Giovanni Angelo Meles received a M.Sc. degree in physics from the
Università Statale di Milano, Milan, Italy, in 2004.
In 2007 he moved to Zurich, where in 2011 he earned a Ph.D. degree from
the Swiss Federal Institute of Technology (ETH) under the
supervision of Professors Alan Green, Stewart Greenhalgh, and Jan van
der Kruk. Research Interests: Giovanni's research interests comprise wave scattering and diffraction, imaging, fullwaveform inversion and tomography. Within the context of sourcereceiver interferometry, he has proposed algorithms to analyze multiply diffracted waves based on moveout invariants (Meles and Curtis, 2014b). More recently, he has devised a new methods based on convolutional representation theorems and Marchenko autofocusing (Meles et al., 2015, Meles et al., 2016) to estimate internal multiples or primary reflections . 
Wavefield finite time focusing with reduced spatial exposure. Wavefield focusing is often achieved by timereversal mirrors, where wavefields emitted by a source located at the focal point are evaluated at a closed boundary and sent back, after timereversal, into the medium from that boundary. Mathematically, timereversal mirrors are derived from closedboundary integral representations of reciprocity theorems. In heterogeneous media, timereversal focusing theoretically involves in and output signals that are infinite in time and the resulting waves propagate through the entire medium. Recently, integral representations have been derived for singlesided wavefield focusing. Although the required input signals for this approach are finite in time, the output signals are not and, similar to timereversal mirroring, the resulting waves propagate through the entire medium. Here, an alternative solution for doublesided wavefield focusing is derived. This solution is based on an integral representation where in and output signals are finite in time, and where the energy of the waves propagating in the layer embedding the focal point is smaller than with timereversal focusing. The potential of the proposed method is explored with numerical experiments involving a head model consisting of a skull enclosing a brain.
Normalized L2 norm of the pressure wavefields associated with standard timereversal focusing (a), standard (doublesided) Marchenko focusing (b), and finite time focusing (c), respectively, plotted as functions of space. In standard timereversal focusing (a), the norm of the pressure wavefield exhibits a peak at the focal point [blue arrow in (a)], and significant values are almost homogeneously distributed throughout the model [red arrows in (a)]. A similar distribution, with large values along the focal plane, is obtained when standard (doublesided) Marchenko focusing is used (b). In finite time focusing, the wavefield is still exhibiting a peak at the focal point [blue arrow in (c)] while being somehow confined into a double cone centered at the focal point [blue cones in (c)]. Black and green arrows point at regions of the brain with minimal wavefield propagation and large amplitude spots associated with the propagation of the coda of the focusing functions, respectively. Red and blue dashed lines indicate horizontal and vertical sections used in (d)?(e), respectively. Horizontal (d) and vertical (e) slices of the maps in (a)?(c), plotted in decibel scale (20?log10(?p?)). Black arrows in (d) indicate large portions of the focal plane [red dashed lines in (a)?(c)] where wavefield propagation in finite time focusing is significantly reduced as opposed to timereversal and standard (doublesided) Marchenko focusing. The red and black arrows in (e) indicate zones along the green dashed lines in (a)?(c) where finite time focusing and timereversal focusing involves slightly larger and slightly smaller wavefield intensity, respectively. Green arrows point at zones outside of the skull where standard (doublesided) Marchenko and finite time focusing involve propagation of coda exhibiting large amplitudes [see green arrows in (c)]. 
Virtual planewave imaging via Marchenko redatuming. Marchenko redatuming is a novel scheme used to retrieve up and downgoing Green?s functions in an unknown medium. Marchenko equations are based on reciprocity
theorems and are derived on the assumption of the existence of functions exhibiting space?time focusing properties once
injected in the subsurface. In contrast to interferometry but similarly to standard migration methods, Marchenko redatuming only requires an estimate of the direct wave from the
virtual source (or to the virtual receiver), illumination from only one side of the medium and no physical sources (or receivers) inside the medium.
We propose to consider a different timefocusing condition within the frame of Marchenko redatuming that leads to the retrieval of virtual planewave responses.
As a result, we obtain multiplefree imaging using only a 1D sampling of the targeted model at a fraction of the computational cost of
standard Marchenko schemes. The potential of the new method is demonstrated on 2D synthetic models.
(a) Migration result using the imaging condition of and Marchenko redatumed virtualplane wavefields. The red arrows point at low amplitude artefacts, whereas the blue arrows point at resolved structures not visible in the standard migration image. The red box encircles an area where dipping interfaces are not imaged. (b) Migration result using standard oneway extrapolation of virtualplane wavefields. Red arrows point at multiplerelated artefacts. (c) Migration result using planewave Marchenko wavefields associated with the tilted planes in Fig. 8(c). Blue arrows indicate dipping interfaces now properly imaged. . 
