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  • 1
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    Hypocentre location: Genetic algorithms incorporating problem-specific information (1994)
    In:  Geophys. J. Int., Warszawa, Elsevier, vol. 118, no. 1-2, pp. 693-706, pp. 1960, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1994
    Keywords: Location ; Seismology ; Hypocentral depth ; Data analysis / ~ processing ; GJI
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Earthquake location - genetic algorithms for teleseisms (1992)
    In:  Phys. Earth Plan. Int., New York, Allerton Press, vol. 75, no. 19, pp. 103-110, pp. L01606, (ISSN: 1340-4202)
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    Publication Date: 1992
    Keywords: Seismology ; Location ; Teleseismic events ; PEPI
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Seismic source characterization using a neighbourhood algorithm (2000)
    In:  Geophys. Res. Lett., New York, Allerton Press, vol. 27, no. 20, pp. 3401-3404, pp. L01606, (ISSN: 1340-4202)
    Details
    Publication Date: 2000
    Keywords: Source ; Seismology ; 3260 ; Mathematical ; geophysics ; (new ; field) ; Inverse ; theory ; 7215 ; Seismology ; Earthquake ; parameters ; 7219 ; Nuclear ; explosion ; seismology ; 7260 ; Theory ; and ; modeling ; Modelling ; Nuclear explosion ; Inversion ; GRL
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    A novel method of hypocenter location (1986)
    In:  Geophys. J. R. astr. Soc., Basel, Inst. f. Geophys., Ruhr-Univ. Bochum, vol. 87, no. 6, pp. 679-697, pp. 2085, (ISSN: 1340-4202)
    Details
    Publication Date: 1986
    Keywords: Seismology ; Location ; GJRaS
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    Boundary value ray tracing in a heterogeneous medium: a simple and versatile algorithm (1990)
    In:  Geophys. J. Int., Basel, Inst. f. Geophys., Ruhr-Univ. Bochum, vol. 101, no. 6, pp. 157-168, pp. 2085, (ISSN: 1340-4202)
    Details
    Publication Date: 1990
    Keywords: Ray tracing ; Seismics (controlled source seismology) ; Inhomogeneity ; GJI
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    BIBLIOGRAPHY SEISMOLOGY
  • 6
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    Seismic event location: nonlinear inversion using a neighbourhood algorithm (2001)
    In:  Pageoph, Basel, Inst. f. Geophys., Ruhr-Univ. Bochum, vol. 158, no. 1-2, pp. 241-257, pp. 2085, (ISSN: 1340-4202)
    Details
    Publication Date: 2001
    Keywords: Seismology ; Seismic networks ; Nuclear explosion ; PAG
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    BIBLIOGRAPHY SEISMOLOGY
  • 7
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    Seismic traveltime tomography of the crust and lithosphere (2003)
    In:  Advances in Geophys., Tübingen, Institut und Museum für Geologie und Paläontologie, vol. 46, no. 1-4, pp. 81-198, pp. 2017, (ISSN: 1340-4202)
    Details
    Publication Date: 2003
    Keywords: Tomography ; Seismology ; Review article
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    BIBLIOGRAPHY SEISMOLOGY
  • 8
    Electronic Resource
    Electronic Resource
    Hypocentre location: genetic algorithms incorporating problem-specific information (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 118 (1994), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: This paper shows how the performance of a fully non-linear earthquake location scheme can be improved by taking advantage of problem-specific information in the location procedure. The genetic algorithm is best viewed as a method of parameter space sampling that can be used for optimization problems. It has been applied successfully in regional and teleseismic earthquake location when the network geometry is favourable. However, on a series of test events with unfavourable network geometries the performance of the genetic algorithm is found to be poor.We introduce a method to separate the spatial and temporal parameters in such a way that problems related to the strong trade-off between depth and origin time are avoided. Our modified algorithm has been applied to several test events. Performance over the unmodified algorithm is improved substantially and the computational cost is reduced. The algorithm is better suited to the determination of hypocentral location whether using arrival times, array information (slowness and azimuth) or a combination of both.A second type of modification is introduced which exploits the weak correlation between the epicentral parameters and depth. This algorithm also improves performance over the standard genetic algorithm search, except in circumstances where the depth and epicentre are not weakly correlated, which occurs when the azimuthal coverage is very poor, or when azimuth and slowness information are incorporated. On a shallow nuclear explosion with only teleseismic P arrivals available, the algorithm consistently converged to a depth very close to the true depth, indicating superior depth estimation for shallow earthquake locations over the unmodified algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1994.tb03994.x
