readme

这是一层析静校正的源码

	This is a README to the FATOMO code (Ver. Oct., 2000)
	 
	  to give a brief overview how to use fatomo 
	  describing the different input & output files.

	  

	  						Dr. St. Husen
							Inst. of Geophysics
							ETH-Hoenggerberg
							8057 Zurich
							Switzerland



					PHONE: ++41-1-6332622
	  				EMAIL: [e-mail]


					Jan., 2001
	  					

  GENERAL REMARKS



    FATOMO inverts for 3D Vp-velocity structure using the fat ray concept (Husen
    & Kissling, Phys. Earth Planet. Int., 123, 127-147, 2001. Travel times are 
    calculated using a FD-scheme proposed by Podvin & Lecomte (Geophys. J.  
    Int., 105, 271-284, 1991). Fat rays resembling Fresnel volumes are used to 
    compute model partial derivatives.

    For more information on the fat ray concept please visit the webpage:
   
    	www.sg.geophys.ethz.ch/aes/husen
 
    FATOMO solves the hypocentral part of the coupled hypocenter-velocity
    problem using a grid search algorithm. The grid search algorithm implemented
    in FATOMO requires well-locatable events and hypocenter locations close to
    the true location, f.e. obtained by relocating the events with a minimum 1D 
    model with including station corrections. The grid search is performed over 
    two grids: First on the coarse, seismic grid and second on the fine
    numerical grid.
    Search radius for the search on the seismic grid is given in the CNTL file 
    in x,y,z direction and in km. The initial search radius show include several
    seismic grid nodes in each direction to ensure that the global minimum is
    included. For the second search on the numerical grid, a box is set up with
    its center at the location of the lowest RMS value of the initial search
    with sided defined by the surrounding seismic grid nodes. For each
    hypocenter location the 2 sigma interval (corresponding to the 95%
    confidence interval) is given in x,y,z direction. 

    A few words to memory handling of FATOMO: Computation of the fat rays
    requires both traveltime fields of the source and the receiver to be
    computed. Traveltime fields of the receivers are calculated ahead of each 
    inversion and stored on disk (files: recXXX.tmp) to reduce RAM allocation 
    of FATOMO. To reduce the burden of loading traveltime fields 
    from disk, traveltime fields for all stations observing the event are read 
    from disk prior to relocation resp. fat ray computation. These traveltime 
    fields are stored in the 2-D array "tt_obs", which is of the dimension 
    maxobs x maxblocks (maxobs: max no. obs per event; maxblocks: max no.  
    cells of the FD grid). Therefore memory allocated by FATOMO depends on the
    size of the velocity model (max. dimension in x,y,z km) and on the maximum 
    numbers of observations per event. The included testcase allocates 260 
    MBytes of RAM (maxobs=25, maxblocks=200x200x100). If your data set is 
    larger, you must modify the corresponding variables in the include file 
    "fatomo_common.inc".

    Parts of the code, i.e. input routines and inversion routines, were
    taken from the SIMULPS13Q code. 
  
  MODEL SET UP
  
    Fatomo uses three different grids in the inversion. 
    The SEISMIC grid consists of grid nodes at intersecting lines with 
    linear interpolation in between as in SIMULPS13Q. Node spacing can be
    uneven and node positions will be given relative to the short distance 
    conversion origin, where east and south are NEGATIVE.
     
    The INVERSION grid consist of blocks, which are defined by their edges 
    in x,y,z. Thereby,two restrictions have to be met:
    A possible block edge must be located at the midpoint between two seismic 
    grid points and spacing must be a MULTIPLE of the numerical gridspacing. 
    By omitting block edges it is possible to combine several seismic grid
    nodes to one inversion block.

    It is possible to vary the number of inversion block edges, i.e. the number
    of inversion blocks, for each layer. This allows, for example, larger 
    inversion blocks with increasing depth to account for decreasing ray 
    coverage. Inversion block edges must be given for each layer in the MOD file
    (see below). Similar to SIMULPS13Q inversion blocks can be individually 
    a priori fixed during the inversion. Inversion blocks to be fixed are 
    specified by their i,j,k-index (i.e. number in x,y,z direction). First block
    which can be fixed is 1,1,1 located in the lower left corner of the first 
    inversion layer.

