Scattered waves from low-frequency earthquakes and plate boundary structure in northern Cascadia

We use 3‐D waveform modeling of LFEs (low‐frequency earthquakes) to investigate their relation to plate boundary structure along a linear transect in northern Cascadia. To account for crustal velocity heterogeneity, a smoothed 3‐D model of subduction zone structure is assembled that incorporates con...

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Bibliographic Details
Published in:Geophysical research letters 2013-08, Vol.40 (16), p.4238-4243
Main Authors: Nowack, Robert L., Bostock, Michael G.
Format: Article
Language:English
Subjects:
Body Waves
Boundaries
Earth sciences
Earth, ocean, space
Earthquakes
Exact sciences and technology
Geological time
Geophysics
Mathematical models
Plate tectonics
Plates (structural members)
Scattering
Seismic phenomena
Seismology
Subduction Zones
Three dimensional models
Waveform analysis
Waveforms
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Summary:We use 3‐D waveform modeling of LFEs (low‐frequency earthquakes) to investigate their relation to plate boundary structure along a linear transect in northern Cascadia. To account for crustal velocity heterogeneity, a smoothed 3‐D model of subduction zone structure is assembled that incorporates constraints from regional tomographic and plate boundary models. Scattered phases within LFE waveforms are identified based on synthetic predictions that incorporate thrust mechanisms aligned parallel to a dipping plate boundary atop a high‐Vp/Vs low‐velocity zone (LVZ). Scattering for near‐vertical paths is dominated by S‐to‐P/S‐to‐S reflections/conversions from the LVZ. The modeling suggests that LFEs lie at or very close to the plate boundary and that the LVZ structure is laterally heterogeneous but broadly consistent with results from teleseismic analysis. Key Points LFE templates are used to constrain plate boundary structure LFE waveforms controlled by focal mechanisms and S‐P and S‐S scattering Modeling of LFE waveforms broadly consistent with teleseismic estimates
ISSN:0094-8276
1944-8007
DOI:10.1002/grl.50826