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| 2012 episodic tremor and slip | |
|---|---|
| Name | 2012 episodic tremor and slip |
| Date | 2012 |
| Type | Slow slip event |
| Region | Cascadia Subduction Zone |
| Magnitude | N/A (slow slip) |
| Depth | Variable (deep episodic) |
2012 episodic tremor and slip was a large slow slip event that occurred in 2012 beneath the Cascadia margin, detected by networks of broadband seismometers, Global Navigation Satellite System arrays, and strainmeters. The event was studied by institutions including the United States Geological Survey, Natural Resources Canada, Pacific Northwest Seismic Network, and researchers at universities such as University of Washington, University of British Columbia, Oregon State University, Simon Fraser University, and University of Victoria. Analyses linked the phenomenon to prior observations of episodic tremor and slip in regions associated with the Cascadia Subduction Zone, Juan de Fuca Plate, North American Plate, Vancouver Island, and the Olympic Peninsula.
The 2012 slow slip episode manifested as transient aseismic slip and accompanying seismic tremor beneath the continental margin offshore of British Columbia, Washington (state), and Oregon. Monitoring by the Canadian Hazard Information Service, Pacific Geoscience Centre, National Oceanic and Atmospheric Administration, and research groups at California Institute of Technology and Massachusetts Institute of Technology provided integrated seismic, geodetic, and tsunami-hazard context. The event contributed to comparative studies involving earlier episodes documented by teams at University of California, Berkeley, University of Alaska Fairbanks, Scripps Institution of Oceanography, and Monterey Bay Aquarium Research Institute.
The episode occurred within the interface between the Juan de Fuca Plate and the North American Plate along the Cascadia Subduction Zone, a complex margin that also involves tectonic features named in regional mappings such as the Explorer Plate and the Gorda Plate. The subduction system has been the focus of large-scale programs like the Cascadia Initiative, the EarthScope project, the Plate Boundary Observatory, and investigations by the USGS Earthquake Hazards Program. Historical contexts include studies referencing the 1700 Cascadia earthquake and paleoseismic work by the National Research Council and organizations such as the Geological Survey of Canada.
The 2012 episode was identified through a sequence of increased tremor rates, coordinated slow slip, and temporally correlated geodetic displacements recorded by continuous GPS sites operated by Canadian Geodetic Survey, Geodetic Survey Division, and university networks. Researchers from Pierre Auger Observatory-adjacent teams and groups associated with Japan Agency for Marine-Earth Science and Technology compared the timing with other slow earthquakes including events off Shikoku, Nankai Trough, and subduction regions cataloged by the International Seismological Centre. Time-series analyses engaged scientists affiliated with Lawrence Berkeley National Laboratory and the Pacific Northwest National Laboratory.
Seismic arrays from the Pacific Northwest Seismic Network and broadband stations within the Global Seismographic Network recorded non-tectonic tremor bursts that correlated with GPS displacement transients observed by the UNAVCO facility and campaign networks maintained by Geoscience Australia collaborators. Instruments including borehole strainmeters from the USArray component of EarthScope and ocean-bottom seismometers deployed by the Integrated Ocean Drilling Program provided corroborating signals. Analytical techniques used by teams at ETH Zurich, Imperial College London, University of Tokyo, and Peking University incorporated spectral analysis, waveform stacking, and inversion approaches developed in literature by the Seismological Society of America community.
Direct ground shaking damage was absent because the event released strain aseismically, but the episode affected stress conditions on portions of the interface that had implications for seismic hazard models maintained by the Pacific Northwest Seismic Hazard Model consortium and planners at municipal entities in Vancouver (city), Seattle, Portland, Oregon, Victoria, British Columbia, and Tacoma, Washington. The event informed tsunami risk assessments conducted by the National Tsunami Warning Center and influenced emergency planning at provincial agencies such as Emergency Management British Columbia and state agencies including Washington State Emergency Management Division.
The 2012 episode advanced understanding of slow slip mechanics, rupture propagation, and tremor generation, prompting publications involving authors at Stanford University, Princeton University, Harvard University, Cornell University, Duke University, Yale University, and University of California, Santa Cruz. Key findings addressed spatial-temporal migration of tremor, coupling heterogeneity along the plate interface, stress transfer to locked patches implicated in megathrust rupture scenarios like the 1700 Cascadia earthquake, and the role of fluids in fault weakening as discussed in workshops convened by the American Geophysical Union and European Geosciences Union. Comparative work connected the episode to slow slip events in the Mexico subduction zone, the Chile subduction zone, and regions analyzed by the International Continental Scientific Drilling Program.
Following detection, monitoring efforts intensified through collaborations among the USGS, Natural Resources Canada, NOAA Pacific Marine Environmental Laboratory, and academic consortia such as the Cascadia Research Collective and the Pacific Northwest Research Station. Upgrades to GNSS processing at Jet Propulsion Laboratory-supported facilities, expansion of seismic networks by the Canadian Hazards Information Service, and increased ocean-bottom instrumentation by the National Science Foundation supported ongoing surveillance. Outreach and communication involved stakeholders including the Washington Emergency Management Division, British Columbia Ministry of Transportation and Infrastructure, City of Seattle, Clackamas County, and regional utilities and transportation agencies.
Category:2012 natural events