NEA-0592 FALT.

FALT, Orientation of Double Coupled Earthquake Source with Given Amplitudes

NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROBLEM OR FUNCTION, METHOD OF SOLUTION, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, UNUSUAL FEATURES OF THE PROGRAM, RELATED AND AUXILIARY PROGRAMS, STATUS, REFERENCES, MACHINE REQUIREMENTS, LANGUAGE, OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED, OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHOR, MATERIAL, CATEGORIES

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1. NAME OR DESIGNATION OF PROGRAM: FALT.

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2. COMPUTERS

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Program name	Package id	Status	Status date
FALT	NEA-0592/01	Tested	01-JUL-1980

Machines used:

Package ID	Orig. computer	Test computer
NEA-0592/01	IBM 3033	IBM 3033

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3. DESCRIPTION OF PROBLEM OR FUNCTION

FALT is a FORTRAN computer program which determines the orientation (with confidence limits) of an assumed double couple earthquake source, given a series of teleseismically observed relative amplitudes, each of which relates the amplitudes of either P and pP, or P and sP, or pP and sP on one seismogram. Appropriate upper and lower limits are assigned in arbitrary units to the observed amplitude of each phase, with or without a polarity specification, and from these limits the program computes the corresponding range(s) of relative amplitudes for each pair of phases. All source orientations which are compatible with the range(s) of relative amplitudes are then identified, and can be displayed graphically. Those orientations which are compatible with all pairs of phases at all stations constitute the focal mechanism solution, with confidence limits which correspond directly to the confidence of the initial measurements. The program can be applied to shallow or deep earthquakes beneath land or sea.

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4. METHOD OF SOLUTION: See (3).

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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM: See (3).

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6. TYPICAL RUNNING TIME

Approximately 6 mins. CPU time on the IBM 370/168 for "typical data set" in data file, but depends entirely on resolution required.

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7. UNUSUAL FEATURES OF THE PROGRAM

The program uses graphic output as the normal method of presenting results. The graphics are generated using subroutine PLOTV. The attached note "Blacknest Graphics" explains the meaning of the graphics calls in subroutine PLOTV.

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8. RELATED AND AUXILIARY PROGRAMS

Subroutine PLOTV (included in File 1 of tape) - generates graphics for FALT.

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9. STATUS

Package ID	Status date	Status
NEA-0592/01	01-JUL-1980	Tested at NEADB

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10. REFERENCES

- R.G. Pearce:
Applications of the Program - Fault Plane Solutions Using Relative    Amplitudes of P and pP
  Geophys. J. R. Astr. Soc., 50, 381-394 (1977).
- R.G. Pearce:
  Fault Plane Solutions Using Relative Amplitudes of P and Surface
  Reflections: Further Studies
  Geophys. J. R. Astr., Soc., 60 (in press), (1980).

NEA-0592/01, included references:

- R.G. Pearce:
  Guide to the Program - Earthquake Focal Mechanisms for Relative
  Amplitudes of P, pP and sP: Method and Computer Program
  HMSO Report No. AWRE 0 41/79 (1979) + Addendum.

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11. MACHINE REQUIREMENTS

256 K bytes to run but requires more to compile. Requirement to run can be altered to suit available resources, with consequent loss or gain of resolution.

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12. PROGRAMMING LANGUAGE(S) USED

Package ID	Computer language
NEA-0592/01	FORTRAN-IV

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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED

Multiple Virtual Storages, but the program does not exploit the MVS features.

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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

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15. NAME AND ESTABLISHMENT OF AUTHOR

          Dr. R. G. Pearce
          MOD (PE)
          Blacknest
          Brimpton
          Reading, Berkshire, RG7 4RS
          United Kingdom.

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16. MATERIAL AVAILABLE

NEA-0592/01

File name	File description	Records
NEA0592_01.001	INFORMATION	20
NEA0592_01.002	SOURCE (F4,EBCDIC)	3069
NEA0592_01.003	SAMPLE PROBLEM INPUT	482
NEA0592_01.004	SAMPLE PROBLEM OUTPUT	20320

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17. CATEGORIES

R. Environmental and Earth Sciences

Keywords: environmental effects, seismic effects.