Local earthquake tomography between rays and waves: fat ray tomography

Abstract The limitations of ray-based forward solutions in seismic tomography are theoretically well known. To correctly represent the physical forward problem in seismic tomography, application of full three-dimensional (3-D) wave theory would be required. Up to now this is not possible for the size of a typical local earthquake study. With the concept of fat rays resembling the waves Fresnel volume, a more complete, physically consistent and accurate solution to the forward problem is available. In this paper, we present an approach to include fat rays in local earthquake tomography, called Fatomo. The comparative study with synthetic data and inversion results with Fatomo and a ray-based approach to local earthquake tomography, SIMULPS, reveals new insights into the role of resolution and model parameterization in local earthquake tomography. Intuitively expected effects of fat rays on resolution estimates, such as higher node sampling values and lower resolution diagonal element values for wider fat rays can be seen in the results. For ideal model parameterization, differences between fat ray and ray tomography are small. Our results document, however, that the influence of model parameterization is less critical for fat ray tomography than for ray tomography.

[1]  M. Worthington,et al.  Resolution limits in ray tomography due to wave behavior: Numerical experiments , 1993 .

[2]  Clifford H. Thurber,et al.  Earthquake locations and three‐dimensional crustal structure in the Coyote Lake Area, central California , 1983 .

[3]  J. Hagedoorn,et al.  A process of seismic reflection interpretation , 1954 .

[4]  Ernst R. Flueh,et al.  Local earthquake tomography of shallow subduction in north Chile: A combined onshore and offshore study , 2000 .

[5]  Ray perturbation theory, dynamic ray tracing and the determination of Fresnel zones , 1998 .

[6]  G. D. Nelson,et al.  Earthquake locations by 3-D finite-difference travel times , 1990, Bulletin of the Seismological Society of America.

[7]  Marta Woodward,et al.  Wave-equation tomography , 1992 .

[8]  Guust Nolet,et al.  Fréchet kernels for finite‐frequency traveltimes—II. Examples , 2000 .

[9]  Clifford H. Thurber,et al.  User's manual for SIMULPS12 for imaging vp and vp/vs; a derivative of the "Thurber" tomographic inversion SIMUL3 for local earthquakes and explosions , 1994 .

[10]  E. Kissling,et al.  Model parametrization in seismic tomography: a choice of consequence for the solution quality , 2001 .

[11]  Jean Virieux,et al.  Ray tracing in 3-D complex isotropic media: An analysis of the problem , 1991 .

[12]  Philip B. Stark,et al.  Toward tubular tomography , 1993 .

[13]  Clifford H. Thurber,et al.  A fast algorithm for two-point seismic ray tracing , 1987 .

[14]  D. Eberhart‐Phillips,et al.  Three‐dimensional P and S velocity structure in the Coalinga Region, California , 1990 .

[15]  J. Virieux,et al.  Three‐dimensional velocity structure and earthquake locations beneath the northern Tien Shan of Kyrgyzstan, central Asia , 1998 .

[16]  J. Vidale.  Finite-difference calculation of travel times , 1988 .

[17]  E. L. Majer,et al.  Wavepath traveltime tomography , 1993 .

[18]  Florian Haslinger,et al.  Velocity structure, seismicity and seismotectonics of northwestern Greece between the Gulf of Arta and Zakynthos , 1998 .

[19]  D. Eberhart‐Phillips,et al.  Three-dimensional velocity structure in northern California Coast Ranges from inversion of local earthquake arrival times , 1986 .

[20]  Guust Nolet,et al.  Wave front healing and the evolution of seismic delay times , 2000 .

[21]  John A. Hole,et al.  3-D finite-difference reflection travel times , 1995 .

[22]  J. Virieux,et al.  Seismic tomography of the Gulf of Corinth: a comparison of methods , 1997 .

[23]  E. Papadimitriou,et al.  3D crustal structure from local earthquake tomography around the Gulf of Arta (Ionian region, NW Greece) , 1999 .

[24]  Guust Nolet,et al.  Fréchet kernels for finite-frequency traveltimes—I. Theory , 2000 .

[25]  P. Podvin,et al.  Finite difference computation of traveltimes in very contrasted velocity models: a massively parallel approach and its associated tools , 1991 .

[26]  J. Garmany,et al.  Smoothing operators for waveform tomographic imaging , 1993 .

[27]  John A. Hole,et al.  Nonlinear high‐resolution three‐dimensional seismic travel time tomography , 1992 .

[28]  J. Virieux.  Fast and accurate ray tracing by Hamiltonian perturbation , 1991 .

[29]  Urs Kradolfer,et al.  Initial reference models in local earthquake tomography , 1994 .

[30]  J. Vidale.  Finite‐difference calculation of traveltimes in three dimensions , 1990 .

[31]  Vlastislav Cerveny,et al.  Fresnel volume ray tracing , 1992 .

[32]  Gerard T. Schuster,et al.  Wave-equation traveltime inversion , 1991 .

[33]  C. Thurber,et al.  ADVANCES IN TRA VEL-TIME CALCULATIONS FOR THREE-DIMENSIONAL STRUCTURES , 2000 .

[34]  Malcolm Sambridge,et al.  A novel method of hypocentre location , 1986 .

[35]  R. V. Allen,et al.  Automatic phase pickers: Their present use and future prospects , 1982 .

[36]  Edi Kissling,et al.  Geotomography with local earthquake data , 1988 .

[37]  Guust Nolet,et al.  Three-dimensional sensitivity kernels for finite-frequency traveltimes: the banana–doughnut paradox , 1999 .

[38]  李幼升,et al.  Ph , 1989 .

[39]  E. Kissling,et al.  Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network , 1999 .

[40]  John E. Peterson,et al.  Beyond ray tomography: Wavepaths and Fresnel volumes , 1995 .

[41]  M. Kvasnička,et al.  3-D network ray tracing , 1994 .