Beyond adaptive subtraction of internal multiples: direct reconstruction of primaries in seismic data sets. Whereas advanced methods of seismic data processing such as
recursive imaging or fullwaveform inversion can properly take into
account data that includes multiply scattered waves, many current
standard processing steps including reversetime migration (RTM) are
based on the socalled Born approximation. This approximation assumes
that waves have only scattered from heterogeneities in the medium once,
thus requiring that data consist only of primaries – singly scattered
energy.
A variety of methods are therefore deployed as preprocessing to predict
multiples (waves reflected several times); however, accurate removal of
those predicted multiples from recorded data using adaptive subtraction
techniques proves challenging, even in cases where they can be
predicted with reasonable accuracy.
To overcome this problem, we propose a new, alternative strategy:
instead of synthetizing and removing multiples, we construct a parallel
data set consisting of only primaries, which is calculated directly from
recorded data. This approach obviates the need for both multiple
prediction and removal methods.
We show how primaries can be constructed using convolutional
interferometry to combine first arriving events of upgoing and
directwave downgoing Green’s functions to virtual receivers in the
subsurface.
The required upgoing wavefields to virtual receivers are constructed by
Marchenko redatuming, a novel technique that estimates up and
downgoing components of Green’s functions between an arbitrary location
inside a medium such as the Earth’s subsurface where no sources (or
receivers) are placed, and real receivers (or sources) located at the
surface.

Fingerprinting ordered diffractions in multiplydiffracted waves We present a method to classify diffractors based on the variation of
acoustic wave travel time variations (their socalled moveouts) across
arrays of sources and receivers. We show that this information is
sufficient to allow the diffraction path of any recorded
multiplydiffracted wave to be determined: each recorded wave can be
associated with the concatenation of an ordered series of known,
irreducible, interdiffractors paths, or equivalently by an ordered
series of singlediffraction interactions. These are determined purely
by data analysis through inspection and comparison of commonsource and
commonreceiver gathers, without the need for synthetic wavefield
computation, or for modelling of the medium through which energy
propagates. The method is effected by a new algorithm that identifies
diffraction paths by wavefield analysis. Applications of the proposed
algorithm within the various fields above range from interpreting
reverberating wave energy associated with multiplydiffracted waves in
terms of the contributions of its individual diffractors, improved
location or characterisation of diffractors or energy sources, removal
of multiplydiffracted energy by muting or filtering to improve the
performance of methods designed only for singlydiffracted energy, and
all of these may lead to improved imaging of the interdiffractors
medium. 
[26] Meles, G.A. , Zhang, L., Thorbecke, J., Wapenaar, K., Slob, E., Datadriven retrieval of primary planewave responses. Submitted to Geophysical Prospecting. [25] Meles, G.A. , van der Neut, J., van Dongen, K., Wapenaar, K., Wavefield finite time focusing with reduced spatial exposure. Journal of the Acoustical Society of America, Volume 145, Pages: 35213530. [24] Meles, G.A., Wapenaar, K., Thorbecke, J., Virtual planewave imaging via Marchenko redatuming. Geophysical Journal International, Volume: 214, Pages: 508519. [23] da Costa Filho, CA., Meles, G.A., Curtis, A., Ravasi M., Kritski A., Imaging strategies using focusing functions with applications to a North Sea field. Geophysical Journal International, Volume: 213, Pages: 561573. [22] da Costa Filho, C., Meles, G.A., Curtis, A., Elastic internal multiple analysis and attenuation using Marchenko and interferometric methods. Geophysics 82 (2), Q1Q12 [21] Löer, K., Curtis, A., Meles, G.A., Relating sourcereceiver
interferometry to an inversescattering series to derive a new method to
estimate internal multiples. Geophysics 81 (3), Q27Q40. [20] Ravasi, M., Vasconcelos, I., Kritski, A., Curtis, A., da
Costa, C., Meles, G. A., Targetoriented marchenko imaging of a North
Sea field. Geophysical Journal International, in press.
[19] Meles, G.A., Wapenaar K., Curtis, A. Synthesising primary reflections by Marchenko redatuming and convolutional interferometry. Geophysics, in press. [18] Meles, G.A., Löer, K., Ravasi, M., Curtis, A., da Costa, C., Internal multiple prediction and removal using Marchenko autofocusing and seismic interferometry. Geophysics, Volume: 80, 2015, Pages: A7A11.
