Development of Software to Digitize Historic Hardcopy Seismograms from Nuclear Explosions.

摘要

One main issue associated with nuclear explosion monitoring research is the paucity of seismic recordings to be used for calibration purposes. The problem is particularly acute for nuclear explosions that occurred in the predigital seismic era. Many of these historic explosions have been detonated under a wide variety of geologic and emplacement conditions and it is important to revisit them in the context of broad area monitoring. Our Phase I work has demonstrated the feasibility of developing software for the digitization of historic hardcopy seismograms from nuclear explosions. We have already begun development of a prototype MATLAB(registered trademark) based Graphical User Interface (GUI) computer code called DigiSeis that is specifically designed to meet this goal. Importantly, our project is conducted by seismologists who have a long history of nuclear explosion monitoring with intimate understanding of the nuances of the signal aspects that are important to this field. The key element of our approach is to use mathematical statistics to automatically determine specified tuning parameters in order to develop spatially adaptive thresholding parameters, accurate timing and calibration information, and signal reconstruction schemes that maintain waveform fidelity. We have implemented some of the statistics algorithms in the current version of DigiSeis and have successfully applied DigiSeis to digitize some WWSSN LP recordings of NTS explosions. Human interaction with the program is facilitated via a graphical user interface. Scanned photographic images can be read in, cropped and rotated. Image processing techniques are used for adaptive contrast enhancement and horizontal noise trace removal prior to digitization. The core methodology used in DigiSeis is global and local histogram enhancement techniques combined with median-value processing.