Software Toolbox for Systematic Evaluation of Seismometer-Digitizer System Responses.

摘要

Measurement of the absolute amplitudes of a seismic signal requires accurate knowledge of the seismometerdigitizer response. When the seismometer and digitizer characteristics are known, deconvolution of the digital system response is relatively straightforward. However, even with a known response, problems in timing and incorrect polarities can often contaminate any calibration parameters derived from these data. When either one or both components of the response for a seismometer system are unknown, the data are often not considered suitable for seismological tasks that require absolute amplitude measurements. We have developed a set of software tools that can recover the sensor/digitizer response function from raw data when the response is either unknown or incorrectly known. These software tools include SACPSD: a power spectral density (PSD) estimator for background noise spectra at a seismic station. SACPSD differs from the current PSD used by NEIC and IRIS in that the smoothed spectra are derived by smoothing over linear frequencies rather than logarithmic periods, resulting in smoothed PSD that tracks the unsmoothed PSD rather than exhibiting a bias where the raw PSD drops rapidly with increasing period. SACPSD is fast and can be used routinely to monitor network performance and metadata validity NOISETRAN: a prototype method of estimating the broadband seismic system response for a seismic station based on the background noise at a nearby reference station GUIs/SCRIPTS: we have developed Graphical User Interfaces (GUIs) and shell scripts that provide seismologists with easy access to the software in the system response recovery toolbox. During Phase I of this Small Business Innovative Research (SBIR) project, we have also compiled an extensive database of seismic sensors and recorders that are in use or have been developed. Information on each instrument includes sensitivities, bit weights, and gains. The database also contains station information and response corrections for many stations actively or previously installed around the world. The information in this database provides another step in determining the proper response correction for an unknown station. Our results indicate that our Phase I project demonstrated both technical feasibility and a high potential to achieve the GNEM R&D goals for system response recovery of important seismic datasets.