    The NUMERICAL grid is used by the FD modeling to compute synthetic 
    travel times. Since the FD-scheme uses a left-handed coordinate system,
    origin of the numerical grid is at the lower left corner (relative to the 
    xy-plane) of the seismic grid. Internally, all station & event coordinates 
    are transformed relative to this origin. Grid spacing of the numerical grid
    is given in the control file and should be as fine as possible. Velocities 
    are linearly extrapolated from the coarser seismic grid. 
    
    NOTE: Due to the definition within the Podvin and Lecomte FD-code 
    velocities in those cells with the highest number, i.e. located at right
    and upper boundary of the model, are set to infinity. Therefore design
    the seismic grid at least one grid spacing larger than required by the 
    station and event distribution.

    Seismic grid nodes and inversion block boundaries are given in the model
    inputfile 'MOD' (see below). Its structure is equivalent to that of 
    SIMULSPS13Q with one EXCEPTION: the position of grid nodes resp. block edges
    in x-direction must be arranged in DECREASING order, because the origin 
    of the numerical grid is at the lower left. In y- and z-direction positions
    are arranged in INCREASING order.

    Counting of seismic grid nodes resp. inversion blocks start at the origin 
    of the numerical grid, i.e. LOWER LEFT corner of the first layer.
    This is contrary to SIMULPS13Q where the first grid node is located at the
    lower right corner. 

    The MOD-file starts with the number of block edges (inv_nz) of the inversion
    grid in z-direction (free format) followed by their position. For each layer
    of the inversion grid (inv_nz-1) the layer number and the number of
    inversion block edges in x and y-direction are given next followed by their
    position (one line for each direction). First and last inversion block edges
    define the model dimension in x,y,z.
    The seimic grid is given by the number of seismic grid nodes (including
    seismic grid nodes at the model boundaries) in x,y,z direction followed by
    their position (one line for each direction).
    Following the seismic grid is a list of inversion blocks  which are a 
    priori fixed during the inversion. The list terminates with '  0  0  0'.
    Finally, the initial velocities are given for each grid node starting with 
    the UPPER LEFT corner of the top layer. X-direction is the fastest index. 
    If the model consists of more than 20 grid nodes in x-direction, a new line 
    must be open for the next 20 grid nodes. 

    Format of the MOD-file is a free-format (*). Position of inversion block 
    edges and seismic grid nodes are given relative to origin of short distance
    origin (E and S are NEGATIVE).

    
    Example MOD file (see Testcase):
   
    12  # inversion grid
   -4.0 1.0 3.0 4.5 7.5 12.5 17.5 22.5 27.5 32.5 37.5 40.0
    1 15 15 
    80.0 72.5 62.5 57.5 52.5 47.5 42.5 37.5 32.5 27.5 22.5 17.5 12.5 5.0 0.0
    0.0 5.0 12.5 17.5 22.5 27.5 32.5 37.5 42.5 47.5 52.5 57.5 62.5 72.5 80.0
    2 15 15 
    80.0 72.5 62.5 57.5 52.5 47.5 42.5 37.5 32.5 27.5 22.5 17.5 12.5 5.0 0.0
    0.0 5.0 12.5 17.5 22.5 27.5 32.5 37.5 42.5 47.5 52.5 57.5 62.5 72.5 80.0
    
    .....

    4 8 8
    80.0 62.5 52.5 42.5 32.5 22.5 12.5 0.0
    0.0 12.5 22.5 32.5 42.5 52.5 62.5 80.0 

    .....
    
    10 15 15 
    80.0 72.5 62.5 57.5 52.5 47.5 42.5 37.5 32.5 27.5 22.5 17.5 12.5 5.0 0.0
    0.0 5.0 12.5 17.5 22.5 27.5 32.5 37.5 42.5 47.5 52.5 57.5 62.5 72.5 80.0 
    14 14 11  # seismic grid   
    80.0 65.0 60.0 55.0 50.0 45.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0 0.0
    0.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 80.0 
    -4.0 0.0 2.0 4.0 5.0 10.0 15.0 20.0 25.0 30.0 40.0
    1  1  1  # inv. blocks a priori fixed
    1  1  4
    1  1  5
    1  1  6
    0  0  0
 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00
 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 ......



     CONTROL FILE (file CNTL)



     Control parameters are given via the file CNTL. Comments start with