Review paper: Virtual sources and their responses,Part II: data‐driven single‐sided focusing          下载免费PDF全文

Kees Wapenaar  Jan Thorbecke  Joost van der Neut  Evert Slob  Roel Snieder 《Geophysical Prospecting》2017,65(6):1430-1451

In Part I of this paper, we defined a focusing wave field as the time reversal of an observed point‐source response. We showed that emitting a time‐reversed field from a closed boundary yields a focal spot that acts as an isotropic virtual source. However, when emitting the field from an open boundary, the virtual source is highly directional and significant artefacts occur related to multiple scattering. The aim of this paper is to discuss a focusing wave field, which, when emitted into the medium from an open boundary, yields an isotropic virtual source and does not give rise to artefacts. We start the discussion from a horizontally layered medium and introduce the single‐sided focusing wave field in an intuitive way as an inverse filter. Next, we discuss single‐sided focusing in two‐dimensional and three‐dimensional inhomogeneous media and support the discussion with mathematical derivations. The focusing functions needed for single‐sided focusing can be retrieved from the single‐sided reflection response and an estimate of the direct arrivals between the focal point and the accessible boundary. The focal spot, obtained with this single‐sided data‐driven focusing method, acts as an isotropic virtual source, similar to that obtained by emitting a time‐reversed point‐source response from a closed boundary.  相似文献   

Solving large linear inverse problems by projection   总被引：2，自引：0，他引：2  

Guust Nolet  Roel Snieder 《Geophysical Journal International》1990,103(2):565-568

  相似文献   

Altimetry with GNSS-R interferometry: first proof of concept experiment   总被引：1，自引：0，他引：1  

Antonio Rius  Oleguer Nogués-Correig  Serni Ribó  Estel Cardellach  Santi Oliveras  Enric Valencia  Hyuk Park  José Miguel Tarongí  Adriano Camps  Hans van der Marel  Roel van Bree  Bas Altena  Manuel Martín-Neira 《GPS Solutions》2012,16(2):231-241

The Global Navigation Satellite System Reflectometry (GNSS-R) concept was conceived as a means to densify radar altimeter measurements of the sea surface. Until now, the GNSS-R concept relied on open access to GNSS transmitted codes. Recently, it has been proposed that the ranging capability of the technique for ocean altimetric applications can be improved by using all the signals transmitted in the bandwidth allocated to GNSS, which includes open access as well as encrypted signals. The main objective of this study is to provide experimental proof of this enhancement through a 2-day experiment on the Zeeland Bridge (The Netherlands). In the experiment, we used a custom built GNSS-R system, composed of high gain GPS antennas, calibration subsystem, and an FPGA-based signal processor which implemented the new concepts, an X-band radar altimeter and a local geodetic network. The results obtained indicate that the new approach produces a significant improvement in GNSS-R altimetric performance.  相似文献   

Real-time single-frequency precise point positioning: accuracy assessment   总被引：1，自引：1，他引：0  

Roel J. P. van Bree  Christian C. J. M. Tiberius 《GPS Solutions》2012,16(2):259-266

The performance of real-time single-frequency precise point positioning is demonstrated in terms of position accuracy. This precise point positioning technique relies on predicted satellite orbits, predicted global ionospheric maps, and in particular on real-time satellite clock estimates. Results are presented using solely measurements from a user receiver on the L1-frequency (C1 and L1), for almost 3?months of data. The empirical standard deviations of the position errors in North and East directions are about 0.15?m, and in Up direction about 0.30?m. The 95% errors are about 0.30?m in the horizontal directions, and 0.65?m in the vertical. In addition, single-frequency results of six receivers located around the world are presented. This research reveals the current ultimate real-time single-frequency positioning performance. To put these results into perspective, a case study is performed, using a moderately priced receiver with a simple patch antenna.  相似文献   

Correcting for bias due to noise in coda wave interferometry     

Huub Douma  Roel Snieder 《Geophysical Journal International》2006,164(1):99-108

  相似文献   

Monitoring in situ stress changes in a mining environment with coda wave interferometry   总被引：2，自引：0，他引：2  

Alexandre Grêt  Roel Snieder  U&#;ur Özbay 《Geophysical Journal International》2006,167(2):504-508

  相似文献   

3-D linearized scattering of surface waves and a formalism for surface wave holography   总被引：3，自引：1，他引：2  

Roel Snieder 《Geophysical Journal International》1986,84(3):581-605

Summary. Scattering of surface waves by lateral heterogeneities is analysed in the Born approximation. It is assumed that the background medium is either laterally homogeneous, or smoothly varying in the horizontal direction. A dyadic representation of the Green's function simplifies the theory tremendously. Several examples of the theory are presented. The scattering and mode conversion coefficients are shown for scattering of surface waves by the root of an Alpine-like crustal structure. Furthermore a 'great circle theorem'in a plane geometry is derived. A new proof of Snell's law is given for surface wave scattering by a quarter-space. It is shown how a stationary phase approximation can be used to simplify the Fourier synthesis of the scattered wave in the time domain. Finally a procedure is suggested to do 'surface wave holography'.  相似文献   

The contrast in upper mantle shear-wave velocity between the east european platform and tectonic Europe obtained with genetic algorithm inversion of rayleigh-wave group dispersion     

Anthony Lomax  Roel Snieder 《Geophysical Journal International》1995,123(1):169-182

  相似文献   

An evaluation of the implicit management procedure used for some ICES roundfish stocks   总被引：1，自引：5，他引：1  

Kell  L.T.; Pilling  G.M.; Kirkwood  G.P.; Pastoors  M.; Mesnil  B.; Korsbrekke  K.; Abaunza  P.; Aps  R.; Biseau  A.; Kunzlik  P.; Needle  C.; Roel  B.A.; Ulrich-Rescan  C. 《ICES Journal of Marine Science》2005,62(4):750-759

  相似文献   

Topography of the 400 km discontinuity from observations of long-period P₄₀₀P phases     

Filip Neele  Roel Snieder 《Geophysical Journal International》1992,109(3):670-682

  相似文献