Tremor Monitoring

A screenshot of the web product resulting from this near-realtime system.
Since their discovery nearly a decade ago, advances in both instrumentation and methodology in subduction zones around the world have brought the causal connection between seismically observed tectonic tremor and geodetically observed slow slip into sharper focus—with it becoming increasingly clear that tremor serves as a proxy for slow slip. Considering geodesy’s lower limits in spatio-temporal resolution together with the abundance of low-level, ageodetic tremor, this connection makes tremor a key component in monitoring when, where, and how much slip is occurring. Because slow slip transfers stress to the updip seismogenic portion of the plate interface, monitoring transient events may serve in forecasting the threat of a megathrust earthquake by inferring the temporal and spatial variations in the loading of the seismogenic zone. We use waveform envelope correlation & clustering [Wech and Creager, 2008] methodology to automatically detect and locate tremor. Applying this technique to TA, PASSCAL, PBO, and regional network data, we map tremor epicenters from northern California to mid-Vancouver Island and present a system that monitors and reports tremor activity in near-realtime on an interactive webpage [Wech, 2010]. Collectively the resulting product is an automatic margin-wide tremor catalog and a website disseminating this information in a way that is accessible and engaging to the general population yet remains valuable as a tool for scientific synergy across institutions and disciplines:
</p><p>Wech, A.G., and K.C. Creager (2008), Automatic detection and location of Cascadia tremor, Geophys. Res. Lett., 35, L20302.
</p><p>Wech, A.G. (2010), Interactive Tremor Monitoring, Seismol. Res. Lett., 81:4, July/August 2010.
</p><p>Audet, P., et al. (2010), Slab morphology in the Cascadia fore arc and its relation to episodic tremor and slip, J. Geophys. Res., 115.
</p><p>Acknowledgements: This work was funded by USGS grant #’s 08HQGR0034, G09AP00024, & G10AP00033. Realtime data are provided by the Pacific Northwest Seismic Network, Pacific Geoscience Center, Plate Boundary Observatory, and Northern California Regional Network.</p>


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