[17] Galetti, E., Curtis, A., Meles, G.A., Baptie, B., Uncertainty Loops
in TravelTime Tomography from Nonlinear Wave Physics. Physical Review
Letter, Volume: 114, 2015, Pages: 148501/15
[16] Ravasi, M., Meles, G.A., Curtis, A., Rawlinson, Z., Liu, Y.,
Seismic interferometry by multidimensional deconvolution without
wavefield separation. Geophysical Journal International, Volume: 221,
2015, Pages: 116. [15] Ravasi, M., Vasconcelos, I., Curtis, A., Meles, G.A., Elastic extended images and velocitysensitive objective functions using multiple reflections and transmissions. Geophysical Journal International, Volume: 202, 2015, Pages: 943960.
[14] Löer, K., Meles, G.A., Curtis, A., Automatic identication of
multiply diffracted waves and their ordered scattering paths. Journal of
the Acoustical Society of America, Volume: 137, 2015, Pages:
18341845. [13] Entwistle, E., Curtis, A., Galetti, E., Baptie, B., Meles, G.A., Constructing new seismograms from old earthquakes: Retrospective seismology at multiple length scales. Journal of Geophysical Research: Solid Earth, Volume: 120, 2015, Pages: 24662490. [12] Meles, G.A., Curtis, A.Discriminating physical and nonphysical diffracted energy in sourcereceiver interferometry. Geophysical Journal International, Volume: 197, 2014, Pages: 16421659. [11] Meles, G.A., Curtis, A.Fingerprinting ordered diffractions in multiply diffracted waves. Geophysical Journal International, Volume: 198, 2014, Pages: 17011713. [10] da Costa, C.A., Ravasi, M., Curtis, A., Meles, G.A. Elastodynamic Green's function retrieval through singlesided Marchenko inverse scattering. Physical Review E, Volume: 90, 2014. [9] Löer, K., Meles, G.A., Curtis, A., Vasconcelos, I. Diffracted and pseudophysical waves from spatially limited arrays using sourcereceiver interferometry (SRI). Geophysical Journal International, Volume: 196, 2013, Pages: 10431059.
[8] Yang, X., Klotzsche, A., Meles, G.A., Vereecken, H., van der Kruk,
J. Improvements in crosshole GPR fullwaveform inversion and application
on data measured at the Boise Hydrogeophysics Research Site. Journal of
Applied Geophysics , Volume: 99, 2013, Pages:114124.
[7] Meles, G.A., Curtis, A. Physical and nonphysical energy in
scattered wave sourcereceiver interferometry. Journal of the Acoustical
Society of America, Volume: 133, 2013, Pages: 37903801. [6] Klotzsche, A., van der Kruk, J., Meles, G., et al. Crosshole GPR fullwaveform inversion of waveguides acting as preferential ow paths within aquifer systems. Geophysics, Volume: 77, 2012, Pages: H57H62. [5] Meles, G.A., Greenhalgh, S.A. Green, A.G., Maurer, H. and Van der Kruk J. GPR Full Waveform Sensitivity and Resolution Analysis using an FDTD Adjoint Method. IEEE Transactions on Geosciences and Remote Sensing, Volume: 50, 2012, Pages: 18811896. [4] Meles, G.A., Greenhalgh, S.A., Van der Kruk, J., Maurer, H. Green, A.G. Taming the nonlinearity problem in GPR fullwaveform inversion for high contrast media. Journal of Applied Geophysics, Volume 73, 2011, Pages: 174186. [3] Klotzsche, A., van der Kruk, J., Meles, G.A., Doetsch, J., Maurer, H., Linde, N. Fullwaveform inversion of crosshole groundpenetrating radar data to characterize a gravel aquifer close to the Thur River, Switzerland. Near surface geophysics 8 (6), 635649[2] Meles, G.A. Van der Kruk, J. Greenhalgh, S.A. Ernst, J.R. Maurer, H. Green, A.G. A New Vector Waveform Inversion Algorithm for Simultaneous Updating of Conductivity and Permittivity Parameters From Combination Crosshole/BoreholetoSurface GPR Data. IEEE Transactions on Geosciences and Remote Sensing, Volume: 48, 2010, Pages:. 33913407.
[1]
Vassena, C., Giudici, M., Ponzini, G., Parravicini, G., Meles, G.A.,
Tomographic Approach to Identify Transmissivity with Differential System
Method, Journal of Hydrologic Engineering, Volume:
12, 2007, Pages: 617625.
Education: 2nd5th September 2016: Marie
Curie WAVES workshop in Doorn, The Netherlands.
17th21st September 2015: Marie
Curie WAVES workshop in Pitlochry, Scotland (UK).
April 2009: 26 Lessons Course on Writing Research Papers for Publication
held by Thomas Armstrong in Zurich (Switzerland).
12th16th May 2008: Course on New Geophysical tools for Hydrological Investigations, held in Zurich (Switzerland).
September 2007: 42 Hours Course on inverse problems, held by Albert Tarantola in Neuchatel (Switzerland). Focus on basic inversion theory, nonlinear inversion, fullwaveform inversion.
