Affiliation:
1. U.S. Geological Survey, Albuquerque Seismological Laboratory, Target Rd 10002 Isleta SE, Kirtland AFB, Albuquerque, NM 87117, USA
2. UNLV, Las Vegas, NV 89154, USA
Abstract
SUMMARY
Variations in atmospheric pressure have long been known to introduce noise in long-period (>10 s) seismic records. This noise can overwhelm signals of interest such as normal modes and surface waves. Generally, this noise is most pronounced on the horizontal components where it arises due to tilting of the seismometer in response to changes in atmospheric pressure. Several studies have suggested methodologies for correcting unwanted pressure-induced noise using collocated microbarograph records. However, how applicable these corrections are to varying geologic settings and installation types (e.g. vault versus post-hole) is unclear. Using coefficients obtained by solving for the residuals of these corrections, we can empirically determine the sensitivity of instruments in a specific location to the influences of 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 analyse three Streckeisen STS-2 broadband seismometers, which are collocated with a microbarograph, at the Albuquerque Seismological Laboratory. We observe periods of high magnitude-squared-coherence (γ2-coherence; γ2 > 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 cases where instruments are not located at a large depth (<100 m), the pressure-induced noise is polarized in a nearly constant direction that is consistent with local topographic features or the geometry of the vault. We also find that borehole instruments at a large depth (>100 m) appear to be unaffected by pressure-loading mechanisms outlined by Sorrells (1971) but possibly by Newtonian attraction. Correlating 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.
Publisher
Oxford University Press (OUP)
Subject
Geochemistry and Petrology,Geophysics
Reference34 articles.
1. The effects of the atmospheric pressure changes on seismic signals or how to improve the quality of a station;Beauduin;Bull. seism. Soc. Am.,1996
2. ObsPy: a Python toolbox for seismology;Beyreuther;Seismol. Res. Lett,2010
3. Effects of thermal variability on broadband seismometers: controlled experiments, observations, and implications;Doody;Bull. seism. Soc. Am.,2017
4. Characteristics and spatial variability of wind noise on near-surface broadband seismometers;Dybing;Bull. seism. Soc. Am.,2019
Cited by
10 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献