of caustics: A synthetic data example, SEG Expanded Abstracts 23, 2060, DOI:10.1190/1.1845197

Malcolm, A. E. and de Hoop, M. V. (2004), Inverse multiple scattering in the downward-continuation approach, SEG Expanded Abstracts 23, 1293, DOI:10.1190/1.1851104

Malcolm, A. E. and Scales, J. A. (2003), Non-contacting ultrasonics for visualizing and exploiting multiple scattering, SEG Expanded Abstracts 22, 1672, DOI:10.1190/1.1817627

Malcolm, A. E., de Hoop, M. V. and Le Rousseau, J. H. (2002) DMO/AMO in the presence of caustics, SEG Expanded Abstracts 21, 2265, DOI:10.1190/1.1817164

Theses:

A. Malcolm, (2005) "Data Regularization for Data Continuation and Internal Multiples," Ph.D. Thesis, Colorado School of Mines, supervisor M. V. de Hoop.

A. Malcolm, " Algorithm Development for the Fast Computation of the Fourier Transform of Unequally Sampled Data with Applications to Seismic and Sediment Core Data" BSc Thesis, University of British Columbia, supervisor T. J. Ulrych.

Teaching Overview

Course websites:

Advanced Seismic Imaging 12.552

Continuum Mechanics 12.005      

Oral communication 12.445

I teach the oil exploration part of 12.021

I advised a benchtop CO2 sequestration experiment in 1.016 in 2010.

Personal

My husband, Scott, and I both hail from the Vancouver area in western Canada, where we still enjoy visiting our families and gawking at the lovely scenery. We are now excited to be exploring the other coast of the continent! Both of us like to travel and spend most of our non-working hours playing with our daughter and just being outdoors.