Evidence for bathymetric control on the distribution of body wave microseism sources from temporary seismic arrays in Africa

• Published in: Geophysical Journal International
• Main Authors: Euler, Garrett G., Wiens, Douglas A., Nyblade, Andrew A.
• Format: Text
• Language: English
• Published: Oxford University Press 2014
• Subjects: Seismology; Southern Ocean; North Atlantic
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/197/3/1869; https://doi.org/10.1093/gji/ggu105

Microseisms are the background seismic vibrations mostly driven by the interaction of ocean waves with the solid Earth. Locating the sources of microseisms improves our understanding of the range of conditions under which they are generated and has potential applications to seismic tomography and climate research. In this study, we detect persistent source locations of P -wave microseisms at periods of 5–10 s (0.1–0.2 Hz) using broad-band array noise correlation techniques and frequency-slowness analysis. Data include vertical component records from four temporary seismic arrays in equatorial and southern Africa with a total of 163 broad-band stations and deployed over a span of 13 yr (1994–2007). While none of the arrays were deployed contemporaneously, we find that the recorded microseismic P waves originate from common, distant oceanic bathymetric features with amplitudes that vary seasonally in proportion with extratropical cyclone activity. Our results show that the majority of the persistent microseismic P -wave source locations are within the 30–60º latitude belts of the Northern and Southern hemispheres while a substantially reduced number are found at lower latitudes. Variations in source location with frequency are also observed and indicate tomographic studies including microseismic body wave sources will benefit from analysing multiple frequency bands. We show that the distribution of these source regions in the North Atlantic as well as in the Southern Ocean correlate with variations in bathymetry and ocean wave heights and corroborate current theory on double-frequency microseism generation. The stability of the source locations over the 13-yr time span of our investigation suggests that the long-term body wave microseism source distribution is governed by variations in the bathymetry and ocean wave heights while the interaction of ocean waves has a less apparent influence.