atten

Group:

SYNTH

Authors:

Igor B. Morozov, 8/97.

Forward atenuation-filtering added from tool ACOMP; 03/2015

Module description:

Applies attenuation filtering to seismic data.

The attenuation filter is based on travel times and can be designed in two ways:

  1. A causal attenuation operator applied to the whole trace (Aki and Richards, 1980). This option is sutable when modeling interested in first arrivals only or in a specific seismic phase.

    The operator is parameterized by the value of t* and the "reference frequency" at which the phase of the signal remains unchanged.

  2. Time-variant attenuation due to various factors, as described in tool ACOMP. This attenuation may include several types of geometric spreading, multiple time-dependent and frequency-dependent Q laws, and scattering. Time-dependences of various factors can be based on the time in the trace or on vertical-incidence time derived in a velocity model. See toool ACOM for details. Most parameter lists are also shared with tool ACOMP.

The two attenuation methods above can also be combined.

See also:

acomp

Module call format:

*call ATTEN MODE TSTAR REFFREQ

Global list parameter(s):

MODE

 Operation mode:
  • STACK - Processing stacked data. This means that parameterization of the various models (velocity, attenuation, geometric spreading) is done in terms of the trace time.
  • PRESTCK - Pre-stack processing. In this case, parameterization of the various models (velocity, attenuation, geometric spreading) is done in terms of the normal-incident travel time, which is obtained by jusing the RMS (list M-RVMS) or interval velocities (list M-VINT)
    •  In each of thes modes, each trace is processed independently of other traces.
    • Format: Selection
    • Selectable Values: (codes in parentheses)
      • Stack (STACK)
      • Prestack (PRESTCK)
    • Default value: STACK

    TSTAR

    		 Apparent attenuation: t* = Integral ( dt/Q ), where t is the wave travel time, ms
    • Format: Trace Header (table entry), name, or numerical value (8 characters)
    • Default value: 0 (no attenuation)

    REFFREQ

    		 Reference frequency (Hz) at which the phase response of the attenuation filter equals zero
    • Format: Trace Header (table entry), name, or numerical value (8 characters)
    • Default value: No default allowed
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    References:

    Aki and Richards, 2002

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    IGeoS version 5.1
    Copyright (c) 1995-2015, I.B.Morozov
    Updated Wed Apr 1 21:42:25 2020