Visual Picker (VIP)

Visual Picker or VIP (Aldersons, 2004) is a MS-Windows companion program to MannekenPix.

The main use of Visual Picker is to build a Reference subset of hand-picked arrival times and weights necessary to calibrate the weighting engine of MannekenPix on a particular data set. Since Visual Picker integrates the Wiener filter of MPX and visual tools for the determination of the Reference picking uncertainty, it is the recommended software for building the Reference set of an MPX project.

Visual Picker can also be used to quickly get a feeling about how the filtering and picking routines of MPX behave on a particular data set, and to help finding appropriate values for the MPX parameters.

Visual Picker screenshots

The Visual Picker screenshot below displays a noisy unfiltered seismogram (yellow) with a Routine Pick (dark blue line) at about 58.0 sec. Visual Picker, as MPX, samples the data in a first and early window (red ribbon) to estimate the power spectral density of a Noise segment, and samples the data in a second and later window (bluish ribbon) to estimate the power spectral density of a Signal + Noise segment. The spectral densities are estimated using the Maximum Entropy Method (MEM), a method particularly well suited to short data segments. The two windows are 2-seconds long each in this example of local data from the Dead Sea basin, where epicentral distances do not exceed 340 km.

The Unfiltered spectra on the next plot are the power spectra before the application of the Wiener Filter, while the Filtered spectra are the power spectra in the sampling windows defined earlier after the application of the Wiener Filter. Only one Wiener Filter is computed (before filtering) but it is displayed in both Frequency plots.

The pink vertical line on the plot below is a tentative manual Reference pick on the unfiltered seismogram (yellow). Since the onset is not well defined, a Reference weight of 2 is selected. The outer solid lines on both sides of the reference pick define the interval of picking uncertainty for current weight class 2, while the two inner dashed lines define the picking uncertainty for weight class 1.

On the filtered seismogram (green), the manual Reference picking time is not different from the one determined on the unfiltered seismogram, but the uncertainty on the pick is a bit lower.

The final automatic picking, displayed as a cyan vertical line on the filtered seismogram, occurs only 1 sample earlier than the Reference pick.

References

Aldersons, F. (2004) Toward a Three-Dimensional Crustal Structure of the Dead Sea region from Local Earthquake Tomography. Ph.D. thesis, Tel-Aviv University, pp. 123.


Download VIP 1.3.0

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