Ground Truth Comparison of Sensor Orientation determined from Polarization Analysis of Large-eatthquake Body-was at USArray Seismic Stations
Abstract
Polarization of teleseismic body-waves from large earthquakes (M > 7.3) recorded from April 2004 to August 2008 at USArray stations are used to estimate the sensor orientation. Three-component broadband recordings at over 500 sites are demeaned and band-pass filtered between 5 and 100 sec to determine the polarization of the arriving wave at all USArray sites. We compute the three-dimensional single value decomposition of say the arriving P-wave and compare the resulting orientation to that of the theoretical plane wave approximation (i.e. azimuth and incidence angle) to obtain the sensor orientation. We do this for body waves of events arriving from multiple directions to obtain an average sensor orientation at each station. In addition, to take advantage of the USArray deployment geometry, we determine an empirical polarization estimate for each event from the robust stack of body-waves recorded at sites located within 150 km of the reference station. This empirical estimate three dimensional single value decomposition is compared to that of the reference station to determine the orientation of the sensor at the reference station for multiple events. Given that since September 2007 ground truth sensor orientation is known at USArray sites because the use of an Octans gyroscope to a level of +/- 0.5 degree, it is possible to test the accuracy of the single station theoretical estimate and that of the nearest neighbor estimate for different body-waves. We present the results of the polarization estimates with body waves of large events that vary within +/-2 degrees for most stations when using the nearest neighbor estimate compared to those of the measured ground truth sensor orientation. The single station estimates variation is larger.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.S13B1798A
- Keywords:
-
- 0520 Data analysis: algorithms and implementation;
- 3270 Time series analysis (1872;
- 4277;
- 4475);
- 7200 SEISMOLOGY;
- 7212 Earthquake ground motions and engineering seismology;
- 7294 Seismic instruments and networks (0935;
- 3025)