The STS-1 seismometer is currently the principal very broad-band (VBB) seismometer used in global or regional seismic networks operated by members of the Federation of Digital Broad-Band Seismograph Networks (FDSN). It is widely viewed as the finest VBB sensor in the world. Unfortunately, many of the STS-1's, which were manufactured and installed 10-20 years ago, are encountering both operational failures and age-related degradation. This problem is exacerbated by the fact that sensors are no longer being produced or supported by the original manufacturer, G. Streckeisen AG. In a first step towards assuring continued high quality of VBB data for decades to come, we have developed and tested new electronics and methods for mechanical repair for the STS-1 very broadband seismometer. A primary goal of this effort was to develop a fully-tested, modern electronics module that will be a drop-in replacement for the original electronics. This new electronics design addresses environmental packaging problems that have led to operational errors and failures in the existing instruments. This effort also provided the opportunity to implement a set of electronic improvements that will make the installation and operation of the sensors more efficient. Metrozet developed the first prototype new electronics for the STS-1, while the BSL engineering staff prepared a test-bed at the Byerly Vault (BKS) and developed the capability to simultaneously test 6-8 STS-1 components. BSL staff then tested and analysed results from successive versions of the electronics.
The first generation prototype electronics did not include centering or calibration functionality. The second generation prototype included remote centering functionality as well as calibration functions. After some observations and refinements, this generation of electronics was operated on two seismometers concurrently and successfully run through the swept and stepped calibration functions on four seismometers. During this final phase, the Metrozet electronics included the ability to initiate and operate the calibrations via a network (ethernet) connection. Most of the calibration testing was performed remotely from Metrozet's Southern California office over the BSL network. Metrozet was able to remotely log into the Berkeley network, establish a connection to the test bed in the Byerly seismic vault, and initiate control of the seismometer, including remote centering and calibration functions.
In the final stage of the project, once the BSL tests were completed and the development appeared complete and satisfactory, the new electronics were finally tested at the Albuquerque Seismological Laboratory's seismic vault, which is located in a quieter environment than BKS. The new electronics are currently being field tested at the BDSN broadband station HOPS.
Berkeley Seismological Laboratory
215 McCone Hall, UC Berkeley, Berkeley, CA 94720-4760
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