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  • 9
    Electronic Resource
    Electronic Resource
    Non-linear arrival time inversion: constraining velocity anomalies by seeking smooth models in 3-D (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 102 (1990), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The problem of constraining 3-D seismic anomalies using arrival times from a regional network is examined. The non-linear dependence of arrival times on the hypocentral parameters of the earthquakes and the 3-D velocity field leads to a multiparameter-type non-linear inverse problem, and the distribution of sources and receivers from a typical regional network results in an enormous 3-D variation in data constraint. To ensure computational feasibility, authors have tended to neglect the non-linearity of the problem by linearizing about some best-guess discretized earth model. One must be careful in interpreting 3-D structure from linearized inversions because the inadequacy of the data window may combine with non-linear effects to produce artificial or phantom ‘structure’.To avoid the generation of artificial velocity gradients we must determine only those velocity variations which are necessary to fit the data rather than merely estimating local velocities in different parts of the model, which is the more common practice. We present a series of inversion algorithms which seek to inhibit the generation of unnecessary structure while performing efficiently within the framework of a large-scale inversion. This is achieved by extending the subspace method of Kennett, Sambridge & Williamson (1988) and incorporating the smoothing strategy proposed by Constable, Parker & Constable (1987). A flexible model parametrization involving Cardinal spline functions is used, and full 3-D ray tracing performed. A comparison between linear and non-linear inversions shows that if a breakdown in the linearizing approximation occurs spurious velocity models may be obtained which would appear acceptable in a linear inversion. Application of the techniques to a SE Australian data set show that unnecessary structure can be suppressed. As the smoothing power of the algorithm is improved a robust low-velocity anomaly dipping to the north becomes the most dominant feature of the P-wave model and much of the complex structure of pure data-fitting models is removed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1990.tb04588.x
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  • 10
    Electronic Resource
    Electronic Resource
    Boundary value ray tracing in a heterogeneous medium: a simple and versatile algorithm (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 101 (1990), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Traveltime calculations in 3-D velocity models have become more commonplace during the past decade or so. Many schemes have been developed to deal with the initial value problem, which consists of tracing rays from a known source position and trajectory usually towards some distant surface. Less attention has been given to the more difficult problem of boundary value ray tracing in 3-D. In this case, source and receiver positions are known and one, or more, minimum time paths are sought between fixed endpoints.A new technique for boundary value ray tracing is proposed. The scheme uses a common numerical integration technique for solving the initial value problem and iteratively updates the take-off angles until the ray passes through the receiver. This type of ‘shooting’ technique is made efficient by using expressions describing the geometrical spreading of the wavefront to determine the relationship between the ray position at any time and the take-off angles from the source. The use of numerical integration allows the method to be compatible with a wide variety of structures. These include models with velocity varying smoothly as a function of position and those with arbitrarily orientated surfaces of discontinuity. An examination of traveltime accuracy is given as well as a discussion of efficiency for a few classes of velocity model.To improve upon the first guess pair of take-off angles, a small-scale non-linear inverse problem must be solved. The difference between the receiver position and the arrival point of a ray, on a plane through the receiver, describe a mis-match surface as a function of the two take-off angles of the ray. The shape of this surface can possess local minima and multiple ‘global’ minima even for relatively simple 1-D velocity models. Its study provides some insight into the non-linearities of a small-scale geophysical inverse problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1990.tb00765.x
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