Despite their importance as a fundamental constraint on Earth properties, regional-scale measurements of body-wave seismic attenuation are scarce. This is partially a result of the difficulty in producing robust estimates of attenuation. In this paper, we focus on measuring differential attenuation on records of teleseismic P waves.We examine a unique data set of five records of the North Korean nuclear test of 2017 measured at five broad-band seismic stations deployed within a few metres of each other but using different installation procedures. Given their extreme proximity, we expect zero differential intrinsic attenuation between the different records. However, we find that different attenuation measurement methods and implementation parameters in fact produce significant apparent differential attenuation (δt∗). Frequency-domain methods yield a wide range of δt∗ estimates between stations, depending on measurement bandwidth and nuances of signal processing. This measurement instability increases for longer time windows. Time domain methods are largely insensitive to the frequency band being considered but are sensitive to the time window that is chosen.We determine that signal-generated noise can affect measurements in both the frequency and time domain. In some cases, the range of results amounts to a significant fraction of the range of differential attenuation across the conterminous United States as determined by a recent study. We suggest some approaches to manage the inherent instability in these measurements and recommend best practices to confidently estimate body wave attenuation.
Bibliographical noteFunding Information:
We are thankful to the property owner who gave us permission to install our stations in his land. Two anonymous reviewers provided comments that helped significantly improve the manuscript. This work was partially funded by the National Science Foundation (NSF) under grant EAR-1827277 to the University of Minnesota.
© The Author(s) 2019.
- Body waves
- Fourier analysis
- Seismic attenuation
- Site effects
- Time-series analysis