Towards Understanding Relationships Between Atmospheric Pressure Variations and Long-Period Horizontal Seismic Data: A Case Study

Session: Recent Advances in Very Broadband Seismology [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Variations in atmospheric pressure are known to introduce noise in long-period (> 10 s) seismic records (Sorrells, 1971; Harrison, 1976). This noise is most pronounced on the horizontal components and can overwhelm signals of interest. Several studies have suggested methodologies for correcting unwanted pressure induced noise using co-located microbarograph records. By using coefficients obtained when solving for the residuals of these corrections, we can empirically determine the sensitivity of instruments in a specific location to the influences of atmospheric pressure. To better understand how long-period, pressure-induced noise changes with time and emplacement, we examine horizontal seismic records along with barometric pressure at five different Global Seismographic Network stations, all with multiple broadband seismometers. We also analyze seismic records from three Streckeisen STS-2 broadband seismometers, which are co-located with a microbarograph, at the Albuquerque Seismological Laboratory.

We observe periods of high magnitude-squared-coherence (>0.8) between the seismic and pressure signals which fluctuate through time, frequency and even between seismic instruments in the same vault. These observations suggest that these tilt-generated signals are highly sensitive to very local (<10 m) site effects. However, we find that in some cases, the pressure induced noise is polarized in a nearly constant direction that is consistent with local topographic features or the geometry of the vault. By using this information to correlate the induced noise polarization direction with times of high coherence, we work to identify sensors that are ultimately limited by pressure induced horizontal noise as well as period bands that can benefit from pressure corrections. We find that while the situation is complex, each sensor appears to have its own unique response to pressure. Our findings suggest that we can determine empirical relationships between pressure and induced tilt on a case by case basis.

Presenting Author: Alexis C. B. Alejandro

Authors