The table below shows the results from a polarization analysis of long-period waveforms (primarily surface waves) recorded on USArray and additional broadband stations from a variety of networks (Ekstrom and Busby, SRL, 2008). The horizontal components have been rotated to maximize the correlation between observed and predicted seismograms for recent earthquakes, and the table shows the median (aqua blue) of the rotation angles, as well as the range (navy blue) for the second and third quartiles of the distribution of angles.
Large (5 degrees or more) anomalies are unlikely to be caused by wave-propagation effects, and are more likely the result of station misorientation.
The table below gives the channel names as well as the time of the first and last observation, the total number of observations, and the number of polarization measurements used in the estimate of the sensor orientation. Estimates based on fewer than 5 measurements are not reliable. The (Azim1, Azim2) columns give the most recently reported sensor orientations for the horizontal components. The orientation anomaly is measured against this orientation.
The waveforms used in the analysis span the period from a year ago through the present.
Alphabetical listing of the polarization results.
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |
| Station | Chan 1 | Chan 2 | T | min time | max time | # obs. | # used | Azim 1 | Azim 2 | 90-26 | 25-21 | 20-16 | 15-11 | 10- 8 | 7- 5 | 4- 2 | 1- 1 | 2- 4 | 5- 7 | 8-10 | 11-15 | 16-20 | 21-25 | 26-90 |