Checking Data Quality of Co-located Broadband and Strong-motion Sensors in Southern California Seismic Network

Zefeng Li, Egill Hauksson, Thomas H. Heaton, Luis Rivera, & Jennifer R. Andrews

Published July 31, 2018, SCEC Contribution #8235, 2018 SCEC Annual Meeting Poster #055

Differences in waveforms recorded by broadband and strong motion sensors at the same site can be caused by sensor failure, mis-orientation in deployment, wrong instrument response parameters etc. Deployed instruments can malfunction and produce unreal seismic records, which may mess up real-time seismic processing and eventually cause wrong estimates of source and structure parameters. Thus, it is important to check sensor health regularly for rapid detection of sensor failures, which is essential for earthquake early warning systems that operate in real time. Here, we detect instrument malfunctions in Southern California Seismic Network (SCSN), by taking advantage of co-located broadband and strong-motion seismometers. We assume that healthy co-located broadband and strong-motion sensors should provide almost identical instrumental corrected waveforms, when the signal is within their common resolution range. Specifically, we remove the instrument response of both records and compare the waveforms of small local earthquakes. We examine two metrics, amplitude ratio and cross-correlation, both of which should be ~1 in normal state. Deviation from 1 in either metric suggests inconsistency between the broadband and strong-motion data. We calculate the two metrics for the year of 2017 and identify several problematic sites. For example, the site WMF has wrong instrument gain on one sensor: the broadband amplitude tends to be twice of the strong-motion amplitude. In addition, in the site SBPX, the strong-motion records are consistently different from the broadband motion records in both amplitude and shape, suggesting one of the two sensors being faulty. Our final goal is to develop an automatic workflow to monitor the sensor health near real-time. Besides local earthquakes, we are in the process of exploring the usefulness of microseism and teleseismic signals for this real-time diagnostic task. Updates will be reported in the meeting.

Citation
Li, Z., Hauksson, E., Heaton, T. H., Rivera, L., & Andrews, J. R. (2018, 07). Checking Data Quality of Co-located Broadband and Strong-motion Sensors in Southern California Seismic Network. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology