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Small-scale heterogeneities in the oceanic lithosphere inferred from guided waves
- Source :
- Geophysical Research Letters. 40:1708-1712
- Publication Year :
- 2013
- Publisher :
- American Geophysical Union (AGU), 2013.
-
Abstract
- [1] We analyze seismic waveforms from deep-focus earthquakes occurring in the subducting slab beneath Japan, recorded by broadband ocean bottom seismometers (BBOBSs) installed on the northwestern Pacific Ocean seafloor. The data reveal waveforms with a low-frequency direct P onset, followed by large-amplitude, high-frequency, long-duration Po and So waves. From the analysis of the BBOBS records and a numerical finite-difference method simulation of seismic wave propagation, we elucidate the generation and propagation processes of such guided waves. We demonstrate that the low-frequency direct P and S waves propagate in the asthenosphere and that the following high-frequency, long-duration Po and So waves are developed by multiple forward scattering of P and S waves. The scattering occurs due to laterally elongated heterogeneities in both the subducting and horizontal parts of the oceanic lithosphere, with the apparent velocities (Vp = 8.1 km/s, Vs = 4.6 km/s) being close to the velocities of oceanic lithosphere.
Details
- ISSN :
- 00948276
- Volume :
- 40
- Database :
- OpenAIRE
- Journal :
- Geophysical Research Letters
- Accession number :
- edsair.doi...........3ff7734d5230391348b8c6e677263f6a